Content uploaded by Vaclav Vetvicka
Author content
All content in this area was uploaded by Vaclav Vetvicka on Nov 08, 2016
Content may be subject to copyright.
CR3 (CD11b/CD18) expressed by cytotoxic T cells and natural killer cells is upregulated in a manner similar to neutrophil CR3 following stimulation with various activating agents
Abstract
CR3 (CD11b/CD18) functions both as an iC3b-receptor and as an adhesion molecule for cellular ligands such as ICAM-1. Although CR3 has been well characterized on phagocytic cells, much less is known about CR3 on lymphocytes. In this study, the expression of CR3 was examined on resting and stimulated B, T, and natural killer (NK) cells by three-color flow cytometry. Biotinylated anti-CR3 mAb and streptavidin-FITC were used in combination with anti-CD3 mAb conjugated with peridinin chlorophyll-alpha protein (PerCP) and phycoerythrin-labeled mAbs to CD4, CD8, CD19, or CD56. Among resting lymphocytes, CR3 was expressed on nearly all NK cells (CD56+CD3-), 1% of CD4+CD3+ helper T cells, 7% of CD8+CD3+ cytotoxic T cells, and 20% of B cells (CD19+). Among the 5% of T cells (CD3+) expressing CR3, the majority was CD56+. Incubation of PBMC for 30 min with PMA induced a three- to fivefold increase in CR3 expression on NK cells and a twofold increase on T cells but did not change the expression of CR3 on B cells. This effect of PMA was not blocked by the presence of cycloheximide, suggesting the presence of cytoplasmic (granule) stores of CR3 in these lymphoid cells resembling those previously reported in neutrophils and monocytes. When PBMC were incubated with rIFN-alpha, rIL-2, beta-glucan, or high concentrations of LPS, expression of CR3 on NK cells increased significantly, but > or = 4 hr of stimulation was required. Other cytokines (rIFN-gamma, rIL-1, rIL-4, rIL-6, TNF-alpha) and rC5a had no significant effect on CR3 expression. Among NK cells, both the CD56bright and the CD56dim cells expressed CR3, and the expression of CR3 on both of these NK cell subsets was increased in a similar manner by PMA. However, rIL-2 stimulated a greater increase in CR3 expression on CD56bright cells than on CD56dim cells. These studies suggest that CR3 expressed by NK cells or cytotoxic T cells resembles phagocyte CR3 in that cellular activation stimulates increased surface expression of CR3 derived from cytoplasmic reserves of the receptor.
... In humans both receptors can be found on myeloid cells, such as neutrophil granulocytes, monocytes, macrophages and dendritic cells [150][151][152]. On lymphoid cells they do not appear uniformly; while NK cells express CR3 constitutively [153,154], these β 2 -integrins are usually present only on certain subpopulations of T and B lymphocytes [153], and may appear after activation [155][156][157] or during pathological conditions [158,159]. ...
... In humans both receptors can be found on myeloid cells, such as neutrophil granulocytes, monocytes, macrophages and dendritic cells [150][151][152]. On lymphoid cells they do not appear uniformly; while NK cells express CR3 constitutively [153,154], these β 2 -integrins are usually present only on certain subpopulations of T and B lymphocytes [153], and may appear after activation [155][156][157] or during pathological conditions [158,159]. ...
... Beside CD11b expressing B-1 cells, Muto et al. found that approximately 20% of all blood B cells express CR3 [153], while Kawai et al. detected around 34% CD11b + cells among B lymphocytes, which were enriched in the CD27 + memory population. The expressed CR3 was shown to contribute to the high migratory potential of this B cell population [160]. ...
The involvement of complement in the regulation of antibody responses has been known for long. By now several additional B cell functions - including cytokine production and antigen presentation - have also been shown to be regulated by complement proteins. Most of these important activities are mediated by receptors interacting with activation fragments of the central component of the complement system C3, such as C3b, iC3b and C3d, which are covalently attached to antigens and immune complexes. This review summarizes the role of complement receptors interacting with these ligands, namely CR1 (CD35), CR2 (CD21), CR3 (CD11b/CD18) and CR4 (CD11c/CD18) expressed by B cells in health and disease. Although we focus on human B lymphocytes, we also aim to call the attention to important differences between human and mouse systems.
... Activation of dectin-1 by β-glucans stimulates phagocytosis, reactive oxygen species (ROS) production, NFκBmediated cytokine secretion (including IL-1β, IL-2, IL-8, IL-10, IL-12, TNF-α), synthesis of chemokine CXCL2, differentiation of naive CD4 + T lymphocytes into Th1 and Th17, and activation of CD8 + T lymphocytes [43]. Complement receptor 3 (CR3) is expressed on neutrophils, monocytes, natural killer (NK) cells, CD8 + T cells, as well as activated CD4 + T cells and likewise has been implicated in the recognition of β-glucans [44,45]. Activation of CR3 upregulates phagocytosis and degranulation of cytotoxic CD8 + T cells [12]. ...
... This may help to overcome tumor resistance to these forms of effector mechanism and lead to higher secretion of IL-6 and IFN-γ [12]. It has been suggested that 1,4-α-d-glucans do not affect macrophages via CR3 binding [58], but activation of T lymphocytes up-regulates expression of CR3 [44,45]. Interestingly, it was found that blocking the CD11b subunit of CR3 contributed to T lymphocyte proliferation inhibition after stimulation with anti-CD3 Abs [44]. ...
Polysaccharides isolated from Lentinula edodes are bioactive compounds with immunomodulatory properties. In our previous studies from L. edodes mycelium, we have isolated a selenium(Se)-enriched fraction (named Se-Le-30), a mixture of linear 1,4-α-glucan and linear 1,3-β- and 1,6-β-glucans. In this study, we analyzed the effects of Se-Le-30 on the activation and proliferation of human T lymphocytes stimulated by anti-CD3 and anti-CD3/CD28 antibodies (Abs) and on the production of cytokines by peripheral blood mononuclear cells (PBMCs). Se-Le-30 had effects on T cell proliferation induced by Abs against CD3 and CD28. It significantly inhibited the proliferation of CD3-stimulated CD4+ and CD8+ T cells and enhanced the proliferation of CD4+ T cells stimulated with anti-CD3/CD28 Ab. Moreover, Se-Le-30 downregulated the number of CD3-stimulated CD4+CD69+ cells, CD4+CD25+ cells, as well as CD8+CD25+ cells, and upregulated the expression of CD25 marker on CD4+ and CD8+ T cells activated with anti-CD3/CD28 Abs. Furthermore, Se-Le-30 enhanced the synthesis of IFN-γ by the unstimulated and anti-CD3/CD28-stimulated PBMCs, inhibited synthesis of IL-2 and IL-4 by CD3-stimulated cells, and augmented the synthesis of IL-6 and IL-10 by unstimulated, CD3-stimulated, and CD3/CD28-stimulated PBMCs. Together, we demonstrated that Se-Le-30 exerts immunomodulatory effects on human T lymphocytes. These observations are of importance for the prospective use of Se-Le-30 in research or as a therapeutic compound.
... 30 CD11b expression on T cells is crucial for the differentiation of pathogenic T cells, and its deficiency results in delayed and attenuated EAE. [31][32][33][34] CD11b + T cells exhibit an activated effector phenotype and their presence suggests a contribution to neuroinflammation. While we cannot confirm its exclusive presence in CLNs, the proportion of CD11b + T cells in CLNs is higher than in the blood, suggesting a strong association. ...
Aim
We aim to identify the specific CD4⁺ T‐cell subtype influenced by brain‐to‐CLN signaling and explore their role during the acute phase of traumatic brain injury (TBI).
Method
Cervical lymphadenectomy or cervical afferent lymphatic ligation was performed before TBI. Cytokine array and western blot were used to detect cytokines, while the motor function was assessed using mNss and rotarod test. CD4⁺ T‐cell subtypes in blood, brain, and CLNs were analyzed with Cytometry by time‐of‐flight analysis (CyTOF) or fluorescence‐activated cell sorting (FACS). Brain edema and volume changes were measured by 9.4T MRI. Neuronal apoptosis was evaluated by terminal deoxynucleotidyl transferase‐mediated dUTP nick end labeling (TUNEL) staining.
Results
Cervical lymphadenectomy and ligation of cervical lymphatic vessels resulted in a decreased infiltration of CD4⁺ T cells, specifically CD11b‐positive CD4⁺ T cells, within the affected region. The population of CD4⁺CD11b⁺ T cells increased in ligated CLNs, accompanied by a decrease in the average fluorescence intensity of sphingosine‐1‐phosphate receptor‐1 (S1PR1) on these cells. Administration of CD4⁺CD11b⁺ T cells sorted from CLNs into the lateral ventricle reversed the attenuated neurologic deficits, brain edema, and lesion volume following cervical lymphadenectomy.
Conclusion
The infiltration of CD4⁺CD11b⁺ T cells exacerbates secondary brain damage in TBI, and this process is modulated by brain‐to‐CLN signaling.
... The surface expression of b 2-integrin is considered to be a marker of leukocyte activation (68). Macrophage cell antigen 1 (CR3) formed by the combination of CD18 and CD11b is expressed in 7% of cytotoxic T cells, which is one of the subsets of CD8+T cells (69). Increased levels of CD18 in neutrophils were present in each stage of DR and were proportional to the severity of the retinopathy (70). ...
Background
CD8+T lymphocytes have a strong pro-inflammatory effect in all parts of the tissue, and some studies have demonstrated that its concentration in the vitreous increased significantly, suggesting that CD8+T cells play a pivotal role in the inflammatory response of diabetic retinopathy (DR). However, the infiltration of CD8+T cells in the DR retina, especially in diabetic macular edema (DME), and its related genes are still unclear.
Methods
Download the GSE16036 dataset from the Gene Expression Omnibus (GEO) database. The ImmuCellAI program was performed to evaluate the abundance of 24 immune cells including CD8+T cells. The CD8+T cell-related genes (DECD8+TRGs) between non-proliferative diabetic retinopathy (NPDR) and DME were detected via difference analysis and correlation analysis. Enrichment analysis and protein-protein interaction (PPI) network mapping were implemented to explore the potential function of DECD8+TRGs. Lasso regression, support vector machine recursive feature elimination (SVM-RFE), CytoHubba plug-in and MCODE plug-in in Cytoscape software, and Weighted Gene Co-Expression Network Analysis (WGCNA) were performed to comprehensively analyze and obtain Hub DECD8+TRGs. Hub DECD8+TRGs expression patterns were further validated in other two DR-related independent datasets. The CD8+TRG score was defined as the genetic characterization of Hub DECD8+TRGs using the GSVA sample scoring method, which can be administered to distinguish early and advanced diabetic nephropathy (DN) as well as normal and DN. Finally, the transcription level of DECD8+TRGs in DR model mouse were verified by quantitative real-time PCR (qPCR).
Results
A total of 371 DECD8+TRGs were identified, of which 294 genes were positively correlated and only 77 genes were negatively correlated. Eight genes (IKZF1, PTPRC, ITGB2, ITGAX, TLR7, LYN, CD74, SPI1) were recognized as Hub DECD8+TRGs. DR and DN, which have strong clinical correlation, have been proved to be associated with CD8+T cell-related hub genes by multiple independent data sets. Hub DECD8+TRGs can not only distinguish PDR from normal and DN from normal, but also play a role in the early and progressive stages of the two diseases (NPDR vs DME, Early DN vs Advanced DN). The qPCR transcription level and trend of Hub DECD8+TRGs in DR mouse model was basically the same as that in human transcriptome.
Conclusion
This study not only increases our understanding of the molecular mechanism of CD8+T cells in the progression of DME, but also expands people’s cognitive vision of the molecular mechanism of crosstalk of CD8+T cells in the eyes and kidneys of patients with diabetes.
... Thus, we can distinguish diverse types of CD18 integrins on the basis of their a-subunit. CD18/CD11a integrin is expressed in all leukocytes, and CD18/CD11b is expressed in neutrophils, monocytes and NK cells (100,103,104). These are the two leukocyte integrins most studied for their role in cerebral ischemia/reperfusion. Leukocyte activation increases the affinity of integrins for specific ligands on the surface of activated endothelia. ...
Despite the enormous progress in the understanding of the course of the ischemic stroke over the last few decades, a therapy that effectively protects neurovascular units (NVUs) and significantly improves neurological functions in stroke patients has still not been achieved. The reasons for this state are unclear, but it is obvious that the cerebral ischemia and reperfusion cascade is a highly complex phenomenon, which includes the intense neuroinflammatory processes, and comorbid stroke risk factors strongly worsen stroke outcomes and likely make a substantial contribution to the pathophysiology of the ischemia/reperfusion, enhancing difficulties in searching of successful treatment. Common concomitant stroke risk factors (arterial hypertension, diabetes mellitus and hyperlipidemia) strongly drive inflammatory processes during cerebral ischemia/reperfusion; because these factors are often present for a long time before a stroke, causing low-grade background inflammation in the brain, and already initially disrupting the proper functions of NVUs. Broad consideration of this situation in basic research may prove to be crucial for the success of future clinical trials of neuroprotection, vasculoprotection and immunomodulation in stroke. This review focuses on the mechanism by which coexisting common risk factors for stroke intertwine in cerebral ischemic/reperfusion cascade and the dysfunction and disintegration of NVUs through inflammatory processes, principally activation of pattern recognition receptors, alterations in the expression of adhesion molecules and the subsequent pathophysiological consequences.
... In this study, we used additional cell surface markers to define the function and fate of CD4 + and CD8 + T cell lineage subsets. Increases in both CD69 and CD11b on CD4 + and CD8 + lymphocytes have been reported following exercise previously, but not on specific T cell subsets as demonstrated in this study herein [58,[83][84][85][86][87][88][89][90][91]. An increase in CD4 + and CD8 + T cell lineage subsets expressing CD69 is evident in both groups, with a larger percentage increase post-exercise observed in healthy participants. ...
Type 1 diabetes (T1D) is a T cell mediated autoimmune disease that targets and destroys insulin-secreting pancreatic beta cells. Beta cell specific T cells are highly differentiated and show evidence of previous antigen exposure. Exercise-induced mobilisation of highly-differentiated CD8 + T cells facilitates immune surveillance and regulation. We aimed to explore exercise-induced T cell mobilisation in T1D. In this study, we compared the effects of a single bout of vigorous intensity exercise on T cell mobilisation in T1D and control participants. N=12 T1D (mean age 33.2yrs, predicted VO 2 max 32.2 mL/(kg·min), BMI 25.3Kg/m 2) and N=12 control (mean age 29.4yrs, predicted VO 2 max 38.5mL(kg.min), BMI 23.7Kg/m2) male participants completed a 30-minute bout of cycling at 80% predicted VO 2 max in a fasted state. Peripheral blood was collected at baseline, immediately post-exercise, and 1 hour post-exercise. Exercise-induced mobilisation was observed for T cells in both T1D and control groups. Total CD8 + T cells mobilised to a similar extent in T1D (42.7%; p=0.016) and controls (39.7%; p=0.001). CD8 effector memory CD45RA + (EMRA) subset were the only T cell lineage subset to be significantly mobilised in both groups though the percentage increase of CD8 + EMRA was blunted in T1D (T1D (26.5%) p=0.004, control (66.1%) p=0.010). Further phenotyping of these subsets revealed that the blunting was most evident in CD8 + EMRA that expressed adhesion (CD11b: T1D 37.70%, Control 91.48%) and activation markers (CD69: T1D 29.87%, Control 161.43%), and appeared to be the most differentiated (CD27-CD28-: T1D 7.12%, Control 113.76%). CD4 + T cells mobilised during vigorous intensity exercise in controls (p=0.001), but not in T1D. The blunted mobilisation response of particular T cell subsets was not due to CMV serostatus or apparent differences in exertion during the exercise bout as defined by heart rate and RPE. Predicted VO 2 max showed a trend to be lower in the T1D group than the control group but is unlikely to contribute to this blunted response. We postulate the reasons for a blunted mobilisation of differentiated CD8 + EMRA cells includes differences in blood glucose, adrenaline receptor density, and sequestration of T cells in the pancreas of T1D participants. In conclusion, mobilisation of CD8 + EMRA and CD4 + subsets T cells is decreased in people with T1D during acute exercise.
... In our analysis of PBMC subpopulations this cell subset constituted 7% of cells in the PBMC pool, and was reduced to 1% following DQT treatment ( Fig. 3A and B). In addition (Fig. 3A), all cells in this subset expressed the CD11b antigen, present on natural killer cells (NK) [32]. Although the role of NK cells in allograft rejection is equivocal [33], this cell subpopulation may contribute to graft rejection using various mechanisms [34]. ...
Azaphenothiazines are predominantly immunosuppressive compounds. We evaluated the efficacy of an azaphenothiazine derivative, 6-chloroethylureidoethyldiquino[3,2-b;2′,3′-e][1,4]thiazine (DQT) in prolongation of survival of skin allografts between BALB/c and C57Bl/6 mice. The mice were treated intraperitoneally (i.p.) with 100 μg of DQT on alternate days, on days 1–13 of the experiment (7 doses). The effect of DQT on a two-way mixed lymphocyte reaction (MLR) in the human model, as well as its effect on production of TNF α and IL-10 in a whole blood cell culture, stimulated by lipopolysaccharide (LPS), were evaluated. In addition, DQT effects were investigated regarding the proportion of T cell subsets in human peripheral blood lymphocytes (PBMC) by flow cytometry. Lastly, the effect of DQT on expression of signaling molecules involved in pro apoptotic pathways was determined by RT PCR. The results showed that DQT significantly extended skin graft survival. The compound also strongly suppressed two-way MLR in the human model at a concentration range of 2.5–5.0 μM. In addition, DQT inhibited LPS-inducible TNF α but not IL-10 production. The compound preferentially caused a loss of the CD3-CD8+CD11b + PBMC cell subset, and transformed CD3+CD8+ high into CD3+CD8+ low cells. Lastly, we demonstrated significant increases in expression of caspases (in particular caspase 8) and of p53 in a culture of Jurkat T cells. We conclude that the immunosuppressive actions of the compound in allograft rejection may be predominantly associated with induction of cell apoptosis and inhibition of TNF α production. The apoptosis could be predominantly selective for the CD3-CD8+CD11b + cell phenotype.
The CD40–CD40 ligand (CD40L) dyad represents a scientific and clinical field that has raised many controversies in the past and cannot be clearly defined as being an either beneficial or harmful pathway. Being crucially involved in physiological immunological processes as well as pathological inflammatory reactions, the signaling pathway has been recognized as a key player in the development of both autoimmune and cardiovascular disease. Even though the possibilities of a therapeutic approach to the dyad were recognized decades ago, due to unfortunate events, detailed in this review, pharmacological treatment targeting the dyad, especially in patients suffering from atherosclerosis, is not available. Despite the recent advances in the treatment of classical cardiovascular risk factors, such as arterial hypertension and diabetes mellitus, the treatment of the associated low-grade inflammation that accounts for the progression of atherosclerosis is still challenging. Low-grade inflammation can be detected in a significant portion of patients that suffer from cardiovascular disease and it is therefore imperative to develop new therapeutic strategies in order to combat this driver of atherosclerosis. Of note, established cardiovascular drugs such as angiotensin-converting enzyme inhibitors or statins have proven beneficial cardiovascular effects that are also related to their pleiotropic immunomodulatory properties. In this review, we will discuss the setbacks encountered as well as new avenues discovered on the path to a different, inflammation-centered approach for the treatment of cardiovascular disease with the CD40–CD40L axis as a central therapeutic target.
Complement receptors CR3 (CD11b/CD18) and CR4 (CD11c/CD18) of myeloid cells are known for long to participate in actin linked functions like phagocytosis, adhesion, and migration. The expression and role of these two β2-integrins however, in human B lymphocytes have only scarcely been studied so far, although it has been shown recently that CD11c⁺ B cells are mainly memory cells. In our systematic study we investigated B cells isolated from tonsils and peripheral blood of healthy donors. We found, that while only 5% of resting tonsillar B cells expressed CD11c, their number increased up to 26% after 3 days of BCR stimulation. Lower, but still remarkable percentage of B lymphocytes were positive for CD11c after stimulation via TLR9 alone or via TLR9 and BCR simultaneously. At the same time, we detected no significant expression of CD11b on resting or activated tonsillar B cells. Blood B lymphocytes showed a similar expression pattern of both β2-integrins. We demonstrated that CD11c molecules appearing on the surface of B cells are newly synthesized, reaching the number of 9,500 per activated B cell. We found that CR4 expressing B cells belong to the memory pool and the increase of CD11c expression on tonsillar B cells upon BCR mediated activation occurs parallel with class switching. Analysis of the function of CD11c revealed, that this β2-integrin contributes to the adhesion and migration of activated B lymphocytes. We also demonstrated that the CR4 mediated adhesion promotes the proliferation of the BCR activated cells. Our studies are the first to demonstrate that CD11c expressed on BCR-activated human B cells are not only passive markers but functional drivers of memory B cell responses.
Objective: CD11b is an integrin molecule located on the surface of leukocytes. CD11b is involved in the processes of cell adhesion and migration. Expression of CD11b increases during inflammation. Therefore, this study was aimed at the evaluation of concentrations of CD11b in the amniotic fluid from pregnancies complicated by preterm prelabor rupture of the membranes (PPROM), with respect to the presence of microbial invasion of the amniotic cavity (MIAC), intra-amniotic inflammation (IAI), and microbial-associated IAI (the presence of both MIAC and IAI).
Methods: Eighty women with singleton pregnancies complicated by PPROM were included. Amniotic fluid samples were obtained by transabdominal amniocentesis. Amniotic fluid CD11b concentrations were determined by enzyme-linked immunosorbent assay. MIAC was determined by a non-cultivation approach. IAI was defined by a bedside amniotic fluid interleukin-6 concentration ≥745 pg/mL.
Result: Women with MIAC or microbial-associated IAI had higher CD11b concentrations in the amniotic fluid than women without these complications (with MIAC: median 0.31 ng/mL versus without MIAC: median 0.17 ng/mL, p = .001; with microbial associated-IAI: median 0.35 ng/mL versus without microbial-associated IAI: median 0.16 ng/mL; p =.02). The presence of IAI was not associated with elevated CD11b concentrations. A weak negative correlation was found between amniotic fluid CD11b concentrations and interleukin-6 concentrations (rho = 0.26; p = .02).
Conclusions: MIAC and microbial-associated IAI are characterized by higher amniotic fluid CD11b concentrations in pregnancies complicated by PPROM.
A viral inhibitor(s) is released in the supernate of mixed cultures containing human or mouse lymphocytes and cells from certain lines. The inhibitor is active against a variety of unrelated viruses and is a protein that is not toxic for cells. It does not inactivate viruses directly, but inhibits viral replication through an intracellular mechanism that involves synthesis by the cells of both RNA and protein. These characteristics identify the inhibitor as an interferon. The anti-viral activity is contained in at least two molecular species, of approximately 25,000 and 45,000 daltons, respectively. In addition to the anti-viral activity, the supernates of the mixed cultures display an anti-cellular activity, the inhibition of DNA synthesis and of cell multiplication. The anti-viral and the anti-cellular activities are positively correlated in supernates from various cultures and in partially purified preparations. The human cell population responsible for interferon production is composed mainly of Fc-receptor positive, surface immunoglobulin negative, non-T-cell lymphocytes. The ability of certain cell lines to induce interferon seems to be preferentially associated with tumor origin or with in vitro transformation by certain viruses (Epstein-Barr virus, murine sarcoma virus).
Natural killer (NK) cells have been defined as CD3 epsilon-, CD16+ and/or CD56+ lymphocytes that mediate major histocompatibility complex (MHC)-unrestricted cytotoxicity against certain tumors and virus-infected cells. Unlike T lymphocytes, NK cells do not rearrange or productively express T cell antigen receptor genes. Moreover, NK cells from adults have been reported to not express CD3 gamma, delta, or epsilon proteins on the cell surface or in the cytoplasm. Nonetheless, NK cells have been shown to share a number of antigenic and functional similarities to T cells that suggest the possibility of common origins. In this report, we demonstrate that functional NK cells exist in liver at early stages of human embryonic development. Freshly isolated fetal NK cells mediated MHC-unrestricted cytotoxicity against NK-sensitive targets and acquired the ability to lyse NK-resistant tumors after overnight culture in interleukin 2. Unlike adult NK cells, freshly isolated fetal liver NK cells and clones derived from these cells, as well as a subset of cord blood NK cells, express substantial levels of CD3 delta and CD3 epsilon proteins in the cytoplasm. Expression of CD3 epsilon and CD3 delta transcripts and cytoplasmic proteins in fetal NK clones was confirmed by polymerase chain reaction and Western blot analysis. These findings support the concept that NK and T cells may arise from a common progenitor that expresses components of the CD3 complex. Alternatively, it is possible that the cytoplasmic CD3 delta, epsilon+ fetal NK cells represent a distinct subpopulation of NK cells that is predominant in the fetus, but replaced by the cytoplasmic CD3 delta,epsilon- adult NK cell population after embryogenesis.
Cells responsible for the natural killer (NK) effect in the human blood can be collected in the low-density lymphocyte subset and the majority of them express CR3. In addition to the iC3b binding site the CR3 molecules possess an epitope which binds beta-glucan. Ligands of this site can deliver activation signals to CR3-carrying monocytes and neutrophils. We found that the function of NK cells was also potentiated by preincubation with beta-glucan. The treatment increased the proportion of target-binding lymphocytes and of the damaged target cells in the conjugates. The monoclonal antibody OKM-1, directed to the beta-glucan-binding site of CR3, abrogated this effect. Another CR3-reactive monoclonal antibody, M522, known to activate monocytes and neutrophils, enhanced the NK function.
The mouse monoclonal antibody MN-41 has been characterized as an anti-human iC3b receptor (CR3) antibody on the basis of its ability to inhibit the binding of EC3bi indicator cells to monocytes and polymorphonuclear cells while having no effect on their Fc and C3b receptors. Use of this monoclonal antibody in indirect immunofluorescence studies with dual fluorochrome labels established the widespread distribution of CR3 in man—detected on 97% of circulating monocytes, 90% of granulocytes, 17% of T lymphocytes, and 28% of B lymphocytes while erythrocytes and platelets were negative. Isolated peritoneal macrophages were 90% positive while pulmonary macrophages were 83% positive. Monocytes in culture for 8 days were universally positive. Within tissues, CR3 reactive cells displayed unique topographical localization within the spleen, tonsil, and lymph nodes whereas numerically fewer positive cells were scattered within hepatic sinusoids, papillary dermis, medullary regions of the thymus, and submucosa of the small intestine. CR3 was not detected on Raji cells, glomerular epithelial cells, or placental stromal cells. Immunoprecipitation and electrophoretic separation of two glycoprotein bands of 150,000 and 95,000 Da suggest possible structural homology of CR3 in man and mouse (Mac-1 antigen).
The modulation of adhesion molecules on human large granular lymphocytes (LGL) by interleukin (IL)-2 was investigated both in vivo and in vitro. Intercellular adhesion molecule-1 (ICAM-1; CD54) expression increased on LGL of cancer patients receiving IL-2 adoptive immunotherapy. ICAM-1 expression on LGL isolated by Percoll gradient centrifugation, LGL purified, and expanded by adherence to plastic surfaces and LGL identified by Leu 19 (CD56) monoclonal antibody were increased significantly in response to IL-2 in vitro. Exposure of LGL to IL-1, interferon (IFN)-gamma, and tumor necrosis factor (TNF) in vitro did not induce ICAM-1. The expression of LFA-1 (CD11a/CD18), a receptor for ICAM-1, and other leukocyte adhesion molecules, including Mac-1 (CD11b/CD18) and p150,95 (CD11c/CD18), was only maintained by IL-2. IL-2 induction of ICAM-1 and the maintenance of CD18 complex expression on small lymphocytes separated by Percoll gradients were similar to that on LGL. We conclude that IL-2 enhances the expression of ICAM-1 on multiple human lymphocyte populations including LGL effectors. Expression of the CD18 complex on LGL does not appear to be highly regulated by IL-2. These findings may have implications relevant to the role of these adhesion molecules in the activities of LGL modulated by IL-2.
Human natural killer (NK) cells can be subdivided into two populations based on the density of cell surface CD56 antigen. The great majority (approximately 90%) of NK cells express CD56 at low levels (the CD56dim phenotype), whereas a small NK cell subset (approximately 10%) exhibits approximately fivefold greater density of surface CD56. Exposure to exogenous interleukin 2 (IL 2) induces tenfold greater proliferation of CD56bright cells compared to CD56dim lymphocytes, even though both subsets constitutively express similar levels of intermediate affinity IL 2 receptor (IL 2R) p75 chains. Incubation with IL 2 alone or irradiated target cells alone could induce expression of the IL 2R p55 chain by both CD56bright and CD56dim NK cells; a combination of both stimuli was most effective. IL 2R p55 induction was evident after co-culture of NK cells with both NK-sensitive and NK-resistant cell lines or with antibody-coated target cells. Activation of NK cells with IL 2 plus target cells resulted in enhanced proliferation compared to activation with IL 2 alone; target cells alone did not induce significant proliferation. Although both NK cell subsets appeared to express high-affinity IL 2R p75/p55 heterodimers after stimulation with target cells and IL 2, proliferation of CD56dim cells remained minimal after such activation; activated CD56dim cells consistently demonstrated less proliferation to IL 2 than did resting CD56bright cells. In contrast, CD56bright NK cells exhibited even greater proliferation after stimulation with target cells. Almost all CD56dim NK cells expressed CD16 (Fc gamma R III) as well as the NK zeta chain, whereas less than 50% of CD56bright cells express either CD16 or zeta. CD56bright and CD56dim lymphocytes, thus, appear to represent distinct subpopulations of NK cells with different functional activities. Unlike CD56bright cells, CD56dim NK cells do not proliferate optimally to IL 2, even after the latter have been stimulated to express both IL 2R p55 and IL 2R p75. Efficient proliferation of CD56dim NK cells may, thus, require additional or alternative signals.