T细胞克隆失能机制的研究进展

T细胞克隆失能是T细胞产生免疫耐受的主要机制一，近几年来一直是免疫学研究得关注的热点，本综述了诱导T细胞克隆失能的几种实验模型，相关分子机制研究进展和共刺激信号对克隆失能的影响，并探讨了调节细胞因子与T细胞失能的关系。     

T细胞克隆失能机制的研究进展

T细胞克隆失能是T细胞产生免疫耐受的主要机制之一 ,近几年来一直是免疫学研究者关注的热点。本文综述了诱导T细胞克隆失能的几种实验模型 ,相关分子机制研究进展和共刺激信号对克隆失能的影响 ,并探讨了调节细胞因子与T细胞失能的关系     

超抗原SEA诱导T细胞失能体外实验模型的建立

目的 建立超抗原诱导T细胞失能的体外实验模型。方法 SEA刺激人外周血淋巴细胞,再加入外源性的rIL-2维持,建立短期SEA反应性T细胞系;进行Ficoll-Hypaque密度梯度离心获取经SEA多次刺激过SEA反应性T细胞;加入处理过的PBMC作APCs,建立超抗原SEA诱导T细胞的化组和失能组。结果 SEA和rIL-2共同作用可得到静息SEA反应性T细胞系;SEA反复刺激使T细胞处于一低反应状态,与活化组相比,其DNA合成能力明显下降,IL－2分泌显著减少,静息一段时间后,其增殖能力慢慢恢复。结论 超抗原SEA多次刺激诱导SEA反应性T细胞处于失能状态。     

T细胞在激活诱导凋亡中的信号途径

淋巴细胞AICD是免疫系统维持稳定的一种重要机制。现在已知的可引发AICD的途径包括CD3/TCR途径、CD2途径、CD47途径、CD30途径。它们最终将信号传递至两条凋亡途径,引起细胞死亡。第一条是死亡受体信号传导途径,其中主要包括Fas/PasL途径、Apo-TRAIL等TNF受体超家族起始的途径。另外,Bcl-2家族构成的线粒体途径可能参与一定的调节作用。     

γ/δT细胞简介

γ/δT细胞是近 10多年来人们新认识到的一种T细胞亚群 ,该细胞有许多独特特征 ,在抗感染、抗过敏、肿瘤监测及自身免疫病中起着一定作用。本文对该细胞亚群的受体基因、抗原特异性、分布、作用等进行了综述。     

015 γ/δT细胞简介

γ/δT细胞是近10多年来人们新认识到的一种T细胞亚群,该细胞有许多独特特征在抗感染、抗过敏、肿瘤监测及自身免疫病中起着一定作用.本文对该细胞亚群的受体基因、抗原特异性、分布、作用等进行了综述.     

T细胞Trail受体表达及Trail诱导的T细胞凋亡

目的 :观察人T细胞Trail(TNF relatedapoptosis inducingligand)受体表达及Trail诱导T细胞凋亡的作用。方法 :通过荧光双标记 ,使用流式细胞仪检测Trail受体阳性细胞和凋亡细胞。结果 :静息Jurkat细胞表达高水平Trail受体〔(49 19±12 2 5 ) %〕 ,激活Jurkat细胞对Trail受体表达无影响。Trail诱导显著的Jurkat细胞凋亡〔(90 0 1± 2 6 71) %〕。正常人外周血淋巴细胞 (PBL)仅激活后表达Trail受体〔(2 5 2 7± 6 42 ) %〕 ,但无细胞凋亡发生。结论 :人T细胞表达Trail受体 ,Trail受体和Trail的相互作用对细胞凋亡有调控作用。     

T细胞耐受的诱导及其机理研究

目的　阐明抗原特异性 Ｔ 细胞无能的诱导条件、无能细胞的特性及其耐受的机理。方法　抗 Ｂ７１ 单抗与 Ｃｓ Ａ 联用诱导抗原特异性 Ｔ 细胞无能, 通过３ Ｈ Ｔｄ Ｒ 掺入法测定 Ｔ 细胞增殖和 Ｍ Ｌ Ｒ, 利用 Ｒ Ｔ Ｐ Ｃ Ｒ 检测细胞因子基因表达。结果　耐受 Ｔ 细胞与异体淋巴细胞比例为０ ．０１∶１时, 可显著抑制 Ｍ Ｌ Ｒ, 转染 Ｂ７１ 分子的 Ｍ Ｄ Ａ４５３ 和３ Ａ Ｏ 能协同刺激 Ｃ Ｄ３ 诱导的 Ｔ 细胞增殖,不表达 Ｂ７ 分子的 Ｍ Ｄ Ａ４５３ 和３ Ａ Ｏ 无此作用。 Ｐ Ｈ Ａ、 Ｃ Ｄ３ 单抗、 Ｐ Ｍ Ａ＋ Ａ２３１８７ 可以逆转本试验所用诱导方法所致的 Ｔ 细胞的耐受状态。无能 Ｔ 细胞 Ｉ Ｌ２ 和 Ｉ Ｆ Ｎγｍ Ｒ Ｎ Ａ 不表达, 而 Ｉ Ｌ４ 和 Ｉ Ｌ１０ ｍ Ｒ Ｎ Ａ可表达。无能 Ｔ 细胞活化后, Ｉ Ｌ２ 和 Ｉ Ｆ Ｎγｍ Ｒ Ｎ Ａ 能够表达。结论　抗原特异性 Ｔ 细胞耐受是可以人为诱导的, 无能 Ｔ 细胞细胞因子基因格局向 Ｔ Ｈ２ 细胞偏离。     

Notch信号途径: T细胞功能调控的新通路

Notch受体及其配体组成了脊椎动物和无脊椎动物胚胎发育中高度保守的Notch信号途径。近年来研究发现,Notch及其介导的信号转导与免疫系统也存在着密切的关系,从多个方面参与T细胞功能的调控,包括T细胞的活化和增殖,细胞因子分泌和Th1/Th2分化,也参与调节性T细胞的产生、扩增和功能发挥等。这说明,Notch信号途径不仅参与免疫系统发育,同时在成熟的免疫细胞功能调节中也具有重要的作用。     

HIV/AIDS感染者体外诱导的γδT细胞亚群的特点

目的:了解HIV/AIDS感染者外周血中γδT细胞亚群的特点以及体外诱导后γδT细胞的增殖情况和Vδ1、Vδ2亚群的变化,为γδT细胞体外扩增方法的建立打下基础。方法:流式细胞术(FCM)检测25例HIV/AIDS感染者(HIV组)和31例健康对照者(HC组)外周血中的γδT细胞、Vδ1亚群、Vδ2亚群的频率和绝对值;选择两组中各10例外周血单个核细胞(PBMC),用anti-γδTCR单克隆抗体(mAb)和IL-2在体外诱导培养14 d,在0 d、7 d、14 d分别进行细胞计数和FCM检测,分析比较γδT细胞亚群的比例和培养情况。结果:HIV组外周血中γδT细胞、Vδ2亚群百分比和绝对值都显著低于HC组,而Vδ1亚群百分比和绝对值显著高于HC组;体外诱导培养14 d时,HC组总细胞数量增加3倍,HIV组总细胞数量稍有增加;HC组的γδT细胞比例可达到80%以上,其中Vδ2亚群可以增加到65%左右,而HIV组的γδT细胞比例达35%左右,Vδ2亚群比例仅增加到17%左右。结论:HIV/AIDS感染者外周血中γδT细胞比例显著降低,Vδ1/Vδ2比值倒置;用anti-γδTCR mAb和IL-2在体外诱导HIV/AIDS感染者的Vδ2亚群扩增效果不佳,不能逆转Vδ1/Vδ2倒置现象。应进一步寻找更加有效的诱导培养方法。     

Induction of anergy in resting human T lymphocytes by immobilized anti-CD3 antibodies

How the T cell receptor (TcR)/CD3 complex mediates not only the induction of T cell activation but also suppressive effects like T cell anergy or apoptosis is not well understood. Here we describe a series of preincubation and restimulation experiments which demonstrate that primary stimulation of resting, unseparated human T cells with mitogenic doses of immobilized anti-CD3 antibodies induces hyporesponsiveness upon restimulation of the cells. Various costimuli can prevent this type of anergy to a variable degree if present during the preincubation period, phorbol 12-myristate 13-acetate (PMA) being the most and anti-CD4 antibody the least effective. If employed together with anti-CD3 antibody during the restimulation phase of the assay, interleukin (IL)-2, IL-4 and anti-CD28 antibody break anergy almost completely. Proliferation induced by a submitogenic dose of anti-CD3 antibody supplemented by costimulatory signals (anti-CD2, anti-CD4, anti-CD28, IL-2, IL-4 or PMA) does not result in hyporesponsiveness. Taken together, these results support a modified view of the two-signal model for T cell activation according to which anergy induction in resting T cells occurs if primary proliferation is induced by high density triggering of the TcR/CD3 complex in the absence of accessory signals. We discuss possible implications of these findings for the induction of peripheral tolerance.     

CTLA-4在超抗原诱导T细胞无能中的作用研究

目的 探讨CTLA—4对T细胞无能的诱导作用。方法 通过使用超抗原SEA作为一种无能诱导剂，建立体外无能模型，检测了无能T细胞在受到SEA的再次刺激时其膜分子CD28和CTLA—4的表达。结果 与活化T细胞相比，无能T细胞在免疫应答的后期阶段表面表达高水平的CTLA—4分子，而CD28的表达则只较活化组T细胞稍高一些。结论 CTLA—4表面表达水平的升高很可能与T细胞无能状态的诱导有关。     

Differential response of CD4+ V7+ and CD4+ V7− T cells to T cell receptor-dependent signals: CD4+ V7+ T cells are co-stimulation independent and anti-V7 antibody blocks the induction of anergy by bacterial superantigen

V7 is a novel cell surface glycoprotein that is expressed on 25% of circulating T lymphocytes. This molecule appears to play a critical role in T cell activation based on the observation that a monoclonal anti-V7 antibody inhibits T cell receptor (TCR)-dependent interleukin-2 (IL-2) production and proliferation of T cells. In the current study, CD4⁺ V7+ and CD4⁺ V7? T cells were separated from one another and their response to various stimuli analyzed. Although there were only minor differences between the two subsets in the expression of activation/differentiation markers, including CD45RA and R0 isotypes, when exposed to immobilized anti-CD3 or anti-TCR antibodies in the absence of APC, CD4⁺ V7+ T cells alone produced IL-2 and proliferated vigorously. By contrast, CD4⁺ V7? cells responded poorly to such stimuli, but they recovered their capacity to respond if antigen-presenting cells (APC) or anti-CD28 antibody were added to the cultures. The enhancement of the V7? T cell response by APC appears to be related to augmentation of TCR signals because the effect could be blocked by antibodies against molecules on APC [major histocompatibility (MHC) class II, CD86] that are known to up-regulate such signals through their interaction with counter-receptors on T cells. To assess the role of V7 in a system independent of co-stimulation, CD4⁺ T cells were stimulated with the bacterial superantigens, staphylococcal enterotoxins A and B. The cells responded by proliferating and then becoming anergic. Addition of anti-V7 antibody at the initiation of culture with superantigen did not inhibit cellular proliferation but prevented T cells from becoming anergic, while addition of anti-CD28 antibody had no effect on either proliferation or anergy induction. These results indicate that V7 and CD28 mediate distinct intracellular signals and suggest that V7 functions to preserve T cell reactivity whether the stimulus is mitogenic or anergizing.     

Clonal anergy to staphylococcal enterotoxin B in vivo: selective effects on T cell subsets and lymphokines

Injection of bacterial superantigens such as staphylococcal enterotoxin B (SEB) in adult mice results in initial proliferation of SEB-responsive Vβ8⁺ T cells followed by induction of a state of non-responsiveness frequently referred to as clonal anergy. We show here that SEB-induced anergy involves selective changes in lymphokine production and that it affects CD4⁺ Vβ 8⁺ and CD8⁺ Vβ 8⁺ T cells in different fashions. Whereas both CD4⁺ Vβ 8⁺ and CD8⁺ Vβ 8⁺ cells from anergic mice exhibit strongly reduced proliferative capacity and interleukin(IL)-2 production upon restimulation with SEB either in vivo or in vitro the CD8⁺ subset from SEB-injected mice produces other lymphokines (such as interferon(IFN)-γ) at normal or slightly increased levels in response to SEB. Changes in the levels of production of IL-2 and IFN-γ protein correlated well with mRNA accumulation both in vivo and in vitro. Collectively these data suggest that superantigen-induced anergy involves selective changes in signal transduction and/or gene regulation in T lymphocytes.     

Oxidized phospholipids induce anergy in human peripheral blood T cells

Lipids are key regulators of immune responses. In this study we investigated the direct impact of oxidized phospholipids (ox-PL) on T cell activation and function. We could demonstrate that ox-PL strongly inhibit proliferation of purified human T cells induced with anti-CD3/CD28 or anti-CD3/CD63 mAb, whereas proliferation of naive T cells from human cord blood was not affected by ox-PL. Unoxidized phospholipids showed no such effect. Inhibition of T cell proliferation by ox-PL was not due to cell death. Moreover, T cell proliferation triggered by PMA/ionomycin activation was not diminished by ox-PL. T cells activated in the presence of ox-PL produced and released low amounts of IFN-gamma and IL-2, whereas IL-4 was only slightly diminished. Ox-PL prevented the expression of de novo synthesized activation markers (CD25, MHC class II) but not expression of CD63 or CD69. We further observed that T cells stimulated in the presence of ox-PL are poorly cytotoxic T cells. Most importantly, T cells activated in the presence of ox-PL failed to proliferate in response to restimulation. This hypo-proliferative state was accompanied with an up-regulation of early growth response gene 3 and Casitas B-lineage lymphoma protein B. Taken together, our results demonstrate that ox-PL are potent and specific regulators of T cell activation and function.     

Direct evidence for anergy in T lymphocytes tolerized by oral administration of ovalbumin

The present study investigated bystander suppression, specific suppression and anergy as mechanisms for oral tolerance. Oral tolerance was induced in mice by a single gastric intubation of 20 mg ovalbumin (OVA) and was evaluated in vitro by the absence of T lymphocyte proliferative responses to OVA after priming by OVA-complete Freund's adjuvant (CFA). T lymphocyte unresponsiveness was antigen specific, systemic and was not affected by the vehicle used for immunization. T lymphocytes derived from tolerant popliteal lymph nodes (PLN) responded to an acetone precipitate (AP) of mycobacteria present in CFA; this response was not suppressed by co-culture with OVA, thereby arguing against a mechanism of bystander suppression in our system. Responses of PLN T lymphocytes derived from OVA-CFA primed, non-tolerant mice, or those of an OVA-specific T lymphocyte line, were not suppressed by PLN or spleen cells derived from OVA tolerant mice. These results excluded the possibility that oral tolerance was induced and maintained by a mechanism of specific suppression. At the cellular level, we found that OVA-tolerant T lymphocytes did not produce interleukin-2 (IL-2) nor express IL-2 receptor in response to OVA stimulation in vitro; both observations are indicative of a state of anergy. Incubation of OVA-tolerant PLN T lymphocytes together with murine recombinant IL-2 for 5 days, released anergic T lymphocytes and a concomitant OVA-specific proliferative response of CD4⁺ T cells was detected. Taken together, our experimental system excludes the involvement of bystander or specific suppression in the induction of oral tolerance to OVA, and provides direct evidence to show that oral tolerance results from specific T lymphocyte anergy.     

Anergic T cells actively suppress T cell responses via the antigen-presenting cell

We here show that anergic T cells are active mediators of T cell suppression. In co-culture experiments, we found that anergic T cells, derived from established rat T cell clones and rendered anergic via T cell presentation of the specific antigen (Ag), were active inhibitors of T cell responses. Anergic T cells inhibited not only the responses of T cells with the same Ag specificity as the anergic T cells, but were also capable of efficiently inhibiting polyclonal T cell responses directed to other epitopes. This suppression required close cell-cell contact between antigen-presenting cells (APC), anergic T cells and responder T cells, and only occurred when the epitope recognized by the anergic T cell was present. The suppression was not caused by passive competition for ligands on the APC surface, IL-2 consumption, or cytolysis, and was not mediated by soluble factors derived from anergic T cells that were stimulated with their specific Ag. When responder T cells were added 24 h after co-culturing anergic cells in the presence of Ag and APC, T cell responses were still suppressed, indicating that the suppressive effect was persistently present. However, anergic T cells were not able to suppress responder T cells that had already received a full activation signal. We propose that suppression by anergic T cells is mediated via the APC, either through modulation of the T cell-activating capacity of the APC (APC/T cell interaction), or by inhibition of T cells recognizing their ligand in close proximity on the same APC (T/T cell interaction).     

Induction and stability of the anergic phenotype in T cells

One of the mechanisms that are in place to control the activation of mature T cells that bear self-reactive antigen receptors is anergy, a long-term state of hyporesponsiveness that is established in T cells in response to suboptimal stimulation. T cells receive signals that result not only from antigen recognition and costimulation but also from other sources, including cytokine receptors, inhibitory receptors or metabolic sensors. Integration of those signals will determine T cell fate. Under conditions that induce anergy, T cells activate a program of gene expression that leads to the production of proteins that block T cell receptor signaling and inhibit cytokine gene expression. In this review we will examine those signals that determine functional outcome following antigen encounter, review current knowledge of the factors that ensure signaling inhibition and epigenetic gene silencing in anergic cells and explore the mechanisms that lead to the reversal of anergy and the reacquisition of effector functions.     

Anergic T cells effect linked suppression

Although the phenomenon of T cell-mediated suppression is well established, particularly in experimental models of transplantation, the mechanisms involved in this form of immunoregulation remain controversial. We have recently demonstrated, using an in vitro system, that anergic T cells can act as suppressor cells by competing for the membrane of the antigen-presenting cell (APC) and for locally produced interleukin-2. In the experiments described here we have explored the ability of anergic T cells to effect linked suppression in antigen-specific and allospecific responses. We observed that anergic antigen-specific CD4⁺ T cells can inhibit T cells restricted by a different major histocompatibility complex (MHC) class II molecule provided that both restriction elements are expressed by the same APC. In addition, anergic allospecific clones could also effect linked suppression since they could regulate not only T cells specific for the same alloantigen but also responder T cells with direct allospecificity for a second allogeneic MHC molecule or with indirect, self MHC-restricted allospecificity for a processed MHC class I alloantigen. Furthermore, the regulatory effect of the anergic T cells was dependent on cell contact, was not dependent upon irradiation, and was maintained during in vitro culture. These data demonstrate that linked suppression can be effected by anergic T cells in vitro. In the clinical context this raises the possibility that induction of tolerance to a single alloantigen could serve to regulate the immune response to an allograft carrying several MHC and minor antigen differences.