黏蛋白1基因磁转染树突状细胞诱导细胞毒性T细胞抗膀胱肿瘤免疫效应的研究

目的:探讨黏蛋白1(mucins 1,MUC1)基因磁转染体外人树突状细胞(dendritic cell,DC)的可行性,观察其诱导的特异性抗MUC1膀胱癌CTL的免疫效应.方法:以葡聚糖磁性纳米颗粒(DMN)作为载体,在多聚赖氨酸(PLL)的辅助下,通过静电作用结合MUC1基因的真核表达载体pEGFP-C1-MUC1,在钕-铁-硼稀土强磁块的磁场作用下转染DC,荧光显微镜下观察及流式细胞术检测转染效率,并用RT-PCR法检测转基因DC中MUC1基因的表达;再将转染MUC1基因的DC与自体T细胞共培养,并分别用乳酸脱氢酶释放法检测所致敏的细胞毒性T淋巴细胞(cytotoxic lymphocyte,CTL)对MUCI特异性抗膀胱癌(膀胱肿瘤BIU87细胞系)的杀伤活性,用透射电镜观察CTL诱导靶细胞凋亡情况;ELISA法测定MUC1基因修饰后的DC刺激自体T细胞分泌IFN-γ的能力.结果:pEGFP-C1-MUC1转染效率为10%左右,荧光显微镜下可观察到明显绿色荧光蛋白的表达,RT-PCR法可检测到MUC1条带,转染MUC1基因的DC与自体T细胞混合培养后能诱导出MUC1特异性的CTL,对BIU87细胞的杀伤实验表明T-DC-MUC1的杀伤活性显著高于对照组T-DC-pEGFP-C1和T-DC诱导的CTL(P均<0.05);在透射电镜下也可观察到部分BIU87膀胱肿瘤细胞出现了细胞核核仁消失,染色质浓集于核膜周围等早期凋亡表现;基因修饰后的DC能刺激自体T细胞分泌高水平的IFN-γ,明显高于未转染的DC(P<0.05).结论:葡聚糖磁性纳米颗粒在同定磁场的作用下成功将MUC1基因转入DC,并可有效诱导出特异性抗MUC1膀胱癌的细胞毒性T细胞.     

小儿急性淋巴细胞白血病血清CD3+ CD4- CD8- T细胞和T细胞亚群的变化及其临床意义

目的 探讨小儿急性淋巴细胞白血病(ALL)外周血CD3+ CD4- CD8- T细胞(DNT细胞)及T淋巴细胞亚群的变化及意义.方法 采用免疫荧光流式细胞术检测30例ALL患儿及24例健康小儿外周血DNT细胞及T淋巴细胞亚群CD3+ T细胞、CD3+ CD4+ T细胞及CD3+ CD8+ T细胞水平.结果 DNT细胞、CD3+ T细胞、CD3+ CD4+ T细胞百分比均明显低于对照组,分别为(4.93±3.75)%比(8.19±3.21)%(t=3.4,P<0.01):(49.99 ±11.70)%比(64.13 ±11.39)%(t=4.1,P<0.01);(28.30 ±7.56)%比(34.61 ±6.43)%(t=3.2,P<0.01);而CD3+ CD8+ T细胞百分比明显高于对照组,为(31.19±9.89)%比(24.33 ±4.24)%(t=3.1,P<0.01).结论 ALL患儿外周血DNT细胞及T亚群的变化提示患儿体内存在免疫功能紊乱,这可能与ALL的发病机制有关.     

细胞黏附分子SLeX和CD24在喉鳞状细胞癌组织中的表达

目的:探讨细胞黏附分子唾液酸化Lewis-X抗原(SLeX)和CD24在喉鳞状细胞癌组织中的表达,阐明其在喉鳞状细胞癌发生发展中的作用.方法:采用免疫组织化学方法分别检测42例喉鳞状细胞癌患者的42个原发灶、24个相应癌旁组织及20例睡眠呼吸暂停低通气综合征(OSAHS)手术患者的咽部正常黏膜组织中SLeX和CD24的表达情况.结果:喉癌组织、癌旁组织及对照正常黏膜组织中SLeX阳性表达率分别为71.4%、37.5%和30.0%;强阳性表达率分别为50.0%、8.3%和5.0%.CD24的阳性表达率分别为64.3%、33.3%和25.0%;强阳性表达率分别为35.7%、4.2%和0.0%.3组间两两比较,喉癌组织与癌旁组织、正常黏膜组织阳性表达率差异均有统计学意义(P<0.01);癌旁组织与正常黏膜组织阳性表达率差异无统计学意义(P>0.05).SLeX、CD24强阳性表达与颈部淋巴结转移情况、临床分期及组织病理学分级相关(P<0.05).SleX和CD24在喉癌组织中的阳性率呈显著正相关关系(r=0.695,P<0.05).结论:SLeX及CD24蛋白表达与喉鳞状细胞癌的发生发展密切相关,其检测对喉癌的生物治疗和预测预后具有一定的临床意义.     

茶多酚与银杏叶提取物联用对人乳腺癌细胞增殖的影响

[目的]研究茶多酚与银杏叶提取物联合作用对人乳腺癌细胞 MDA-MB-231增殖的影响.[方法]采用MTT 法测定茶多酚、银杏叶提取物单独及联合应用对人乳腺癌细胞系MDA-MB-231的抑制作用;利用光镜观察茶多酚、银杏叶提取物对人乳腺癌系MDA-MB-231形态的影响.[结果]MTT 法显示银杏叶提取物与低浓度(10、20μg/ml)的茶多酚联合使用,对乳腺癌细胞抑制率明显高于单独用药组,但是联合用药组只有在一定的浓度范围内才会产生协同作用抑制乳腺癌细胞增殖;在细胞形态方面,与单独用药组、对照组相比,联合用药组乳腺癌细胞生长状况差,折光性弱,贴壁细胞皱缩,变圆.[结论]银杏叶提取物在低浓度下对人乳腺癌细胞系MDA-MB-231 生长无明显抑制作用,茶多酚和茶多酚联合银杏叶提取物均可抑制MDA-MB-231 细胞生长,联合用药组强于单独用药,在一定浓度范围内起协同作用.     

乳腺癌细胞MDA-MB-231肺转移模型的建立及其评价

目的:探讨用绿色荧光蛋白(GFP)标记的乳腺癌细胞MDA-MB-231建立可量化评估的自发性肺转移和实验性肺转移动物模型,为研究乳腺癌的转移机制提供依据.方法:采用慢病毒载体介导的病毒包装体系,获得稳定表达GFP的细胞系MDA-MB-231-GFP,通过皮下注射方式将细胞接种于Balb/C裸鼠皮下,建立自发性肺转移模型,通过尾静脉注射方式将细胞接种到重症联合免疫缺陷(SCID)小鼠体内,建立实验性肺转移模型,分别于8周和5周后处死小鼠,取肺组织于体视显微镜下观察.结果:自发性肺转移小鼠接种细胞8周后,原位形成直径约为15 mm的肿瘤块;处死小鼠后肺部大体标本未见结节状转移灶,但488 nm激发光下见转移灶呈绿色点状分布.实验性肺转移小鼠接种细胞5周后处死小鼠,肺部形成的转移灶肉眼不可见,但在488 nm激发光波长下同样呈现绿色点状分布.肺转移灶易于观察和统计.结论:成功建立了可以量化的MDA-MB-231细胞肺转移动物模型.     

成年人伴CD2表达B系急性淋巴细胞白血病免疫表型特征分析

目的 了解成年人伴CD2表达B系急性淋巴细胞白血病(CD+2 B-ALL)的免疫表型特征,为临床诊断、治疗及预后判断提供依据.方法 应用流式细胞术及多种单克降抗体检测18例成年人CD+2B-ALL及68例CD-2 B-ALL患者的免疫表型,并对其结果进行分析比较.结果 CD+2 B-ALL的发病年龄明显小于CD-2 B-ALL,18例成年人CD+2 B-ALL的大部分表面标志物与CD-2 B-ALL相似,其中CD10表达水平[(73.78±26.67)%]高于CD-2 B-ALL[(52.84±35.25)%],差异有统计学意义(t=2.35,P<0.05),CD33表达水平[(15.46±27.41)%]则低于CD-2 B-ALL[(31.15±27.72)%],差异有统计学意义(t=2.16,P<0.05);所有B-ALL患者都高表达CD34,阳性表达率分别为72.2%(13/18)和80.9%(55/68),差异无统计学意义(χ2=0.64,P>0.05).CD+2 B-ALL的CD20阳性率明显低于CD-2 B-ALL,差异有统计学意义(χ2=11.38,P<0.05).CD+2 B-ALL伴髓系抗原(CD13或CD33)表达率为44.4%(8/18),明显低于CD-2 B-ALL的72.1%(49/68),差异有统计学意义(χ2=4.86,P<0.05).结论 成年人CD+2 B-ALL与CD-2 B-ALL具有相似的免疫表型,主要来源于造血干细胞的恶性转化,CD+2 B-ALL伴髓系抗原(CD13、CD33)及CD20表达明显低于CD2 B-ALL,提示成年人CD+2 B-ALL可能有较好的预后.     

CD133免疫磁珠分选脑肿瘤干细胞及其生物学特性

目的:从人脑肿瘤组织中分离、培养、纯化和鉴定脑肿瘤干细胞(BTSCs),探讨CD133免疫磁珠分选方法获取BTSCs的可行性及BTSCs的生物学特性.方法:留取人脑胶质母细胞瘤新鲜标本,分离获得脑肿瘤细胞.应用CD133免疫磁珠分选方法纯化BTSCs;流式细胞仪检测分选阳性率;神经球计数法分析CD133+/-亚群细胞神经球形成情况;免疫荧光方法检测CD133+/-亚群细胞表面神经干细胞(NSCs)标记物CD133、神经巢蛋白(nestin)表达情况;检测CD133+/-亚群细胞经诱导分化后细胞表面分化标记物β-TubulinⅢ、GFAP表达情况.结果:CD133+亚群细胞具有干细胞特性,可形成明显的神经球,具有自我更新和明显的增殖能力,并且NSCs标记物CD133、nestin表达阳性,经诱导分化后分化标记物β-TubulinⅢ、GFAP表达阳性;CD133-亚群细胞无上述特性.结论:CD133免疫磁珠分选方法获得的CD133+亚群细胞即为BTSCs,该方法可以得到高纯度的BTSCs,可以用于BTSCs的实验研究.     

吉西他滨联合树突状细胞对HepG2细胞增殖的抑制作用

目的:观察肿瘤细胞裂解物致敏的树突状细胞(DC)联合吉西他滨(GEM)体外抑制肝癌HepG2 细胞系增殖的作用,为临床探索有效的肝癌综合治疗方案提供实验依据.方法:采用反复冻融法裂解HepG2 细胞,提取肿瘤细胞抗原后致敏DC,并以DC刺激自身T 细胞的增殖和活化.按不同处理因素分组:①空白对照组,只含空白培养液;②阴性对照组,只含HepG2 细胞;③单纯T 细胞组,将未经致敏DC 刺激的T细胞与靶细胞按20∶1 的比例接种;④单纯活化T 细胞组,将经致敏DC 刺激后的活化T 细胞与靶细胞按20∶1 的比例接种;⑤单纯GEM 处理组,靶细胞接种后在培养基中分别添加终浓度为50、100、150、200 μg·L-1 的GEM;⑥T细胞+GEM 处理组,在单纯T 细胞组的培养基中分别添加上述4个浓度梯度的GEM;⑦活化T 细胞+GEM 处理组,在活化T 细胞组的培养基中分别添加上述4个浓度梯度的GEM.MTT 法检测细胞杀伤率,流式细胞仪检测细胞凋亡率,观察应用T 细胞、不同浓度的GEM 以及两者联合应用对HepG2 细胞的体外杀伤效应.结果:空白对照组刺激指数(SI)为1.34,阴性对照组SI 为3.48,两者比较差异有统计学意义(P<0.01).与单纯T细胞组[(4.81±2.54)%]比较,单纯活化T 细胞组细胞杀伤率[(21.68±4.39)%]明显升高(P<0.01);与活化T细胞+50、100 和150 μg·L-1 GEM组比较,活化T细胞+200 μg·L-1 GEM组细胞杀伤率明显升高(P<0.05).单纯T 细胞组细胞凋亡率为(5.45±0.94)%,与阴性对照组 [(4.47±1.98)%]比较差异无统计学意义(P>0.05);活化T 细胞组细胞凋亡率为(14.32±1.16)%,与前两组比较差异有统计学意义(P<0.01).活化T细胞+100 μg·L-1 GEM组细胞凋亡率为(24.52±0.85)%,与其他各组比较差异均有统计学意义(P<0.05).结论:负载肿瘤细胞抗原的DC 可诱导出抗肿瘤的细胞毒性T细胞,活化的T细胞联合GEM 能显著提高其杀伤肿瘤细胞的作用.     

淋巴细胞功能相关抗原-1/细胞间黏附分子-1介导的细胞因子诱导的杀伤细胞体外抑瘤机制

目的 探讨淋巴细胞功能相关抗原-1(LFA-1)/细胞间黏附分子-1(ICAM-1)介导的细胞因子诱导杀伤细胞(CIK)的体外抑瘤机制.方法 从白血病患儿外周血分离淋巴细胞,经过干扰素-γ(IFN-γ)、抗CD3单克隆抗体(CD3McAb)、白细胞介素-2(IL-2)诱导并与树突状细胞(DC)共培养,获得大量的DC-CIK.在经10、20μg/ml等不同质量浓度小鼠抗人LFA-1单克隆抗体处理后,采用MTT法研究DC-CIK细胞对多种白血病细胞株的杀伤活性,RT-PCR与Western blotting方法检测GATA-3和T-bet基因表达水平的变化.ELISA方法测定DC-CIK细胞释放细胞因子IL-12、IFN-γ、肿瘤坏死因子-α(TNF-α)的表达水平.结果 诱导后的DC-CIK细胞形态规则,经不同浓度的LFA-1单克隆抗体处理后,MTT结果:20μg/ml LFA-1单克隆抗体封闭组DC-CIK细胞对B95细胞杀伤作用下降最为明显(t=10.138,P＜0.05);RT-PCR与Western blotting结果:20μg/ml LFA-1单克隆抗体封闭的B95细胞组,GATA-3基因mRNA水平和蛋白水平表达增加最为明显(t=16.386,P＜0.05;t=22.652,P＜0.05);同时T-bet基因mRNA水平和蛋白水平表达降低最为明显(t=17.728,P＜0.05;t=17.452,P＜0.05);ELISA结果:20μg/ml LFA-1单克隆抗体封闭的B95细胞组中细胞因子IL-12、IFN-γ、TNF-α分泌水平下降最为明显(t=21.621,P＜0.05;t=13.739,P＜0.05;t=15.278,P＜0.05).结论 GATA-3和T-bet基因参与了LFA-1/ICAM-1介导的DC-CIK抑瘤途径,并且通过分泌Th1型细胞因子IL-12、IFN-γ、TNF-α等发挥抑瘤作用.     

健康人外周血树突状细胞的体外诱导及其功能分析

目的 分析以健康人AB血清与rhCD40L体外诱导健康人外周血树突状细胞(DC)的功能.方法 对健康人外周血单个核细胞进行体外培养,在以健康人AB血清为基础的培养体系中加入粒细胞巨噬细胞集落刺激因子(GM-CSF)、重组人白细胞介素(rhIL)-4、rhCD40L等细胞因子,诱导单个核细胞分化形成DC,采用倒置显微镜及瑞特-吉姆萨染色观察,流式细胞术行DC表型鉴定,四甲基偶氮唑蓝比色(MTT)法进行混合淋巴细胞反应(MLR),检测其抗原刺激能力,酶联免疫吸附(ELISA)法检测DC培养上清IL-12的分泌.结果 培养7 d后的细胞具有典型的DC形态,并上调表达DC特征性表面分子CD83及共刺激分子CD40、CD80、CD86,第0、1、3、5、7天,5个时间点间CD83、CD40、CD80、CD86、CD14表达差异有统计学意义(F值分别为50.253、243.769、248.181、191.267、226.339,均P＜0.05).培养后的DC可较强地刺激同种自体淋巴细胞增殖,GM-CSF加rhIL-4、rhCD40L组较GM-CSF加rhIL-4组刺激反应能力强.培养的DC自培养第5天始即有IL-12分泌,未加CD40L组IL-12 p40分泌量为(42.92±1.54)pg/ml,加CD40L组为(136.18±5.27)pg/ml;培养第7天,IL-12 p40分泌明显增多,两组分别为(60.09±2.27)pg/ml及(322.30±30.60)pg/ml,差异有统计学意义(t=-44.941、-22.611,均P＜0.05).结论 健康人外周血单个核细胞可在以健康人AB血清与rhCD40L为主的培养体系中诱导成DC.     

CD19+ pro-B cells can give rise to dendritic cells in vitro

Dendritic cells (DC) have the specific capacity of initiating primary T cell responses and ultimately derive from precursors in bone marrow. DC were originally thought to be only of myeloid origin, and myeloid precursor cells could be induced to differentiate into functional DC in response to granulocyte-macrophage (GM)-CSF. However, early CD4low precursor cells from the thymus can also develop into DC when cultured in IL-1beta, IL-3, IL-7, TNF-alpha, stem cell factor, and Flt-3L. In that case, GM-CSF was not required. We now show that CD19+ pro-B cells develop into DC with T cell stimulatory properties when cultured under similar conditions. These pro-B cells acquired the DC-related markers CD11c and NLDC145/DEC205, along with CD80/B7-1, CD86/B7-2, and a high density of MHC class II Ags. The marrow-derived DC did not express CD4 or CD8alpha, which are markers related to thymic DC. These findings are consistent with a new pathway through which DC are generated from B lymphoid precursors.     

CD8+ memory T cells (CD44high, Ly-6C+) are more sensitive than naive cells to (CD44low, Ly-6C-) to TCR/CD8 signaling in response to antigen

Memory CD8+ T cells from mice previously primed with alloantigen (alloAg) can respond in vitro to IL-2 and purified class I alloAg presented on microspheres, while no response can be detected using cells from naive mice. Similar results have been obtained using cells from OT-1 mice expressing a transgenic TCR that is specific for OVA(257-264) (SIINFEKL) peptide bound to H-2Kb. A population of resting memory cells (defined on the basis of low forward scatter and CD44high, Ly-6C+, CD25-, CD69-surface phenotype) that is present in the OT-1 mice exhibits a substantially higher sensitivity to Ag-stimulation than do naive cells (CD44low, Ly-6C-) expressing the same TCR. CD44high cells respond vigorously to H-2Kb immobilized on microspheres and pulsed with peptide, while CD44low cells respond weakly and only at high class I density and peptide concentration. The Ag-presenting surface only has ligands for TCR and CD8 (class I and peptide), thus ruling out the possibility that differences are due to ligand binding by other adhesion or costimulatory receptors that are expressed at high levels on the memory cells. Experiments using anti-TCR mAb as the stimulus and coimmobilized non-Ag class I as a ligand for CD8 suggest that the difference between naive and memory cells may be at the level of stimulation through the TCR. Thus, in addition to expressing increased levels of adhesion receptors that may enhance responses to Ag on APCs, memory CD8+ T cells appear to be intrinsically more sensitive than naive cells to stimulation through the TCR/CD8 complex.     

Antigen-specific B cells preferentially induce CD4+ T cells to produce IL-4

The bone marrow microenvironment influences whether a given B cell proliferates, differentiates, or undergoes apoptosis. In this report, we demonstrate that apoptosis of primary murine B lymphocyte precursors can be regulated either positively or negatively by stroma. Several stromal lines that support lymphocyte outgrowth suppressed the spontaneous apoptosis of pre-B cells by as much as 90%. Direct contact with stromal cells more effectively protected lymphocytes than did stromal cell-CM or a collection of recombinant cytokines. In contrast, one unique stromal cell clone actually induced lymphocyte apoptosis, and a second line appeared inert. A survey of adherent cell lines suggested that expression of life-sparing molecules is widespread but not ubiquitous. Experiments with neutralizing Abs to CD44, vascular cell adhesion molecule-1 (VCAM-1), CD9, intercellular adhesion molecule-1 (ICAM-1), or ICAM-2 suggested that these interaction molecules do not deliver short-term survival signals to B cell precursors. Of particular interest, direct interaction with lymphocyte-supportive stromal cells minimized the negative regulatory effects of IL-1alpha, and a glucocorticoid, but not IFN-beta or PGE2. These results demonstrate that the effect of negative regulators depends upon the context in which these signals are presented. As molecules that influence B lymphopoiesis are better defined, it will be important to consider the role of each in combination with other stimuli.     

Flt3 ligand enhances the yield of primitive cells after Ex vivo cultivation of CD34+ CD38dim cells and CD34+ CD38dim CD33dim HLA-DR+ cells

Flt3 ligand (FL) has been proposed as a possible modulator of early hematopoietic cell growth. The purpose of this study was to analyze the impact of FL on ex vivo expansion of hematopoietic cells obtained from adult donors. We sought to precisely identify hematopoietic populations responsive to FL and to quantitate the ability of FL to enhance the survival and/or proliferation of early hematopoietic precursors in a stroma-free culture system. Towards that end, four CD34+ subsets were isolated and their response to FL was characterized. In methylcellulose, FL significantly increased colony formation by CD34+ CD38dim cells but not CD34+ CD38+ cells. In suspension culture, the enhancement of cell expansion by FL was 10 times greater with the CD34+ CD38dim fraction than the CD34+ CD38+ fraction. FL stimulated the generation of colony-forming unit-granulocyte-macrophage (CFU-GM) from the CD34+CD38dim fraction by 14.5- +/- 5.6-fold. To determine if CD34+ CD38dim cells responded uniformly to FL, the population was subdivided into a CD34+ CD38dim CD33dim HLA-DR+ (HLA-DR+) fraction and a CD34+ CD38dim CD33(dim) HLA-DRdim (HLA-DRdim) fraction. FL was far more effective at stimulating cell and progenitor growth from the HLA-DR+ fraction. To determine if FL enhanced or depleted the number of precommitted cells in expansion culture, CD34+ CD38dim and HLA-DR+ fractions were incubated in liquid culture and analyzed by flow cytometry. Inclusion of FL enhanced the absolute number of primitive CD34+ CD33dim cells and CD34+ HLA-DRdim cells after 5 to 12 days of cultivation. To confirm immunophenotypic data, the effect of FL on long-term culture-initiating cells (LTCIC) was determined. After 2 weeks of incubation of CD34+ CD38dim or HLA-DR+ cultures, LTCIC recoveries were significantly higher with FL in 5 of 6 trials (P < . 05). For HLA-DR+ cells, LTCIC recoveries averaged 214% +/- 87% of input with FL and 24% +/- 16% without FL. In contrast, HLA-DRdim LTCIC could not be maintained in stroma-free culture. We conclude that less than 10% of CD34+ cells respond vigorously to FL and that those cells are contained within the HLA-DR+ fraction. FL stimulates the expansion of total cells, CD34+ cells, and CFU-GM and enhances the pool of early CD34+ CD33(dim) cells, CD34+ HLA-DRdim cells, and LTCIC. These data indicate that it is possible to expand hematopoietic progenitors from adult donors without losing precursors from the precommitted cell pool.     

Position-dependent variegation of a CD4 minigene with targeted expression to mature CD4+ T cells

The CD4 gene follows a complex and highly regulated pattern of expression throughout T cell development. This expression is governed by different regulatory elements that have been partly identified, including a promoter, a proximal enhancer, and a silencer. Here we show that a CD4 minigene comprising a combination of these elements is specifically expressed in mature CD4+ T cells of transgenic mice, but not in CD4+CD8+ double positive thymocytes. The proportion of transgene-expressing CD4+ T cells was constant within a given transgenic line, but varied greatly from one line to another. We demonstrate that this pattern of expression is due to integration of the transgene within or in the vicinity of centromeric heterochromatin. This position-effect variegation demonstrated with a short CD4 transgene has not been observed with larger ones containing additional regulatory sequences, suggesting that the CD4 gene contains a locus control region. Such position-dependent effects must be taken into consideration when developing transgenic models or gene transfer vectors because they can result in the absence of transgene expression in a subpopulation of target cells. Finally, the combination of the CD4 gene silencer, proximal enhancer, and promoter provides an interesting tool to selectively express genes of interest in mature CD4+ T cells of transgenic mice and for the development of gene therapy vectors.     

CD45RA(bright)/CD11a(bright) CD8+ T cells: effector T cells

An important aspect of peripheral T cell development is the differentiation from naive into memory cells. To distinguish naive from memory cells, CD45RA and CD11a are commonly used: CD45RA+ or CD11a(dim) T cells are regarded as naive, while CD45RA- or CD11a(bright) T cells are thought to be of memory type. There is, however, a CD8+ T cell subset which is CD45RA+ and at the same time CD11a(bright). It increases with age and in patients with systemic viral infections, though its functional role in the immune response is unknown. In the present study, we give evidence that this subset is related to memory-like T cells as it produces IFN-gamma and tumor necrosis factor-alpha, contains high levels of perforin, and expresses CD95 in the same way as memory-type CD45RA-/CD11a(bright) CD8+ T cells. Since it contains a high percentage of CD28- and CD57+ cells, is increased in size and granularity, and is transiently expressed following in vitro stimulation of naive CD8+ T cells, we speculate that this subset mainly represents recently activated effector T cells that are able to interact with CD80 and CD86 (B7-1 and B7-2 respectively) negative tissue cells.     

Mycobacterium tuberculosis exploits the CD95/CD95 ligand system of gammadelta T cells to cause apoptosis

Vgamma9/Vdelta2+ T cells specifically recognize Mycobacterium tuberculosis in vitro and are precociously recruited in early mycobacterial lesions. Even if gammadelta T cells are only fortuitously detected in granulomas or bronchoalveolar lavages of patients with active pulmonary tuberculosis, a role in shaping the mature alphabeta T cell response against M. tuberculosis is substantiated. Here we provide a molecular explanation for this paradox: the engagement of the gammadelta TCR by mycobacterial antigens induced the expression of CD95 ligand (CD95L) by chronically activated CD95+/CD95L- gammadelta T lymphocytes. The receptor was functional, as CD95/CD95L interaction triggered the bystander death of CD95+ cells by apoptosis. Cell death was abolished by CD95-blocking antibodies. The transient accumulation at the site of infection of CD95L+ gammadelta lymphocytes, capable of interacting with CD95+ leukocytes attracted by the response towards the pathogen, may determine the characteristics of the ensuing granulomatous disease.