CD4~+CD25~+T细胞在CD8~+T细胞抗肿瘤免疫中的调节作用

实验旨在研究CD4+CD25+T细胞在CD8+T细胞抗肿瘤免疫中的调节作用。将小鼠脾脏中分离的单个核细胞分为两组,即去除CD4+CD25+T细胞组和未去除CD4+CD25+T细胞组,测定树突状细胞提呈的肿瘤抗原多肽刺激不同T细胞增殖活性、细胞因子IFN-γ分泌,以及多肽特异性CD8+T细胞对同源性胃癌细胞株MFC的杀伤活性。结果显示预先去除未致敏T细胞中的CD4+CD25+T细胞,所诱导的特异性CD8+CTL对肿瘤细胞免疫应答增强,表现为反应性T细胞对树突状细胞提呈的肿瘤抗原多肽增殖反应增强,IFN-γ分泌量提高及CD8+T细胞对MFC杀伤活性增强。这些结果表明,预先去除未致敏T细胞中的CD4+CD25+T细胞,肿瘤抗原多肽修饰的树突状细胞肿瘤疫苗效能可明显增加。CD4+CD25+T细胞在CD8+T细胞抗肿瘤免疫中起下调作用。     

CD4+ CD25+调节性T细胞对树突状细胞的杀伤作用

目的 探讨CD4^＋CD25^＋调节性T细胞是否对树突状细胞发挥免疫调节作用及其可能的机制。方法 用MACS（magnetic cell sorting）从BALB／c小鼠静息T细胞分离纯化CD4^＋CD25^＋T细胞，体外细胞增殖实验观察其对CD4^＋CD25^＋T细胞的免疫抑制作用；GM-CSF／IL-4培养自体小鼠骨髓来源DC，FACS（fluorescence-activated cell sorting）鉴定其表面分子特性；以CD3／CD28单克隆抗体活化CD4^＋CD25^＋调节性T细胞，FACS体外杀伤实验研究其对自体DC的调节作用，并观察穿孔素抑制剂EGTA对上述作用的影响。结果 用MACS法成功分离出CD4^＋CD25^＋T细胞，纯度可达98％，特异性表达而Faxp3基因，能明显抑制CD4^＋CD25^＋T细胞的体外增殖；骨髓来源的DC表达CDllc、MHCⅡ及少量协同刺激分子CD80、CD86；FACS体外杀伤实验证实以CD3／CD28抗体体外活化的CD4^＋CD25^＋调节性T细胞对自体DC有显著杀伤作用（P〈0．05），穿孔素抑制剂EGTA能部分抑制该杀伤效应（P〈0．05）。结论 CD4^＋CD25^＋调节性T细胞可通过杀伤作用对自体DC发挥免疫调节作用，穿孔素／颗粒酶杀伤途径可能参与其中。     

肺癌患者CD4+CD25high Foxp3+调节性T细胞的格局变化及意义

目的：研究肺癌患者外周血（PBMC）及肿瘤浸润淋巴细胞（TIL）中CD4^＋ CD25^high Foxp3^＋调节性T细胞（Treg）的比例改变，探讨其在抗肿瘤免疫中的调节作用。方法：分离肺癌患者PBMC及TIL，FACS分析CD4^＋／CD8^＋T细胞的比值及CD4^＋ CD25^highT细胞占CD4^＋T细胞的比例。Real-time PCR检测Treg特异性转录因子Foxp3基因在PBMC及TIL中的表达。结果：肺癌患者PBMC及TIL中CD4^＋／CD8^＋比值降低；而CD4^＋ CD25^high T细胞在CD4^＋T细胞中所占比例升高；Foxp3基因仅在TIL中高表达，而在PBMC中低或不表达，表明肿瘤局部的CD4^＋ CD25^high T细胞主要是CD4^＋ CD25^high Foxp3^＋ Treg。结合临床资料分析显示Treg在肺腺癌比例较高。结论：CD4^＋ CD25^high Foxp3^＋ Treg在肺癌患者肿瘤浸润淋巴细胞中明显升高，可能与其通过细胞与细胞间接触抑制CD8^＋T细胞的杀伤效应，最终发挥免疫抑制效应相关。     

CD4+CD25+调节性T细胞的生物学特性及功能

对自身抗原产生免疫耐受是防止发生自身免疫病的关键。自1995年日本学者Sakaguchi等首次报道CD4^＋CD25^＋调节性T（Treg）细胞以来，越来越多的研究证明这群T细胞在自身耐受的维持中发挥着重要的作用。CD4^＋CD25^＋调节性T细胞具有以下特点：①自身免疫防御作用；②自然条件下是处于无能（Anergy）状态；③抑制其他CD4^＋T细胞和CD8^＋T细胞的生物活性；④抑制活性是抗原非特异性的；⑤抑制方法可能通过细胞与细胞间直接接触，或经分泌抑制性细胞因子发挥免疫抑制效应；     

CD4+ CD25+调节性T细胞AICD机制的研究

目的探讨CD4^＋CD25^＋调节性T细胞活化诱导的细胞死亡（AICD）发生的机制。方法CD4^＋CD25^＋T细胞以磁性细胞分离器（MACS）从BALB／c小鼠或DO11．10小鼠的静息T细胞分离纯化。体外细胞增殖抑制实验证实其免疫调节作用。CD4^＋CD25^＋T细胞的AICD以CD3／CD28单克隆抗体活化或以特异性OVA323-339肽、抗原提呈细胞活化等两种方法获得。CD4^＋CD25^＋T细胞凋亡相关基因的表达通过实时定量PCR检测。流式细胞仪检测细胞的凋亡率。进一步观察FasL中和抗体、TRAIL中和抗体及caspase抑制剂zVAD-fmk对CD4^＋CD25^＋T细胞凋亡的影响。结果MACS成功分离CD4^＋CD25^＋T细胞，纯度可达98％，该细胞可特异性表达Foxp3基因，能明显抑制效应性T细胞的体外增殖。CD3／CD28抗体以及OVA特异性抗原活化8d的CD4^＋CD25^＋调节性T细胞AICD达39％～45％。活化前后的CD4^＋CD25^＋调节性T细胞死亡受体家族表达发生明显变化；FasL、TRAIL中和抗体及zVAD-fmk可明显抑制CD4^＋CD25^＋调节性T细胞的凋亡。结论FasL／Fas及其他凋亡相关分子可能参与了CD4^＋CD25^＋调节性T细胞的凋亡。     

树突状细胞扩增抗原特异性CD4+ CD25+调节性T细胞研究进展

CD4+CD25+调节性T细胞(Tr)是同时具有免疫低反应性和免疫抑制性功能两大特征的T细胞.研究证实,CD4+ CD25+ Tr在抑制器官特异性自身免疫性疾病及GVHD是抗原特异性的,因此,应用器官特异性而不是多克隆性的Tr将大大促进以Tr为基础的免疫治疗.而具有调节活性的CD4+ CD25+ Tr仅占人类外周血CIM+ T细胞的1%～2%,因此,研究体外大量扩增的方法 对于以Tr基础的治疗至关重要.研究表明,树突状细胞(DC)作为机体强有力的专职抗原递呈细胞可以扩增具有抗原特异性的CD4+ CD25+ Tr且能增加后者的抑制活性,这为治疗自身免疫性疾病及GVHD提供了新的治疗前景.     

CD4~+T细胞识别的肿瘤抗原的研究进展

在以往的肿瘤免疫研究中 ,人们往往关注肿瘤特异性CD8+ T细胞的抗肿瘤效应 ,并由此鉴定出许多CD8+ T细胞识别的肿瘤抗原。随着研究的深入 ,CD4 + T细胞在抗肿瘤免疫中的作用逐渐为人们所关注。联合应用MHCⅠ类和MHCⅡ类限制性抗原的肿瘤疫苗将有可能取得更好的抗肿瘤效果。本文就近年来鉴定的CD4 + T细胞识别的肿瘤特异性抗原进行了综述。     

CD4+CD25+调节性T细胞与系统性红斑狼疮病情活动性关系的研究

目的：检测系统性红斑狼疮患者外周血CD4^＋CD25^＋、CD4^＋CD8^＋调节性T细胞亚群，探讨其与疾病活动性、肾脏损伤、血清抗ds-DNA抗体及免疫球蛋白和补体C3含量的关系。方法：采用流式细胞术检测北京协和医院住院和门诊SLE患者（n=37）外周血CD4^＋CD25^＋T、CD4^＋CD8^＋T细胞群比例，以15例RA和15例SS组成自身免疫性疾病对照，30例健康体检者作为正常对照，观察调节性T细胞亚群与SLE患者疾病活动性指标SLEDAI、IgG、C3及血清抗ds-DNA抗体的关系。结果：①疾病活动期SLE患者外周血CD4^＋CD25^＋调节性T细胞群比例显著低于正常对照组（P〈0.01），疾病稳定期和风湿性疾病对照组与正常对照组结果差异无统计学意义。疾病活动期和稳定期SLE患者CD4＋CD8＋T细胞群比例都略高于正常对照组，但未发现结果差异有统计学意义（P〉0.05）。②疾病活动期SLE患者外周血CD4^＋CD25^＋T细胞比例及CD4^＋CD25^＋/CD4^＋值显著低于稳定期患者（P〈0.01）。SLE患者外周血CD4^＋CD25^＋/CD4^＋值与SLEDAI、补体C3呈低度相关（r分别为-0.491、0.368，P〈0.05），CD4^＋CD25^＋T细胞数量与SLEDAI呈负相关（r=-0.578，P〈0.05）。③SLE并发肾病组外周血CD4^＋CD25^＋T细胞群比例及CD4^＋CD25^＋/CD4^＋值显著低于非肾病组（P〈0.01；P〈0.05）。同一SLE患者治疗前后CD3^＋CD4^-CD8^-细胞和NK细胞降低，CD4^＋CD25^＋细胞、CD4^＋CD25^＋/CD4^＋值及CD8^＋T细胞增加，但未发现这些结果差异有统计学意义。本次研究未发现NK细胞、CD4^＋CD8＋T细胞、CD4^＋CD25^＋T细胞群比例在ds-DNA＋组与ds-DNA-组之间结果差异有统计学意义。结论：SLE患者外周血CD4^＋CD25^＋T细胞群比例与SLEDAI成负相关，与肾脏的损害也有密切关系，但与血清抗ds-DNA抗体产生的关系不明显。活动期SLE患者外周血CD4^＋CD25^＋T细胞减少，稳定期CD4^＋CD25^＋T细胞比例回升，因此推测CD4^＋CD25^＋T细胞的变化可能是导致疾病发生和病情发展及相关器官（如肾脏）损伤的关键环节之一。     

CD4^＋T细胞识别的肿瘤抗原的研究进展

在以往的肿瘤免疫研究中，人们往往关注肿瘤特异性CD8^ T细胞的抗肿瘤效应，并由此鉴定出许多CD8^ T细胞识别的肿瘤抗原。随着研究的深入，CD4^ T细胞在抗肿瘤免疫中的作用逐渐为人们所关注。联合应用MHCI类和MHCⅡ类限制性抗原的肿瘤疫苗将有可能取得更好的抗肿瘤效果。本文就近年来鉴定的CD4^ T细胞识别的肿瘤特异性抗原进行了综述。     

成人隐匿性自身免疫性糖尿病患者CD4+CD25+T细胞的变化研究

目的：通过观察成人隐匿性自身免疫性糖尿病（LADA）患者CD4^＋CD25^＋T细胞的变化并与速发性1型糖尿病（T1 DM）比较，了解成人隐匿性自身免疫性糖尿病患者T细胞免疫功能的变化及与1型糖尿病的异同点。方法：LADA组24例，速发性T1DM18例，对照组20例，应用流式细胞技术测定3组人选者T细胞表面分子CD4、CD8、CD25、CD4^＋CD25^＋、CD8^＋CD25^＋、CD4^＋CD25^＋CD62L^＋，以百分比表示各表面分子阳性T细胞占外周血淋巴细胞的比例。结果：LADA与T1DM组CD4^＋T细胞、CD4／CD8比值明显高于健康对照组（P〈0．01），LADA与T1DM对比无差异。LADA组CD25^＋、CD4^＋CD25^＋、CD4^＋CD25^＋CD62L^＋T细胞高于健康对照组（P〈0．05），明显高于T1 DM组（P〈0．01）。T1 DM组CD25^＋、CD4^＋CD25^＋、CD4^＋CD25^＋CD62L^＋T细胞略低于健康对照组，但无统计学意义（P〉0．05）。结论：LADA患者外周血中诱导免疫耐受的CD4^＋CD25^＋、CD4^＋CD25^＋CD62L^＋T细胞较对照组升高并明显高于T1 DM患者。LADA患者胰岛B细胞功能下降较速发性T1 DM患者相对缓慢可能与CD4^＋CD25^＋T细胞的免疫保护有关。     

CD4+CD25+ T cells as immunoregulatory T cells in vitro

We have further characterized the in vitro phenotype and function of anergic and suppressive CD4(+)25(+) T cells. Following TCR ligation, DO.11.10 CD4(+)25(+) T cells suppress the activation of OT-1 CD8(+)25(-) T cells in an antigen nonspecific manner. Although suppression was seen when using a mixture of APC from both parental strains, it was very much more marked when using F1 APC. APC pretreated with, and then separated from CD4(+)25(+) T cells did not have diminished T cell costimulatory function, suggesting that APC are not the direct targets of CD4(+)25(+) T cell regulation. CTLA-4 blockade failed to abrogate suppression by CD4(+)25(+) T cells in mixing experiments. Although CD4(+)25(+) T cells failed to respond following cross-linking of TCR, they could be induced to proliferate following the addition of exogenous IL-2, allowing the generation of a T cell line from CD4(+)25(+) T cells. After the first in vitro restimulation, CD4(+)25(+) T cells were still anergic and suppressive following TCR engagement. However, after three rounds of restimulation, their anergic and suppressive status was abrogated.     

Activated CD4+ CD25+ T cells suppress antigen-specific CD4+ and CD8+ T cells but induce a suppressive phenotype only in CD4+ T cells

CD4(+) CD25(+) regulatory T cells are increasingly recognized as central players in the regulation of immune responses. In vitro studies have mostly employed allogeneic or polyclonal responses to monitor suppression. Little is known about the ability of CD4(+) CD25(+) regulatory T cells to suppress antigen-specific immune responses in humans. It has been previously shown that CD4(+) CD25(+) regulatory T cells anergize CD4(+) T cells and turn them into suppressor T cells. In the present study we demonstrate for the first time in humans that CD4(+) CD25(+) T cells are able to inhibit the proliferation and cytokine production of antigen specific CD4(+) and CD8(+) T cells. This suppression only occurs when CD4(+) CD25(+) T cells are preactivated. Furthermore, we could demonstrate that CD4(+) T-cell clones stop secreting interferon-gamma (IFN-gamma), start to produce interleukin-10 and transforming growth factor-beta after coculture with preactivated CD4(+) CD25(+) T cells and become suppressive themselves. Surprisingly preactivated CD4(+) CD25(+) T cells affect CD8(+) T cells differently, leading to reduced proliferation and reduced production of IFN-gamma. This effect is sustained and cannot be reverted by exogenous interleukin-2. Yet CD8(+) T cells, unlike CD4(+) T cells do not start to produce immunoregulatory cytokines and do not become suppressive after coculture with CD4(+) CD25(+) T cells.     

Neuropilin-1+T细胞与CD4+CD25+调节性T细胞的比较

目的:分析Neuropilin-1 T细胞(Nrp-1 T细胞)与经典CD4 CD25 调节性T细胞(Treg)的关系并比较二者的免疫调节作用。方法:流式细胞术分析BALB/c小鼠脾脏T细胞上Nrp-1与CD4、CD25的表达关系并分选Nrp-1 T细胞及CD4 CD25 Treg,通过B16-F10-luc-G5黑色素肿瘤细胞体外培养实验并利用萤光成像系统,观察比较两种细胞对NK细胞杀伤B16-F10-luc-G5黑色素瘤细胞的影响。结果:CD4 CD25 Treg中表达Nrp-1的比例为(27.28±1.17)%,明显高于CD4 CD25-T细胞的(1.63±0.08)%(P<0.01);在体外实验中,Nrp-1 T细胞与CD4 CD25 Treg均能抑制NK细胞杀伤B16-F10-luc-G5黑色素瘤细胞,Nrp-1 T细胞组的肿瘤细胞数目在6、24、48、72h分别为984±15、1015±14、1261±21、1323±38,高于CD4 CD25 Treg组的931±4、983±8、1201±18、1256±18,两组肿瘤细胞数目在各时间点均有统计学意义(P<0.01)。结论:经典CD4 CD25 Treg中表达Nrp-1的细胞比例较高,Nrp-1 T细胞有负性免疫调节作用,抑制功能比CD4 CD25 Treg更强,可以作为一类新的Treg亚群。     

Human CD4+CD25+ regulatory T cells

In this report, we review studies of human CD4+CD25+ regulatory T cells (T-reg). Although lagging a few years behind the discovery of these cells in the mouse, the equivalent population of CD4+CD25+ regulatory T cells has also been isolated from human peripheral blood, thymus, lymph nodes and cord blood. In general, the characteristics of this T cell subset are strikingly similar between mouse and man. In the recent explosion of research reports on human CD4+CD25+ cells, although the majority of the characteristics ascribed to these cells appear to be consistent, contrasting results have been found primarily in regards to potential involvement of TGFbeta and production of IL-10. One explanation for this variability may reside in the fact that markedly different techniques are used to isolate human CD4+CD25+ T-reg cells and thus may result in the comparison of T-reg populations that differ in cellular composition and/or activation state. Another potential explanation for differences in human T-reg function may rest on the extreme variability of the culture conditions and TCR stimuli that have been used to test the functional properties of these cells in vitro. The strength of the TCR signal provided to the culture greatly affects the functional outcome of the co-culture and can result in the difference between suppression and full activation. Surprisingly, it appears that stronger stimulation has a greater and more rapid effect on the T-resp cell than on the T-reg cell as it causes T-resp cells to quickly become resistant to suppression. Thus, the details of in vitro culture conditions may at least partially account for disparate findings in regard to the functional characterization of human CD4+CD25+ cells. Here we review the evidence regarding the identification of human CD4+CD25+ regulatory T cells and their possible mechanism(s) of function.     

Alloantigen-induced regulatory CD8+CD103+ T cells

Regulatory T cells (Tregs) appear of great importance in the balance between alloreactivity and tolerance and subsets of both CD4(+) and CD8(+) T cells have been recognized to function as regulatory T cells after allogenic transplantation. Among the CD8(+) T-cell subsets, the CD103(+) cells were most recently identified as regulatory. In this review, we describe their phenotypical and functional properties, as well as their relevance for the alloimmune response in vivo. These CD8(+)CD103(+) Tregs are generated within mixed lymphocyte cultures (MLCs) and are elevated by additional transforming growth factor-beta. Interestingly, myeloid dendritic cells are the responsible cell type for induction of CD103(+) Tregs. Allostimulated CD8(+)CD103(+) Tregs display an antigen-experienced effector phenotype with limited effector functions such as cytotoxicity and interferon-gamma production and show a reduced proliferation capacity after restimulation. Beside this anergic phenotype, CD8(+)CD103(+) Tregs are able to suppress alloreactive effector T cells. Through intracellular cytokine staining and transwell assays, we showed that the mechanism of suppression is cytokine independent, but close cell-cell contact is required for suppression.     

Generation of peptide-specific CD8+ T cells by phytohemagglutinin-stimulated antigen-mRNA-transduced CD4+ T cells

Functional analysis of antigen-specific CD8(+) T cells is important for understanding the immune response in various immunological disorders. To analyze CD8(+) T cell responses to a variety of antigens with no readily defined peptides available, we developed a system using CD4(+) phytohemagglutinin (PHA) blasts transduced with mRNA for antigen molecules. CD4(+) PHA blasts express MHC class I and II, and also CD80 and CD86 and are thus expected to serve as potent antigen presenting cells. EGFP mRNA could be transduced into and the protein expressed by more than 90% of either LCL or CD4(+) PHA blasts. Its expression stably persisted for more than 2 weeks after transduction. In experiments with HLA-A*2402 restricted CD8(+) CTL clones for either EBNA3A or a cancer-testis antigen, SAGE, mRNA-transduced lymphoid cells were appropriate target cells in ELISPOT assays or (51)Cr releasing assays. Finally, using CD4(+) PHA blasts transduced with mRNA of a cancer-testis antigen MAGE-A4, we successfully generated specific CTL clones that recognized a novel HLA-B*4002 restricted epitope, MAGE-A4(223-231). Messenger RNA-transduced CD4(+) PHA blasts are thus useful antigen presenting cells for analysis of CD8(+) T cell responses and induction of specific T cells for potential immunotherapy.     

High-avidity CD8+ T cells

The primary goal of vaccination is the establishment of protective immunity. Thus there has been significant effort put toward the identification of attributes of the immune response that are associated with optimal protection. Although the number of virus-specific cells elicited is unquestionably important, recent studies have identified an additional parameter, functional avidity, as critical in determining the efficiency of viral clearance. T-cell avidity is a measure of the sensitivity of a cell to peptide antigen. High-avidity cells are those that can recognize antigen-presenting cells (APC) bearing very low levels of peptide antigen, whereas low-avidity cells require much higher numbers of peptide major histocompatibility complex (MHC) complexes in order to become activated or exert effector function. We are only now beginning to gain insights into the molecular control of avidity and the signals required for the optimal activation, expansion, and retention of high-avidity cells in vivo. This review summarizes the current knowledge regarding CD8⁺ T-cell avidity and explores some of the important issues that are, as of yet, unresolved.     

CD4+CD25+Foxp3+ regulatory T cells induce cytokine deprivation-mediated apoptosis of effector CD4+ T cells

A key issue in mammalian immunology is how CD4+CD25+Foxp3+ regulatory T cells (T(reg) cells) suppress immune responses. Here we show that T(reg) cells induced apoptosis of effector CD4+ T cells in vitro and in vivo in a mouse model of inflammatory bowel disease. T(reg) cells did not affect the early activation or proliferation of effector CD4+ T cells. Cytokines that signal through the common gamma-chain suppressed T(reg) cell-induced apoptosis. T(reg) cell-induced effector CD4+ T cell death required the proapoptotic protein Bim, and effector CD4+ T cells incubated with T(reg) cells showed less activation of the prosurvival kinase Akt and less phosphorylation of the proapoptotic protein Bad. Thus, cytokine deprivation-induced apoptosis is a prominent mechanism by which T(reg) cells inhibit effector T cell responses.     

CTLA-4 x Ig converts naive CD4+CD25- T cells into CD4+CD25+ regulatory T cells

CTLA-4 x Ig was originally designed as an immunosuppressive agent capable of interfering with the co-stimulation of T cells. In the present study, we demonstrate that CTLA-4 x Ig, in combination with TCR ligation, has the additional capacity to convert naive CD4+CD25- T cells into Foxp3+ regulatory T (T(reg)) cells, as well as to expand their numbers. The CD4+CD25+Foxp3+ T(reg) generated by CTLA-4 x Ig treatment in vitro potently suppress effector T cells. Extending this in vivo, we show that systemic administration of CTLA-4 x Ig increases the percentage of CD4+CD25(hi)Foxp3+ cells within mixed lymphocyte reaction-induced murine lymph nodes. Significantly, the in vitro conversion of naive CD4+CD25- T cells into T(reg) cells is antigen-presenting cell (APC) dependent. This finding, together with the further observation that this conversion can also be driven in vitro by an antibody that engages B7-2 ligand, suggests that CTLA-4 x Ig-driven T(reg) induction may be predicated upon active CTLA-4 x Ig to B7-2 signaling within APC, which elicits from them T(reg)-inducing potential. These findings extend CTLA-4 x Ig's functional repertoire, and at the same time, reinforce the concept that T cell anergy and active suppression are not entirely distinct processes and may be linked by some common molecular triggers.