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。     

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。     

流式细胞术检测CFSE标记人T细胞亚群增殖反应

目的探讨应用流式细胞术和活细胞荧光染料CFSE检测T淋巴细胞各亚群增殖反应的方法学。方法人外周血单个核细胞（PBMC）经CFSE染色后,分别用植物凝血素（PHA）、CD3 mAb和结核杆菌抗原（Mtb-Ag）刺激,加IL-2扩增后,用流式细胞术检测活化增殖后T细胞各亚群的比例,并用ModFit软件分析各亚群的增殖动力模型。结果PHA和CD3 mAb主要活化总T细胞,CD8^＋T细胞的增殖优于CD4^＋T细胞,但CD4^＋T细胞前4代细胞明显多于CD8^＋T细胞。Mtb-Ag主要刺激γδT细胞增殖。结论以CFSE标记淋巴细胞,结合流式细胞术可有效检测出不同T细胞亚群对不同刺激剂的增殖反应以及增殖动力学变化。     

CD4+CD25-T细胞凋亡机制的研究

目的：探讨CD4^＋CD25^-T细胞AICD发生的机制.方法：磁性细胞分离器（MACS）分离CD4^＋CD25^- T细胞.以CD3/CD28单克隆抗体活化BALB/c小鼠CD4^＋CD25^-T细胞或以OVA323-339肽、抗原递呈细胞活化DO11.10小鼠CD4^＋CD25^-T细胞两种方式建立AICD模型.基因芯片检测CD4^＋CD25^-T细胞和CD4＋CD25＋T细胞凋亡相关基因的表达.流式细胞仪检测细胞的凋亡率.并观察FasL中和抗体、TRAIL中和抗体及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%.建立了CD3/CD28抗体以及OVA特异性抗原活化的CD4^＋CD25^-T细胞AICD模型,CD4^＋CD25^-T细胞凋亡率达35%～40%.基因芯片分析发现CD4^＋CD25^-T细胞相对高表达TRAIL、FAS,而CD4^＋CD25^-T细胞相对高表达DR5、FasL.FasL、TRAIL中和抗体及zVAD-fmk可明显抑制CD4＋CD25＋T细胞的凋亡.结论：FasL、TRAIL及其它凋亡相关分子可能参与了CD4^＋CD25^-T细胞的凋亡.     

手足口病患儿T淋巴细胞亚群与CD3^＋CD4ˉCD8ˉ双阴性调节性T细胞的检测及其临床意义

目的探讨外周血T淋巴细胞亚群及CD3^＋CD4ˉCD8ˉ双阴性调节性T细胞在手足口病病人发病中的临床意义。方法采用流式细胞术检测了46例手足口病患者以及17例健康体检者外周血T细胞亚群CD3^＋、CD3^＋CD4ˉCD8^＋、CD3^＋CD4^＋CD8^＋、CD3^＋CD4^＋CD8ˉ与CD3^＋CD4ˉCD8ˉ双阴性调节性T细胞水平。结果与正常对照组相比,手足口病患者组CD3^＋、CD3^＋CD4ˉCD8’、CD3^＋CD4ˉCD8ˉ双阴性调节性T细胞的百分率降低（P值分别为0．008、0．050、0．025）。CD3^＋CD4^＋CD8^＋、CD3^＋CD4^＋CD8ˉ百分率以及CD4／CD8比值差异无统计学意义（P值分别为0．847、0．775、0．149）,以上各细胞亚群的百分率以及CD4／CD8比值在年龄与性别方面差异无统计学意义。结论手足口病患者CD3^＋CD4ˉCD8ˉ双阴性调节性T细胞、CD3^＋、CD3^＋CD4ˉCD8^＋异常变化提示其免疫功能异常。     

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+CD25+T细胞在系统性红斑狼疮中的表达及意义

目的：探讨CD4^＋ CD25^＋ T细胞、IL-10在系统性红斑狼疮（SLE）患者外周血的表达及临床意义。方法：入组30例SLE患者和20例正常对照者，其中活动性SLE患者17人，非活动性SLE患者13人。用流式细胞仪检测SLE患者和正常对照者的外周血CD4^＋ CD25^＋ T细胞阳性率，用酶联免疫吸附试验（ELISA）检测血清中IL-10浓度。结果：活动性和非活动性SLE患者CD4^＋ T细胞总数均低于正常对照者；活动性和非活动性SLE患者CD4^＋ CD25^＋ T细胞阳性率高于正常对照者；活动性SLE患者IL-10浓度显著高于非活动性SLE患者和正常对照者。SLE患者CD4^＋ CD25^＋ T细胞阳性率和血清IL-10浓度与补体C3、抗DNA抗体水平及SLEDAI积分均无相关性。结论：SLE患者外周血CD4^＋ CD25^＋ T细胞是活化T细胞的标志，IL-10分泌异常与SLE的发病有关。     

Th17细胞:一种新的效应CD4+T细胞亚群

当CD4^＋T细胞被激活以后，通过不同的分化途径获得特定的生物学功能。根据产生细胞因子和生物功能的不同，传统上将CD4^＋T细胞分为Th1和Th2细胞亚群。Th1细胞产生IFN-1和IL-2，通过活化巨噬细胞清除胞内病原微生物并介导迟发型变态反应；Th2细胞产生IL-4、IL-5和IL—13，介导由嗜酸性粒细胞引起的炎性反应，清除细胞外病原微生物并参与变态反应。IFN-γ和IL-4相互拮抗，调控着Th1和Th2细胞的扩增和功能。     

淋巴细胞共刺激信号和凋亡信号异常与RA免疫效应亢进的研究

目的：探究T淋巴细胞表面多种细胞信号分子所介导的细胞活化或凋亡信号在RA患者免疫功能紊乱中的作用。方法：采用流式细胞术检测RA患者外周血T细胞亚群及其表面共刺激分子cD154（cD40L）、CD30和凋亡受体CD95（Fas）的表达。结果：RA患者外周血T细胞亚群偏移，CD4^＋T细胞增加，CD8^＋T细胞减少；共刺激分子CD154在CD4^＋和CD8^＋T细胞上的表达均上调，但CD30分子的表达均降低，并以CD4^＋T细胞降低更为明显。同时，凋亡受体CD95分子在T细胞亚群上的表达均明显增加。结论：RA患者T淋巴细胞表面多种信号分子表达异常，共同导致了RA患者免疫功能紊乱。     

CD4+效应T细胞的新成员——Th17细胞

在抗原的刺激下，初始CD4^＋T细胞被诱导分化为效应或调节T细胞，传统上CD4^＋效应T细胞因产生的细胞因子的不同被分为两个亚群：Th1细胞——主要促进细胞内感染的病原体的清除，由IL-12诱导分化，产生的主要细胞因子是IFN-γ；和Th2细胞——主要促进寄生虫感染的清除（如蠕虫），由IL-4诱导分化，主要产生IL-4、IL-5、IL-13。     

可溶性嵌合补体抑制分子的构建及表达

目的：制备能抑制补体活化的2个关键环节（C3/C5转化酶和MAC的形成）的一种新型、高效补体抑制剂。方法：先设计引物，然后通过PCR技术扩增重组可溶性CD46/CD55/CD59嵌合分子cDNA片段，重组于pSecTagA真核表达载体上，分别利用COS-7细胞和中国仓鼠卵巢（Chinese hamster ovary，CHO）细胞进行表达，并用抗人CD46多克隆抗体及抗人CD55、CD59单克隆抗体对表达产物进行western bolting鉴定。结果：DNA测序证实，前端带有小鼠IgGκ链前导序列，后端融合有编码6个组氨酸碱基的CD46/CD55/CD59嵌合分子cDNA片段的阅读框完整。免疫印迹结果显示，表达的重组蛋白分别能与抗人CD46多克隆抗体和抗人CD55、CD59单克隆抗体结合。结论：成功构建并在真核细胞内表达了重组可溶性CD46/CD55/CD59嵌合分子，为进一步研制和开发新一代多功能、多靶点补体抑制剂奠定了基础。     

Early increase of CD4+ CD45RA+ and CD4+ CD95− cells with conserved repertoire induced by anti-retroviral therapy in HIV-infected patients

Administration of anti-retroviral drugs induces a decrease of viral load associated with increase of CD4⁺ cell count in most HIV-infected patients. To investigate the early changes in CD4⁺ cell phenotype induced by anti-retroviral therapy, six patients with CD4⁺ cell count > 100/mm³ and never treated with anti-HIV therapy were enrolled and blood samples collected several times within 14 days from the initiation of therapy with Zidovudine plus Didanosine. CD4⁺ cell count and HIV viraemia were investigated at each time point, as well as the expression of CD45RA, CD45RO and CD95/Fas molecules on CD4⁺ cells, and the T cell receptor (TCR) Vβ repertoire of CD4⁺ cells. All patients showed a rapid and dramatic decrease in viral load with a corresponding increase of CD4⁺ cell count. The main remodelling of CD4⁺ cell subpopulations took place in the first 14 days of therapy, and consisted of: (i) increased CD4⁺ CD45RA⁺/CD4⁺ CD45RO⁺ ratio; (ii) decrease of CD95/Fas expression. The rise in absolute number of CD4⁺ CD45RA⁺ cells was paralleled by an increase of CD4⁺ CD95/Fas^? cells and accounted for most of the early increment of CD4⁺ cell count. The TCR Vβ repertoire of CD4⁺ cells was conserved after anti-HIV therapy, with the exception of two patients with expanded CD4⁺ Vβ12⁺ cells, which also tested CD45RA⁺ and CD95/Fas^?. These experiments show that newcomer CD4⁺ lymphocytes are CD45RA⁺ CD95/Fas^? cells, suggesting that blocking HIV replication causes an early and antigen-independent proliferation of possibly ‘naive’ cells unprimed for CD95/Fas-mediated apoptosis. These cells expressed a conserved and widespread TCR repertoire, suggesting that their capability for antigenic recognition is intact.     

Increased CD11/CD18 expression on peripheral blood leucocytes of patients with sarcoidosis.

Sarcoidosis is a multisystem disease of unknown etiology characterized by non-caseating granulomata, formed mainly from macrophages surrounded by lymphocytes and plasma cells. Using a novel method for the preparation of blood leucocytes for flow cytometry, we report increased expression of LeuCAMs (CD11/CD18) on peripheral blood leucocytes of 11 Caucasian and 10 Afro-Caribbean patients with sarcoidosis compared with age-, sex- and race-matched controls. Whilst the percentages of the cells expressing CD11/CD18 were no different, the density, expressed as mean fluorescence intensity (MFI), was greater for all leucocytes in sarcoids than in normal individuals. The expression of intercellular adhesion molecule-1 (ICAM-1), a ligand for LFA-1 which is expressed on all leucocytes, was not significantly different from normal, whereas HLA-DR was expressed more intensely on sarcoid monocytes (P less than 0.01) and blood lymphocytes (P less than 0.005) than control cells. Our findings are consistent with leucocyte activation although we were unable to confirm reports of elevated tumour necrosis factor-alpha (TNF-alpha) in the patients' plasma using an ELISA. Increased expression of adhesion molecules on peripheral blood leucocytes may play a role in the cellular extravasation, aggregation, and granuloma formation seen in sarcoidosis.     

Induction of CD95 ligand expression on T lymphocytes and B lymphocytes and its contribution to apoptosis of CD95-up-regulated CD4+ T lymphocytes in macaques by infection with a pathogenic simian/human immunodeficiency virus

Using an established SIV/HIV-C2/1-infected cynomolgus monkey model displaying stable CD4+ T cell depletion, the kinetics of apoptosis and the levels of expression of CD95 membrane-associated CD95L on lymphocytes were investigated to test the involvement of the CD95/CD95L system in CD4+ T lymphocyte loss in vivo. Rapid depletion of CD4+ T cells occurred up to 2 weeks after infection, with chronic CD4+ T lymphopenia thereafter. During the initial CD4+ T cell loss, which was accompanied by viraemia, about 90% of the peripheral CD4+ T cell subset underwent spontaneous apoptotic cell death during 24 h of culture. Increased expression of CD95 was observed on both CD4+ and CD8+ T cell subsets, with CD95 expression on CD8+ cells declining rapidly, but high CD95 expression being maintained on CD4+ cells. Since CD95L was expressed on CD8+ T cells, B cells and to a lesser extent on CD4+ T cells, this suggests that CD95-mediated apoptosis might be controlled in an autocrine/paracrine fashion.     

Mouse CD146/MCAM is a marker of natural killer cell maturation

CD146/melanoma cell adhesion molecule is an adhesion molecule expressed by endothelial cells and by a small fraction of activated T and B lymphocytes in humans. In order to analyze the pattern of CD146 expression in mouse leukocytes at steady-state conditions, we generated a set of novel rat anti-mouse CD146 monoclonal antibodies. CD146 expression was undetectable on monocytes, dendritic cells, T cells or B cells, but was expressed on about 30% of neutrophils and 60% of NK cells. Within murine lymphocytes, CD146 was defined as a novel NK-specific surface molecule. An increased percentage of CD146+ cells was found in the most mature CD27(-)CD11b+ NK cell subpopulation, which also displays higher expression of Ly49C/I, Ly49D and KLRG1 and lower expression of NKG2A/C/E molecules. CD146+ NK cells were found to be less cytotoxic and produce less IFN-gamma than CD146(-) NK cells upon stimulation with target cells or activating antibodies. These findings define CD146 as a marker of mouse NK cell maturation that may be used as an alternative to the combined use of CD27 and CD11b staining to detect final stages of NK cell maturation.     

CD30 expression on circulating memory CD4+ T cells as a Th2-dominated situation in patients with atopic dermatitis

Th2 clones have been reported to express CD30 preferentially, but whether T cells producing Th2-type cytokines may favor CD30 expression in the in vivo state remains unknown. We investigated the expression of CD30 on circulating T cells in atopic dermatitis (AD) as a Th2-dominated disorder. Peripheral blood mononuclear cells were prepared from 51 AD patients and 14 nonatopic controls, and their phenotypes were analyzed with flow cytometry. Cytokine production by stimulated CD4+ T cells was also assessed by the single-cell-staining method. Flow cytometric analysis clearly revealed that CD30+ T cells were identifiable in the blood of AD patients with greater frequency compared to controls. The important finding was that CD30 expression was restricted to a small but substantial population of memory (CD45RO+) CD4+ T cells, but not CD8+ ones. In AD patients, it was demonstrated that the percentages of CD30+ cells within CD45RO+ CD4+ T cells correlated well with the disease severity, serum IgE levels, peripheral eosinophil counts, and tendency toward Th2-dominant cytokine pattern as determined by the ratio of interleukin-4 to interferon-gamma production. This study suggests that CD30 expression in circulating T cells might serve as an in vivo marker for the Th2-dominated condition.     

Altered expression of CD11/CD18 on the peripheral blood phagocytes of patients with tuberculosis.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is characterized by granulomatous lesions made up of epithelioid cells, giant cells and mononuclear leucocytes. Cell-cell adhesion is important in granuloma formation and in the leucocyte migration which accompanies it. We have recently shown increased expression of the adhesion molecules CD11/CD18 (LeuCAMs, beta 2 integrins) on peripheral blood leucocytes from patients with sarcoidosis (Shakoor & Hamblin, 1992). Here we have studied the expression of CD11/CD18 and CD29 (VLA beta 1 integrin) on the peripheral blood leucocytes of 10 TB patients by flow cytometry. The density (expressed as mean fluorescence intensity) of CD11b on monocytes and polymorphs was increased (P < 0.005), as was CD11c (P < 0.005) and CD18 (P < 0.05) on polymorphs. CD11a expression was significantly reduced on polymorphs (P < 0.05). No differences were found in the expression of CD29, the percentages of cells expressing any molecule and, in contrast to sarcoidosis, the density of any molecule on lymphocytes. Although the cytokine tumour necrosis factor (TNF) has been implicated in the process of up-regulation, an ELISA for TNF failed to detect significant levels in plasma. The results suggest increased peripheral phagocyte CD11/CD18 expression is a feature of TB, which may contribute to the pathological processes involved.     

Canine leukocyte cell adhesion molecules (LeuCAMs): Characterization of the CD11/CD18 family

The canine LeuCAM (CD11/CD18) family is characterized using a panel of newly developed anti-canine LeuCAM monoclonal antibodies (mAb) as well as a cross-reactive anti-human CD11b mAb. The new anti-canine LeuCAM mAb were developed by immunizing mice with purified canine CD11/CD18 antigen derived from an anti-canine CD18 affinity column. Six mAb with reactivity to the canine LeuCAM family were cloned and characterized. These 6 included a new anti-canine CD18 mAb, 2 anti-canine CD11a mAb, 2 anti-canine CD11c mAb, and a mAb which recognizes a novel canine CD11/CD18-related macrophage antigen, designated LeuCAMmac, which is described in a separate report. The cell and tissue distribution of canine LeuCAMs was found to be similar to that reported in other species with a few notable exceptions. One prominent exception was the finding that canine CD11c, in contrast to human CD11c, was much more widely distributed on dendritic cells than it was on tissue macrophages. The molecular organization of the canine LeuCAM family was also found to be similar to that reported in other species, with the possible exception of the canine CD11b alpha chain, which may exist as several different species. It is anticipated that these anti-canine LeuCAM mAb will prove useful in immunophenotypic studies of canine hemolymphatic system neoplasia.     

Differential gene expression in CD8+ cells exhibiting noncytotoxic anti-HIV activity

Suppressive subtractive hybridization with polymerase chain reaction was used to identify the gene(s) associated with the CD8+ cell noncytotoxic anti-HIV response. The differences in gene expression profiles of CD8+ cells from a pair of discordant HIV-positive identical twins were studied. Forty-nine genes were identified as expressed at higher levels in the CD8+ cells from the infected twin that inhibited viral replication. The differential expression of these genes was then evaluated using Q-PCR to determine if this gene expression pattern is evident in CD8+ cells from other HIV-positive subjects showing this antiviral activity. Three genes, including one unknown, were found to have significantly increased expression in antiviral CD8+ cells.     

Importance of CD80/CD86-CD28 interactions in the recognition of target cells by CD8+CD122+ regulatory T cells

CD8+CD122+ regulatory T cells are a newly identified, naturally occurring type of regulatory T cell that produce interleukin-10 (IL-10) and effectively suppress interferon-gamma (IFN-gamma) production from both CD8+ and CD4+ target cells. Molecular mechanisms responsible for the recognition of target cells by CD8+CD122+ regulatory T cells were investigated in this study by using an in vitro culture system that reconstitutes the regulatory action of these cells. CD8+CD122( regulatory T cells did not produce IL-10 and did not suppress the IFN-gamma production of allogeneic target T cells when they were stimulated by immobilized anti-CD3 antibody alone, but they clearly produced IL-10 and suppressed the IFN-gamma production of target cells when stimulated by anti-CD3 plus anti-CD28-coated beads. IFN-gamma production by major histocompatibility complex-class I-deficient T cells was also suppressed by CD8+CD122+ regulatory T cells stimulated with anti-CD3 plus anti-CD28 antibody but was not suppressed by cells stimulated by anti-CD3 alone. Experiments examining the blockade of cell surface molecules expressed on either the regulatory cells or the target cells by adding specific neutralizing antibodies in the culture indicated that CD80, CD86, and CD28 molecules were involved in the regulatory action, but cytotoxic T lymphocyte antigen-4, inducible costimulatory molecule (ICOS) and programmed death-1 (PD-1) molecules were not. Finally, CD8+CD122+ cells isolated from CD28-knockout (CD28-/-) mice showed no regulatory activity. These results indicate that CD8+CD122(+) regulatory T cells recognize target T cells via the interaction of CD80/CD86-CD28 molecules to become active regulatory cells that produce suppressive factors such as IL-10.