CD27-CD70轴与自身免疫性疾病的关系

CD27-CD70共刺激信号途径是除了经典CD28-CD80/86轴外,初始T细胞活化第二个重要的共刺激信号途径.CD70-CD27轴为T、B细胞提供刺激信号、调节其免疫应答.对CD27-CD70轴的作用及与自身免疫性疾病关系的研究,有助于更加了解自身免疫性疾病的发病机制,为免疫治疗提供新思路.     

抗CD3,CD28单抗对人T淋巴细胞共刺作用的影响因素

以抗ＣＤ３和抗ＣＤ２８作为Ｔ细胞激活的第一和第二信号,观察二者不同浓度,不同作用顺序和不同作用时间对人Ｔ淋巴细胞增殖反应的影响。结果显示单一的抗ＣＤ３和抗ＣＤ２８不能刺激Ｔ细胞增殖,只有同时域在一定时间内接受二者的共同刺激才能促使细胞增殖。     

CD40-CD40L与疾病

T淋巴细胞与抗原提呈细胞之间的信号传递调控着免疫系统的发展 ,其中CD4 0与其配体CD4 0L(CD154)的相互作用 ,不仅对T细胞活化和效应功能的表现起重要作用 ,且在抗感染、抗病毒及抗肿瘤和动脉粥样硬化症中扮演重要角色。本文综述了CD4 0 -CD4 0L与人类疾病关系的研究进展。     

032 CD40-CD40L与疾病

T淋巴细胞与抗原提呈细胞之间的信号传递调控着免疫系统的发展,其中CD40与其配体CD40L(CD154)的相互作用,不仅对T细胞活化和效应功能的表现起重要作用,且在抗感染、抗病毒及抗肿瘤和动脉粥样硬化症中扮演重要角色.本文综述了CD40-CD40L与人类疾病关系的研究进展.     

CD40系统在B淋巴细胞激活中的作用

本文述及Ｂ淋巴细胞表面的ＣＤ４０分子和活化Ｔ细胞的ＣＤ４０配体的结构，ＣＤ４０互联在ＣＤ４０系统和Ｔ细胞依赖性Ｂ细胞激活、Ｂ细胞凋亡、淋巴因子分泌中的作用及细胞因子的调节变化。     

CD28/B7信号在再生障碍性贫血T淋巴细胞异常活化中的作用

目的 通过淋巴细胞输注诱导自身免疫性再生障碍性贫血动物模型,探讨CD28/B7信号在淋巴细胞异常活化中的作用及可能机制.方法 将来自父本的淋巴细胞悬液(40×106个几左右)通过尾静脉注入CBYB6 F1代受鼠体内,采用CFDA-SE标记法跟踪淋巴细胞在体内的分布,尾静脉注射CD80和CD86阻断性单克隆抗体(单抗),不同时段检测受体小鼠外周血象的变化,病理切片观察骨髓及主要脏器的变化.将骨髓造血细胞与淋巴结淋巴细胞进行共培养,通过计数造血细胞的集落形成数来观察不同数量淋巴结淋巴细胞对骨髓造血细胞的影响.体外测试不同浓度环孢菌素A(cyclosporine A,CsA)对骨髓造血细胞的影响.结果 输注淋巴细胞后可诱导受体小鼠在第5天出现骨髓衰竭的表现,主要是白细胞、血红蛋白、血小板下降,21 d左右受体鼠出现死亡.不同时间段受体小鼠主要脏器冰冻切片显示荧光标记的淋巴细胞主要分布在骨髓组织中;病理切片显示有骨髓组织的破坏.同时注射CD80及CD86阻断性单抗的受体鼠同样出现上述表现;体外集落形成试验证实B6淋巴结淋巴细胞数量和F1造血细胞为5:1时,红系集落形成单位(CFU-E)和粒细胞集落形成单位(CFU-G)集落形成数目与空白组比较差异无统计学意义(P>0.05);将比例提高至10:1,CFU-E集落形成数目明显减少(P<0.05);至50:1时,则可完全抑制CFU-E集落的形成,CFU-E和CFU-G集落形成数日的减少呈现淋巴细胞剂量依赖性,加入CsA可显著提高CFU-E和CFU-G形成率.结论 通过模型证实T细胞在再生障碍性贫血的发生过程中起重要作用,仅通过阻断CD28/B7信号并不能阻断T淋巴细胞的异常活化.     

CD40系统在B淋巴细胞激活中的作用

本文述及Ｂ淋巴细胞表面的ＣＤ４０分子和活化Ｔ细胞的ＣＤ４０配体的结构，ＣＤ４０互联在ＣＤ４０系统和Ｔ细胞依赖性Ｂ细胞激活、Ｂ细胞凋亡、淋巴因子分泌中的作用及细胞因子的调节变化。     

小干扰RNA特异性抑制淋巴细胞共刺激分子CD28基因表达的研究

目的 :为了探讨体外转录法合成的小干扰RNA(smallinterferingRNA ,siRNA)对人淋巴细胞共刺激分子CD2 8基因表达和功能的影响。方法 :设计并合成 3条siRNA(siRNA 1、siRNA 2、siRNA 3) ,在阳离子脂质体的介导下转染淋巴细胞。于转染后 2 4、4 8、72小时收集细胞 ,用半定量RT PCR方法检测CD2 8mRNA的变化 ;流式细胞仪检测CD2 8表达的变化。结果 :体外合成的 3条siRNA通过脂质体转染淋巴细胞后 ,均能不同程度地抑制共刺激分子CD2 8的表达。转染后 4 8小时的流式细胞仪检测显示siRNA 1、siRNA 2和siRNA 3组的CD2 8表达抑制率分别为 2 2 10 %± 1 6 3%、73 5 0 %± 1 0 2 %和 4 2 90 %± 0 89% ,以siRNA 2的CD2 8抑制作用最强。半定量RT PCR检测显示siRNA 1、siRNA 2、siRNA 3转染后淋巴细胞的CD2 8mRNA均受到不同程度的抑制 ,其中siRNA 2组的抑制作用最明显 (74 10 %± 1 6 5 % )。结论 :siRNA可特异性抑制淋巴细胞共刺激分子CD2 8基因的转录和表达 ,从而为进一步研究siRNA在移植免疫耐受及防治GVHD方面的应用提供了理论和实验基础。     

CD40-CD40L共刺激途径在体液免疫和细胞免疫中的作用

CD40与CD40配体(CD40L)是体内炎症和免疫反应系统的一对共同刺激分子,参与机体的体液免疫和细胞免疫反应.CD40-CD40L共刺激途径能促进T细胞活化并放大T淋巴细胞依赖的免疫应答,是产生记忆性CD8+T细胞的基础,能够促进CD8+T细胞的扩增和多能性,在CD4+T细胞分化的过程中起重要作用,介导更强的抗肿瘤效应和杀伤靶细胞的能力.CD40-CD40L共刺激途径参与T淋巴细胞依赖的B淋巴细胞应答过程、生发中心的形成、长期记忆性R细胞的产生、抗体的产生及抗体类别转换,并可诱导和扩增CD4+ CD25+ Treg细胞.CD40-CD40L共刺激途径在多种疾病的发生、发展中起作用,有广阔的临床应用前景.     

CD70 represents the human ligand for CD27

The recently identified CD27 ligand (L) Is a type II transmembranemolecule with significant structural homology to tumor necrosisfactor (TNF)-, TNF-ß, lymphotoxin ß, CO40L,and CD30L. Using a CD27L specific mAb we examined the tissuedistribution of the molecule, and found Its expression to berestricted to B cells in occasional germinal centers, stromalcells in the thymic medulla, and scattered T cells in tonsils,skin and gut. As the limited expression of CD27L closely resembledthe reported distribution of the activation antigen CD70, wetested whether CD70 represents the human CD27L. CD70 mAb werefound to react with CD27L-expressing transfected mouse fibroblasts.Moreover a number of CD70 mAb could specifically interfere withthe cellular binding of CD27L mAb. Thus, CD70 Is Identical tothe human CD27L.     

CD27/CD70 interaction directly drives B cell IgG and IgM synthesis

CD27 is a T cell activation antigen expressed on a majority of peripheral blood T cells. CD27 is also expressed on a subpopulation of human B cells, and it is reported that CD27⁺ B cells secrete both IgG and IgM. CD70, a ligand for CD27, is expressed on activated T and B cells, suggesting an interaction between T and B cells via CD27/CD70 ligation. Here, we analyze B cell immunoglobulin synthesis using a CD70 transfectant and present functional data showing that B cells secrete large amounts of IgG and IgM as a result of the CD27/CD70 interaction. A flow cytometric analysis showed that CD27 expression was increased and CD70 was expressed on tonsillar and peripheral blood B cells after activation with Staphylococcus aureus Cowan strain (SAC) plus interleukin (IL-2). In addition, the proliferation of B cells was enhanced mildly by the addition of CD70 transfectant, and its proliferation was blocked by anti-CD70 mAb. More importantly, the CD70 transfectant enhanced IgG and IgM production by purified B cells greatly in the presence of SAC plus IL-2. The enhancement was completely blocked by the addition of either anti-CD70 mAb or anti-CD27 mAb. Strongly suggesting that the interaction of CD27 with its ligand, CD70, on B cells plays an important role in B cell growth and differentiation to produce IgG and IgM.     

Phenotype and function of human B cells expressing CD70 (CD27 ligand)

CD70, the cellular ligand of the tumor necrosis factor receptor family member CD27, can be found on a limited number of germinal center (GC) B cells in some tonsils, on scattered lymphocytes residing in secondary lymphoid organs, and on a fraction of the circulating B cell population. Due to the restricted expression of CD70 in vivo, we analyzed signals that determine CD70 expression levels and characterized the phenotype and function of CD70⁺ B cells. Expression of CD70 on B cells activated in vitro was found to be dependent on the continuous presence of a B cell antigen receptor cross-linking agent, and induced or potentiated by CD40 ligation but was down-modulated by the Th2 cytokines interleukin (IL)-4 and IL-13. Both in peripheral blood and tonsil cell suspensions, CD70⁺ B cell subpopulations were found to be enriched for CD27-and IgG-expressing cells, but contained less IgD⁺ B cells. Additional analysis of markers which define specific differentiation stages (Bm1-5) of mature B cells within human tonsils did not place CD70-expressing B cells in one of these subsets. Functional experiments revealed that whereas both CD70⁻ and CD70⁺ B cells can secrete immunoglobulin after activation with a combination of Staphylococcus aureus Cowan strain I and IL-2, only CD70⁺ B cells can produce large quantities of antibodies when stimulated in a T cell-dependent fashion. Our combined data imply that CD70 is a marker for mature B cells which have recently been primed by antigen in vivo.     

Control of lymphocyte function through CD27–CD70 interactions

In contrast to the expression of other TNFR/TNF family members, expression of CD27 and its ligand CD70 is predominantly confined to lymphocytes. High expression levels of CD27 appear to be dependent on proper ligation of antigen receptors, whereas for the induction of CD70 expression additional (co–stimulatory and/or pro–inflammatory) signals are required. Next to membrane–bound CD27 also a soluble form of CD27 is produced in the course of the immune response. Soluble CD27 (sCD27) is found in body fluids and can be used to monitor local and systemic immune activation. In addition, elevated serum concentrations of sCD27 are found in patients with B cell malignancies and levels of sCD27 strongly correlate with tumor load. Based on functional experiments andin vitroexpression regulation data, we propose that interactions between activated lymphocytesin vivocan result in CD27–CD70 interactions that may regulate the size and function of antigen–primed lymphocyte populations.     

CD27 and CD70 do not play a critical role in the development of experimental allergic conjunctivitis in mice

CD27, which belongs to the TNF receptor family, is a costimulatory molecule that participates in T-cell activation. Unlike costimulatory molecules such as OX40 and 4-1BB, little is known about the role CD27 plays a role in the development of experimental diseases. We asked whether CD27 and its ligand CD70 participate in the development of experimental allergic conjunctivitis (EC) in BALB/c mice, which is generated by immunization with ragweed (RW) in alum and challenged 10 days later with RW in eye drops. The roles of CD27 and CD70 were tested by intraperitoneally injecting the mice with anti-CD27, anti-CD70 or a control Ab during the induction or effector phase. Twenty-four hours after challenge, the conjunctivas, blood and spleens were harvested for histological analysis, measuring Ig levels and cytokine analysis, respectively. Regardless of when the mice were treated, anti-CD27 or anti-CD70 Ab treatment did not significantly affect the severity of EC as evaluated by conjunctival eosinophil numbers. However, anti-CD27 or anti-CD70 Ab treatment during the induction phase did significantly modulate systemic humoral and cellular immune responses. In vitro treatment of RW-primed splenocytes with anti-CD27 or anti-CD70 Ab did not affect the EC-inducing capability of the splenocytes. Taken together, CD27 and CD70 do not play a critical role in the development of EC.     

Involvement of CD27/CD70 interactions in antigen-specific cytotoxic T-lymphocyte (CTL) activity by perforin-mediated cytotoxicity

CD27 molecules are shown to be essential in the regulation of the death, activation and differentiation of T and B cells. However, the influence of CD27 on cytotoxic T-cell function remains obscure. Autologous EBV transformed B-cell lines (LCL), which highly express CD27 ligand CD70, here stimulated T cells and induced the cytotoxic T-lymphocyte (CTL) activity via T-cell antigen receptors (TCR). The cytotoxicity against LCL was diminished when anti-CD70 blocking MoAb was added initially in the culture. Resting T cells killed more CD70-transfected P815 cells than wild type P815 cells in the presence of anti-CD3 MoAb as measured by a 4-h 51Cr release assay, and the cytotoxicity of both of the cell populations completely disappeared in the presence of concanamycin A (CMA). The expression of the perforin by the LCL-induced CTL in the presence of anti-CD70 blocking MoAb was diminished as compared with that without the blockage of CD27/CD70 interactions. The CTL induced by LCL did not kill Fas-transfected WR cells. CD27 signalling in the T cells did not affect Fas ligand (FasL) mRNA expression, LAK activity and IFN-gamma synthesis in humans. Our data demonstrate that CD27/CD70 interactions enhance the cytotoxicity of CTL in the induction phase through enhancement of killing activity induced via the perforin-dependent mechanism, but not via the Fas/FasL system.     

CD27/CD70 interactions regulate T dependent B cell differentiation

CD27 is a tumor necrosis factor (TNF) receptor family member whose expression is limited to cells of the lymphoid lineage. Constitutively expressed on T lymphocytes, it is a constimulatory molecule for a regulatory subset. Induced on B lymphocytes after antigenic challenge, it is a marker of memory cells. CD70, CD27 ligand, is a TNF related trans-membrane protein induced upon activation on T and B cells. In complement of ligation of CD40, another TNF receptor family member expressed by B cells CD27/CD70 interaction plays a key role in T dependent B cell responses and is responsible for plasma cell differentiation. B lymphocyte responses appear thus controlled by different T cell subsets expressing CD 154 (CD40 ligand), CD27, or CD70 (CD27 ligand).     

T cells compete by cleaving cell surface CD27 and blocking access to CD70‐bearing APCs

T cells compete against each other for access to molecules on APCs in addition to peptide/MHC complexes. However, the identity of cell surface molecules that influence T‐cell competition, other than peptide/MHC, have yet to be defined. Here, we identify CD70, a TNF ligand expressed on activated APCs, as an important mediator of T‐cell competition for APCs. Upon engagement of CD27 by CD70, CD27 is proteolytically cleaved from the surface of the interacting CD8⁺ T cell and captured by CD70 expressing dendritic cells. The capture of CD27 effectively masks CD70 on APCs, disallowing the interaction with CD27 on other competing T cells. Collectively, our data indicate that T cells compete against each other for access to the TNF‐ligand CD70, an interaction that affects the duration and potency of T cell/DC interactions, thus influencing the repertoire of responding CD8⁺ T cells to self or foreign antigens.