MECHANISMS OF B CELL ACTIVATION BY CLASS II MHC AND CD40

B细胞激活是一个高度受调控的过程，涉及多个 不同的信号。这些相互作用的信号通路的净效应是 目的：测定B细胞对抗原识别的反应。一个详细的 了解B细胞上的信号转导分子是如何工作的 对理解和潜在地控制B细胞至关重要 增殖和抗体分泌。因此，专门针对 B细胞增生性疾病的治疗，如B细胞 恶性肿瘤，需要了解B细胞信号通路是如何 起作用并相互作用。大多数B淋巴细胞活化事件 涉及B细胞膜Ig与抗原的特异性结合和相互作用 辅助性T细胞通过多态和非多态跨膜 分子。非特异性B细胞激活信号可由T细胞提供 细胞分泌的淋巴因子和非多态T细胞膜分子， 如活化T细胞表面的CD40配体(CD40L)。然而，这是我们的 假设与抗原的特定相互作用使B细胞准备 对随后的T细胞介导的信号做出最佳反应，并具有特异性 T细胞受体与B细胞MHC-II类分子的相互作用 保持T细胞-B细胞相互作用的特异性。我们的实验室和 其他人已经证明了第二类MHC分子保存了 T细胞与B细胞相互作用的特异性。我们的实验室和其他实验室有 证明了第二类MHC分子向B细胞传递调节信号 这些信号与淋巴细胞传递的信号协同作用 抗原与膜的结合。此外，II类介导的信号 抵消抗原介导的无能信号，这可能是一种机制，通过 哪些T细胞刺激B细胞在恶性肿瘤中过度增殖和 自身免疫性疾病。最近，我们获得的数据表明， 通过II类传递的信号与传递给B细胞的信号协同工作 通过与T细胞CD40L、B细胞CD40结合。因此，我们认为这些信号 由抗原和与T细胞的同源相互作用传递(即，信号 通过结合MiG和MHC II类分子来传递)增加了 CD40介导的信号在T细胞激活后的有效性，以及 通过以下途径降低B细胞不适当激活的可能性 “旁观者”效应。拟议中的实验将测试确定 这种信号受体之间相互作用的分子基础。三大 实验方法将被用来检验我们的假设。首先，我们 将使用重组DNA技术来产生基因的改变 编码MHC II类和CD40分子。以B细胞系为模型，我们 将引入这些改变的基因并研究信号转导功能 它们产生的蛋白质，以定义结构之间的详细关系 并为这些信号分子发挥作用。第二，我们将使用State-of=- -ART生化信号分析以识别细胞内事件 这是通过II类MHC和CD40分子进行信号传递的结果。最后， 我们将进行体外和体内实验，检测分子 这些信号在B细胞调节中的协同作用机制 激活。这三种方法的结合将产生更好的 了解如何操纵B细胞活化的过程， 通过更好地了解的机制和相互作用 流程的组成部分。

B cell activation is a highly regulated process involving multiple different signals. The net effect of these interacting signal pathways is to determine the B cell response to recognition of antigen. A detailed understanding of how signal transducing molecules on B cells work is essential to understanding, and potentially controlling, B cell proliferation and antibody secretion. Thus, specifically targeted therapies for B cell hyperproliferative diseases, such as B cell malignancies, require an understanding of how B cell signaling pathways function and interact. The majority of B lymphocyte activation events involve specific binding of B cell membrane Ig to antigen, and interaction with T helper cells via both polymorphic and non-polymorphic transmembrane molecules. Nonspecific B cell activation signals can be provided by T cell-secreted lymphokines and nonpolymorphic T cell membrane molecules, such as CD40 ligand (CD40L) on activated T cells. However, it is our hypothesis that specific interactions with antigen prepare B cells to respond optimally to subsequent T cell-mediated signals, and specific interactions between T cell receptors and B cell MHC class II molecules preserve the specificity of T cell-B cell interactions. Our laboratory and others have demonstrated that class II MHC molecules preserve the specificity of T cell-B interactions. Our laboratory and others have demonstrated that class II MHC molecules deliver regulatory signals to B lymphocytes, and that these signals synergize with signals delivered by the binding of antigen to membrane ig. In addition, class II-mediated signals counteract antigen-mediated anergy signals, which may be a mechanism by which T cells stimulate B cell hyperproliferation in malignancy and autoimmune disease. More recently, we have obtained data indicating that signals delivered via class II cooperate with signals delivered to B cells by the binding of T cell CD40L B cell CD40. We thus believe that signals delivered by antigen and cognate interaction with T cells (i.e., signals delivered by binding of mig and MHC class II molecules) increase the effectiveness of CD40-mediated signals following T cell activation, and decrease the probability of inappropriate B cell activation through "bystander" effects. Thr proposed experiments will test determine the molecular basis of this interaction between signal receptors. Three major experimental approaches will be used to test our hypotheses. First, we will use recombinant DNA technology to produce alterations in the genes encoding MHC class II and CD40 molecules. Using B cell lines as models, we will introduce these altered genes and study the signaling function of the proteins they produce, to define a detailed relationship between structure and function for these signaling molecules. Second, we will use state-of=- the-art biochemical signaling assays to identify the intracellular events which result from signaling via class II MHC and CD40 molecules. Finally, we will perform in vitro and in vivo experiments examining the molecular mechanisms by which these signals cooperate in the regulation of B cell activation. The combination of these three approaches will yield a better understanding of how to manipulate athe process of B cell activation, through better understanding of the mechanism of, and interactions between the component parts of the process.