CD3/TCR复合物抗体诱导不成熟胸腺细胞亚群的凋亡

目的：采用AnnexinV,PI染色，流式细胞仪分析的方法、DNA琼脂糖电泳法检测不同CD3/TCR复合物抗体对小鼠胸腺T淋巴细胞亚群的促凋亡作用。方法：新鲜分离胸腺细胞，加入PMA、anti-TCR anti-CD28 mAb,anti-TCR mAb等培养20小时，AnnexinV,PI,CD4,CD8细胞染色以及TCR三染，进行FACS分析，同时抽提培养细胞DNA进行琼脂糖电泳。结果：PMA IONO诱导胸腺T细胞的凋亡作用最强，anti-TCR anti-CD28 mAb次之，anti-TCR mAb最弱。结论：AnnexinV,PI细胞染色，流式细胞仪分析的方法可以灵敏检测T淋巴细胞的凋亡；anti-TCR anti-CD28 mAb能明显增强anti-TCR mAb促不成熟的CD4^ CD8^ TCR^ 和CD4^ TCR^ 细胞的凋亡作用；不成熟T细胞经TCR与自身抗原结合的活性过程能产生克隆删除从而产生自我耐受。     

人胎儿胸腺细胞表型分析

利用流式细胞计分析了人中期妊娠引产胎儿胸腺细胞的某些表面分子的表达,结果表明从胎儿发育的第17周直到儿童期,胸腺细胞 CD1、CD2、CD3、CD4、CD8、CD38、TCR 以及 HLA 抗原的表达无明显变化.在这一发育阶段,胸腺细胞表型呈现以下特征:1.CD3/TCRαβ分子的表达呈现从弱到强的连续性分布,可以分为三个亚群,从弱到强依次称为 L-CD3/TCRαβ、M-CD3/TCRαβ和 H-CD3/TCRαβ.个体之间三个亚群含量差异很大.2.大部分单阳性成熟型胸腺细胞也表达 CD1抗原.3.HLA Ⅰ类抗原在胸腺细胞上表达呈现密度不等的变化.大部分胸腺细胞为弱阳性,少部分为强阳性.HLA Ⅰ类抗原表达量和胸腺细胞成熟度相关.4.根据胸腺细胞比重将胸腺细胞分为 Thy-L 和 Thy-H2个亚群.Thy-L 亚群中成熟型和早期胸腺细胞含量较多,而 Thy-H 主要由中间发育阶段的胸腺细胞构成.     

小鼠CD^3＋TCRαβ^＋CD^—CD8^—胸腺细胞特性分析

目的：分析CD^3 TCRαβ^ CD^-CD8^-胸腺细胞的特性，推断其在胸腺发育中表型和功能的成熟过程。方法：分离纯化小鼠胸腺DN细胞，用多重染色的方法分析CD^3 TCRαβ^ CD^-CD8^-细胞的表型和TCR库，并与外周淋巴结的相应细胞进行对比。结果：DNA胸腺细胞为异质性细胞，包括CD3^-DN细胞和CD3^ DN细胞，而CD3^ DN细胞又分为CD^3 TCRαβ^ 和CD3^ TCRγδ^ 2个亚群。其中，CD^3 TCRαβ^ DN细胞体积较小，绝大部分细胞对可的松耐受，细胞中能与自身反应的Vβ^3 和Vβ11^ 细胞比例极低，表型较为成熟，与髓质型SP（single positive) 细胞相似。结论：CD^3 TCRαβ^ DN细胞不同于CD^3 TCRαβ^－DN细胞，是一个独特的细胞亚群，只有在经历表型和功能的进一步成熟才能迁出胸腺，移至外周。     

TCR抗体诱导不成熟胸腺细胞亚群凋亡的敏感性研究

为比较小鼠不同胸腺细胞亚群对抗TCR抗体诱导凋亡的敏感性，用体外抗TCR抗体刺激分离胸腺细胞．BALB／c小鼠体内注射抗TCR抗体，FACS检测胸腺细胞。结果显示，CD4^ CD8^ DP胸腺细胞和CD4^-CD8^ CD3^-TCR-细胞对抗TCR抗体诱导的凋亡敏感，但CD4^-CD8^-CD3^-TCR-胸腺前体细胞自发凋亡率低，且抗TCR抗体诱导的凋亡．表明胸腺细胞对凋亡的敏感点产生于CD4^-CD8^ CD3^-TCR-细胞表达后，胸腺细胞的凋亡敏感性受发育调节。     

Fas／Fas—L与体外热应激胸腺细胞亚群变化及凋亡的关系

目的 探讨体热应激胸腺细胞的亚群变化及凋亡与胸腺细胞表达Fas、Fas-L的关系。方法 用流式细胞术检测体外热应激后再培养的胸朱细胞不同时间的凋亡率、CD4CD8亚群及表达Fas、Fas-L的阳性率。结果 体外热应激胸腺细胞的凋亡率和表达Fas及Fas-L的阳性率均呈时间依赖性增高,凋亡的胸腺细胞以CD4^ CD8^ 双阳性胸腺细胞为主。结论 热应激主要诱导CD4^ CD8^ 胸腺细胞凋亡;Fas与Fas-L是介导热应激胸腺细胞凋亡的重要分子。     

抗鼠T细胞受体抗体抑制胸腺细胞的迁出

目的 通过检测抗仓鼠T细胞受体抗体对胸腺T细胞输出的影响，进一步研究胸腺是提供外周免疫细胞输出的有关机理。方法 体内注射抗TCR抗体48h后FACS分析新迁出细胞在胸腺、淋巴结的表达。结果 小鼠成熟髓质区高表达T细胞受体的单阳性细胞数目成倍增加，同时皮质区低表达T细胞受体的不成熟双阳性细胞数目减少。成熟的单阳性胸腺细胞高表达归巢受体L-Selectin，表型分析(TCRαβ、CD69、HAS、Vβ7-integrin、Qa-2)显示增加的这群细胞为胸腺的新迁出细胞，此群成熟细胞的高表达，表明胸腺的细胞迁出受到了抑制。胸腺内注射异硫氰酸荧光素16h后，抗TCR抗体注射小鼠外周淋巴结及脾脏CD4^ 、CD8^ 新迁出细胞数量减少。结论 抗TCR抗体能抑制胸腺T细胞向外周迁移。     

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。     

T细胞凋亡受体和共刺激分子的表达变化与终末期肾功能衰竭患者细胞免疫功能的关系研究

目的：探究终末期肾功能衰竭患者T细胞亚群的凋亡受体CD95分子与共刺激分子CD28、CDl52（CTLA-4）的表达与细胞免疫功能的关系。方法：采用流式细胞术检测外周血T细胞的凋亡受体CD95（Fas）与共刺激分子CD28／CDl52表达。结果：终末期肾功能衰竭患者CD3^＋T细胞和CD4^＋T细胞比例明显高于健康对照组，CD4／CD8比值增加（P=0．008），CD4^＋T细胞和CD8^＋T细胞上CD95分子表达均上调（P=0．001），以CD8^＋T细胞上CD95分子增加更为明显；CD28和CD152分子在不同T细胞亚群上的表达均上调（P〈0．05），然而，CD4^＋T细胞以CD28分子表达增加为主，而CD8^＋T细胞则CD152分子表达增加为主。结论：终末期肾功能衰竭患者的细胞亚群失衡，共刺激分子CD28和CD152表达异常增加，提示T细胞活化与抑制性调节发生紊乱。T细胞亚群上凋亡受体CD95分子表达增加，以CD8^＋T细胞为主，说明终末期肾功能衰竭者淋巴细胞的减少可能通过两种途径——受体配体途径和负性共刺激分子CD152抑制信号途径，其中以CD8^＋T细胞减少为主，造成患者细胞免疫缺陷。     

CD3^—CD4^—CD8^＋小鼠胸腺细胞表型的研究

目的 分析CD3^－CD4^－CD8^＋胸腺细胞的表型特征,阐明其在胸腺发育中所处地位。方法 分离纯化小鼠CD4^－CD8^＋单阳性胸腺细胞,进行CD3与其他表面标志的染色,然后进行FACS分析。结果 CD3^－CD4^－CD8^＋细胞体积较大,对可的松敏感,TGRαβ阴笥,高度表达不成熟标志6C10和HSA,不表达活化标志CD69和成熟标志Qa-2。结论 CD4^－CD8^＋单阳性胸腺细胞可明显分为CD3^＋和CD3^－两个亚群,后者代表了胸腺发育过程中由CD4^－CD8^－双阴性细胞向CD4^＋CD8^＋双阳性细胞转变的过渡状态。     

CD3~-CD4~-CD8~ 小鼠胸腺细胞表型的研究

目的　分析CD3-CD4-CD8 胸腺细胞的表型特征 ,阐明其在胸腺发育中所处地位。方法　分离纯化小鼠CD4-CD8 单阳性胸腺细胞 ,进行CD3与其他表面标志的染色 ,然后进行FACS分析。结果　CD3-CD4-CD8 细胞体积较大 ,对可的松敏感 ,TCRαβ阴性 ,高度表达不成熟标志 6C10和HSA ,不表达活化标志CD6 9和成熟标志Qa 2。结论　CD4-CD8 单阳性胸腺细胞可明显分为CD3 和CD3-两个亚群 ,后者代表了胸腺发育过程中由CD4-CD8-双阴性细胞向CD4 CD8 双阳性细胞转变的过渡状态。     

TCR signaling inhibits glucocorticoid-induced apoptosis in murine thymocytes depending on the stage of development

Signaling by either the TCR or glucocorticoid receptor (GR) induces apoptosis in thymocytes. Interestingly, it has been shown previously that hybridoma T cells escape apoptosis induced by either TCR or GR when both of these receptors signal simultaneously. Whether such mutual antagonism is present in primary thymocytes was the subject of the present study. Both glucocorticoids (GC) and anti-TCR/CD28 (or anti-CD3/CD28) mAb induced apoptosis in total thymocytes. When these signals were present at the same time, GC-induced apoptosis was partially inhibited by TCR/CD3 signaling. Costimulation by anti-CD28 enhanced the inhibitory effects of anti-CD3 on GC-induced apoptosis about 30-fold. However, subset analysis revealed that most cells rescued from GC-induced apoptosis were mature CD4+ and CD8+ thymocytes, and these cells were resistant to TCR/CD3-induced apoptosis in the absence of GC. Similar results were obtained with mature splenic CD4+ and CD8+ T cells. TCR/CD3 signaling alone, while inducing apoptosis in CD4+(CD8+)TCRlow thymocytes, rescued a small subset of CD4+(CD8+)TCRlow thymocytes from GC-induced apoptosis. Thus, TCR signaling increasingly reverses GC-induced apoptosis as thymocyte development progresses. As GC are infinitely present in vivo, these findings support a model wherein TCR signaling may be required to prevent GC-induced apoptosis both under basal and immune challenging conditions.     

Glucocorticoid (GC) sensitivity and GC receptor expression differ in thymocyte subpopulations

Positive and negative selection steps in the thymus prevent non-functional or harmful T cells from reaching the periphery. To examine the role of glucocorticoid (GC) hormone and its intracellular receptor (GCR) in thymocyte development we measured the GCR expression in different thymocyte subpopulations of BALB/c mice with or without previous dexamethasone (DX), anti-CD3 mAb, RU-486 and RU-43044 treatment. Four-color labeling of thymocytes allowed detection of surface CD4/CD8/CD69 expression in parallel with intracellular GCR molecules by flow cytometry. Double-positive (DP) CD4+CD8+ thymocytes showed the lowest GCR expression compared to double-negative (DN) CD4-CD8- thymocytes and mature single-positive (SP) cells. DX treatment caused a concentration-dependent depletion of the DP cell population and increased appearance of mature SP cells with reduced GCR levels. GCR antagonists (RU-486 or RU-43044) did not influence the effect of DX on thymocyte composition; however, RU-43044 inhibited the high-dose GC-induced GCR down-regulation in SP and DN cells. GCR antagonists alone did not influence the maturation of thymocytes and receptor numbers. Combined low-dose anti-CD3 mAb and DX treatment caused an enhanced maturation (positive selection) of thymocytes followed by the elevation of CD69+ DP cells. The sensitivity of DP thymocytes with a GCRlow phenotype to GC action and the ineffectiveness of the GCR antagonist treatment may reflect a non-genomic GC action in the thymic selection steps.     

Phosphatidylinositol 4,5-bisphosphate hydrolysis accompanies T cell receptor-induced apoptosis of murine thymocytes within the thymus

Regulation of the development of thymocytes into mature T cells within the thymus is now known to involve antigen-induced deletion, by apoptosis, of potentially autoreactive thymocytes, and it can be mimicked either by stimulating the T cell receptor (TcR) complex by monoclonal antibody (mAb) or by ionophore-induced elevation of cytosolic [Ca²⁺]. To identify signaling pathways employed by the TcR complex of immature thymocytes, we examined the effects of anti-CD3 and anti-TcRß constant (c) region mAb, staphylococcal enterotoxin B (SEB) and pharmacological agents on the generation of inositol phosphates through hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P₂] both in cultured fetal mouse thymic lobes and in the CD4⁺CD8⁺ immature thymocyte cell line, TM10G. Stimulation of the TcR complex with anti-CD3 mAb provoked an accumulation of inositol phosphates diagnostic of the occurrence of receptor-stimulated phosphoinositidase C (PLC) activation. Anti-TcRCß mAb and SEB provoked smaller but similar responses. The PLC activation evoked by anti-CD3 mAb was suppressed by inhibitors of receptor tyrosine kinases and was unmodified by protein kinase C activation or elevation of cytosolic [Ca²⁺]. It thus appears that apoptosis triggered by TcR stimulation is associated with PLC activation by a receptor-regulated tyrosine kinase. Treatment of thymic lobes or TM10G cells with fluoroaluminate provoked apoptosis of a wider range of thymocyte subtypes and such stimulation also provoked an accumulation of inositol phosphates. The responses to fluoroaluminate were not prevented by inhibitors of tyrosine kinases, suggesting that unidentified GTP-binding proteins which couple to PLC activation may also be capable of initiating apoptosis by a route independent of the TcR. These results, when considered alongside previous studies of mature T cells, indicate that stimulation of immature thymocytes or of mature T cells through their TcR complex activates the PLC-catalyzed PtdIns(4,5)P₂ hydrolysis signaling pathway, and thus that this signaling pathway may be implicated both in provoking apoptosis in immature T cells and in initiating proliferation in mature T cells.     

T cell-specific gene targeting reveals that alpha4 is required for early T cell development

Alpha4-mediated signaling is involved in a variety of functions in mammalian cells. To determine whether this is true for immunocompetent cells, we generated mutant (Lck-alpha4-) mice in which the alpha4 gene was deleted in a T cell-specific manner using the Cre/loxP system. These mice showed impaired early T cell development. Thymi at most ages were small and their architecture was disorganized. This defect was not due to increased thymocyte apoptosis but to decreased cell proliferation. T cell development was found to be severely arrested at the CD4/CD8 double-negative 3 stage and the thymus contained very few double-positive or single-positive (SP) mature thymocytes. The mutant thymocytes showed impaired proliferative responses to anti-CD3 monoclonal antibody (mAb) stimulation or to the cytokines IL-2, IL-1 or TNF. In the spleen, the numbers of mature SP T cells were decreased and their proliferative responses to anti-CD3 plus IL-2 or to anti-CD28 mAb were impaired. A severe impairment of CD3-induced expression of CD25 was also observed. These data suggest that alpha4 plays a critical role in the proliferation of thymocytes, which is necessary for early T cell development.     

Gene expression analysis of thymocyte selection in vivo

Self versus non-self discrimination is a key feature of immunorecognition. Through TCR-activated apoptotic mechanisms, autoreactive thymocytes are purged at the CD4(+)CD8(+) double-positive (DP) precursor stage prior to maturation to CD4(+) or CD8(+) single-positive (SP) thymocytes. To investigate this selection process in vivo, gene expression analysis by oligonucleotide array was performed in TCR transgenic mice. In total, 244 differentially expressed DP thymocyte genes induced or repressed by TCR triggering in vivo were identified. Genes involved in the biological processes of apoptosis, DNA recombination, antigen processing and adhesion are coordinately engaged. Moreover, analysis of gene expression in thymocyte subsets revealed that TCR ligand-induced expression profiles vary according to their developmental stage, with 48 genes showing DP preference and nine showing SP thymocyte preference. Finally, our data suggest that both the extrinsic and the intrinsic apoptosis pathways are operating in thymic selection.     

Cross-Linking the TCR Complex Induces Apoptosis in CD4+8+ Thymocytes in the Presence of Cyclosporin A

Although it is generally agreed that TCR ligation is a minimal requirement for negative selection in the CD⁺8⁺ double-positive (DP) thymocyte subset, the costimulatory requirements and specific signaling events necessary to induce apoptosis are not well defined. We have explored the consequences of cross-linking CD3/TCR complexes on thymocytes from H-Y TCR transgenic (Tg) mice. In agreement with previous reports, we demonstrate that culturing DP thymocytes with plate-bound anti-TCR antibody induces downregulation of CD4 and CD8 and upregulation of CD69 expression. Nevertheless, the activated cells did not undergo apoptosis, as determined by viable cell recoveries and by quantitation of DNA fragmentation using the TUNEL assay. However, specific depletion of the DP subset occurred within 24 hr when thymocytes were incubated in the presence of both anti-TCR and the immunosuppressant cyclosporin A (CsA). CsA also induced depletion of anti-CD3 stimulated normal DP thymocytes. Using mice homozygous for the lpr or gld mutation, we also have shown that Fas/Fas ligand interactions are not involved in the CsA-induced death of TCR-stimulated DP thymocytes. These data verify that TCR cross-linking alone is insufficient to induce apoptosis of DP thymocytes and further suggest that TCR stimulation activates a CsA-sensitive protective pathway that interferes with signaling events leading to apoptosis in DP thymocytes.     

Low glucocorticoid receptor (GR), high Dig2 and low Bcl-2 expression in double positive thymocytes of BALB/c mice indicates their endogenous glucocorticoid hormone exposure

Several studies have shown that of the four major thymocyte subsets, the CD4/CD8 double positive (DP) thymocytes are the most sensitive to in vivo glucocorticoid hormone (GC)-induced apoptosis. Our aim was to analyse fine molecular differences among thymocyte subgroups that could underlie this phenomenon. Therefore, we characterised the glucocorticoid hormone receptor (GR) expression of thymocyte subgroups both at the mRNA and protein levels by real-time PCR and flow cytometry, and correlated these features to their apoptotic sensitivity. We also investigated the time-dependent effects of the GC agonist dexamethasone (DX) with or without GC antagonist (RU486) treatments on GR mRNA/protein expression. We also analysed the expression of two apoptosis-related gene products: dexamethasone-induced gene 2 (Dig2) mRNA and Bcl-2 protein. We found that DN thymocytes had the highest GR expression, followed by CD8 single positive (SP), CD4 SP and DP thymocytes in 4-week-old BALB/c mice, both at the mRNA and protein levels, respectively. In DP cells, the Dig2 expression was significanty higher, while the Bcl-2 expression was significantly lower than in DN, CD4 SP and CD8 SP thymocytes. Single high dose DX treatment caused time-dependent depletion of DP thymocytes due to their higher apoptosis rate, which could not be abolished with RU486 pretreatment. After a single high dose DX treatment, there was a transient, significant increase of the GR mRNA and protein level of unsorted thymocytes after 8 and 16 h, followed by a significant decrease at 24 h, respectively. The time-dependent GR expression changes after DX administration could not be inhibited by the GC antagonist RU486. Twenty-four hours after exposure to high dose DX the DN, CD4 SP and CD8 SP cells showed a significant decrease of GR mRNA and protein expression, whereas the DP thymocytes, showed no significant alteration of GR mRNA or protein expression. The kinetical analysis of GR expression and apoptotic marker changes upon single high dose GC analogue administration revealed a two-phase process in thymocytes: early events, within 4–8 h, include GR upregulation and early apoptosis induction, while the late events appear most prominently at 16–20 h, when the GR is already downregulated and apoptotic cell ratio reaches its peak, with marked DP cell depletion. The low GR, high Dig2 and low Bcl-2 expression, coupled with the absence of homologous downregulation of GR after exogenous GC analogue treatment, could contribute to the high GC sensitivity of DP thymocytes. The downregulated GR and Bcl-2 together with the upregulated Dig2 level in DP cells indicates the significance of intrathymic GC effects at this differentiation stage. Since GR expression changes and apoptotic events could not be completely inhibited by GC antagonist, we propose the involvement of non-genomic GR mechanisms in these processes.     

Comparison of thymocyte development and cytokine production in CD7-deficient, CD28-deficient and CD7/CD28 double-deficient mice

CD7 and CD28 are Ig superfamily molecules expressed on thymocytes and mature T cells that share common signaling 0mechanisms and are co-mitogens for T cell activation. CD7-deficient mice are resistant to lipopolysaccharide (LPS)-induced shock syndrome, and have diminished in vivo LPS-triggered IFN-gamma and tumor necrosis factor (TNF)-alpha production. CD28-deficient mice have decreased serum Ig levels, defective IgG isotype switching, decreased T cell IL-2 production and are resistant to Staphylococcus aureus enterotoxin-induced shock. To determine synergistic roles CD7 and CD28 might play in thymocyte development and function, we have generated and characterized CD7/CD28 double-deficient mice. CD7/CD28-deficient mice were healthy, reproduced normally, had normal numbers of thymocyte subsets and had normal thymus histology. Anti-CD3 mAb induced similar levels of apoptosis in CD7-deficient, CD28-deficient and CD7/CD28 double-deficient thymocytes as in control C57BL/6 mice (P = NS). Similarly, thymocyte viability, apoptosis and necrosis following ionomycin or dexamethasone treatment were the same in control, CD7-deficient, CD28-deficient and CD7/CD28-deficient mice. CD28-deficient and CD7/CD28-deficient thymocytes had decreased [3H]thymidine incorporation responses to concanavalin A (Con A) stimulation compared to control mice (P < or = 0.01 and P < or = 0.05 respectively). CD7/CD28 double-deficient mice had significantly reduced numbers of B7-1/B7-2 double-positive cells compared to freshly isolated wild-type, CD7-deficient and CD28-deficient thymocytes. Con A-stimulated CD4/CD8 double-negative (DN) thymocytes from CD7/CD28 double-deficient mice expressed significantly lower levels of CD25 when compared to CD4/CD8 DN thymocytes from wild-type, CD7-deficient and CD28-deficient mice (P < 0.05). Anti-CD3-triggered CD7/CD28-deficient thymocytes also had decreased IFN-gamma and TNF-alpha production compared to C57BL/6 control, CD7-deficient and CD28-deficient mice (P < or = 0.05). Thus, CD7 and CD28 deficiencies combined to produce abnormalities in the absolute number of B7-1/B7-2-expressing cells in the thymus, thymocyte IL-2 receptor expression and CD3-triggered cytokine production.