THYMIC B CELL ACTIVATION IN MYASTHENIA GRAVIS

虽然胸腺通常不被认为是B细胞的部位， 活动，在重症肌无力（MG）是一个突出的场景B细胞 应答 这种活动，这是强调生产抗乙酰胆碱受体 抗体（抗AChR），可能反映了胸腺内免疫事件， 在疾病发病机制中重要。 有几个原因可以解释 胸腺B细胞反应显著但不一致。 它们包括：（1） 胸腺B细胞是一种特别反应性的细胞群， 基于表型特性与血B细胞区分，2） 胸腺微环境特别支持B细胞 分化和3）胸腺B细胞已经经历了一定程度的 在体内的分化可能是由于局部遇到的刺激。 本提案中描述的实验将有助于1）充分 表征这些不寻常的胸腺B细胞的表型特性; 2） 将这些细胞的体外功能与它们的表型 3）确定抗原特异性胸腺辅助性T细胞的表型 细胞，从而阐明了发育阶段，在该阶段，辅助活动 在胸腺中获得; 4）确定MG胸腺细胞是否组成型 产生支持B细胞分化所需的可溶性因子和5） 在确定是否表达AChR之前， 这种受体细胞提供抗AChR产生的刺激。 每当 如果可能，将在1）MG胸腺细胞和 自体血细胞，2）对照受试者的胸腺细胞。 实现上述目标的技术途径包括： 利用单克隆抗体沿着自动化流程进行亚群分析 细胞计数和免疫荧光显微镜，亚群分级， 用于几种体外细胞亲和层析和FACS分选 培养系统，以及用于测量IG的ELISA和放射免疫测定 分泌到培养上清液中。 增加对机制的了解 潜在的异常胸腺B细胞反应可能会增强 我们对异常局部胸腺内免疫事件的理解， 最终可能有助于澄清负责启动的机制， 增强或延续疾病。

Although the thymus is not generally considered to be a site of B cell activity, in myasthenia gravis (MG) it is a scene of prominent B cell responses. This activity, which is highlighted by production of anti-AChR antibody (anti-AChR), likely reflects intrathymic immune events that are important in disease pathogenesis. Several reasons could account for the prominent albeit incongruous thymic B cell responses. They include: 1) thymic B cells are a particularly reactive population, one which can be distinguished on the basis of phenotypic properties from blood B cells, 2) the thymic microenvironment is particularly supportive of B cell differentiation and 3) thymic B cells have undergone some degree of differentiation in vivo perhaps as a result of locally encountered stimuli. The experiments described in this proposal will help to 1) fully characterize the phenotypic properties of these unusual thymic B cells; 2) correlate in vitro function of these cells with their phenotypic properties; 3) determine the phenotype of antigen specific thymic helper T cells and thus elucidate the developmental stage at which helper activity is acquired in the thymus; 4) determine if MG thymus cells constitutively produce soluble factors required to support B cell differentiation and 5) characterize the thymic populations expressing AChR prior to determining if such receptor cells provide a stimulus for anti-AChR production. Whenever possible, comparisons will be made between 1) MG thymic cells and autologous blood cells, 2) thymic cells of control subjects. Technical approaches to accomplish the above objectives include: cell subset analysis with monoclonal antibodies along with automated flow cytometry and immunofluorescence microscopy, subset fractionation by affinity chromatography and FACS sorting for use in several in vitro cell culture systems, and ELISA and radioimmunoassay for measurement of Ig secreted into culture supernatants. Increased knowledge of the mechanisms underlying the anomalous thymic B cell responses in MG will likely enhance our understanding of aberrant local intrathymic immune events and ultimately may help to clarify mechanisms responsible for initiation, potentiation or perpetuation of disease.