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Genetic Susceptibility to Ankylosing Spondylitis
Abstract
Ankylosing spondylitis is a highly heritable, common rheumatic condition, primarily affecting the axial skeleton. The association with HLA-B27 has been demonstrated worldwide, and evidence for a role of HLA-B27 in disease comes from linkage and association studies in humans, and transgenic animal models. However, twin studies indicate that HLA-B27 contributes only 16% of the total genetic risk for disease. Furthermore, there is compelling evidence that non-B27 genes, both within and outwith the major histocompatability complex, are involved in disease aetiology. In this post-genomic era we have the tools to help elicit the genetic basis of disease. This review describes methods for genetic investigation of ankylosing spondylitis, and summarises the status of current research in this exciting area.
... Расшифровка патогенезаTRAPS позволила предположить, что сходный механизм может лежать в основе анкилозирующего спондилита -АС (болезни Бехтерева), характеризующегося воспалением суставов позвоночника и илеосакрального сочленения с развитием нарушений их подвижности. Более 30 лет назад доказано увеличение риска развития АС у лиц с лейкоцитарной экспрессией HLA-B27 [131], однако патогенез заболевания длительное время оставался неясным. Согласно современным представлениям, при нарушении конформационной сборки тяжелых цепей HLA-B27 в эндоплазматической сети гранулоцитов эти цепи способны образовывать димеры благодаря дисульфидным взаимодействиям [132,133]. ...
... Согласно современным представлениям, при нарушении конформационной сборки тяжелых цепей HLA-B27 в эндоплазматической сети гранулоцитов эти цепи способны образовывать димеры благодаря дисульфидным взаимодействиям [132,133]. Недавно выявлено, что другим фактором риска развития данного заболевания является мутация гена ARTS1, относящегося к генам кластера IL-1 [131,134]. Этот ген кодирует белок, выполняющий как минимум две иммунологические функции, одна из которых связана с адаптивным иммунным ответом, а другая -с реакциями врожденного иммунитета. В эндоплазматической сети макрофагов данный белок расщепляет пептиды для презентации молекулам главного комплекса гистосовместимости I типа, а на поверхности клеток расщепляет и инактивирует рецепторы таких провоспалительных цитокинов, как IL-1, IL-6 и TNF-α. ...
Autoinflammatory disease (AID) is a new concept formulated from the results of studying the pathogenesis of familial periodic fevers, a heterogeneous group of genetically determined diseases characterized by causelessly recurrent exacerbations of the inflammatory process due to genetically determined disorders of innate immunity and accompanied by uncontrolled hypersecretion of interleukin-1 (IL-1). These mechanisms were a basic model for understanding a wide range of rheumatologic and other inflammatory diseases of the internal organs. The late diagnosis of AIDs and their ineffective treatment increase the risk for the development and progression of secondary AA amyloidosis. Elaboration of both clinical and effective laboratory criteria for diagnosing autoinflammation is of great importance for determining the tactics of anti-inflammatory therapy and prevention of complications.
... Linkage between HLA-B27 and AS remains the strongest association between an HLA class I molecule and disease, 6-8 as has been demonstrated worldwide and evidence for the role of HLA-B27 in AS comes from linkage and association studies in humans and transgenic animal models. 39,40 HLA-B27 represents a family of at least 39 closely related alleles: B2701 to 2739, which differ in their ethnic distribution and whose heterogeneity has been previously determined in different populations. 41,42 HLA-B27 has a peptide binding cleft formed by the α1 and α2 domains of the heavy chain that has six side-pockets (designated by the letters A through F), which accommodate the side chains of the amino acids of the bound nonamer peptides. ...
... However, studies indicate that HLA-B27 contributes only about 16% of the total genetic risk for disease. 39 There are nonB27 genes, both within and outside the HLA, that also seem to be involved in disease etiology. With respect to the association with the MHC region, located in the short arm of chromosome 6, MHC class II alleles, genes that encode TNF or complement and genes which are involved in the antigenic presentation of class I molecules (TAP, LMP2 and LMP7) 46 were investigated. ...
Cellular activity of natural killer cells (NK cells) is defined by the balance between activating and inhibitory signals coming from their receptors. With respect to this response, killer immunoglobulin-like receptors (KIR) are unique because of their diversity and capacity to recognize specific human leukocyte antigen (HLA) class I allotypes. Up to the present few studies have experimentally been developed concerning the role of KIR genes in spondyloarthropathies (SpA) and its clear relationship with HLA-B27. However, the role of the HLA-B27 heavy chain homodimers and their possible recognition by KIR receptors in the pathogenesis of spondylarthritides has been studied. Moreover, it has been suggested that NK cells and their receptors could play a role in ankylosing spondylitis (AS) development. Several association studies based on a model in which KIRs synergize with HLAs have also been published. This interaction may generate compound genotypes which provide different levels of activation or inhibition. Furthermore, some of these have been associated with certain SpA, such as ankylosing spondylitis (AS) and psoriatic arthritis (PsA).
... HLA-B*27 is strongly associated with ankylosing spondylitis (AS), and HLA-B*27 detection is routinely applied in the diagnosis of this disease. The percentages of HLA-B*27 positivity in the general population and among AS patients are 5-10% and 90%, respectively [9]. Multiple molecular diagnostic techniques are applied for the routine typing of HLA-B*27, including PCR with sequence-specific primers, PCR with restriction fragment length polymorphism, and also PCR with sequence-based typing, flow cytometry, melting curve analysis, and real-time PCR assay [10][11][12][13][14]. Thus far, a fully automated procedure has not been applied to the detection of HLA-B*27. ...
The adoption of an automated system can decrease the hands-on time requirements in a clinical laboratory setting. For the detection of HLA-B*27, implementing a high-throughput and fully automated system has several advantages over using manual methods. Therefore, this study aimed to evaluate automation efficiency for the detection of HLA-B*27. Peripheral blood samples were obtained from 50 participants, and DNA was isolated from these samples. A Pharmigene PG27 detection kit was used for the qualitative detection of HLA-B*27. The performances of the semi-automated and fully automated LabTurboTM AIO systems in the detection of HLA-B*27 were compared. The mean absorbance (optical density) values for the MaelstromTM 8 and LabTurboTM AIO systems were found to be 1.88 and 1.9, respectively. The housekeeping gene was amplified and quantified using a real-time PCR assay across all DNA extracts to check the quality of the extracted human DNA. The results were expressed as the cycle threshold (Ct) values for all DNA extracts from both platforms. The mean Ct values for the Roche Cobas z480 and LabTurboTM AIO systems were found to be 22.7 and 20.4, respectively. This study demonstrated that the semi-automated method and the LabTurboTM AIO system yield consistent results for the detection of HLA-B*27. However, compared to the semi-automated method, the LabTurboTM AIO system provides standardized procedures, avoids manual handling, and improves turnaround time.
... A causa da doença é desconhecida[5]. Tem-se que a doença é cerca de 300 vezes mais freqüente em pessoas que herdam um determinado grupo sangüíneo dos glóbulos brancos, quando comparadas com aquelas que não possuem esse marcador genético, denominado HLA B27[1,[6][7][8][9][10]. ...
A espondilite ancilosante é uma patologia inflamatória sistêmica que afeta, predominantemente, a coluna vertebral, quadris, ombros e articulações sacro-ilíacas, acompanhada por inflamação dos tecidos conjuntivos. A doença evolui com erosão óssea, formação de tecido de granulação, que é substituído por tecido fibroso, e conseqüente anquilose das articulações acometidas. A sintomatologia desta doença é característica, apresentando dores crônicas, persistentes e progressivas, rigidez aos movimentos, cansaço, falta de apetite, dificuldade respiratória, entre outros. O presente estudo, com aplicação de protocolo hidroterapêutico para portador de espondilite ancilosante objetivou promover alívio da dor e do espasmo muscular; manutenção da mobilidade da coluna, ombros e quadris; minimizar a rigidez e o encurtamento dos tecidos moles; promover fortalecimento muscular; trabalhar consciência corporal e postural. Palavras-chave: espondilite ancilosante, tratamento, exercícios aquáticos.
... However, in spite of the identification of various genes, molecules and cells involved, the mechanism underlying the pathogenesis of AS is still poorly understood. Since studies in twins have shown that genetic make-up forms an important risk factor for the development of AS (5)(6)(7), several studies were performed to identify the responsible genetic factors. By far the strongest genetic association with AS is the HLA-B27 allele; whereas 90% of patients carry this allele it is present in only 7-8% of the healthy Caucasian population (8). ...
Ankylosing Spondylitis (AS) is an autoimmune disease that mainly affects the sacroiliac joints and the spine of the lower back. The disease is strongly associated with HLA-B27. Additional genes, single nucleotide polymorphisms and molecular components have been identified to be associated with AS, but the exact mechanism that drives disease development remains poorly understood. The killer immunoglobulin-like receptors (KIRs) are regulators of cytotoxicity of natural killer cells and T-cell subsets and may be relevant in binding to HLA-B27 and the development of AS.
To identify possible associations of KIR genotype with susceptibility to AS and disease characteristics including the presence of the HLA-B27 allele, disease severity and uveitis.
Complete genotyping of the KIR locus of 303 Caucasian AS patients, 119 random healthy Caucasian controls and 50 HLA-B27 positive healthy Caucasian controls by multiplex ligation-dependent probe amplification (MLPA) assay for detection of gene presence and copy number.
We did not observe a significant association of any specific KIR gene or haplotype with susceptibility to AS or any other clinical manifestation. Disease severity, as measured by fulfilling the criteria for treatment with TNF-α blocking therapy, was linked to a lower number of genes for the functional variant of KIR3DL1 (p=0.007).
Our exploratory study indicates that KIR genes do not form a major risk factor for susceptibility to AS. However, the data do suggest a role for KIRs in progression of the disease, whereby KIR3DL1 has a protective effect against the more severe manifestations of AS. This article is protected by copyright. All rights reserved.
© 2015, American College of Rheumatology.
... In the past decade, we have already known that human leukocyte antigen (HLA)-B27 and B27 subtypes were associated with AS [6]. However, studies indicated that HLA-B27 contributes only 16 % of the total genetic risk to the disease [7]. It is proposed that the involvement of genes outside the major histocompatibility complex (MHC) region contributes to the development of AS. ...
The aim of this study was to explore the interaction between FCRL4 gene and environmental factors in patients with ankylosing spondylitis. Two hundred ninety-seven ankylosing spondylitis (AS) Han Chinese patients were selected who were diagnosed at the Department of Rheumatology, First Affiliated Hospital, Anhui Medical University, in accordance with the modified New York criteria. The single nucleotide polymorphism (SNP) was genotyped by multiplex SNaPshot technique. The interaction between FCRL4 gene and ten environmental factors in AS patients was assessed by using a case-only study. The interaction between FCRL4 gene (rs2777963) and environmental factors was analyzed by chi-square test and logistic models. p values, odds ratio, and 95 % confidence intervals (CIs) were used for estimating the effects of interaction. Odds ratio (OR) for the interaction of gene × environment (G × E) between drinking group and non-drinking group was 2.61 [95 % CI (1.30, 5.23), p = 0.007], with statistical significance. Within the cooking oil group, there also may be an interaction of G × E between main animal oil and main plant oil [OR = 10.55, 95 % CI (5.55, 20.04), p < 0.001]. However, there was no interaction between FCRL4 gene and the other eight environmental factors in patients with AS. The observed significant gene-environment interaction suggests that drinking and cooking oil with FCRL4 gene has a significant interaction. Drinking and cooking oil may be risk exposure factors to take a combined action with predisposing genes in patients with AS. A larger sample case-control study is needed to illustrate the interaction mechanism in the further study.
... 1-3 Indeed, more than 90% of patients with AS are born with the HLA-B27 gene, while only 5-15% of carriers are present in the total population. 4,5 Nevertheless, twin studies indicate that HLA-B27 contributes to only 16% of the total genetic risk, 6 suggesting that AS has multiparameter heritability. Deciphering the heritable factors that contribute to AS is important in understanding the mechanisms of disease initiation and progression. ...
Increasing evidence points to a role for killer immunoglobulin-like receptors (KIRs) in the development of autoimmune diseases. In particular, a positive association of KIR3DS1 (activating receptor) and a negative association of KIR3DL1 (inhibitory receptor) alleles with ankylosing spondylitis (AS) have been reported by several groups. However, none of the studies analyzed these associations in the context of functionality of polymorphic KIR3DL1. To better understand how the KIR3DL1/3DS1 genes determine susceptibility to AS, we analyzed the frequencies of alleles and genotypes encoding functional (KIR3DL1*F) and non-functional (KIR3DL1*004) receptors. We genotyped 83 AS patients and 107 human leukocyte antigen (HLA)-B27-positive healthy controls from the Russian Caucasian population using a two-stage sequence-specific primer PCR, which distinguishes KIR3DS1, KIR3DL1*F and KIR3DL1*004 alleles. For the patients carrying two functional KIR3DL1 alleles, those alleles were additionally genotyped to identify KIR3DL1*005 and KIR3DL1*007 alleles, which are functional but are expressed at low levels. KIR3DL1 was negatively associated with AS at the expense of KIR3DL1*F but not of KIR3DL1*004. This finding indicates that the inhibitory KIR3DL1 receptor protects against the development of AS and is not simply a passive counterpart of the segregating KIR3DS1 allele encoding the activating receptor. However, analysis of genotype frequencies indicates that the presence of KIR3DS1 is a more important factor for AS susceptibility than the absence of KIR3DL1*F. The activation of either natural killer (NK) or T cells via the KIR3DS1 receptor can be one of the critical events in AS development, while the presence of the functional KIR3DL1 receptor has a protective effect. Nevertheless, even individuals with a genotype that carried two inhibitory KIR3DL1 alleles expressed at high levels could develop AS.
... It commonly affects young men more frequently than women, with an estimated male-female ratio of 5:1. Up to 15% of children with juvenile chronic arthritis are classified with juvenile spondylitis The association with HLA-B27 has been demonstrated worldwide, and evidence for a role of HLA-B27 in disease comes from linkage and association studies in humans, and transgenic animal models [43]. ...
Association of HLA and diseases is well known. Several population studies are available suggesting evidence of association of HLAs in more than 40 diseases. HLA found across various populations vary widely. Some of the reasons attributed for such variation are occurrence of social stratification based on geography, language and religion, consequences of founder effect, racial admixture or selection pressure due to environmental factors. Hence certain HLA alleles that are predominantly associated with disease susceptibility or resistance in one population may or may not show any association in other populations for the same disease. Despite of these limitations, HLA associations are widely studied across the populations worldwide and are found to be important in prediction of disease susceptibility, resistance and of evolutionary maintenance of genetic diversity. This review consolidates the HLA data on some prominent autoimmune and infectious diseases among various ethnic groups and attempts to pinpoint differences in Indian and other population.
... A genetic association between AS and human leukocyte antigen (HLA)-B27 has been identified in different populations, and the significance of B27-subtype studies is that they provide important information that is useful for research into the mechanism by which B27 causes AS [2]. However, twin studies indicate that HLA-B27 contributes only 16 % of the total genetic risk for disease [3]. It is proposed that non-major histocompatibility complex (non-MHC) genes predispose to AS [4]. ...
Objective:
Recent studies have explored the role of killer cell immunoglobulin-like receptors (KIRs) in chronic autoimmune diseases. The purpose of this study was to demonstrate whether KIR genes contribute to the pathogenesis of ankylosing spondylitis (AS) in Chinese populations.
Methods:
Sixteen KIR genes were genotyped from 60 unrelated patients with AS and 60 HLA-B27-positive matched healthy controls by PCR-SSP. The frequencies of the KIR alleles and genotypes in the AS and control groups were assessed by the χ(2) test.
Results:
Our results showed that the frequency of the activator receptor KIR3DS1 gene in the AS group was significantly increased compared to the controls (χ(2) = 5.263, P = 0.006, OR = 3.059, 95 % CI = 1.357-6.896). Moreover, the frequency of the KIR3DL1/3DS1 genotype was greater in the AS group than in the control group (P = 0.039, OR = 3.059, 95 % CI = 1.357-6.896). In contrast, the frequency of the no KIR3DL1/no 3DS1 genotype was lower in patients with AS compared with the controls (P = 0.032, OR = 0.110, 95 % CI = 0.013-0.911).
Conclusion:
KIR3DS1, in addition to HLA-B27, may play an important independent role in the pathogenesis of AS in the Chinese population.
... One of the bestknown and strongest associations is between ankylosing spondylitis (AS) and HLA-B*27. About 90% of AS patients are HLA-B*27 positive, compared to 5-10% of the general population [1,2]. In addition, an increased prevalence of HLA-B*27 has been reported in patients with Reiter's syndrome, anterior uveitis, psoriatic arthritis and inflammatory bowel disease [3]. ...
To develop a duplex real-time TaqMan PCR assay for genotyping HLA-B*27 in the Chinese Han population.
A standard curve was constituted to deduce amplification efficiency, dynamic range and detection limit of the duplex real-time TaqMan PCR assay, whereas PCR-SBT (PCR with sequence-based typing) was used to evaluate the accuracy of the assay.
A linear standard curve for determining HLA-B*27 was obtained within the range of 10(1)-10(9) copies per reaction with the correlation coefficient of 0.99 and amplification efficiency of 98.30%. The detection limit was 3.09 copies per reaction. Complete concordance was found between the results obtained by the duplex real-time TaqMan PCR assay and PCR-SBT. Fifty-nine of the 178 genomic samples were HLA-B*27 positive and the other 119 were HLA-B*27 negative.
The duplex real-time TaqMan PCR approach appears to be a reliable, sensitive, rapid and high-throughput method to genotype HLA-B*27 in the Chinese Han population.
... Despite intensive research, the pathogenic role of the gene and its product has not yet been resolved. However, studies indicate that HLA-B27 contributes only about 16% of the total genetic risk for disease [2]. Non-B27 genes exist, both within and outside the HLA, that also seem to be involved in disease etiology. ...
Killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) loci are both highly polymorphic. The aim of this study was to perform a KIR genotype analysis and examine, in concert with HLA-B27 genotypes, their influence on ankylosing spondylitis (AS) susceptibility in two Asian populations (one from China, 42 patients and 30 controls, and another from Thailand, 30 patients and 16 controls). In the Chinese population, we observed an increase of KIR3DS1, KIR2DS5, and KIR2DL5 gene frequencies in AS patients (p(c) < 0.005, p(c) < 0.001, and p(c) < 0.01, respectively). A similar increase was reported in the Thai population: KIR3DS1, KIR2DS5, and KIR2DL5 gene frequencies were higher in AS (p(c) < 0.05, p < 0.05, and p(c) < 0.05, respectively). Upon analyzing the KIR3DL1/3DS1 genotypes, we determined significant differences in both populations. The frequency of 3DL1/3DL1 was decreased in AS (p(c) < 0.005 and p(c) < 0.05 in the Chinese and Thai populations, respectively), whereas 3DL1/3DS1 demonstrated an increased frequency in AS (p(c) < 0.005 in the Chinese population and p(c) < 0.05 in the Thai population).
... Pinpointing the specific genes involved is a challenging task, given that the MHC is characterized both by extreme diversity of specific loci, and by extreme and complex linkage disequilibrium patterns that must be tightly controlled for to avoid confusing findings due to linkage disequilibrium from true association. Several small association studies have implicated other MHC genes in AS, although the studies have been too small and targeted to determine whether these are primary associations or are due to linkage disequilibrium with other loci (reviewed in [31]). Studying MHC markers (SNPs and microsatellites) on HLA- B27-DRB1 haplotypes, we recently showed convincing evidence for the existence of non-B27 MHC genes in AS carried on both B27-positive and B27-negative strands [32]. ...
The advent of high-throughput SNP genotyping methods has advanced research into the genetics of common complex genetic diseases such as ankylosing spondylitis (AS) rapidly in recent times. The identification of associations with the genes IL23R and ERAP1 have been robustly replicated, and advances have been made in studies of the major histocompatibility complex genetics of AS, and of KIR gene variants and the disease. The findings are already being translated into increased understanding of the immunological pathways involved in AS, and raising novel potential therapies. The current studies in AS remain underpowered, and no full genomewide association study has yet been reported in AS; such studies are likely to add to the significant advances that have already been made.
... 67 Hence, the contribution of HLA-B27 into the overall genetic predisposition is only estimated to be around 16 % , as concluded from twin studies. 68 These questions have sparked the search for additional predisposing genes. ...
The tight connection between intestinal inflammation and arthritis in spondyloarthritis (SpA) has been studied extensively. Subclinical gut inflammation, which can be considered as a model for early Crohn's disease, was shown to be strongly associated with joint inflammation. Several early mucosal abnormalities were uncovered even in the absence of histological signs of inflammation, providing clues into the pathogenesis of SpA. Nevertheless, many questions remain unanswered. In this review, we highlight recent progress on this intimate relationship between gut and joint inflammation. Emerging evidence exists favoring a role for genes beyond human leukocyte antigen B27 in the genetic predisposition of SpA and intestinal inflammation. Furthermore, the role of these predisposing genes in modulating host-pathogen interaction at mucosal surfaces and the subsequent link between gut and joint inflammation are of utmost importance in understanding the pathogenesis of SpA.
... 29 However, several data argue that HLA-B27 plays a direct and important role in the pathogenesis, although it is not the only factor able to generate SpA. 41 The MHC (major histocompatibility complex), situated on chromosome 6 (6p21.3), extends over 3.6 Mb and contains about 220 genes, many of which have immunoregulatory functions. ...
Spondylarthropathies revolve around the strongest known contributing factor, HLA-B27. However, the role of HLA-B27 remains unclear. Its subtypes are reported here in the particular context of developing countries. Non-MHC factors are also being described. The role of immunity is being elucidated. Cytokine expression has been proved to play a major role in ankylosing spondylitis (AS). Recently shown are IL23R, which encodes a critical cytokine receptor in the TH17 subset of T cells, and ARTS1, loss of function of which could have pro-inflammatory effects. This constitutes a major breakthrough in the understanding of AS which could potentially lead to a therapy. New imaging techniques and therapies have substantially improved the earlier diagnosis and management of the disease. However, criteria for an early diagnosis remain to be settled. Such criteria are particularly important for developing countries where they could help in decreasing the socioeconomic burden of the disease.
... We do know, however, that 80-90% of the pathogenesis of AS has a genetic basis and that HLA-B27 accounts for a small increment of that genetic load; the rest is unknown. 20 The association with HLA-B27 has been demonstrated worldwide, and evidence for a role of HLA-B27 in ankylosing spondylitis comes from linkage and association studies in humans and transgenic animal models. However, twin studies indicate that HLA-B27 contributes only 16% of the total genetic risk for the disease. ...
The advent of novel biological therapies for the treatment of rheumatic disease has renewed interest in the seronegative spondyloarthropathies (SpAs). International efforts are redefining disease classification and measures of disease activity, outcome, metrology, and imaging. However, opinion is divided between those who propose that the SpA group represents the same disease with variable expression (the "lumpers") and those who consider these to be separate diseases with shared clinical features (the "splitters"). This review presents the evidence for both approaches.
... The association of ankylosing spondylitis (AS) with human leukocyte antigen (HLA)-B27 has been demonstrated worldwide, and evidence for the role of HLA-B27 in AS comes from linkage and association studies in humans and transgenic animal models. However, twin studies indicate that HLA-B27 contributes only 16% of the total genetic risk for disease[1]. Genome-wide scans have implicated regions on chromosomes 2q, 6p, 6q, 10q, 11q, 16q, 17q, and 19q in AS[2,3]. ...
Killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) loci are both highly polymorphic, and some HLA class I molecules bind and trigger cell-surface receptors specified by KIR genes. We examined whether the combination of KIR3DS1/3DL1 genes in concert with HLA-B27 genotypes is associated with susceptibility to ankylosing spondylitis (AS). Two HLA-B27-positive Caucasian populations were selected, one from Spain (71 patients and 105 controls) and another from the Azores (Portugal) (55 patients and 75 controls). All were typed for HLA-B and KIR (3DS1 and 3DL1) genes. Our results show that in addition to B27, the allele 3DS1 is associated with AS compared with B27 controls (p < 0.0001 and p < 0.003 in the Spanish population and Azoreans, respectively). We also observed that the association of KIR3DS1 to AS was found in combination with HLA-B alleles carrying Bw4-I80 in trans position in the Spanish population (30.9% in AS versus 15.2% in B27 controls, p = 0.02, odds ratio (OR) = 2.49) and in Azoreans (27.2% in AS versus 8.7% in B27 controls, p = 0.01, OR = 4.4 in Azoreans). On the other hand, 3DL1 was decreased in patients compared with B27 controls (p < 0.0001 in the Spanish population and p < 0.003 in Azoreans). The presence of this allele in combination with Bw4-I80 had a protective effect against the development of AS in the Spanish population (19.7% in AS, 35.2% in B27 controls; p = 0.03, OR = 0.45). The presence of KIR3DS1 or KIR3DL1 in combination with HLA-B*27s/HLA-B Bw4-I80 genotypes may modulate the development of AS. The susceptibility to AS could be determined by the overall balance of activating and inhibitory composite KIR-HLA genotypes.
Background:
Ankylosing spondylitis (AS) is a type of chronic progressive inflammatory disease, which often causes significant damage to the patients on the physical function, labour ability and quality of life. The study found that the enzyme system tissue inhibitor of matrix metalloproteinases (TIMPs) was important for the development of AS. The aim of this study was to investigate the association of polymorphisms of TIMP3 gene with AS in Chinese Han population.
Methods:
To evaluate the correlation of TIMP3 polymorphisms with AS risk, Agena MassARRAY was used to determine the genotypes of 268 AS patients and 654 controls. The correlation between TIMP3 variants and AS risk was examined by unconditional logistic regression analysis. Haplotype construction and analysis in TIMP3 were also applied to detect the potential association.
Results:
We identified that rs11547635 in the TIMP3 gene (odds ratio[OR] = 0.79, 95% confidence intervals [CI]: 0.63-0.98, p = .029) was significantly associated with a decreased risk of AS in the alleles model. Rs715572 AG genotype (OR = 1.57, 95% CI: 1.05-2.34, p = .041) was potentially associated with an increased risk of AS, and also rs715572 in the dominant model (OR = 1.61, 95% CI: 1.10-2.36, p = .013) and log-additive model (OR = 1.41, 95% CI: 1.07-1.86, p = .016) adjusted by age and gender were significantly correlated with an increased AS risk.
Conclusion:
These findings suggested that polymorphisms of the TIMP3 gene may be associated with susceptibility to AS.
Ankylosing spondylitis (AS) is a highly heritable kind of arthritis that affects the vertebral column. AS risk has been associated strongly with Human leukocyte antigen (HLA)-B*27. In fact, some HLA-B*27 subtypes have been associated with the increased disease risk, although some specific subtypes have not shown such associations. It is supposed that HLA-B*27 plays a major role in the etiopathogenesis of the disease. However, the difference in pathogenic outcomes of HLA-B*27 certain subtypes needs to be clarified. The purpose of this review article is to overview on the detailed implications of the HLA-B*27 subtypes in the etiopathogenesis of AS. Moreover, the role of ERAP1 in AS and its epistasis with HLA-B*27 have been reviewed.
Background : Ankylosing spondylitis (AS) represents a progressive and debilitating disease that affects approximately 0.9% worldwide. So far the precise mechanisms underlying the initiation and progression of AS is still unclear. Linkage between HLA-B27 and AS remains the strongest association between a human leukocyte antigen (HLA) class I molecule and disease. Despite intensive research, the pathogenic role of this gene and its product has not yet been resolved. Non-HLA-B27 genes exist that also seem to be involved in disease etiology. The killer immunoglobulin-like receptor (KIR) gene cluster is located on chromosome 19q13.4 in the leukocyte receptor complex. The KIR genes encode a group of proteins that are expressed on natural killer (NK) cells and in some T cells. KIR proteins act as receptors that recognize HLA class I molecules and are directly involved in the activation and inhibition of NK cells. KIRs and their HLA class I ligands contribute to the pathogenesis of diverse kinds of autoimmune diseases. The genetic imbalance of inhibitory and activating KIRs may be the key factor, which influences the pathogenesis of AS. However, the role of balance between inhibitory and activating KIRs in determining susceptibility to AS a topic of debatable. This review summarizes the major features of these genes and discusses how they may be involved in AS pathogenesis.
Keywords: Killer immunoglobulin-like receptors, Human leukocyte antigen, Spondylitis ankylosing.
The polymorphisms of genes involved in pathogenesis, including cytokines and proteins involved in antigen processing and their association with disease susceptibility and/or severity, demonstrated that these processes could be due to multiple genetic defects. The association of these polymorphisms with specific HLA alleles reflects the complexity of these associations. During inflammation, oxidant stress and DNA hypomethylation appear to be important factors in the complex interplay of mononuclear cells, synovial fibroblasts, and joint destruction. Genotoxic stress appears to result in DNA damage and may be directly causing somatic mutations. While the investigation of T cell repertoire has been disappointing, the search for potential infectious agents including retroviral sequences has resulted in new hypotheses regarding the involvement of DNA hypomethylation and endogenous retroviral sequences in a cytokine-independent pathway of chronic and erosive arthritis. In addition, clarifying the role of TLRs and innate immunity will be a major focus of future research. Rheumatic disorders arise in certain individuals depending on the interaction of genetic and environmental factors, the contribution for each varying with the specific disease. A third variable, that is, random or "stochastic" processes, may be important, but this has been poorly studied. In fact, it is important to note that only a small number of random events need to occur in a predisposed population to allow the emergence of a rheumatic disorder. These random events might be environmental (e.g., infections or exposure to toxins) or due to acquired genetic changes (e.g., somatic mutations involving pivotal immune or growth/repair genes).
Introduction Recent years have witnessed major advances in our understanding of the genetic basis for many skeletal disorders. In several instances, particularly with the less common Mendelian diseases, the responsible gene has been mapped, mutations identified, and their functional significance determined, contributing significantly to our understanding of the molecular basis for pathogenesis. For more common disorders where susceptibility is complex, a complete picture of the responsible genetic polymorphisms and how they influence pathogenesis has been more difficult to achieve. In this chapter we focus on our current understanding of the genetic basis and pathogenic mechanisms for disorders of bone homeostasis. For readers interested in the genetic basis of developmental disorders of the skeleton, we recommend a recent review (Kornak and Mundlos, 2003). Bone resorption and bone formation are ongoing processes in both the developing and mature skeleton. Even during growth, where the balance favors bone formation, bone resorption is necessary to remove calcified cartilage prior to the formation of mature bone. In the adult skeleton, there continues to be a dynamic balance between these processes that serves both metabolic and mechanical needs of the individual. Although bone mass continues to increase during childhood, it peaks between the ages of 25 and 35 years, and then begins a steady decline that becomes most prominent after age 50 years when bone formation does not fully compensate bone loss. The delicate balance between bone formation and bone resorption is maintained largely by the coordinated actions of two cell types, osteoblasts and osteoclasts. © Cambridge University Press 2007 and Cambridge University Press, 2009.
Ankylosing spondylitis (AS) is a chronic disease characterized by inflammatory back pain and progressive stiffening of the spine. The association between AS and HLA-B27, a major histocompatibility complex class I molecule, has been known since 1973. Despite intense interest and active investigations into the role of HLA-B27 in the pathogenesis of AS, the specific role of HLA-B27 in AS is not yet known. One of the postulated hypotheses states that misfolding of the HLA-B27 heavy chains causes activation of the unfolded protein response, which sensitizes cells to proinflammatory cytokine production. The IL-23/Th17 axis may play an important role in this pathway. As AS is a multifactorial disease, not only genetic factors are of interest, but environmental factors, such as biomechanical stress, may also play an important role in the pathogenesis. None of the postulated mechanisms regarding the pathogenesis of AS have been strictly proven, but current results from studies are promising.
The prevalence of axial spondyloarthritis (AxSpA) is approximately 1% of the general population. Ankylosing spondylitis (AS) affects 0.2–0.5% of the northern European population, the prevalence varying with the prevalence of HLA-B27. AS affects men three times more often than women, but AxSpA (without X-ray changes) affects men and women equally. Symptoms usually begin in the third decade of life with inflammatory back pain. The key pathological element is enthesitis, though the main diagnostic feature is sacroiliitis. Approximately one-third of patients develop peripheral lesions including lower limb oligoarthritis, heel enthesitis, iritis, inflammatory bowel disease and psoriasis. Vertebral osteoporosis is not uncommon and cardiovascular disease and renal impairment may complicate severe AS. The diagnosis of AxSpA can be made on the basis of imaging (X-ray or MRI) or on clinical features alone.
The cause(s) of AS remain unknown. Genetic factors, including HLA-B27 and the interleukin 23 receptor, confer susceptibility to AS but environmental precipitating factors have not been identified. Treatment involves the maintenance of spinal movement and comfort through exercise supported, where necessary, by analgesia and anti-inflammatory treatment. Disease-modifying anti-rheumatoid drugs are not effective for spinal disease, but TNF-α inhibitor drugs provide dramatic improvements in symptoms, function and quality of life.
Ankylosing spondylitis (AS) affects 0.2–0.5% of the northern European population, the prevalence varying with the prevalence of HLA-B27. It is a member of the spondyloarthropathy family and affects men three times more often than women. Symptoms usually begin in the third decade of life with inflammatory spinal pain. The key pathological element is enthesitis, though the main diagnostic feature is sacroiliitis. Approximately one-third of patients develop peripheral lesions including lower limb oligoarthritis, heel enthesitis, iritis, inflammatory bowel disease and psoriasis. Vertebral osteoporosis is not uncommon and cardiovascular disease and renal impairment may complicate severe AS. The diagnosis of AS is based on the modified New York criteria but criteria for early diagnosis, based on the co-occurrence of inflammatory spinal pain and demonstration of sacroiliitis by magnetic resonance scanning, are emerging. The cause(s) of AS remain unknown. Genetic factors, including HLA-B27 and the IL-23 receptor, confer susceptibility to AS but environmental precipitating factors have not been identified. Treatment involves the maintenance of spinal movement and comfort through exercise, supported, where necessary by analgesia and anti-inflammatory treatment. Disease-modifying anti-rheumatoid drugs are not effective for spinal disease but TNF-α inhibitor drugs provide dramatic improvements in symptoms, function and quality of life.
Accumulating evidences indicate that killer cell immunoglobulin-like receptors (KIRs) and their corresponding specific HLA-C ligands contribute to the pathogenesis of multiple autoimmune diseases via the modulation of natural killer (NK) cell and T cell functions. The present study was performed to investigate whether the polymorphism of KIR genes and HLA ligands associates with the susceptibility of ankylosing spondylitis (AS). Previous studies have demonstrated a strong association between HLA-B27 gene and the pathogenesis of AS. In this study, 115 unrelated HLA-B27-positive AS patients and 119 HLA-B27-positive healthy controls were recruited. Polymerase chain reaction using sequence-specific primers was used to determine the genotypes of KIR genes and HLA-C alleles. The results showed that the frequencies of KIR2DL1 and KIR2DL5 were significantly higher in the AS patient group than those in the control group (p = 0.012 and p = 0.009, respectively). Meanwhile, individuals with AS showed an increased frequency of HLA-Cw*08 (p = 0.001, p
c
= 0.008) compared with that in controls. Our findings indicate that with the genetic background of HLA-B27, variation at the KIRs and their corresponding specific HLA-C ligands may influence the ability of NK cells and T cells to recognize and lyse targets in immune responses, which thereby contributes to pathogenesis of AS.
Der Oberflächenrezeptor HLA-B27 wird bei 85 - 95 % aller Patienten mit ankylosierender Spondylitis (AS) nachgewiesen und ist damit das MHC-Klasse-I-Molekül mit der höchsten Krankheitsassoziation beim Menschen. Es besteht eine starke Korrelation zwischen dem Auftreten von HLA-B27, der Prävalenz von ankylosierender Spondylitis und den anderen Spondyloarthritiden. Es wird ferner vermutet, dass zusätzliche Umweltfaktoren eine Rolle bei der Krankheitsentstehung spielen. Hierbei scheinen vor allem Bakterien und deren Interaktion mit HLA-B27 von großer Bedeutung zu sein. Obwohl bereits zahlreiche Krankheitsmodelle zur Rolle von HLA-B27 und Mikroben bei der AS vorgestellt worden sind, bleibt die Pathogenese dieser Erkrankung ungeklärt. HLA-B27 ist zwar das Gen mit der höchsten bisher dargelegten Assoziation mit AS, es gibt aber daneben noch eine sehr große Anzahl weiterer Gene, die auch mit der AS und den anderen Spondyloarthritiden assoziiert zu sein scheinen. Die Bedeutung von HLA-B27 und der anderen bisher bekannten assoziierten Gene werden in dieser Arbeit vorgestellt und bewertet.
We investigated two nonsynonymous variants (rs30187 and rs27044) of ERAP1 gene in HLA-B27 positive individuals (150 spondyloarthritis and 108 controls) and in general ankylosing spondylitis (AS) patients (n = 137) vs random controls (n = 139). Both single nucleotide polymorphisms (SNPs) were associated with the risk of spondyloarthritis [odds ratio (OR) 1.80, 95% confidence interval (CI) 1.24-2.62, P = 0.001 for rs30187, OR 1.58, 95% CI 1.07-2.34, P = 0.02 for rs27044]. The CC haplotype was a protective factor (P = 0.002), while the TG haplotype was a risk factor (P = 0.01) for spondyloarthritis. The SNP rs30187 was also associated with the risk of HLA-B27+ AS. For the general group of AS, the carriers of minor alleles showed an increased risk for the disease (OR 1.92, 95% CI 1.17-3.13 for rs30187, OR 1.74, 95% CI 1.08-2.80 for rs27044). This is the first study that shows the association of ERAP1 gene variants and haplotypes with HLA-B27 positive spondyloarthritis.
HLA-B27 is the major genetic susceptibility factor for ankylosing spondylitis (AS). However, its precise role in the pathogenesis of AS still remains unclear, even though its gene has been cloned and sequenced, and its crystallographic structure has been defined. Arthritogenic peptide and molecular mimicry hypotheses propose mechanisms related to an antigen-presenting function of HLA-B27 to be responsible for disease development. However, peculiar aspects of its immunobiology, such as its misfolding and heavy chain dimerization raise the possibility of involvement of pathogenic mechanisms unrelated to its physiological function. Moreover, HLA-B27 is not a single allele, but a family of 31 different alleles, named HLA-B*2701 to HLA-B*2727. Studies worldwide indicate that the relatively common alleles (subtypes) HLA-B*2705, B*2704, and B*2702 are strongly associated with AS, whereas HLA-B*2706 which is prevalent in South-east Asia and HLA-B*2709 which is prevalent on the Italian island of Sardinia, seem to lack such an association. The distinction between the disease-associated subtypes and those that are not associated, may provide clues to the actual role of HLA-B27 in disease pathogenesis. B*2706 differs from B*2704 by only two residues, and B*2709 differs from B*2705 by only one residue. Moreover, both B*2706 and B*2709 bind an endogenous peptide (derived from vasoactive intestinal peptide type 1 receptor) and also an exogenous peptide (latent membrane protein 2 of Epstein-Barr virus) but in two drastically diverse conformations. These recent X-ray diffraction studies of individual peptides in the context of different HLA-B27 alleles broaden our perception of the possible pathogenetic role of this molecule in the development of AS and related spondyloarthopathies. In summary, the pathogenetic role of HLA-B27 in AS seem to be quite heterogenous, and cannot be explained by a single mechanism, and new ideas have been raised based on the aberrant immunobiologic features of HLA-B27.
Ankylosing spondylitis (AS) belongs to a group of autoimmune diseases affecting the axial skeleton. Beside thehla-b*27allele, several other human genes that control the variety processes of immune homeostasis are considered to be associated with AS manifestation in different human populations. Among strong associated non-MHC geneserap1 encodingthe endoplasmic reticulum aminopeptidase 1 isoform was recently identified by single nucleotide polymorphisms (SNPs) meta analysis. In our study we inspected the genetic association of five non-synonymous coding SNPs fromerap1 withAS in Caucasians. We implemented the SSP-PCR system for precise genotyping of 87hla-b*27positive AS patients and 77hla-b*27healthy donors from the Russian population. Considerable differences in allele's frequencies within patients vs control cohort were shown for 3 of 5 SNPs under investigation. Using the EM-algorhitm we reconstructed 3-marker haplotypes that distinguish with high probability two cohorts due to differences in the haplotypes frequencies. In such a way both the sensitive, CCT, haplotype and the protective, TTC, one were predicted. To verify the calculation we determined genuine frequencies of 5-marker haplotypes in AS cohort by haplotyping of individual cDNA samples using improved SSP-PCR primer set. We demonstrated that the frequencies ofin silicareconstucted haplotypes and the frequencies of experimentally detected haplotypes are in a good agreement. Frequency of the risk haplotype CCT (rs17482078/10050860/2287987) detected within AS cohort reaches 88%, as well as the frequency calculated by EM-algorhitm.
Genetic factors are thought to be crucial in the pathogenesis of ankylosing spondylitis (AS). Recent studies have reported that ERAP1, TGBβ1 and TLRs genes are likely to have association with AS in different populations. We carried out this study to determine whether single-nucleotide polymorphisms covering the three genes are associated with AS in a Chinese Han population. Genomic DNA was isolated from the peripheral blood of 328 patients with AS and 627 healthy blood donors from Jinan region as a case-control study. The diagnosis of AS was made according to the modified New York criteria. The ERAP1 rs27044, TGBβ1 rs1800470 and TLR9 rs55704465 were genotyped by a polymerase chain reaction--restriction fragment length polymorphism method. Strong association with AS was observed for marker rs27044, but no significant differences were observed between AS patients and controls in the frequencies of the carriership of the alleles rs55704465 and rs1800470. Our data thus indicate that ERAP1 likely constitutes one of AS-associated loci of susceptibility after HLA in Chinese Han population. On the contrary, TGFB1 and TLR9 variations show no association with the susceptibility of AS.
Contribution of killer cell immunoglobulin-like receptors (KIR) and their human leucocyte antigen (HLA) class I ligands in the pathogenesis of autoimmune diseases has been shown in several studies. In this study, the possible association of KIR genes, their known HLA ligands and compound KIR/HLA genotypes with ankylosing spondylitis (AS) was assessed. Combined KIR/HLA ligand genotyping was performed by a polymerase chain reaction-sequence-specific primers assay in 35 Iranian patients with AS, and genotypes were compared to those in 200 healthy individuals. The frequencies of telomeric cluster genes KIR2DL5A, KIR2DS1 and KIR3DS1 were significantly increased in AS patient group (P(c) = 0.0082, P(c) = 0.0195 and P(c) = 0.0328, respectively). Conversely, HLA-Bw4 ligand (the presence of one or more -B Bw4(Ile80) , -B Bw4(Thr80) and -A Bw4 epitopes) (P(c) = 0.0004) and HLA-B Bw4(Ile80) (P(c) = 0.053) were less frequent in these patients. Meanwhile, compound KIR/HLA genotype analyses revealed lower frequency of KIR3DL1+HLA-B Bw4(Ile80) (P(c) = 0.0343) and higher frequency of KIR2DS1+HLA-C2 (P(c) = 0.0308) combinations in patients with AS than in controls. In addition, the genotypes iKIR+HLA > aKIR+HLA (P(c) = .0308) and iKIR+HLA > aKIR (P(c) = 0.0258) were statistically less common, and genotypes iKIR+HLA = aKIR+HLA (P(c) = 0.0081) and iKIR+HLA < aKIR (P(c) = 0.077) were more common in patient group. Our findings suggest a role for excessive or inappropriate NK cell activation through 'KIR/HLA' system in AS disease.
To examine the interaction between IL-1F7 gene and environmental factors in patients with ankylosing spondylities (AS). 150 AS Han Chinese patients (all human leukocyte antigen-B27 positive) were genotyped using a panel of single-nucleotide polymorphism markers within IL-1F7 gene (rs3811047) by ligase detection reactions. Polymerase chain reaction with sequence-specific primer was used to determine HLA-B27 subtypes. We analyzed the interaction between IF-1F7 gene and eight environmental factors in AS patients by using a case-only study. The genetic polymorphism and environmental factors were considered as dependent variables in logistic models, and P-values, ORi and 95% confidence intervals were used for estimating the effects of interaction. The different frequency of A/G between drinking group and non-drinking group was significant (ORi 3.163, 95% CI 1.368-7.317, P=0.006). Within the cooking oil group, odds ratio for interaction of G×E between main plants fats and half plants -half animal fats subunits was 4.273 (95% CI 1.590-11.479, P=0.004). Our data show that there was no interaction between IL-1F7 alleles and the other six environmental factors in AS patients (all P>0.05). We observed that there was an interaction between IF-1F7 gene and drinking in AS patients. Thus, drinking may be a risk exposure factor to take combined action with predisposing genes in AS patients. This action may increase the incident risk of AS. Also, main plants fats may be protective factors to AS.
Increasing evidence points to a role for killer immunoglobulin-like receptors (KIRs) in the development of autoimmune diseases. In particular, a positive association of KIR3DS1 (activating receptor) and a negative association of KIR3DL1 (inhibitory receptor) alleles with ankylosing spondylitis (AS) have been reported by several groups. However, none of the studies analyzed these associations in the context of functionality of polymorphic KIR3DL1. To better understand how the KIR3DL1/3DS1 genes determine susceptibility to AS, we analyzed the frequencies of alleles and genotypes encoding functional (KIR3DL1*F) and non-functional (KIR3DL1*004) receptors. We genotyped 83 AS patients and 107 human leukocyte antigen (HLA)-B27-positive healthy controls from the Russian Caucasian population using a two-stage sequence-specific primer PCR, which distinguishes KIR3DS1, KIR3DL1*F and KIR3DL1*004 alleles. For the patients carrying two functional KIR3DL1 alleles, those alleles were additionally genotyped to identify KIR3DL1*005 and KIR3DL1*007 alleles, which are functional but are expressed at low levels. KIR3DL1 was negatively associated with AS at the expense of KIR3DL1*F but not of KIR3DL1*004. This finding indicates that the inhibitory KIR3DL1 receptor protects against the development of AS and is not simply a passive counterpart of the segregating KIR3DS1 allele encoding the activating receptor. However, analysis of genotype frequencies indicates that the presence of KIR3DS1 is a more important factor for AS susceptibility than the absence of KIR3DL1*F. The activation of either natural killer (NK) or T cells via the KIR3DS1 receptor can be one of the critical events in AS development, while the presence of the functional KIR3DL1 receptor has a protective effect. Nevertheless, even individuals with a genotype that carried two inhibitory KIR3DL1 alleles expressed at high levels could develop AS.
Programmed cell death 1 (PD-1) has been reported to have a genetic association in several autoimmune diseases. The aim of this study was to investigate the association of PD-1 polymorphisms and haplotypes with ankylosing spondylitis (AS) in Chinese Han population. In a case-control association study, three single-nucleotide polymorphisms (SNP), PD-1.3 G/A, PD-1.5 C/T and PD-1.9 T/C, were genotyped in 216 AS patients and 264 healthy controls using polymerase chain reaction-restriction fragment length polymorphism assay. All genotype distributions in the patients and in the controls were in Hardy-Weinberg equilibrium. The associations of genotypes and alleles with AS were analyzed. The genotype distributions of PD-1.9 were significantly different between the patients with AS and the controls (P = 0.025). The frequencies of TC genotype and T allele of PD-1.9 were higher in the patients than those in the controls (P = 0.026 and 0.004). No association for PD-1.5 in AS was found, and PD-1.3 was non-polymorphic in Chinese Han population. Moreover, the frequency of the CT haplotype (PD-1.5 C/T, PD-1.9 T/C) was significantly higher in AS patients than the controls (21.6 vs. 13.9%, P = 0.002). The CC haplotype was more common in the controls than in the patients (57.1 vs. 44.6%, P = 0.000). The results support a genetic association between the PD-1 polymorphism and susceptibility to AS in Chinese Han population.
The aim of this retrospective study is to assess the frequency of HLA-B27 and HLA-B51 in healthy subjects from the center of Tunisia and to investigate their usefulness in the diagnosis of ankylosing spondylitis (AS) and Behçet's disease (BD), respectively. Microlymphocytotoxicity test was used to perform serologic HLA typing in a group of 124 healthy volunteers and a group of 365 patients suffering from clinical manifestations of AS and/or BD. HLA-B27 was found in 3.2% of healthy subjects and in 42.9% of patients with AS (P < 0.00006). HLA-B51 is, however, found in 16.1% of healthy subjects and in 30.0% of patients with BD (P > 0.05). Unlike HLA-B51, which seems to be as frequent in Tunisian patients with BD as in healthy subjects, HLA-B27 is more frequent in patients with AS than in controls. This highlights the usefulness of HLA-B27, rather than that of HLA-B51, in the diagnosis of the respective diseases.
Efforts to identify genes other than HLA-B27 in AS have been driven by the strength of the evidence from genetic epidemiology studies indicating that HLA-B27, although a major gene in AS, is dearly not the only significant gene operating. This is the case for both genetic determinants of disease-susceptibility and phenotypic characteristics such as disease severity and associated disease features. In this chapter the genetic epidemiology of AS and the gene-mapping studies performed to date will be reviewed and the future direction of research in this field discussed.
The aim of this study was to investigate the association of the B27 subtypes with ankylosing spondylitis (AS) in the Wuhan population of China. We selected 317 HLA-B27-positive individuals (145 controls and 172 patients with ankylosing spondylitis). The B27 subtypes were characterized using a PCR-SSP method. Six B27 subtypes were determined: B*2702, 03, 04, 05, 06 and B*13. HLA-B*2704 and HLA-B*2705 were the two high frequency genotypes in controls and patients. Compared with the controls, the AS patients had high frequency of B*2704 (patients 69.2% vs. controls 53.8%) and low frequency of B*2705 (patients 23.8% vs. controls 33.1%). B*2703 was detected in 10 (5.8%) patients and in 13 (8.9%) controls. B*2702, 06 and B*2713 were relatively rare. Our results show that the allele conferring risk to AS in the Wuhan population of China was B*2704 and B*2705. B*2704 is strongly associated with AS.
The autoinflammatory diseases are characterized by seemingly unprovoked episodes of inflammation, without high-titer autoantibodies or antigen-specific T cells. The concept was proposed ten years ago with the identification of the genes underlying hereditary periodic fever syndromes. This nosology has taken root because of the dramatic advances in our knowledge of the genetic basis of both mendelian and complex autoinflammatory diseases, and with the recognition that these illnesses derive from genetic variants of the innate immune system. Herein we propose an updated classification scheme based on the molecular insights garnered over the past decade, supplanting a clinical classification that has served well but is opaque to the genetic, immunologic, and therapeutic interrelationships now before us. We define six categories of autoinflammatory disease: IL-1beta activation disorders (inflammasomopathies), NF-kappaB activation syndromes, protein misfolding disorders, complement regulatory diseases, disturbances in cytokine signaling, and macrophage activation syndromes. A system based on molecular pathophysiology will bring greater clarity to our discourse while catalyzing new hypotheses both at the bench and at the bedside.
Class II major histocompatibility complex (MHC) molecules are classically expressed on antigen-presenting cells of the hematopoietic lineage but have also been described on epithelial cells in association with autoimmunity. In this context, however, it remains debatable whether class II MHC molecules are the initiating event or rather the consequence of the autoimmune attack. In addition, the role of epithelial class II expression once the autoimmune attack has begun is unknown. We generated transgenic mice expressing in the thyroid follicular cells the class II transactivator, the master regulator of all the genes in the class II MHC pathway. The study used a cohort of 245 CBA/J mice (127 wild-type and 118 transgenic), both in basal conditions (n = 63) and at different time points after immunization with mouse thyroglobulin (n = 182). In basal conditions, transgenic mice were similar to wild-type controls and did not develop spontaneous autoimmune thyroiditis, despite the aberrant expression of class II MHC molecules on thyrocytes. After immunization, thyroiditis was 8% more severe in transgenics than controls (95% confidence interval from 1.8-13.4%; P = 0.033), especially during the florid stages of disease. These findings suggest that expression of class II MHC molecules on epithelial cells is not sufficient to initiate autoimmunity but mildly modulates an already established autoimmune attack against the target organ.
Receptors on cytotoxic T lymphocytes and natural killer cells play well-established roles in the immunological response and share a common ligand in the form of MHC-I. We discuss how a variety of MHC-I receptors are also expressed on myelomonocytic cells such as macrophages and dendritic cells. Since myelomonocytic MHC-I receptors recognise a broad range of alleles and MHC-I structures, we propose that their task is to discern expression levels and folding forms of MHC. We describe a model in which these recognition events would regulate bidirectional cross talk between cells of innate and adaptive immune systems to organise an ongoing combined immune response. We discuss how such a model is supported by recent literature and might function in a variety of contexts, including immunoregulation during pregnancy. Our model also offers an alternative explanation of immune dysregulation rather than autoimmunity during HLA-B27-associated spondyloarthropathies and addresses a number of conundrums in this field.
In this review on the genetic aspects of rheumatic diseases, the approach was taken (i) to discuss, in general, important principles in the identification of susceptibility genes and (ii) to focus on five autoimmune rheumatic diseases that have the characteristics of complex diseases and in which important advances have been made in the identification of the genetic component. A decade ago, most reviews on the genetics of rheumatic diseases focused almost exclusively on a discussion of the human leukocyte antigen (HLA) but in this fast-moving field it is now apparent that genes outside the HLA also contribute to susceptibility. Current hypotheses concerning the pathogenesis of autoimmunity have led to the inclusion of hundreds of genes as potential candidates. Almost any molecule involved in immune recognition, cell interaction, intracellular signalling, cytokine pathways or programmed cell death can be reasonably proposed. The identification of the genes involved in complex diseases will contribute to an understanding of disease mechanisms and disease biology. The disease pathways by which the genes exert their effects or functions could lead to the discovery of new therapeutic targets that may be modulated. An increased understanding of the interactions between genes and environment might also be attained.
The objective of the study was to investigate potential triggering events for the onset of ankylosing spondylitis (AS). A large retrospective population survey of 1,080 AS patients was carried out by multi-faceted questionnaire. A nested case-control study compared the cohort to 102 patients with lumbar disc prolapse. Participants with AS had a mean age of 49.8 years, mean age of disease onset was 25.2 years and 63% of the cohort were male. Seventy-nine per cent knew they were human leucocyte antigen (HLA)-B27-positive, and a further 12.5% were unaware of their HLA-B27 status. Infections were relatively common in the 3 months leading to the first symptoms, 4.6% reporting gastrointestinal infection, 2.5% reporting urinary tract infection and 2.6% respiratory infection. Five per cent reported heavy physical activity in the 3 months prior to the onset of symptoms, 4.2% emotional stressors and 3.1% work stressors. Injury and surgery were less commonly reported (1.7 and 0.7%, respectively). Pregnancy was reported by 7.4% of the female participants. When the 12 months leading up to the first symptoms was compared to the 12 months previous to that, work stressors (OR 1.5), and pregnancy (OR 2.5) infection (OR 1.5 to 1.8) were significantly more common closer to disease onset. Infection and work stressors are potential triggers for the onset of AS; however, low rates suggest they are only a small part of the environmental milieu that combines with a genetic predisposition to cause the development of this chronic inflammatory disease.
More than three decades after the discovery of HLA-B27 as a major genetic clue to the origins of ankylosing spondylitis, much has been learned about pathogenesis. However, the role of this major histocompatibility complex class I allele remains undefined. Studies from animal models have demonstrated that HLA-B27 overexpression can cause inflammatory disease with spondyloarthritis features, and together with investigations of patient-derived material, both innate adaptive and immune responses have been implicated. The gastrointestinal immune response to pathogens and even normal flora, with subclinical or overt inflammation, may play a role as an environmental component of these diseases. Although there has been a large conceptual emphasis on mechanisms involving autoreactive T-cell recognition of HLA-B27 complexes displaying arthritogenic peptides, and more recently non-canonical recognition of abnormal forms of HLA-B27 free of beta(2)m (heavy-chain dimers or monomers), it remains unclear whether immunological recognition plays a role in pathogenesis. The recognition that the HLA-B27 heavy chain misfolds during assembly, and causes endoplasmic reticulum 'stress', has led to the observation that this activates the unfolded protein response. This has opened additional areas of investigation into the response of immune system cells to protein misfolding, and suggested novel alternative concepts that may explain the role of HLA-B27 in pathogenesis. This chapter will discuss available data and current concepts regarding the pathogenesis of ankylosing spondylitis.
Between 5 and 10% of cases of ankylosing spondylitis (AS) are associated with inflammatory bowel disease (IBD), either Crohn's disease or ulcerative colitis. A much larger percentage of AS patients have subclinical gut inflammation manifested either by endoscopic findings or by histology. The association with HLA-B27 is less strong in IBD-associated AS than in idiopathic AS, and there is evidence for an association between gut inflammation in AS with the Crohn's-disease-related CARD15 mutations. Despite the different genetics, the immunopathology suggests common inflammatory pathways in gut and joint inflammation in AS, and in gut inflammation in AS and IBD. Although this observation is of interest to unravel the pathophysiology of the disease, systematic screening of AS patients by ileocolonoscopy is not indicated in the absence of gut symptomatology as only a small proportion of AS patients with subclinical gut inflammation will develop overt IBD over time. Treatment of AS associated with IBD with non-steroidal anti-inflammatory drugs (NSAIDs) is problematic because of concerns of potential re-activation of IBD by NSAIDs. Major advances have been made in recent years with the establishment of anti-tumour necrosis factor (TNF) therapy in AS, the other spondyloarthritides and IBD. Anti-TNF agents are of particular relevance to AS patients with concomitant IBD who are at risk of exacerbation of the underlying bowel disease when treated with NSAIDs. In IBD, infliximab, unlike etanercept, is effective in treating clinical symptoms, inducing and maintaining remission, and mucosal healing. Adalimumab appears to be effective in treating both AS and IBD; however, official approval is pending. Currently, infliximab is the drug of choice for the treatment of patients with active AS associated with IBD.
This study was to investigate the frequency of HLA-B27 and its subtypes in the Han population of Hunan province, southern China. One hundred and sixty-nine healthy unrelated donors were tested for HLA-B27 by polymerase chain reaction-sequence-specific primer (PCR-SSP). One hundred and twenty-eight B27-positive spondyloarthropathy patients and 18 B27-positive healthy controls were subtyped using the high-resolution PCR-SSP. The phenotype frequency of human leukocyte antigen (HLA)-B27 was found to be 2.36% in healthy population. Five B27 alleles were identified: B*2704, B*2705, B*2706, B*2707, and B*2724. No significant difference was found in the distribution of HLA-B27 subtypes between the patients and controls studied. Notably, B*2724 was observed in a juvenile patient with ankylosing spondylitis. This subtype has not been previously reported in Chinese ankylosing spondylitis (AS) patients and other ethnic groups.
Research into the pathogenesis of the spondyloarthropathies has examined the role of HLA-B27 and other genes in susceptibility to these diseases. Novel characteristics of HLA-B27 have been discovered, which have allowed hypotheses for an influence of HLA-B27 on disease to be developed that do not reflect its ability to present arthritogenic peptides to CD8(+) T cells. Although a role for CD8(+) T cells has not been excluded, they are not required in the HLA-B27 transgenic rat model, and do not dominate at sites of disease in humans. Studies have also focused on the consequences of the (rather inefficient) intracellular folding of the HLA-B27 heavy chain, the ability of cells to deal with intracellular infection, and their expression of unusual forms of HLA-B27 on cell surfaces (including free heavy chains and dimers). Unusual surface forms of HLA-B27 interact with a different set of receptors from those that recognize conventional class I MHC molecules and thus can be implicated in driving inflammatory responses. Additional candidate susceptibility genes are being identified, either using gene-targeting technology in mice, or genomic screening approaches in humans. In several cases, as with HLA-B27, the evidence suggests that these genes influence the response of the host to bacteria, including pathogens and commensal organisms of the skin and gastrointestinal tract. The concept that spondyloarthropathies are the result of interactions between susceptibility genes, bacteria and the immune system remains a useful model for the pathogenesis of these diseases.
Functional single nucleotide polymorphisms within the ectoplasmic domain of the Toll-like receptor 4 (TLR4) gene have been shown to result in an endotoxin-hyporesponsive phenotype and aberrant signal transduction for bacterial agonists. TLR4 is in proximity to a genome-wide linkage peak in 9q32-33. Given the proposed function and location of TLR4, we examined the association of 2 functional variants of TLR4 in patients with ankylosing spondylitis (AS) in Newfoundland.
In total, 101 AS patients and 100 ethnically matched controls were genotyped, using the Sequenom MassArray platform, for 2 functional variants in the TLR4 gene: Asp299Gly (A/G polymorphism) and Thr399Ile (C/T polymorphism).
The minor allele frequency for the Asp299Gly variant (G) was significantly higher in AS cases compared to controls (7.5% vs 2.6%, respectively; OR 3.10, p = 0.037). The minor allele frequency for the Thr399Ile variant (T) for cases and controls was 7.4% vs 3.0% (OR 2.59, p = 0.071). Haplotype analysis using Haploview noted a higher proportion of GT in the cases (for GT, chi-squared p = 0.023).
Given the functional role of TLR4 variants in the innate immune system, larger studies are now warranted to elucidate the association of TLR4 variants in AS.
Ankylosing spondylitis (AS) is a chronic inflammatory spinal and large-joint arthritic and potentially disabling condition, mainly affecting males of young age groups. Extensive literature based on the results of various genetic, microbiological, molecular and immunological studies carried out by independent research groups suggests that Klebsiella pneumoniae is the main microbial agent being implicated as a triggering and/or perpetuating factor in the etiopathogenesis of AS. Novel diagnostic markers and criteria based on the association with high anti-Klebsiella antibodies could be used in the detection of AS patients during early stages of the disease, and together with the current treatments might help in implementing the use of new therapeutic anti-microbial measures in the management of AS. Prospective longitudinal studies with the use of anti-microbial measures in patients with AS are required to establish the therapeutic benefit of this microbe-disease association.
HLA-B27 is implicated in the pathogenesis of spondylarthritis (SpA), yet the molecular mechanisms are incompletely defined. HLA-B27 misfolding has been associated with endoplasmic reticulum stress and activation of the unfolded protein response (UPR) in macrophages from HLA-B27/human beta(2)-microglobulin-transgenic (B27-transgenic) rats. This study was performed to assess the mechanisms that drive activation of the HLA-B27-induced UPR and to determine whether splenocytes respond in a similar manner.
Splenocytes were isolated and bone marrow macrophages were derived from B27-transgenic and wild-type rats. Cells were treated for up to 24 hours with cytokines that induce class I major histocompatibility complex expression. HLA-B27 expression and misfolding were assessed by real-time reverse transcription-polymerase chain reaction, flow cytometry, and immunoblotting. Activation of the UPR was measured by quantifying UPR target gene expression and X-box binding protein 1 messenger RNA (mRNA) splicing.
HLA-B27 mRNA up-regulation was accompanied by a dramatic increase in the accumulation of misfolded heavy chains and preceded robust activation of the UPR in macrophages. When macrophages were treated with various cytokines, the magnitude of the UPR correlated strongly with the degree of HLA-B27 up-regulation. In contrast, B27-transgenic splenocytes exhibited only low-level differences in the expression of UPR target genes after exposure to interferon-gamma or concanavalin A, which resulted in minimal HLA-B27 up-regulation.
These results suggest that HLA-B27-associated activation of the UPR in macrophages is attributable to the accumulation of misfolded heavy chains, and that certain cell types may be more susceptible to the effects of HLA-B27 misfolding. Strategies that eliminate HLA-B27 up-regulation and/or the accumulation of misfolded heavy chains may be useful in evaluating the role of these events in the pathogenesis of SpA.
In the past year, data about the level and nature of linkage disequilibrium between alleles of tightly linked SNPs have started to become available. Furthermore, increasing evidence of allelic heterogeneity at the loci predisposing to complex disease has been observed, which has lead to initial attempts to develop methods of linkage disequilibrium detection allowing for this difficulty. It has also become more obvious that we will need to think carefully about the types of populations we need to analyze in an attempt to identify these elusive genes, and it is becoming clear that we need to carefully reevaluate the prognosis of the current paradigm with regard to its robustness to the types of problems that are likely to exist.
HLA-B27 is highly associated with ankylosing spondylitis (AS), but the mechanism is unknown. Among the HLA-B27 alleles, B*2709, which differs by one amino acid from the susceptible B*2705, is not associated with the disease. Here, we analyze the reactivity, in patients with AS and in healthy controls carrying the B*2709 or B*2705 alleles, to an EBV epitope derived from LMP2 (236-244) and to a sequence-related self-peptide from vasoactive intestinal peptide receptor 1 (VIP1R 400-408). We found that both B*2705+ and B*2709+ subjects possess LMP2 236-244–specific, HLA-B27–restricted T cells, whereas only the B*2705+ individuals respond significantly to VIP1R 400-408. These results prompted us to compare, by IFN-γ ELISPOT analysis, the T-cell response to VIP1R 400-408 in patients with AS versus B*2705 healthy controls. The data show that VIP1R 400-408–specific reactivity is a major feature of the patients with AS. These findings show, for the first time to our knowledge, a widespread reactivity in patients with AS against a self-epitope that exhibits some features of a putative “arthritogenic” peptide.
In an epidemiological survey in Tromsø, northern Norway a prevalence of definite ankylosing spondylitis (AS) of between 1.1% and 1.4% was found (males: 1.9-2.2% and females: 0.3-0.6%). The ratio of male to female was between 3.9 and 6.1 in favour of the male sex. It was calculated that 6.7% of the B27 positive individuals had AS, and that 22.5% of the B27 positive subjects with back pain or stiffness suffered from AS.
To investigate the potential influence of the HLA-linked LMP (low molecular weight polypeptide) genes on disease susceptibility in HLA-B27 individuals with ankylosing spondylitis (AS).
A polymorphic CfoI restriction enzyme site in the coding region of one proteasome gene was evaluated in 125 genomic DNA samples from B27 individuals with well documented AS, 55 of whom had had acute iritis, and 42 samples from normal, ethnically matched B27 blood donors where AS was excluded.
Analysis of individuals with B27 AS with iritis revealed significant differences in allelic distribution of this biallelic locus compared to patients with B27 AS without iritis. Furthermore, homozygosity for the disease associated allele was significantly more prevalent in patients with AS with iritis (72.7%) than in patients without iritis (38.6%) (p(uncorrected) = 0.0003) or B27 controls (45.2%) (p(uncorrected) = 0.01).
Our findings support the involvement of additional HLA linked genes in the phenotypic expression of disease in B27 individuals and suggest a role for the non-B27 HLA haplotype in susceptibility to iritis.
The evaluation of the role of polymorphism within the class II encoded antigen processing genes, LMP2 and TAP, in susceptibility to ankylosing spondylitis (AS).
Eighty five patients with ankylosing spondylitis, 35 B27 positive healthy controls, and 55 unrelated healthy controls were studied. TAP1 and TAP2 alleles were assigned by ARMS PCR, and LMP2 alleles were assigned by restriction enzyme digestion of a PCR product.
The TAP1C allele was increased in the AS group (6%) compared with random controls (1%), p = 0.03 and TAP2E was increased in AS (3.5%) compared with random controls (0%), p = 0.05. However, the frequencies of these alleles were also increased in B27 matched controls. There were no differences in LMP2 allele or genotype frequencies between AS and either of the control groups. Partitioning of patients according to presence or absence of uveitis did not reveal any significant associations.
Increases of the minor TAP alleles, 1C and 2E, in AS reflect linkage disequilibrium between these alleles and HLA-B27. Polymorphism of the class I antigen processing pathway does not contribute significantly to AS susceptibility nor to the development of anterior uveitis associated with AS.
To investigate the HLA class I associations of ankylosing spondylitis (AS) in the white population, with particular reference to HLA-B27 subtypes.
HLA-B27 and -B60 typing was performed in 284 white patients with AS. Allele frequencies of HLA-B27 and HLA-B60 from 5926 white bone marrow donors were used for comparison. HLA-B27 subtyping was performed by single strand conformation polymorphism (SSCP) in all HLA-B27 positive AS patients, and 154 HLA-B27 positive ethnically matched blood donors.
The strong association of HLA-B27 and AS was confirmed (odds ratio (OR) 171, 95% confidence interval (CI) 135 to 218; p < 10(-99)). The association of HLA-B60 with AS was confirmed in HLA-B27 positive cases (OR 3.6, 95% CI 2.1 to 6.3; p < 5 x 10(-5)), and a similar association was demonstrated in HLA-B27 negative AS (OR 3.5, 95% CI 1.1 to 11.4; p < 0.05). No significant difference was observed in the frequencies of HLA-B27 allelic subtypes in patients and controls (HLA-B*2702, three of 172 patients v five of 154 controls; HLA-B*2705, 169 of 172 patients v 147 of 154 controls; HLA-B*2708, none of 172 patients v two of 154 controls), and no novel HLA-B27 alleles were detected.
HLA-B27 and -B60 are associated with susceptibility to AS, but differences in HLA-B27 subtype do not affect susceptibility to AS in this white population.
The role of germline polymorphisms of the T-cell receptor A/D and B loci in susceptibility to ankylosing spondylitis was investigated by linkage studies using microsatellite markers in 215 affected sibling pairs. The presence of a significant susceptibility gene (lambda > or = 1.6) at the TCRA/D locus was excluded (LOD score < -2.0). At the TCRB locus, there was weak evidence of the presence of a susceptibility gene (P = 0.01, LOD score 1.1). Further family studies will be required to determine whether this is a true or false-positive finding. It is unlikely that either the TCRA/D or TCRB loci contain genes responsible for more than a moderate proportion of the non-MHC genetic susceptibility to ankylosing spondylitis.
Tapasin is a resident ER protein believed to be critical for antigen presentation by HLA class I molecules. We demonstrate that allelic variation in MHC class I molecules influences their dependence on tapasin for peptide loading and antigen presentation. HLA-B*2705 molecules achieve high levels of surface expression and present specific viral peptides in the absence of tapasin. In contrast, HLA-B*4402 molecules are highly dependent upon human tapasin for these functions, while HLA-B8 molecules are intermediate in this regard. Significantly, HLA-B*2705 like HLA-B*4402, requires tapasin to associate efficiently with TAP (transporters associated with antigen processing). The unusual ability of HLA-B*2705 to form peptide complexes without associating with TAP or tapasin confers flexibility in the repertoire of peptides presented by this molecule. We speculate that these properties might contribute to the role of HLA-B27 in conferring susceptibility to inflammatory spondyloarthropathies.
Stimulation of human blood cultures with bacterial lipopolysaccharide (LPS) shows large inter-individual variation in interleukin 10 (IL-10) secretion, which has been shown to have a genetic component of over 70%. Alleles at two microsatellite loci in the 4 kb immediately upstream of the human IL-10 transcription initiation site in 132 individuals from 56 Dutch families were defined and assigned as haplotypes. LPS-induced IL-10 secretion was measured by ELISA and related to the IL-10 promoter haplotypes present in 78 unrelated individuals obtained from these families. Analysis showed that LPS-induced IL-10 secretion from unrelated individuals varied with IL-10 promoter haplotypes (P = 0.024; Kruskal-Wallis test). Two observations were made in relation to secreted IL-10 levels and promoter haplotypes; first, those haplotypes containing the allele IL10.R3 were associated with lower IL-10 secretion than haplotypes containing any other IL10.R allele. Second, the haplotype IL10.R2/IL10.G14 was associated with highest IL-10 secretion overall, whereas the haplotype IL10.R3/IL10.G7 was associated with lowest IL-10 secretion. These data demonstrate that the ability to secrete IL-10 can vary in man according to the genetic composition of the IL-10 locus.
To investigate whether HLA-B27 influences the expression of murine progressive ankylosis (MPA), a single-gene autosomal recessive mouse model of ankylosing spondylitis that arises in mice homozygous for the ank gene.
Mice transgenic for HLA-B27 were bred with ank/ank mice, and the phenotypes of the F1 and F2 progeny were observed.
ank/+ mice showed no abnormalities, and ank/ank mice showed the typical phenotype of MPA, irrespective of B27 status.
HLA-B27 and the ank/ank genotype both predispose to diseases involving progressive bony ankylosis. These findings suggest that these disease processes are distinct and noninteractive, and they provide no support for the hypothesis that the human homolog of the ank locus participates in the pathogenesis of ankylosing spondylitis.
It has long been suspected that susceptibility to ankylosing spondylitis (AS) is influenced by genes lying distant to the major histocompatibility complex. This study compares genetic models of AS to assess the most likely mode of inheritance, using recurrence risk ratios in relatives of affected subjects.
Recurrence risk ratios in different degrees of relatives were determined using published data from studies specifically designed to address the question. The methods of Risch were used to determine the expected recurrence risk ratios in different degrees of relatives, assuming equal first degree relative recurrence risk between models. Goodness of fit was determined by chi(2) comparison of the expected number of affected subjects with the observed number, given equal numbers of each type of relative studied.
The recurrence risks in different degrees of relatives were: monozygotic (MZ) twins 63% (17/27), first degree relatives 8.2% (441/5390), second degree relatives 1.0% (8/834), and third degree relatives 0. 7% (7/997). Parent-child recurrence risk (7.9%, 37/466) was not significantly different from the sibling recurrence risk (8.2%, 404/4924), excluding a significant dominance genetic component to susceptibility. Poor fitting models included single gene, genetic heterogeneity, additive, two locus multiplicative, and one locus and residual polygenes (chi(2) >32 (two degrees of freedom), p<10(-6) for all models). The best fitting model studied was a five locus model with multiplicative interaction between loci (chi(2)=1.4 (two degrees of freedom), p=0.5). Oligogenic multiplicative models were the best fitting over a range of population prevalences and first degree recurrence risk rates.
This study suggests that of the genetic models tested, the most likely model operating in AS is an oligogenic model with predominantly multiplicative interaction between loci.
To test the hypothesis that ankylosing spondylitis (AS) is a T helper cell type 2 polarised disease by quantifying the T cell cytokines interferon gamma (IFNgamma), interleukin 4 (IL4), tumour necrosis factor alpha (TNFalpha), and IL10 at the single cell level in patients with AS in comparison with healthy HLA-B27 negative and HLA-B27 positive controls.
Peripheral blood mononuclear cells from 65 subjects (25 HLA-B27 positive patients with active AS, 18 healthy HLA-B27 positive controls, and 22 healthy HLA-B27 negative controls) were stimulated with phorbol myristate acetate/ionomycin for six hours, surface stained for CD3 and CD8, intracellularly stained for the cytokines IFNgamma, TNFalpha, IL4, and IL10, and analysed by flow cytometry. TNFalpha production was related to the genotype of the TNFalpha promoter at the -308 and -238 polymorphisms.
In peripheral blood the percentage of TNFalpha+ T cells was significantly lower in HLA-B27 positive patients with AS (median 5.1% for CD4+ T cells) than in healthy HLA-B27 negative controls (median 9.5%; p=0.008). Surprisingly, the percentage of TNFalpha+ T cells was also significantly lower in healthy HLA-B27 positive controls (median 7.48%) than in healthy HLA-B27 negative controls (p=0.034). Furthermore, the percentage of IFNgamma+ T cells was lower in patients with AS and in healthy HLA-B27 positive controls than in healthy HLA-B27 negative controls (p=0.005 and p=0.003, respectively). The percentage of IL10+/CD8+ T cells was higher in patients with AS than in both control groups. In HLA-B27 positive subjects, TNF1/2 heterozygosity at -308 (n=6) was associated with a higher percentage of TNFalpha+ T cells than TNF1/1 homozygosity (n=25; median 9.97% v 5.11% for CD4+ T cells; p=0.017). In contrast, in HLA-B27 negative controls (n=18) there was no such genotype/phenotype correlation (median 9.4% v 10.6%).
The lower T cell production of TNFalpha and IFNgamma shown at the single cell level in HLA-B27 positive patients with AS and healthy HLA-B27 positive controls may contribute to the increased susceptibility of HLA-B27 positive subjects to develop AS. Preliminary genotype-phenotype correlations suggest that in HLA-B27 positive subjects TNF2 at -308 or a linked gene results in higher TNFalpha production and, therefore, might be a marker for a protective haplotype.
The objective of this study was to investigate TNF promoter region polymorphisms for association with susceptibility to ankylosing spondylitis (AS). The TNF -238 and -308 polymorphisms were genotyped in 306 English AS cases and 204 ethnically matched healthy B27-positive controls, and 96 southern German AS cases, 58 B27-positive and 251 B27-negative ethnically matched controls. Additionally, the TNF -376 polymorphism was genotyped in the southern German cases and controls. In the southern German AS patients a significant reduction in TNF -308.2 alleles was seen, compared with B27 positive controls (odds ratio 0.4, P = 0.03, 95% confidence interval 0.2-0.9), but no difference in allele frequencies was observed at TNF -238. Significant association between AS and both TNF -238 and TNF -308 was excluded in the English cases. These results confirm previous observations in the southern German population of association between TNF promoter region polymorphisms and AS, but the lack of association in the English population suggests that these polymorphisms themselves are unlikely to be directly involved. More likely, a second, non-HLA-B, MHC locus is involved in susceptibility to AS in these two populations.
Ankylosing spondylitis (AS) is a common inflammatory arthritis predominantly affecting the axial skeleton. Susceptibility to the disease is thought to be oligogenic. To identify the genes involved, we have performed a genomewide scan in 185 families containing 255 affected sibling pairs. Two-point and multipoint nonparametric linkage analysis was performed. Regions were identified showing "suggestive" or stronger linkage with the disease on chromosomes 1p, 2q, 6p, 9q, 10q, 16q, and 19q. The MHC locus was identified as encoding the greatest component of susceptibility, with an overall LOD score of 15.6. The strongest non-MHC linkage lies on chromosome 16q (overall LOD score 4.7). These results strongly support the presence of non-MHC genetic-susceptibility factors in AS and point to their likely locations.
Crohn's disease is a chronic inflammatory disorder of the gastrointestinal tract, which is thought to result from the effect of environmental factors in a genetically predisposed host. A gene location in the pericentromeric region of chromosome 16, IBD1, that contributes to susceptibility to Crohn's disease has been established through multiple linkage studies, but the specific gene(s) has not been identified. NOD2, a gene that encodes a protein with homology to plant disease resistance gene products is located in the peak region of linkage on chromosome 16 (ref. 7). Here we show, by using the transmission disequilibium test and case-control analysis, that a frameshift mutation caused by a cytosine insertion, 3020insC, which is expected to encode a truncated NOD2 protein, is associated with Crohn's disease. Wild-type NOD2 activates nuclear factor NF-kappaB, making it responsive to bacterial lipopolysaccharides; however, this induction was deficient in mutant NOD2. These results implicate NOD2 in susceptibility to Crohn's disease, and suggest a link between an innate immune response to bacterial components and development of disease.
Crohn's disease and ulcerative colitis, the two main types of chronic inflammatory bowel disease, are multifactorial conditions of unknown aetiology. A susceptibility locus for Crohn's disease has been mapped to chromosome 16. Here we have used a positional-cloning strategy, based on linkage analysis followed by linkage disequilibrium mapping, to identify three independent associations for Crohn's disease: a frameshift variant and two missense variants of NOD2, encoding a member of the Apaf-1/Ced-4 superfamily of apoptosis regulators that is expressed in monocytes. These NOD2 variants alter the structure of either the leucine-rich repeat domain of the protein or the adjacent region. NOD2 activates nuclear factor NF-kB; this activating function is regulated by the carboxy-terminal leucine-rich repeat domain, which has an inhibitory role and also acts as an intracellular receptor for components of microbial pathogens. These observations suggest that the NOD2 gene product confers susceptibility to Crohn's disease by altering the recognition of these components and/or by over-activating NF-kB in monocytes, thus documenting a molecular model for the pathogenic mechanism of Crohn's disease that can now be further investigated.
Eighteen different HLA-B*27 alleles (B*2701-B2718) have so far been recognized by the WHO Nomenclature Committee for Factors of the HLA System. Frequency and disease association of these alleles with spondyloarthropathies differ among ethnic groups. We describe here a novel HLA-B*27 subtype identified in a Lebanese patient suffering from ankylosing spondylitis (AS). This new variant differs from the common HLA-B*2705 DNA sequence at five different nucleotide positions. These nucleotide changes lead to three amino acid differences in the alpha2 domain; Thr to Ile at position 94, Leu to Ile at position 95 and Asn to Arg at position 97. Since this novel allele is encountered in an AS patient, the associated sequence changes are not expected to affect significantly neither the presentation of a putative arthritogenic peptide nor the conformation-dependent recognition by effector cells.
The polymorphic TAP1 and TAP2 genes encode subunits of the transporter that delivers peptides to the HLA class I molecules. Because the polymorphism of the TAP genes has been shown to affect peptide transport, it has been suggested that TAP genes are potential regulators of the immune response. We studied TAP1 and TAP2 polymorphism in two multifactorial HLAB27-associated diseases, ankylosing spondylitis (N = 30) and reactive arthritis (N = 30), in order to establish whether TAP genes are involved in the different pathogenesis of these diseases. Healthy HLA-B27-positive individuals (N = 55) were chosen as the primary controls and 93 individuals represented the random Finnish population as secondary controls. We found differences between the random and HLAB27-positive populations, thus suggesting that certain TAP alleles are prevalent in HLA-B27 haplotypes. No differences were found between the AS and ReA groups nor between either of them and the healthy HLA-B27-positive controls. Thus it seems unlikely that TAP polymorphism, at the level studied, has a dominant role in the pathogenesis of these diseases. However, a family study is needed in order to determine whether the same TAP complexes are carried by the same haplotypes in these diseases. Human Immunology 44, 236–242 (1995)
PCR in combination with SSO probes was used to analyze the polymorphism in exons 2 and 3 of HLA-B27 subtypes and HLA-C-related alleles in two genetically distant Caucasian groups: Spanish and Jewish populations. AS patients and healthy B27 donors from both populations were analyzed in order to ascertain B27-Cw haplotypes. Three different ancestral haplotypes were found to be represented in both populations: B∗2705/Cw∗0102, B∗2705/Cw∗02022, and B∗2702/Cw∗02022. The B∗2705 (92.5%) was the most frequent allele found in the Spanish population, carried by B∗2705/Cw∗0102 (60.9%) and B2705/Cw∗02022 (30.4%) haplotypes. In contrast, B∗2702 (59.4%) was the most prevalent allele found in the Jewish population and was carried by the B∗2702/Cw∗02022 (63.3%) haplotype. No different allelic and haplotypic distributions were among healthy and AS patients in either Spanish or Jewish populations. The differences found in the distribution of B27 haplotypes among Spanish and Jewish Caucasian populations are consistent with the genetic distance of these ethnic groups. When the Jewish population was subdivided into Ashkenazi (A) and non-Ashkenazi (NA) groups, no significant differences were observed in the distribution of B∗2702/Cw∗02022 haplotype. Minor differences were observed in the underrepresented B∗2705 haplotypes. The present results reflect the ancestral affinities of A and NA Jewish populations. A possible HLA-B27 evolutive pathway in Caucasians is proposed according to the data available for the B27/Cw ancestral haplotypes in Spanish and Jewish groups.
We have examined the expression of HLA B∗2705 in the mutant cell line 721.220, which lacks endogenous HLA A and B alleles and expresses a defective tapasin molecule. Several peptide sensitive mAbs distinguish between HLA B∗2705 expressed on the surface of 721.220 cells (B27.220) and 721.220 cells co-transfected with human tapasin (B27.220.hTsn). This differential staining defines subtle differences in the conformation of HLA B27, which most likely reflect changes in the repertoire of antigenic peptides bound to B27 in the presence and absence of wild type tapasin. HLA B27 molecules expressed on the surface of 721.220 display increased levels of “free” B27 heavy chain (HC-10 staining), an epitope that is dependent on TAP-translocated peptides. The conformation and stability of B27 molecules was examined by investigating the integrity of mAb epitopes and the half-lives of these complexes on cells cultured with and without serum. The decay of surface B27 epitopes occurred more rapidly in B27.220 and this effect was exaggerated in serum free media. Importantly, the decay of surface B27 molecules in B27.220.hTsn cells was characterized by an early increase in HC-10 staining when the cells were grown in serum free media. This decay of B27 molecules via HC-10 reactive intermediates was not observed in B27.220 cells, implying molecules on these cells may already have passed through this stage prior to surface expression. Taken together these observations indicate that tapasin has a significant contribution to the composition and stability of the B27-bound peptide repertoire.
The close association of HLA-B27 with arthritic conditions has led to the suggestion that these diseases are mediated by cytotoxic T lymphocytes that recognize self-peptides presented by HLA-B27 molecules. The further association with enteric bacterial infections suggests that bacterial antigens may prime the CTL that later crossreacts on self. Bacterial infections do not usually generate CTL responses. We speculate here that unusual properties of HLA-B27 molecules may predispose to such responses. Thus, HLA-B27-related disease may be an unfortunate consequence of the generation of a suitable, self-mimicking HLA-B27-binding peptide by certain bacteria, plus an unusual propensity for the HLA-B27 molecule to bind and present such peptides.
Sequence studies indicate that the alpha-1 domain of the HLA-B27 molecule has a characteristic unpaired cysteine residue at position 67, adjacent, because of secondary structure, to a lysine at position 70. Simple chemical considerations predict that this cysteine should have an exceptionally reactive sulphydryl group. We have shown by ELISA and flow cytometry that the binding of some monoclonal antibodies to B27 on lymphoid cell lines can be inhibited by reagents which react with sulphydryl groups. However this inhibition is never complete: the evidence suggests 2 forms of B27 molecule, one of which is already blocked. We propose that some HLA molecules with oxidised sulphydryls are recognised as different from the reduced forms. Whether they are also recognised as foreign will depend on an individual's history of thymic learning. Oxidation to 'foreign' HLA in the adult is likely to predispose to inflammatory reactions.
The remarkable association between HLA-B27 and ankylosing spondylitis (AS) remains an enigma. While previous reviews have discussed the controversies surrounding the involvement of bacteria in the etiology of this disease and the sequence variability between subtypes of HLA-B27, concepts of disease mechanism remain ill-defined. In this article Richard Benjamin and Peter Parham synthesize new data on the structure and function of HLA class I molecules into possible mechanisms that might underly the pathogenesis of AS.
Ankylosing spondylitis and Reiter's syndrome are the two major spondyloarthropathies highly associated with human leukocyte antigen (HLA) B27. Although the development of spondylitis is unclear, it has been hypothesized that HLA-B27 may predispose to spondyloarthropathies via the phenomenon of molecular mimicry. A computer search for homologies between HLA-B27 and microbes revealed a sequence of six consecutive amino acids (glutamine-threonine-aspartic acid-arginine-glutamic acid-aspartic acid) shared by HLA-B27.1 (residues 72 to 77), and Klebsiella pneumoniae nitrogenase (residues 188 to 193). Antibodies raised against a peptide derived from HLA-B27 containing this six-amino-acid sequence cross-reacted with the peptide derived from Klebsiella that contained these six amino acids, and vice-versa. These antibodies also reacted with articular tissues from HLA-B27-positive patients with ankylosing spondylitis. Sera from 53 percent of Reiter's patients and 27 percent of patients with ankylosing spondylitis showed binding to these same peptides. These results suggest that molecular mimicry may have a role in disease development.
Family studies and investigation of the HLA associations have in recent years added to our understanding of the spondyloarthropathies. In regard to ankylosing spondylitis it is likely that B27 itself is the major susceptibility gene but that additional genes may play a secondary role. Heterogeneity of the B27 antigen has been demonstrated but has not yet been shown to be relevant to disease susceptibility. Haplotypes including Cw6 are related to susceptibility to psoriasis and psoriatic arthritis and although the risk for the arthropathy is increased in B27-positive individuals, there is some uncertainty regarding the association with other B locus antigens and further work is needed. There is also uncertainty as to whether B27-associated disorders occur randomly within families, or whether particular disorders cluster in certain families and further evidence in this field would be of considerable interest. Genetic studies, as here outlined, have not as yet had a major impact in clinical medicine but it is anticipated that a deeper understanding of the mechanisms of HLA-linked susceptibility genes and in particular of how they interact with environmental agents, will improve our ability to treat and possibly prevent the relevant diseases.
We examined the distribution of non-B27 alleles of the HLA-B locus among B27+ patients with ankylosing spondylitis (AS), to detect any additional HLA-B locus allele(s) that may act in conjunction with B27 to increase susceptibility to AS. HLA-Bw60 (or B40 when the Bw60,61 split of B40 was not typed for) was shown to be increased among B27+ AS patients in each of 5 independent data sets. This increase was statistically significant in 4 of the 5 data sets studied, and the overall significance was P less than 0.00001. Susceptibility to AS in B27+ individuals was further increased by a factor of approximately 3 when Bw60 was also present. The distribution of HLA-A alleles on the B27-bearing haplotypes in AS patients was not significantly different from that in normal controls. On the other hand, the distribution of HLA-A alleles on Bw60-bearing haplotypes was significantly different from the distribution of A alleles on Bw60 haplotypes in the general population (P less than 0.0005). Bw60 was not increased in B27- patients with AS. A dominant mode of inheritance generally fits AS; however, our sib pair analysis indicates that the B27,Bw60 disease subgroup follows a more recessive mode of inheritance.
Progressive ankylosis mice rapidly develop an ankylosing spondyloarthropathy that rapidly affects all of the articulations of the vertebral column. The disorder symmetrically affects the nonsynovial synchondroses and symphyses of the intervertebral spaces, the diarthrodial synovial apophyseal and costovertebral joints, and the sacroiliac joint. These joints present a clear progression from syndesmophyte formation through joint bridging to total fusion. The similarities and differences of the disorder identified in this mouse and human spondyloarthropathies are discussed.
Subtypes of HLA-B27 have been identified by cellular, serological and biochemical techniques. Comparison of the various B27 subtype designations showed the existence of seven B27 subtypes. The new WHO nomenclature (1987) of the B27 subtypes is included. We further report on different linkage disequilibria (ld) of the B27 subtypes. In Caucasoids, the prevalent subtype B27.5 is in ld with Cw1 and Cw2, whereas B27.2 is linked only with Cw2. In Orientals, the most frequent subtypes B27.4 and B27.6 usually occur with Cw3 or Cw blank; B27.5 mostly occurs with Cw2, and B27.2 is almost absent.
Ileocolonoscopy and microscopic examination of ileum biopsies have been performed on patients with reactive synovitis, ankylosing spondylitis (AS) and on a control group. Histological signs of gut inflammation were present in practically all patients with reactive synovitis, with the exception of the patients with sexually-acquired disease. In the AS group, inflammation of the ileum was observed in the HLA-B27 negative patients and in AS B27 positive patients with peripheral joint involvement. Occasionally, changes of the ileum were seen in the B27 positive AS patients without peripheral joint involvement. Signs of gut inflammation were absent in all controls. These data suggest that chronic inflammation of the ileum could be implicated in the pathogenesis of some cases of reactive synovitis and even in the peripheral joint involvement frequently seen in ankylosing spondylitis. In the second part of the study, sulfasalazine (Salazopyrin) was administered to 15 HLA-B27 positive patients with reactive synovitis, who had failed to respond to non-steroidal anti-inflammatory drugs. In 11 of the 15 patients, a clinical and biological remission occurred 3 to 11 months after the start of sulfasalazine treatment. The frequency of spontaneous remissions in reactive synovitis calls for confirmation of these encouraging results in double-blind controlled studies.
The association of HLA-B27 with ankylosing spondylitis (AS) can be explained by a cross-tolerance hypothesis, which suggests that Gram-negative bacteria, such as Klebsiella, possess antigens which resemble HLA-B27. Experimental studies with human tissue-typing sera and rabbit anti-Klebsiella sera would appear to be compatible with this hypothesis. Clinical studies indicate that faecal Klebsiella can be isolated more readily from AS patients during active phases of the disease, when this is defined either clinically, with or without uveitis, or biochemically by elevation in ESR and C-reactive protein levels. The cross-tolerance hypothesis proposes that ankylosing spondylitis is a reactive arthritis following infection by Gram-negative bacteria and tissue damage is produced by antibacterial antibody binding to cross-reacting self-antigens.
The aim of this study was to investigate the contribution of the different B27 subtypes to ankylosing spondylitis (AS) susceptibility. The polymerase chain reaction (PCR) in combination with the sequence-specific oligonucleotide probes (SSOs) was used to analyse the polymorphism in exon 2 and 3 of HLA-B27 in two Asian groups with different genetic HLA structures: Indian (I) and Thai (T) populations. The same number of AS patients (45) and healthy B27 positive donors (n = 17) from both populations were analysed in order to ascertain the B27 subtypes. Three different findings can be concluded from this study: 1) B*2707 has been found to be associated with AS in both populations. This association has not been previously reported in either ethnic group. 2) B*2704 is strongly associated with AS in the Thai patients (91% in AS vs. 47% in C; RR = 11.5; EF = 0.83). In contrast, B*2704 was found with similar frequency in Asian Indians AS patients and controls (41% in AS vs. 41% in C.). 3) B*2706 was found overrepresented in control populations and absent in AS patients (0% in AS vs. 47% in C.; pc < 10(-6)) showing the maximum value of protective fraction (PF = 1). The B*2706 negative association with AS has not been previously described in other ethnic groups and could indicate a protective effect of this subtype on AS susceptibility. The B*2706 allele has two changes relative to B*2704 at residue 114 (His to Asp) and 116 (Asp to Tyr) in the pockets D/E. The importance that these differences can play in the pathogenesis of AS are discussed.
Although human leukocyte antigen (HLA) B27 has been directly implicated in the pathogenesis of ankylosing spondylitis (AS), additional evidence favours the involvement of an additional genetic factor(s). In a previous population analysis of AS patients selected for a history of acute anterior uveitis (AAU), we had demonstrated a phenotypic association between polymorphism in an HLA-linked proteasome subunit gene, LMP2, and the development of AAU and peripheral arthritis. In the present study, we have assessed the relative risk of homozygosity for the LMP2 arginine variant, the disease-associated genotype, for these complications in an unselected group of 86 patients with AS seen sequentially in 1 centre by 1 rheumatologist over a 2-y period. LMP2 genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using the CfoI restriction enzyme. Homozygosity for the LMP2 arginine variants was observed in 68.4% of AS patients who had had AAU as compared to 41.7% without AAU (relative risk 3.0; chi 2 = 6.1, p < 0.02). The proportion of AS patients with peripheral arthritis homozygous for the arginine residue was 55.2% as compared to 52.6% without this complication (relative risk 1.1; p > 0.05). Our data suggest a primary association with the development of AAU and provide evidence for genetic heterogeneity in distinct clinical subgroups of patients with AS as a basis for phenotypic variation.
To obtain information on the rate of concordance for ankylosing spondylitis (AS) in a population-based series of twins.
AS cases were identified by record linkage of the population-based Finnish Twin Cohort and the nationwide registry for fully reimbursed medications. A clinical examination was performed to establish concordance for AS.
There were 6 monozygotic (MZ) pairs and 20 dizygotic (DZ) pairs with at least 1 member affected by AS. Three MZ pairs and 3 DZ pairs were concordant for the disease. All affected subjects were HLA-B27 positive. The pairwise concordance rate was 50% in MZ twins and 20% in HLA-B27 positive DZ twins (95% confidence intervals 11.8-88.2% and 4.3%-48.1%, respectively).
These results indicate that AS disease expression is largely, but not entirely, genetically based, with a gene or genes other than B27 probably playing a role.
The spondarthropathy (Sp)-associated HLA-B27 antigen includes at least seven subtypes, B*2701-07, of which 01, 02, 05 and 07 occur in Caucasians. This study examined the B27 subtype distribution in British patients with Sp. The 133 HLA-B27+ subjects comprised 94 European Caucasian Sp (58 ankylosing spondylitis (AS), 22 reactive arthritis (ReA; 11 sexually acquired (SARA), 11 enteric (EReA)), eight undifferentiated Sp (USp), and six pauciarticular juvenile-onset chronic arthritis (pJCA)) patients, and 34 healthy Caucasian controls, together with four Asian Indian and one Chinese. 35S-labelled B27 was immunoprecipitated with anti-B27 MoAbs, and subtyped according to isoelectric point (pI) following isoelectric focussing. The use of B27 MoAb permitted subtype assignment without full class I HLA typing. The vast majority (95%) were B*2705 (Caucasian controls 31/34; AS 55/58; ReA 21/22; USp 8/8, and pJCA 6/6; Indian control 1/1 and AS 2/3; Chinese pJCA 1/1), and the remainder B*2702. No B*2701 or 07 subjects were identified. AS occurs in both B*2702 and 05 subjects, and we extend this observation to small numbers of ReA and of Indian AS subjects. This implicates molecular features shared between B27 subtypes, rather than subtype-determining regions of the antigen, in Sp pathogenesis.
To determine whether particular genotypes for the cytochrome P450 enzyme CYP2D6, a polymorphic enzyme, are associated with susceptibility to ankylosing spondylitis (AS) and rheumatoid arthritis (RA), or linked with any specific clinical or familial features of the two conditions.
CYP2D6 genotypes were determined in 54 patients with AS, 53 patients with RA, and 662 healthy controls. Leucocyte DNA was analysed for the presence of mutations by restriction fragment length polymorphism analysis with the restriction enzyme Xbal and by two separate polymerase chain reaction assays.
On the basis of odds ratio (OR), individuals with two inactive CYP2D6 alleles were more susceptible to AS than controls (OR 2.71, 95% confidence interval (CI) 1.04 to 7.08), with a stronger effect for the CYP2D6B allele (OR 4.11, 95% CI 1.54 to 11.0). No significant differences in the distribution of overall genotypes and allele frequencies were observed between RA and controls. No significant relationships were found between the skeletal, extraskeletal or familial features of AS or RA (iritis, psoriasis, inflammatory enteropathy and rheumatoid nodules, kerato-conjunctivitis sicca, pleuritis, rheumatoid and antinuclear factors) and the overall genotype.
Our findings suggest a modest association between homozygosity for inactive CYP2D6 alleles, particularly CYP2D6B alleles, and susceptibility to AS. However, our results fail to demonstrate a genetic link between CYP2D6 genotype and RA.
Murine progressive ankylosis is an autosomal recessive disorder in mice similar to the human spondyloarthropathies. The gene responsible for progressive ankylosis, ank, has not been identified and its product is unknown. We investigated whether the immune system plays a role in the pathogenesis of progressive ankylosis.
Reciprocal transfers of spleen or bone marrow cells or serum between ank/ank and normal mice were performed. CD4 T cells were depleted in vivo by injection with monoclonal antibody. Ank/ank; nu/nu mice were bred from double heterozygote offspring of homozygote parents.
Disease was neither ameliorated nor induced by these immune system manipulations.
We conclude that progressive ankylosis is not immune mediated. The similarities between ankylosing spondylitis and murine progressive ankylosis may be due to mechanisms producing osteogenesis in nonosseous tissues.
To determine the prevalence of ankylosing spondylitis in the Fula ethnic group in The Gambia, and relate the disease prevalence to the B27 frequency and subtype distribution of that population.
215 first degree relatives of 48 B27 positive Fula twin pairs, and 900 adult Fula males were screened for ankylosing spondylitis by clinical and, where appropriate, radiographic means. The B27 prevalence was determined by PCR/sequence specific oligonucleotides on finger prick samples from 100 unrelated Fula, and B27 subtype distribution by SSCP on unrelated B27 positive individuals. This data were then compared with the prevalence of ankylosing spondylitis among B27 positive Caucasians.
No case of ankylosing spondylitis was seen. Six per cent of Fula are B27 positive, of which 32% are B*2703 and 68% B*2705. Assuming the penetrance of ankylosing spondylitis in B27 positive Fula is the same as in B27 positive Caucasians, the probability of not observing any cases of ankylosing spondylitis among the Fula examined is remote (P = 6.7 x 10(-6)). Similarly, the chance of not seeing any cases among those expected to be either B*2705 or B*2703 was small (P = 3.2 x 10(-4) for B*2705, and P = 0.02 for B*2703).
The risk of developing ankylosing spondylitis in B27 positive Fula is lower than in B27 positive Caucasians. This is not explained by the B27 subtype distribution among Fula, and suggests the presence of some non-B27 protective factor reducing the prevalence of ankylosing spondylitis in this population.
Recent studies have suggested that HLA DRB1*0103 and allele 2 of the interleukin 1 receptor antagonist (IL-1RA) gene predict severe and extensive ulcerative colitis, respectively. The aim of this study was to test these hypotheses in patients undergoing surgery for their colitis.
HLA DRB1 and DQB1 genotyping was performed in 99 patients and 472 controls. Genotyping for polymorphisms of genes encoding tumor necrosis factor alpha and IL-1RA was performed in 107 patients and 89 controls. Measurement of antineutrophil cytoplasmic antibody (ANCA) was performed in 72 patients and 58 healthy subjects by fixed neutrophil enzyme-linked immunosorbent assay and indirect immunofluorescence.
The DRB1*0103 allele was increased in patients (14.1% vs. 3.2% in controls; P < 1 x 10[-5]). This association was greatest in patients with extensive disease (15.8%; P < 0.0001) or extraintestinal manifestations (22.8%; P < 0.0001): mouth ulcers (25.8%; P < 0.0001), arthritis (27.2%; P < 0.0001), and uveitis (35.7%; P < 0.0001). The DRB1*04 alleles were reduced in patients (P = 0.005). Differences were noted between extensive and distal disease in the frequency of allele 2 of IL-1RA (10.9% in distal vs. 28.6% in extensive; P = 0.01) and allele 2 homozygosity. ANCA was detected in 76.4% of patients. Carriage of IL-1RA allele 2 and tumor necrosis factor 2 allele was increased in ANCA-positive patients.
Genetic markers may predict disease behavior in ulcerative colitis.
The B*2710 subtype differs from the HLA-B27 prototype (B*2705) only by having Glu instead of Val at position 152, in the alpha2 helix of the peptide-binding site. In spite of its structural similarity most alloreactive CTL raised against B*2705 fail to cross-react with B*2710. Indeed, of the residues that are polymorphic among HLA-B27 subtypes, the Val>Glu152 change has the greatest influence on HLA-B27 T-cell antigenicity. The molecular basis for this antigenic disparity was analyzed in this study. Sequence analysis indicated that B*2710-bound peptides have very similar motifs to B*2705-bound ones both at the main and auxiliary anchor positions. In addition, most of the individual ligands sequenced from B*2710 were previously found in B*2705. Together these results indicate that both subtypes have largely overlapping peptide repertoires. Molecular dynamics simulations of a common ligand in complex with either B*2710 or B*2705 failed to detect significant conformational changes in the peptidic main chain or in solvent accessibility of the side chains. In addition, modeling of the Val>Glu152 change into the MHC-peptide-TCR structure suggested a direct role of residue 152 in interaction with the TCR. Thus, the large differences in T-cell recognition between B*2710 and B*2705 are not explained by an effect of the Glu152 change on peptide specificity or conformation, but by different direct interactions with the TCR.
We have characterized HLA-B27 alleles in a sample of the population from the Azores (n=46) with the aim of investigating the contribution of different subtypes to ankylosing spondylitis (AS). The study was carried out using PCR-SSOP and in some samples genomic sequencing was conducted. Some significant new finding have arisen from this study. First, B*2705,B*2702,B*2703,B*2707 and B*2708 alleles were found to be represented in this population. The polymorphism of B27 alleles found in a sample of the population from the Azores is higher than the Caucasian groups described. B*2703 and B*2707 have not previously been described to be represented in Caucasians and this could indicate admixtures with different populations of the world. In addition, the B*2708 allele was found to be associated with AS in a large family from the Azores. This association has not been previously reported in either ethnic group and needs to be confirmed in other population studies. This is of considerable interest since has only been described as a rare subtype underrepresented in the British population and has not been previously found to be associated with AS. B*2708 carries the sequence specifying the Bw6 epitope in contrast to most B27 alleles which carry a Bw4 sequence. Differences in this region (residues 77–83) can alter the F-pocket and affect T-cell recognition. The importance that these molecular changes can play in the pathogenesis of AS is discussed.
“Thus far, O Portuguese, it is granted to you to glimpse into the future and to know the exploits that await your stout-hearted compatriots on the ocean that, thanks is now no longer unknown”.
The Lusiads (L. Camoes)
Recently, attention has focused on the use of whole-genome linkage disequilibrium (LD) studies to map common disease genes. Such studies would employ a dense map of single nucleotide polymorphisms (SNPs) to detect association between a marker and disease. Construction of SNP maps is currently underway. An essential issue yet to be settled is the required marker density of such maps. Here, I use population simulations to estimate the extent of LD surrounding common gene variants in the general human population as well as in isolated populations. Two main conclusions emerge from these investigations. First, a useful level of LD is unlikely to extend beyond an average distance of roughly 3 kb in the general population, which implies that approximately 500,000 SNPs will be required for whole-genome studies. Second, the extent of LD is similar in isolated populations unless the founding bottleneck is very narrow or the frequency of the variant is low (<5%).
To determine the effects of HLA Class II genes, particularly LMP2 and previously implicated Class I genes, on susceptibility and disease expression in HLA-B27 negative ankylosing spondylitis (AS).
Patients included 41 HLA-B27 negative Caucasians from a total AS population of 546 and 17 HLA-B27 negative Mexican Mestizo. Controls included 4352 random HLA-B27 negative Caucasians. LMP2 genotype assignments were made on all patients and 282 random Caucasian controls by polymerase chain reaction-restriction fragment length polymorphism with the Cfo I restriction enzyme while HLA typing was performed on patients and controls using microcytotoxicity assays for Class I, and sequence specific probe-PCR for HLA-B60, B39, B38, and DR.
The LMP2BB genotype was significantly decreased in Caucasian AS patients without extraspinal (ES) disease (25%) compared to AS patients with ES (64.7%) (p = 0.01) and random Caucasian controls (53.9%) (p = 0.007), even when those with colitis and psoriasis were excluded from analysis (ES+ 55.6% versus ES- 22.2%). This finding remained significant after stratification by HLA-DR. Similar trends were noted in the Mexican population. A potential role for HLA-DR8 and DR2 in susceptibility to disease was observed in Caucasian patients, although this observation requires confirmation. We could not confirm reported associations with HLA-B60 or B39. Peripheral arthritis was significantly more commonly observed in those who had had acute anterior uveitis (AAU) (75%) than in those who had not developed AAU (27.3%) (p = 0.04).
HLA Class II encoded genes may have effects on disease susceptibility and/or phenotype in HLA-B27 negative individuals similar to those noted in HLA-B27 positive AS. Eccentric and axial phenotypes of disease may be immunogenetically determined.
To investigate the possible association between the recently described interleukin 6 (IL-6) promoter polymorphisms at position -174, and susceptibility to ankylosing spondylitis (AS).
Ninety-two patients with AS, 157 healthy controls, and an additional group of 52 HLA-B27 positive unrelated individuals were included in this study. The -174 polymorphic site in the promoter region of IL-6 gene was typed by polymerase chain reaction-restriction fragment length polymorphism.
No statistically significant differences were observed when IL-6 promoter genotype and allele distribution between patients with AS and healthy controls were compared.
Our results suggest the -174 IL-6 polymorphism does not play an important role in susceptibility to AS. Larger studies are needed to provide more conclusive evidence on the role of -174 IL-6 polymorphism in AS.
Ankylosing spondylitis (AS) affects 0.25-1.0% of the population, and its etiology is incompletely understood. Susceptibility to this highly familial disease (lambda(s) = 58) is primarily genetically determined. There is a significant sex bias in AS, and there are differences in recurrence risk to the offspring of affected mothers and fathers, suggesting that there may be an X-linked recessive effect. We undertook an X-chromosome linkage study to determine any contribution of the X-chromosome to AS susceptibility.
A linkage study of the X-chromosome using 234 affected sibling pairs was performed to investigate this hypothesis.
No linkage of the X-chromosome with susceptibility to AS was found. Model-free multipoint linkage analysis strongly excluded any significant genetic contribution (lambda > or = 1.5) to AS susceptibility encoded on the X-chromosome (logarithm of odds [LOD] <-2.0). Smaller genetic effects (lambda > or = 1.3) were also found to be unlikely (LOD <-1.0).
The sex bias in AS is not explained by X-chromosome-encoded genetic effects. The disease model best explaining the sex bias in occurrence and transmission of AS is a polygenic model with a higher susceptibility threshold in females.
HLA-B27 is strongly linked with a group of human diseases called spondyloarthropathies. Even though HLA-B27 as an MHC class I molecule would be expected to present endogenously processed peptides such as cytosolic or viral proteins, many of the B27-linked diseases begin after an infection with an enterobacteria, an exogenous antigen. In our previous studies, we have described development of spontaneous inflammatory disease in HLA-B27 transgenic mice expressing beta(2)m free heavy chains on the cell surface. In order to address the role of endogenous versus exogenous antigens and a role for Tap genes in the development of spontaneous diseases, mice lacking Tap-1 (knockout) were mated to HLA-B27/human beta(2)m transgenic mice. B27(+)/human beta(2)m(+) double-transgenic mice (without mouse beta(2)m) lacking the Tap-1 gene developed spontaneous inflammatory disease similar to wild-type Tap-1 gene-expressing counterparts. Our data demonstrate that peptide transporters (Tap) were not involved in the development of spontaneous inflammatory disease in B27(+)/human beta(2)m transgenic animals.
Human geneticists withhold judgment on any report of linkage or allelic association until it is independently replicated. But the independent replication criterion has become harder to meet. Does this signal the demise of the reverse genetics paradigm or a problem with the replication requirement itself?