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IL-15 regulates transcriptional activity and alters histone chromatin modification specifically at the V5 gene segment independent of RAG-mediated Tcrg rearrangement in thymocytes.(a) Semiquantitative RT-PCR assay (one of four experiments) for relative amounts of unrearranged sterile V gene–specific transcripts in thymocytes of Rag1-/- mice exposed to various amounts of IL-15. Wedges, fivefold serial cDNA sample dilutions. RT-, no reverse transcriptase (control). (b,c) Chromatin immunoprecipitation assays of relative AcH3 patterns across the Tcrg-C1 cluster in thymocytes of Rag1-/- mice with various amounts of IL-15. (b) Agarose gel electrophoresis. Input DNA control was serially diluted fourfold. (c) Quantitative real-time PCR assay. Bound/input DNA ratios are the mean s.e.m. of triplicate data points from one representative experiment of three using pooled thymocytes from four mice of each genotype. (d) Quantitative real-time chromatin immunoprecipitation assay of relative AcH3 patterns across the Tcrg-C1 cluster in sorted (more than 95% pure) precursor triple-negative thymocytes of Il15-Tg or control B6 mice. Bound/input DNA ratios are the mean s.e.m. of triplicate data points. Data represent one of two independent experiments with similar results.
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The gammadelta T cells are prevalent in the mucosal epithelia and are postulated to act as 'sentries' for maintaining tissue integrity. What these gammadelta T cells recognize is poorly defined, but given the restricted T cell receptor (TCR) repertoire, the idea that they are selected by self antigens of low complexity has been widely disseminated....
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... and can be used to predict the developmentally regulated Tcrg rearrangement pattern 35 . In adult Rag1 -/-thymocytes, unrearranged V g 2 and V g 5 gene segment-specific transcripts were detectable, whereas V g 3 gene-specific sterile tran- scripts were absent, reflecting the developmental stage-specific rear- rangement pattern of these V genes (Fig. 3a). In addition, the V g 2 sterile transcripts were relatively more abundant than those of V g 5 in adult Rag1 -/-thymocytes, correlating with the TCR repertoire of gd thymocytes in normal B6 mice (among adult gd thymocytes, about 50% are V g 2 + , whereas about 5% express V g 5). Notably, whereas the V g 2 (and V g 1.1 or V g 4; data not ...
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... histone acetylation pattern correlated strongly with the sterile transcription assay. Unlike the pattern in Il7r -/-mice, thymocytes of Rag1 -/-mice showed a histone acetylation pattern consistent with adult V g gene usage: E Cg1 and HsA were active, as shown by the relatively large amounts of colocalized AcH3 (Fig. 3b,c). In addition, among the V g gene segments, the V g 2 gene was associated with the most acetylated histones, whereas the fetal-specific V g 3 gene was hypoacetylated, consistent with published results 36 . The V g 5 gene had small but notable amounts of acetylated histone bound to it (Fig. 3b), again correlating with the low frequency ...
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... by the relatively large amounts of colocalized AcH3 (Fig. 3b,c). In addition, among the V g gene segments, the V g 2 gene was associated with the most acetylated histones, whereas the fetal-specific V g 3 gene was hypoacetylated, consistent with published results 36 . The V g 5 gene had small but notable amounts of acetylated histone bound to it (Fig. 3b), again correlating with the low frequency of V g 5 + gd thymocytes in normal adult B6 mice. Similar results have been interpreted to support the chromatin accessibility model of develop- mental regulation of V(D)J recombination at the Tcrg locus 36 . Notably, in the absence of IL-15, there were consistently fewer acetylated histones on ...
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... with the low frequency of V g 5 + gd thymocytes in normal adult B6 mice. Similar results have been interpreted to support the chromatin accessibility model of develop- mental regulation of V(D)J recombination at the Tcrg locus 36 . Notably, in the absence of IL-15, there were consistently fewer acetylated histones on V g 5 gene segments (Fig. 3b,c). This pattern was present in all experiments using thymocytes and intestinal intraepithelial cells (and was much more prominent in the latter; discussed below) and was consistent with results from the sterile transcription assay (Fig. 3a). However, the difference was difficult to quantify because of the low basal acetylated histone ...
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... Notably, in the absence of IL-15, there were consistently fewer acetylated histones on V g 5 gene segments (Fig. 3b,c). This pattern was present in all experiments using thymocytes and intestinal intraepithelial cells (and was much more prominent in the latter; discussed below) and was consistent with results from the sterile transcription assay (Fig. 3a). However, the difference was difficult to quantify because of the low basal acetylated histone detectable at the V g 5 gene of normal thymic precursors using this assay. In contrast, in thymocytes of Il15-Tg-Il7r -/-mice, there was much more AcH3 at the V g 5 gene, again confirming the sterile transcription pattern. The H3 acetylation ...
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... Il7r -/-and Rag1 -/-mice were also present in normal thymocytes, we sorted the triple-negative thymic precursor cell subset (CD3 -CD4 - CD8 -) from B6 mice and repeated the chromatin immunoprecipita- tion assay. Increased expression of IL-15 led to enhanced association of AcH3 specifically with the V g 5 gene segment in normal precursor cells (Fig. 3d). These results collectively demonstrate that the basis for IL-15-mediated generation of V g 5 + gd T cells is the selective enhancement of V g 5 gene segment activity before the RAG-mediated Tcrg ...
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... V g 5 gene segment (Fig. 4b). This result was consistent with the sterile transcription assay showing biased V g 5 gene activity (Fig. 4a) and strongly supports the idea of the existence of distinct 'pre-rearrangement' V g segment accessibility in favor of the V g 5 gene in immature intestinal intraepithelial cells versus thymocyte precur- sors (Fig. 3a). Critically, this basal V g 5 gene specific H3 acetylation was dependent on IL-15, as demonstrated by the diminution in AcH3 detected in Il15 -/-Rag1 -/-intraepithelial cell preparations (Fig. 4b,c). Conversely, increased IL-15 in the intestines of Rag1 -/- (Fig. 4b,c) and Il7r -/-mice (Fig. 4d,e) resulted in greatly increased AcH3 ...
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The interleukin-2 receptor beta chain (IL-2R beta) is expressed on a variety of hematopoietic cell types, including natural killer (NK) cells and nonconventional T lymphocyte subsets such as intestinal intraepithelial lymphocytes (IEL). However, the importance of IL-2R beta-mediated signaling in the growth and development of these cells has yet to...
In this study, the role of IL-15 and its regulation by the transcription factor IFN regulatory factor-1 (IRF-1) in murine V gamma 3 T cell development and activity is assessed. Compared with wild-type (WT) mice, reduced numbers of mature V gamma 3 cells were found in the fetal thymus of IL-15(-/-) mice, while IRF-1(-/-) mice displayed normal freque...
Citations
... Upon binding to its receptors, IL-15 activates JAK-STAT, PI3K, and MAPK pathways, induces expression of antiapoptotic Bcl-2 and proto-oncogenes c-Myc, c-Fos, c-Jun, c-Myc, and NF-kB, and promotes cell proliferation and maturation (83)(84)(85)(86). IL-15 and IL-15Ra are expressed by enterocytes and dendritic cells in lamina propria, forming an IL-15/IL-15Ra complex transpresented to gd T cells (87,88). IECs are the main source of IL-15 in the intestine, and IEC-specific IL-15 knockout leads to a decrease in gd T percentage and absolute number in the intestine and to impairment of functional maturation, such as the decrease in granzyme B expression, whereas IL-15 knockout in blood vascular endothelial cells (BECs) and hematopoietic cells does not affect intestinal gd T cells (88). ...
Located in the frontline against the largest population of microbiota, the intestinal mucosa of mammals has evolved to become an effective immune system. γδ T cells, a unique T cell subpopulation, are rare in circulation blood and lymphoid tissues, but rich in the intestinal mucosa, particularly in the epithelium. Via rapid production of cytokines and growth factors, intestinal γδ T cells are key contributors to epithelial homeostasis and immune surveillance of infection. Intriguingly, recent studies have revealed that the intestinal γδ T cells may play novel exciting functions ranging from epithelial plasticity and remodeling in response to carbohydrate diets to the recovery of ischemic stroke. In this review article, we update regulatory molecules newly defined in lymphopoiesis of the intestinal γδ T cells and their novel functions locally in the intestinal mucosa, such as epithelial remodeling, and distantly in pathological setting, e.g., ischemic brain injury repair, psychosocial stress responses, and fracture repair. The challenges and potential revenues in intestinal γδ T cell studies are discussed.
... The intestinal mucosa can be used as an example. Under normal circumstances, γδT cells rely on the communication between aryl hydrocarbon receptors (AhRs) and interleukin (IL)-15 produced by intestinal epithelial cells stimulated by microorganisms [18]. In GF models, Bifidobacteriaceae and Bacillaceae are positively related to intestinal γδT cells, while bacteria belonging to the families Rhodospirillaceae, Flavobacteriaceae and Prevotellaceae have the opposite relationship [16]. ...
γδT cells are a mixture of innate programming and acquired adaptability that bridge the adaptive and innate immune systems. γδT cells are mainly classified as tissue-resident Vδ1 or circulating Vδ2 γδT cells. In the tumor microenvironment, tumor immunity is influenced by the increased quantity and phenotype plasticity of γδT cells. Commensal bacteria are ubiquitous in the human body, and they have been confirmed to exist in various tumor tissues. With the participation of commensal bacteria, γδT cells maintain homeostasis and are activated to affect the development and progression of tumors. Here, we summarize the relationship between γδT cells and commensal bacteria, the potential protumor and antitumor effects underlying γδT cells, and the new developments in γδT cell-based tumor therapy which is expected to open new opportunities for tumor immunotherapy.
... Compared with the recombination of TCRb V-DJ and TCRa V-J, the assembly of TCRgd occurs within a short range of TCRg clusters or local segments of TCRd in the TCRa locus, depending on their own enhancers. The accessibility and recombination of the TCRg locus rely on IL-7/IL-15-Stat5 signaling (115,116). Therefore, we speculate that the low RAG1 and RAG2 protein levels are sufficient for RAG-RC to drive local TCR recombination in cooperation with cytokine signaling. ...
Cell type-specific gene expression is driven through the interplay between lineage-specific transcription factors (TFs) and the chromatin architecture, such as topologically associating domains (TADs), and enhancer-promoter interactions. To elucidate the molecular mechanisms of the cell fate decisions and cell type-specific functions, it is important to understand the interplay between chromatin architectures and TFs. Among enhancers, super-enhancers (SEs) play key roles in establishing cell identity. Adaptive immunity depends on the RAG-mediated assembly of antigen recognition receptors. Hence, regulation of the Rag1 and Rag2 (Rag1/2) genes is a hallmark of adaptive lymphoid lineage commitment. Here, we review the current knowledge of 3D genome organization, SE formation, and Rag1/2 gene regulation during B cell and T cell differentiation.
... This signaling pathway induces γδ T-cell resistance to activation-induced cell death and proliferation 83 . However, gut-residing intraepithelial γδ T cells tend to be relatively more dependent on IL-15 84 . On the other hand, IFNγ-producing γδ T cells require IL-15 and IL-2, but not IL-7 22 . ...
T cells of the γδ lineage are unconventional T cells with functions not restricted to MHC-mediated antigen presentation. Because of their broad antigen specificity and NK-like cytotoxicity, γδ T-cell importance in tumor immunology has been emphasized. However, some γδ T-cell subsets, especially those expressing IL-17, are immunosuppressive or tumor-promoting cells. Their cytokine profile and cytotoxicity are seemingly determined by cross-talk with microenvironment components, not by the γδTCR chain. Furthermore, much about the TCR antigen of γδ T cells remains unknown compared with the extreme diversity of their TCR chain pairs. Thus, the investigation and application of γδ T cells have been relatively difficult. Nevertheless, γδ T cells remain attractive targets for antitumor therapy because of their independence from MHC molecules. Because tumor cells have the ability to evade the immune system through MHC shedding, heterogeneous antigens, and low antigen spreading, MHC-independent γδ T cells represent good alternative targets for immunotherapy. Therefore, many approaches to using γδ T cells for antitumor therapy have been attempted, including induction of endogenous γδ T cell activation, adoptive transfer of expanded cells ex vivo, and utilization of chimeric antigen receptor (CAR)-T cells. Here, we discuss the function of γδ T cells in tumor immunology and their application to cancer therapy.
... The mixed results appeared in clinical trials suggest that the therapeutical use of γδ T cells can be further improved. Rapid advances in molecular biology of IL-15, and its receptor complex have provided a rationale for more optimal use of this cytokine in attempts to expand and activate immune effectors in patients with cancer [19,20]. In this study, we demonstrate that IL-15 are able to induce γδ T cells proliferation and significantly upgrade γδ T cells cytotoxicity against RCC cell lines. ...
Adoptive transfer of γδ T cells is an attractive approach for cell-based immunotherapy in treatment of renal cell carcinoma (RCC). Interleukin-15 (IL-15) is the key physiological cytokine that regulates γδ T cell differentiation, proliferation and survival. In this work, we determined that IL-15 have the capacity to enhance the anti-tumoral functions of γδ T cells. IL-15 can induce the upregulation of cytotoxicity-associated molecules on the γδ T cell surface, incite γδ T cell proliferation and decrease apoptosis. Moreover, the enhanced cytotoxicity of IL-15-induced γδ T cell was dependent on the interaction of NKG2D and MICA. Most importantly, we found that IL-15-induced γδ T cells effectively suppressed the tumor growth in vivo and prolonged the survival time of RCC-bearing patient‑derived xenograft (PDX) mice. These results are important for the prospective use of γδ T cells in clinical practice when designing novel cell-based immunotherapies against RCC.
... As demonstrated in murine model, the development and the homeostasis of γδT cells depend on IL-7, IL-15 and IL-2 cytokines (Malissen et al., 1997;Baccala et al., 2005). In the dermis, IL-7 supports the development and the survival of resident γδT cells and promotes the expansion of human and murine IL-17-producing γδT cells (Zhao et al., 2005). Concerning IL-15, it plays an important role in sustaining the intraepithelial γδ T cell group present in the gut . ...
T cells is a minor subgroup of T lymphocytes expressing γδ-T Cell Receptor (TCR), with many subsets, dominated by Vδ2 and Vδ1. γδT cells recognize antigens independently of the context of MHC class I, MHC class II, or CD1 presenting molecules. However, this recognition requires the expression of the transmembrane Butyrophilin proteins by the presenting cells. Their activation is controlled by many surface receptors, namely, co-stimulatory receptors, cytokines receptors, NK receptors and inhibitory receptors. Once activated, γδT cells polarize into Th1, Th2, Th17, follicular T helper or Treg cells. They can play direct anti infectious and antitumor roles through perforin-granzyme molecules, FasL and Tumor-necrosis-factor Related Apoptosis Inducing Ligand (TRAIL), antibody-dependent cellular cytotoxicity and by IFN-γ and TNF-α cytokine's release. They also exert an indirect antitumor activity by cooperating with B cells, dendritic cells, αβT cells and NK cells. Additionally, γδT cells can infiltrate solid cancers and display a selective cytolytic activity. Conversely, γδT cells might promote cancer progression either directly through IL17 and/or VEGF, or indirectly by impairing other antitumor immune cell activities. Given its complex functions, γδT cell-based immunotherapy seems efficient and well tolerated, yet needs to overcome many obstacles including those related to the tumor environment.
... As a result, while a high dose of IL-2 is required to preferentially expand effector T cells, Treg cells are able to respond rapidly to IL-2 at low concentrations (at single doses from 0.33 to 4.5 million IU) [69,70]. Additionally, the presence of IL-15 stimulates the production and recruitment of intestine intraepithelial γδ T cells; these results have not been observed with IL-2 [71,72]. Ex vivo cultured γδ T cells in the presence of IL-15 displayed prolonged survival and improved effector functions, as compared with IL-2. ...
Simple Summary
Emerging knowledge of the two type I cytokine family members IL-2 and IL-15 has led to critical therapeutic implications for cancer treatment. Here we discuss the distinct roles of IL-2 and IL-15 in activating various functions of T and NK cells with a particular focus on the signals that contribute to the resistance of immune suppressive factors within the tumor microenvironment. We furthermore highlight efforts to modify these cytokines to amplify their antitumor efficacy while minimizing toxicity. Finally, we summarize the clinical applications of IL-2 and IL-15 in metastatic cancer.
Abstract
The type I cytokine family members interleukin-2 (IL-2) and IL-15 play important roles in the homeostasis of innate and adaptive immunity. Although IL-2 and IL-15 receptor complexes activate similar signal transduction cascades, triggering of these receptors results in different functional activities in lymphocytes. While IL-2 expands regulatory T cells and CD4+ helper T cells, IL-15 supports the development of central memory T cells and NK cells. Recent data have provided evidence that IL-2 and IL-15 differ in their ability to activate T and NK cells to resist various forms of immune suppression. The diverse roles of these two cytokines have on immune cells lead to critical therapeutic implications for cancer treatment. In this review, we discuss the distinct roles of IL-2 and IL-15 in activating various functions in T and NK cells with a particular focus on the signals that participate in the resistance of tumor-derived immune suppressive factors. Furthermore, we summarize current clinical applications of IL-2 and IL-15 in metastatic malignancies, either as monotherapy or in combination with other agents, and highlight the future trends for research on these cytokine-based immunotherapies.
... However, the role of IL-15 in the development of γδ IELs diverges from its role in DETC development. While in DETC development, IL-15 signaling appears to impact the proliferation and survival of precursors [45], in γδ IEL development IL-15 signaling controls the accessibility of the Vγ5 gene segment for rearrangement by inducing chromatin modifications [90]. Additionally, in the absence of IL-15 signaling the γδ IEL compartment is significantly reduced [91,92], and this cytokine has also been described to play a role in the differentiation [93], proliferation [94], survival [95,96], and motility [97] of γδ IELs. ...
While forming a minor population in the blood and lymphoid compartments, T cells are significantly enriched within barrier tissues. In addition to providing protection against infection, these tissue-resident T cells play critical roles in tissue homeostasis and repair. T cells in the epidermis and intestinal epithelium produce growth factors and cytokines that are important for the normal turnover and maintenance of surrounding epithelial cells and are additionally required for the efficient recognition of, and response to, tissue damage. A role for tissue-resident T cells is emerging outside of the traditional barrier tissues as well, with recent research indicating that adipose tissue-resident T cells are required for the normal maintenance and function of the adipose tissue compartment. Here we review the functions of tissue-resident T cells in the epidermis, intestinal epithelium, and adipose tissue, and compare the mechanisms of their activation between these sites.
... IL-15 supports the survival of CD8αα IELs through up-regulating their Bcl-2 expression (8)(9)(10)(11). In addition, IL-15 controls the development of CD8αα + TCRαβ + IELs through T-bet (12) and regulates the generation of the TCR repertoire of TCRγδ + IELs (13). As IEL precursors (IELPs) originate from the thymus and reside in the intestine as mature CD8αα IELs, it is unclear from where and how they receive IL-15 signals. ...
Interleukin-15 (IL-15) is a cytokine critical for maintenance of intestinal intraepithelial lymphocytes (IELs), especially CD8αα+ IELs (CD8αα IELs). In the intestine, IL-15 is produced by intestinal epithelial cells (IECs), blood vascular endothelial cells (BECs) and hematopoietic cells. However, the precise role of intestinal IL-15 on IELs is still unknown. To address the question, we generated two kinds of IL-15 conditional knockout (IL-15cKO) mice: villin-Cre (Vil-Cre) and Tie2-Cre IL-15cKO mice. IEC-derived IL-15 was specifically deleted in Vil-Cre IL-15cKO mice, whereas IL-15 produced by BECs and hematopoietic cells is deleted in Tie2-Cre IL-15cKO mice. The cell number and frequency of CD8αα IELs and NK IELs were significantly reduced in Vil-Cre IL-15cKO mice. By contrast, CD8αα IELs were unchanged in Tie2-Cre IL-15cKO mice, indicating that IL-15 produced by BECs and hematopoietic cells is dispensable for CD8αα IELs. Expression of an anti-apoptotic factor, Bcl-2, was decreased, whereas Fas expression was increased in CD8αα IELs of Vil-Cre IL-15cKO mice. Forced expression of Bcl-2 by a Bcl-2 transgene partially restored CD8αα IELs in Vil-Cre IL-15cKO mice, suggesting that some IL-15 signal other than Bcl-2 is required for maintenance of CD8αα IELs. Furthermore, granzyme B production was reduced, whereas PD-1 expression was increased in CD8αα IELs of Vil-Cre IL-15cKO mice. These results collectively suggested that IEC-derived IL-15 is essential for homeostasis of IELs by promoting their survival and functional maturation.
... A large fraction of γδ IEL express the Vγ5 TCR (79,183). The preferential expression of Vγ5 is controlled at the chromatin level by IL-15-STAT5 signals, which regulate the accessibility of the Vγ5 gene and favor its expression in thymocytes and immature IEL (184). Despite the overrepresentation of the Vγ5 TCR among γδ IEL, the overall γδTCR repertoire in the intestinal epithelium is diverse. ...
Epithelial and mucosal barriers are critical interfaces physically separating the body from the outside environment and are the tissues most exposed to microorganisms and potential inflammatory agents. The integrity of these tissues requires fine tuning of the local immune system to enable the efficient elimination of invasive pathogens while simultaneously preserving a beneficial relationship with commensal organisms and preventing autoimmunity. Although they only represent a small fraction of circulating and lymphoid T cells, γδ T cells form a substantial population at barrier sites and even outnumber conventional αβ T cells in some tissues. After their egress from the thymus, several γδ T cell subsets naturally establish residency in predetermined mucosal and epithelial locations, as exemplified by the restricted location of murine Vγ5⁺ and Vγ3Vδ1⁺ T cell subsets to the intestinal epithelium and epidermis, respectively. Because of their preferential location in barrier sites, γδ T cells are often directly or indirectly influenced by the microbiota or the pathogens that invade these sites. More recently, a growing body of studies have shown that γδ T cells form long-lived memory populations upon local inflammation or bacterial infection, some of which permanently populate the affected tissues after pathogen clearance or resolution of inflammation. Natural and induced resident γδ T cells have been implicated in many beneficial processes such as tissue homeostasis and pathogen control, but their presence may also exacerbate local inflammation under certain circumstances. Further understanding of the biology and role of these unconventional resident T cells in homeostasis and disease may shed light on potentially novel vaccines and therapies.
