THYMIC B CELL ACTIVATION IN MYASTHENIA GRAVIS

重症肌无力（MG）是一种自身免疫性疾病， 弱点MG患者的神经肌肉传递受损， 与烟碱乙酰胆碱受体（nAChR）反应的抗体。 基于临床、病理和免疫学证据， 长期以来，胸腺被认为在发病机制中起关键作用 这种疾病。 重症肌无力的胸腺是B细胞的异常部位 活动 在超过75%的乳腺癌患者中可见生殖中心（GC）增生。 患者回收的B细胞具有与先前的 在体内活化，并分泌自身抗体抗AChR。AChR 在胸腺中表达的蛋白可能在 自我敏化过程或耐受机制的崩溃， 通常阻止自身免疫的表达。这个项目的总体目标是 该项目旨在提高我们对免疫学和分子生物学的理解， 胸腺B细胞和胸腺nAchR α的特性。 具体目标是： l）确定MG胸腺GC B的功能和分子性质 细胞2）确定胸腺抗AChR α的VH和VL基因利用 抗体，和3）进一步表征nAChR α链（nAChR α） 在正常和肌无力的人胸腺中表达，关于a）蛋白质 表达，B）定量mRNA，c）mRNA的组织定位，d） e）mRNA表达的个体发生，和l）细胞因子对mRNA的调节， 胸腺nAChR诱导特异性免疫无应答的能力。 这些目标将部分通过使用胸腺和血细胞来实现 在MG患者的胸腺切除术和对照的心脏手术中获得 科目有待检验的一个假设是，抗AChR是GC的产物， B细胞。我们还将检验胸腺GC B细胞将显示 抗原刺激的分子特征和显示偏斜的V-基因 如果GC是由常见的病理事件引起的，则应使用GC。一 丝状噬菌体系统将用于克隆和测序抗AChR α 胸腺B细胞使用的VH和VL基因。新生小鼠将经历 胸腺内注射携带AChR的细胞，以确定是否引入 AChR进入胸腺可诱导对这种自身抗原的无反应性 当其随后以免疫原性方式施用时。我们将 还对胸腺AChR α表达的个体发生进行了分析 以确定自身反应性T细胞是否可能在表达 胸腺乙酰胆碱受体胸腺nAChR α的定量和定性特征 将使用最近开发的定量RT-PCR测定， 原位杂交这些发现具有很大的临床应用价值 由于抗AChR抗体在MG中是致病性， 通常对这种疾病有益。

Myasthenia gravis, (MG) is an autoimmune disorder characterized by muscle weakness. MG patients have impaired neuromuscular transmission caused by antibodies reactive with the nicotinic acetylcholine receptor (nAChR). Based on clinical, pathologic, and immunologic lines of evidence, the thymus has long been considered to play a pivotal role in the pathogenesis of this disease. The thymus in MG is an anomalous site of B cell activity. Germinal center (GC) hyperplasia is seen in greater than 75% of patients. The recovered B cells have properties consistent with antecedent in vivo activation and they secrete the autoantibody anti-AChR. AChR expressed in the thymus may play an important role in the autosensitization process or in the breakdown of tolerance mechanisms that normally prevent the expression of autoimmunity. The overall goal of this project is to enhance our understanding of the immunologic and molecular properties of thymic B cells and thymic nAchRalpha. Specific aims are to: l) determine the functional and molecular properties of MG thymic GC B cells 2) determine VH and VL gene utilization of thymic anti-AChRalpha antibodies, and 3) further characterize nAChR alpha chain (nAChRalpha) expressed in normal and myasthenic human thymus with regard to a) protein expression, b) quantitative mRNA c) tissue localization of mRNA, d) regulation of mRNA by cytokines e) ontogeny of mRNA expression, and l) the capacity of thymic nAChR to induce specific immunologic unresponsiveness. These aims will be approached, in part, by using thymic and blood cells obtained at thymectomy of MG patients and cardiac surgery of control subjects. One hypothesis to be tested is that anti-AChR is a product of GC B cells. We will also test the hypothesis that thymic GC B cells will show the molecular features of antigen stimulation and show skewed V-gene utilization if GC's are induced by a common pathologic event. A filamentous phage system will be used to clone and sequence anti-AChRalpha VH and VL genes used by thymic B cells. Neonatal mice will undergo intrathymic injection with AChR-bearing cells to determine if introduction of AChR into the thymus can induce unresponsiveness to this autoantigen when it is subsequently administered in an immunogenic manner. We will also carry out an analysis of the ontogeny of thymic AChRalpha expression to determine if autoreactive T cells might escape prior to expression of thymic AChR. Quantitative and qualitative features of thymic nAChRalpha will be determined using a recently developed quantitative RT-PCR and in situ hybridization. These findings are of great potential clinical importance since anti-AChR antibody is pathogenic in MG and thymectomy is often beneficial in this disorder.