Induction of allopeptide-specific human CD4+CD25+ regulatory T cells ex vivo

Although CD4+CD25+ regulatory T cells are pivotal in the prevention of autoimmunity and appear to mediate transplantation tolerance, little is known concerning their antigen specificity. Here we describe the induction of a human CD4+CD25+ regulatory T-cell line specific for a defined peptide alloantigen (human leukocyte antigen A2 [HLA-A2] 138-170) by priming purified CD4+CD25+ cells ex vivo. The regulatory cells were anergic and retained their ability to suppress antigen-driven responses of CD4+CD25- cells. They inhibited not only interleukin 2 (IL-2) secretion by CD4+CD25- T cells specific for the same peptide but also direct alloresponse of naive CD4+CD25- T cells stimulated by semiallogeneic dendritic cells (DCs) in the presence of the peptide ("linked suppression"). They also suppressed the response of CD4+ T cells specific for viral and bacterial antigens. The suppressive T-cell line showed sustained high CD25 expression. These findings suggest that peripheral CD4+CD25+ regulatory cells are a precommitted cell lineage from which cells with specificity for non-self-peptides can be selected. This may pave the way for inducing and expanding peptide antigen-specific regulatory T cells ex vivo for cell therapy in transplantation, allergy, and autoimmune disease.     

Foxp3+ CD25- CD4 T cells constitute a reservoir of committed regulatory cells that regain CD25 expression upon homeostatic expansion

Expression of the IL-2 receptor alpha chain (CD25) by peripheral CD4 T cells follows cellular activation. However, CD25 expression by CD4 cells is widely used as a marker to identify regulatory T cells (T(R)), although cells with regulatory properties are also found in the CD4+CD25- subset. By using in vivo functional assays and Foxp3 expression as a faithful marker of T(R) differentiation, we have evaluated the requirements for CD25 expression by peripheral T(R). We first show that in vivo depletion of CD25+ cells prevents the development of spontaneous encephalomyelitis in recombination-activating gene (RAG)-deficient anti-myelin basic protein T cell antigen receptor (TCR) transgenic mice, and allows disease induction in otherwise healthy RAG-competent transgenic mice. Similar treatment in normal thymectomized animals is followed by the fast recovery of a normal number of CD25+ T(R). Consistently, Foxp3-expressing T(R) encompassed in the CD25- cell population convert to CD25+ after homeostatic expansion and are selectable by IL-2 in vitro. Surface expression of CD25 on T(R) is controlled by the activity of conventional CD4 cells and is fully labile because it can be lost and regained without affecting the functional potential of the cells. These findings reveal that Foxp3-expressing CD25- cells constitute a peripheral reservoir of differentiated T(R), recruited to the CD25+ pool upon homeostatic expansion and/or activation. This analysis, together with the notion that physiological commitment of T(R) takes place exclusively in the thymus should help for the interpretation of experiments assessing peripheral T(R) differentiation from naive CD4 T cells, defined as CD25-.     

Induction of antigen-specific tolerance to bone marrow allografts with CD4+CD25+ T lymphocytes

Thymus-derived regulatory T lymphocytes of CD4(+)CD25(+) phenotype regulate a large variety of beneficial and deleterious immune responses and can inhibit lethal graft-versus-host disease in rodents. In vitro, CD4(+)CD25(+) T cells require specific major histocompatibility complex (MHC)/peptide ligands for their activation, but once activated they act in an antigen-nonspecific manner. In vivo, regulatory T cells are also activated in an antigen-specific fashion, but nothing is known about antigen specificity of their suppressor-effector function. Here we show that CD4(+)CD25(+) regulatory T lymphocytes isolated from naive mice and activated in vitro with allogeneic antigen-presenting cells (APCs) induced specific long-term tolerance to bone marrow grafts disparate for major and minor histocompatibility antigens; whereas "target" bone marrow was protected, third-party bone marrow was rejected. Importantly, in mice injected with a mix of target and third-party bone marrows, protection and rejection processes took place simultaneously. These results indicate that CD4(+)CD25(+) regulatory T cells can act in an antigen-specific manner in vivo. Our results suggest that CD4(+)CD25(+) regulatory T cells could in the future be used in clinical settings to induce specific immunosuppression.     

Activated CD4+CD25+ T cells selectively kill B lymphocytes

The suppressive capacity of naturally occurring mouse CD4+CD25+ T cells on T-cell activation has been well documented. The present study is focused on the interaction of CD4+CD25+ T cells and B cells. By coculturing preactivated CD4+CD25+ T cells with B cells in the presence of polyclonal B-cell activators, we found that B-cell proliferation was significantly suppressed. The suppression of B-cell proliferation was due to increased cell death caused by the CD4+CD25+ T cells in a cell-contact-dependent manner. The induction of B-cell death is not mediated by Fas-Fas ligand pathway, but surprisingly, depends on the up-regulation of perforin and granzymes in the CD4+CD25+ T cells. Furthermore, activated CD4+CD25+ T cells preferentially killed antigen-presenting but not bystander B cells. Our results demonstrate that CD4+CD25+ T cells can act directly on B cells and suggest that the prevention of autoimmunity by CD4+CD25+ T cells can be explained, at least in part, by the direct regulation of B-cell function.     

Therapeutic vaccination using CD4+CD25+ antigen-specific regulatory T cells

Autoimmune disease results from the dysregulation of basic tolerogenic processes designed to control self/non-self-discrimination. Approaches to treat autoimmunity have focused historically on potent immunosuppressives that block the activation and expansion of antigen-specific T cells before they differentiate into pathogenic T cell responses. These therapies are very efficient in reducing clonal expansion and altering early signaling pathways. However, once the pathogenic responses are established (i.e., autoimmunity), the interventions are less effective on activated and differentiated T cell subsets (including memory T cells) or acting in the presence of an inflammatory milieu to abort immune responses at the target tissue and systemically. Moreover, the current immunotherapies require continuous use because they do not redirect the immune system to a state of tolerance. The continuous treatment leads to long-term toxicities and can profoundly suppress protective immune responses targeted at viruses, bacteria, and other pathogens. Over the past decade, there have been tremendous advances in our understanding of the basic processes that control immune tolerance. Among the most exciting has been the identification of a professional regulatory T cell subset that has shown enormous potential in suppressing pathologic immune responses in autoimmune diseases, transplantation, and graft vs. host disease. In this review, we summarize current efforts to induce and maintain tolerance in the autoimmune diabetes setting by using therapeutic vaccination with CD4(+)CD25(+) regulatory T cells. Emphasis will be placed on approaches to exploit regulatory T cells either directly or through the use of anti-CD3 immunotherapy.     

CD4+CD25+ regulatory T cells inhibit immune-mediated transgene rejection

Like cellular transplantation, gene therapy is often limited by immune rejection of the newly expressed antigen. In a model of gene transfer in muscle, delivery of the influenza hemagglutinin (HA) membrane protein by adeno-associated virus (AAV) is impaired by a strong immune response that leads to a rapid rejection of the transduced fibers. We show here that injection of HA-specific CD4+CD25+ T cells from T-cell receptor (TCR)-transgenic animals, concomitant with gene transfer, down-regulates the anti-HA cytotoxic and B-lymphocyte responses and enables persistent HA expression in muscle. This demonstrates for the first time that adoptive transfer of antigen-specific CD4+CD25+ regulatory T cells can be used to induce sustained transgene engraftment in solid tissues.     

结核性胸膜炎患者胸液中CD4~+ CD25~+ FoxP3~+调节T细胞抑制抗结核免疫

目的研究结核性胸膜炎患者胸液中CD4+CD25+FoxP3+调节T细胞是否增多,这些调节T细胞是否抑制结核的特异细胞免疫反应。方法使用细胞分离、流式细胞分析及体外细胞培养作细胞增殖及增殖抑制等实验方法,对15例结核性胸膜炎患者及17例健康正常人群胸液及外周血白细胞中CD4+CD25+FoxP3+调节T细胞的量及特征作研究。结果结核性胸膜炎患者胸液中CD4+CD25+FoxP3+调节T细胞明显高于患者及健康人群外周血。在体外,结核性胸膜炎患者胸液中单核细胞对BCG刺激产生γ-干扰素(IFN-γ)的能力明显强于患者及健康人群外周血中单核细胞;把这些调节T细胞从胸液单核细胞中清除,增强了结核患者胸液单核细胞对BCG刺激产生IFN-γ;从结核患者胸液分离的这些调节T细胞能抑制结核患者Th1细胞产生IFN-γ。结论结核性胸膜炎患者胸液CD4+CD25+FoxP3+调节T细胞增多,抑制结核性胸膜炎患者Th1细胞免疫反应,从而参与了结核性胸膜炎的发病。     

IL-10-dependent infectious tolerance after the treatment of experimental allergic encephalomyelitis with redirected CD4+CD25+ T lymphocytes

How small numbers of CD4+CD25+ regulatory T cells suppress autoimmune responses in vivo is unclear. In this report we analyze the immunomodulatory activity of CD4+CD25+ T cells that are antigen-specifically redirected against myelin basic protein (MBP)89-101-specific autoreactive T cells by a MBP89-101-IA(s)-zeta chimeric receptor. We have previously shown that these redirected regulatory T cells are highly potent in treating a model autoimmune disease, experimental allergic encephalomyelitis. We show here that they have only limited effect in vivo on autoreactive T cell proliferation and therefore do not act by deleting or suppressing the expansion of pathologic effector cells. Rather, the redirected CD4+CD25+ T cells divert the pathologic T helper 1 self-specific T cell response to one characterized by high IL-10 and lower IL-4 production. Significantly, when isolated from the inducing CD4+CD25+ regulatory T cells, these self-specific T cells can independently suppress the autoreactive T cell response and experimental allergic encephalomyelitis development in an IL-10-dependent manner. These results provide evidence that CD4+CD25+ regulatory T cells can manipulate the adaptive immune response in vivo through the infectious induction of tolerance, specifically by promoting the formation of antigen-specific, IL-10-secreting regulatory T cells.     

IL-5 promotes induction of antigen-specific CD4+CD25+ T regulatory cells that suppress autoimmunity

Immune responses to foreign and self-Ags can be controlled by regulatory T cells (Tregs) expressing CD4 and IL-2Rα chain (CD25). Defects in Tregs lead to autoimmunity, whereas induction of Ag-specific CD4+CD25+ Tregs restores tolerance. Ag-specific CD4+CD25+ FOXP3+Tregs activated by the T helper type 2 (Th2) cytokine, IL-4, and specific alloantigen promote allograft tolerance. These Tregs expressed the specific IL-5Rα and in the presence of IL-5 proliferate to specific but not third-party Ag. These findings suggest that recombinant IL-5 (rIL-5) therapy may promote Ag-specific Tregs to mediate tolerance. This study showed normal CD4+CD25+ Tregs cultured with IL-4 and an autoantigen expressed Il-5rα. Treatment of experimental autoimmune neuritis with rIL-5 markedly reduced clinical paralysis, weight loss, demyelination, and infiltration of CD4+ (Th1 and Th17) CD8+ T cells and macrophages in nerves. Clinical improvement was associated with expansion of CD4+CD25+FOXP3+ Tregs that expressed Il-5rα and proliferated only to specific autoantigen that was enhanced by rIL-5. Depletion of CD25+ Tregs or blocking of IL-4 abolished the benefits of rIL-5. Thus, rIL-5 promoted Ag-specific Tregs, activated by autoantigen and IL-4, to control autoimmunity. These findings may explain how Th2 responses, especially to parasitic infestation, induce immune tolerance. rIL-5 therapy may be able to induce Ag-specific tolerance in autoimmunity.     

Innate CD4+CD25+ regulatory T cells are required for oral tolerance and inhibition of CD8+ T cells mediating skin inflammation

To elucidate the role of CD4+CD25+ regulatory T cells in oral tolerance, we used the model of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB), which is mediated by CD8+ Tc1 effector cells independently of CD4+ T-cell help. Conversely to normal mice, invariant chain knock-out (KO) (Ii degrees / degrees ) mice, which are deficient in CD4+ T cells, cannot be orally tolerized and develop a chronic hapten-specific CHS response. Transfer of naive CD4+ T cells before hapten gavage into Ii degrees / degrees mice restores oral tolerance by a mechanism independent of interleukin-10 (IL-10) production by CD4+ T cells. That naturally occurring CD4+CD25+ T cells are critical for oral tolerance induction is demonstrated by the finding that (1) transfer of CD4+CD25+ but not CD4+CD25- T cells into Ii degrees / degrees recipients completely prevents the CHS response and skin infiltration by CD8+ T cells, by blocking development of hapten-specific CD8+ T cells; (2) in vivo depletion of CD4+CD25+ cells by antibody treatment in normal mice impairs oral tolerance; and (3) CD4+CD25+ T cells inhibit hapten-specific CD8+ T-cell proliferation and interferon gamma (IFN gamma) production, in vitro. These data show that naturally occurring CD4+CD25+ T cells are instrumental for orally induced tolerance and are key actors for the control of antigen-specific CD8+ T-cell effectors mediating skin inflammation.     

CD4+CD25+T细胞延长同种异体胰岛移植物存活

探讨CD4+ CD25+调节性T细胞作为细胞疫苗抑制小鼠同种异体胰岛移植物排斥反应的作用,采用免疫磁珠分离技术分选CD4+ CD25+调节性T细胞联合BALB/cByJ小鼠同种异体胰岛移植.结果 显示,CD4+ CD25+调节性T细胞可明显延长同种异体移植物的存活时间.     

CD4+CD25+调节性T细胞在肿瘤免疫逃逸机制中的作用研究进展

CD4+CD25+调节性T细胞是一类具有免疫抑制功能的T细胞亚群,能阻止肿瘤免疫和逃避肿瘤对抗原的有效识别.Foxp3是近年来发现的一种转录因子,是CD4+CD25+调节性T细胞表面特异性标志,检测其表达可以作为判定CD4+CD25+调节性T细胞的方法.最近,大量研究已经证实CD4+CD25+调节性T细胞与各种肿瘤生存期和不良预后密切相关.目前,CD4+CD25+调节性T细胞的靶向治疗和选择性清除成为新的免疫治疗方法.     

CD4+ CD25+ regulatory T cells control the induction of antigen-specific CD4+ helper T cell responses in cancer patients

A proportion of cancer patients naturally develop CD4+ T-helper type 1 (Th1) cell responses to NY-ESO-1 that correlate with anti-NY-ESO-1 serum antibodies. To address the role of T-cell regulation in the control of spontaneous tumor immunity, we analyzed NY-ESO-1-specific Th1 cell induction before or after depletion of CD4+CD25+ T cells in vitro. While Th1 cells were generated in the presence of CD25+ T cells in cancer patients seropositive for NY-ESO-1, seronegative cancer patients and healthy donors required CD25+ T-cell depletion for in vitro induction of NY-ESO-1-specific Th1 cells. In vitro, newly generated NY-ESO-1-specific Th1 cells were derived from naive precursors, whereas preexisting memory populations were detectable exclusively in patients with NY-ESO-1 antibody. Memory populations were less sensitive than naive populations to CD4+CD25+ regulatory T cells. We propose that CD4+CD25+ regulatory T cells are involved in the generation and regulation of NY-ESO-1-specific antitumor immunity.     

CD4+CD25+调节性T细胞及其分子标记物与支气管哮喘

CD4+CD25+调节性T细胞是一类以免疫抑制和免疫无能为特征的淋巴细胞群,FOXP3是CD4+CD25+调节性T细胞一个特征性的分子标志物,并且对CD4+CD25+调节性T细胞的发育、外周表达和功能维持有着关键性的作用.近年来,多项研究显示CD4+CD25+调节性T细胞参与并影响了支气管哮喘的发生、发展过程,对调节性T细胞或其相关基因的干预也许会成为支气管哮喘治疗的新方向.     

Depletion of CD25^＋CD4^＋T cells （Tregs） enhances the H BV-specific CD8^＋ T cell response primed by DNA immunization

AIM: Persistent hepatitis B virus (HBV) infection is characterized by a weak CD8+ T cell response to HBV. Immunotherapeutic strategies that overcome tolerance and boost these suboptimal responses may facilitate viral clearance in chronically infected individuals. Therefore, we examined whether CD25+CD4+ regulatory T (Treg) cells might be involved in a inhibition of CD8+T cell priming or in the modulation of the magnitude of the 'peak' antiviral CD8+ T cell response primed by DNA immunization. METHODS: B10.D2 mice were immunized once with plasmid pCMV-S. Mice received 500 μg of anti-CD25 mAb injected intraperitoneally 3 d before DNA immunization to deplete CD25+ cells. Induction of HBV-specific CD8+ T cells in peripheral blood mononuclear cells (PBMCs) was measured by S28-39 peptide loaded DimerX staining and their function was analyzed by intracellular IFN-γ staining. RESULTS: DNA immunization induced HBV-specific CD8+ T cells. At the peak T cell response (d 10), 7.1±2.0% of CD8+ T cells were HBV-specific after DNA immunization, whereas 12.7±3.2% of CD8+ T cells were HBV-specific in Treg-depleted mice, suggesting that DNA immunization induced more antigen-specific CD8+ T cells in the absence of CD25+ Treg cells (n = 6, P<0.05). Similarly, fewer HBV specific memory T cells were detected in the presence of these cells (1.3±0.4%) in comparison to Treg-depleted mice (2.6±0.9%) on d 30 after DNA immunization (n - 6, P<0.01). Both IFN-γ production and the avidity of the HBV-specific CD8+ T cell response to antigen were higher in HBV-specific CD8+ T cells induced in the absence of Treg cells. CONCLUSION: CD25+ Treg cells suppress priming and/or expansion of antigen-specific CD8+ T cells during DNA immunization and the peak CD8+ T cell response is enhanced by depleting this cell population. Furthermore, Treg cells appear to be involved in the contraction phase of the CD8+ T cell response and may affect the quality of memory T cell pools. The elimination of Treg cells or their inhibition may be important in immunotherapeutic strategies to control HBV infection by inducing virus-specific cytotoxic T lymphocyte responses in chronically infected subjects.     

CD25+CD4+ T cells contribute to the control of memory CD8+ T cells

Previously we demonstrated that IL-15 and IL-2 control the number of memory CD8+ T cells in mice. IL-15 induces, and IL-2 suppresses the division of these cells. Here we show that CD25+CD4+ regulatory T cells play an important role in the IL-2-mediated control of memory phenotype CD8+ T cell number. In animals, the numbers of CD25+CD4+ T cells were inversely correlated with the numbers of memory phenotype CD8+ T cells with age. Treatment with anti-IL-2 caused CD25+CD4+ T cells to disappear and, concurrently, increased the numbers of memory phenotype CD8+ T cells. This increase in the numbers of CD8+ memory phenotype T cells was not manifest in animals lacking CD4+ cells. Importantly, adoptive transfer of CD25+CD4+ T cells significantly reduced division of memory phenotype CD8+ T cells. Thus, we conclude that CD25+CD4+ T cells are involved in the IL-2-mediated inhibition of memory CD8+ T cell division and that IL-2 controls memory phenotype CD8+ T cell numbers at least in part through maintenance of the CD25+CD4+ T cell population.     

Functional avidity directs T-cell fate in autoreactive CD4+ T cells

Major histocompatibility complex class II tetramer staining and activation analysis identified 2 distinct types of antigen-specific CD4+ T cells in the peripheral blood of humans with type 1 (autoimmune) diabetes. T cells with low-avidity recognition of peptide-MHC ligands had low sensitivity to activation and inefficient activation-induced apoptosis. In contrast, high-avidity T cells were highly sensitive to antigen-induced cell death through apoptotic mechanisms, and both apoptosis-resistant high- and low-avidity T cells that survived prolonged tetramer treatment were rendered anergic to restimulation by antigen. In addition, however, apoptosis-resistant high-avidity T cells acquired regulatory features, being able to suppress both antigen-specific and nonspecific CD4+ T-cell responses. This suppression was contact-dependent and correlated with the down-regulation of HLA class II and costimulatory molecules on antigen-presenting cells, including B cells and dendritic cells. T cells face a variety of fates following antigen exposure, including the paradoxic maintenance of high-avidity autoreactive T cells in the peripheral circulation, perhaps due to this capability of acquiring anergic and suppressive properties. Regulation via down-modulation of antigen-presenting cell function, a form of cell-to-cell licensing for suppression, also offers possibilities for the application of peptide-MHC therapeutics.