Tolerance in polyclonal and oligoclonal immune systems

描述(申请人提供)：自身反应性B细胞通常在离开骨髓或到达外周淋巴器官之前被耐受机制消除。尽管如此，已知在健康个体中存在分泌自身抗体的B细胞，它们不仅是许多自身免疫性疾病的主要效应者，而且还与淋巴增生性疾病有关。这项应用的长期目标是1)定义参数，确定几种可用的B细胞耐受机制中的哪一种用于审查自身反应性B细胞；2)这些机制如何失败并允许自身反应性B细胞迁移到外围；以及3)一旦进入外围，自身反应性B细胞如何被激活以分泌自身抗体。在B细胞耐受的小鼠模型中，已证明自身反应性B细胞通过共表达非自身反应性免疫球蛋白特异性来逃避中枢耐受机制。在健康和疾病个体中也发现了罕见的双重免疫球蛋白表达的人类B细胞，尽管目前尚不清楚这些细胞是否为病理条件的效应者。这项建议阐述了表达B细胞的双重免疫球蛋白作为自身免疫的可能介体的作用。 受体编辑是B细胞耐受的主要机制，它通过二级免疫球蛋白基因重排在新产生的自体反应性B细胞内运作，最常消除自体反应性。有趣的是，最近的证据表明，受体编辑也可能产生表达B细胞的双重免疫球蛋白。这项提案中概述的研究将确定受体编辑产生双重免疫球蛋白表达的自体反应性B细胞的潜力，以及这些细胞产生自身抗体的能力。具体地说，该提案中描述的目标将决定：1)表达双重免疫球蛋白的B细胞的流行程度取决于自身抗原的亲和力；2)表达免疫球蛋白的双重自体反应性B细胞是通过受体编辑在野生型动物中产生的；3)抗原刺激表达双重免疫球蛋白的自体反应性B细胞可以驱动自身抗体的产生。利用不同同源野生型小鼠的抗MHC I免疫球蛋白敲入细胞的骨髓嵌合体，分析抗原亲和力和自身反应性B细胞克隆频率对受体编辑程度和表达双重抗体的自身反应性B细胞发育的影响。受体编辑将在体内被抑制，以确定这种耐受机制是否是双重抗体表达B细胞存在的基础。表达B细胞的双重免疫球蛋白在体外和体内过继细胞转移系统中建立免疫反应的能力将被确定。

DESCRIPTION (provided by applicant): Autoreactive B cells are typically eliminated by mechanisms of tolerance before exiting the bone marrow or upon arrival in peripheral lymphoid organs. Despite this, autoantibody-secreting B cells are known to exist in healthy individuals and are not only the primary effectors of many autoimmune diseases, but they are also linked to lymphoproliferative disorders. The long-term goal of this application is to 1) define the parameters that determine which of the several available mechanisms of B cell tolerance is used to censor autoreactive B cells; 2) how these mechanisms may fail and allow autoreactive B cells to migrate to the periphery; and 3) how, once in the periphery, autoreactive B cells become activated to secrete autoantibodies. In mouse models of B cell tolerance, autoreactive B cells have been shown to evade mechanisms of central tolerance by co-expressing a non-autoreactive immunoglobulin specificity. Rare dual immunoglobulin-expressing human B cells are also found in healthy and diseased individuals, although it is not clear whether these cells are effectors of pathologic conditions. This proposal addresses the role of dual immunoglobulin expressing B cells as possible mediators of autoimmunity. Receptor editing is a major mechanism of B cell tolerance that operates within newly generated autoreactive B cells by secondary immunoglobulin gene rearrangements that most frequently eliminate autoreactivity. Interestingly, recent evidence has suggested that receptor editing may also generate dual immunoglobulin expressing B cells. The studies outlined in this proposal will define the potential of receptor editing to generate dual immunoglobulin-expressing autoreactive B cells and the ability of these cells to produce autoantibodies. Specifically, the Aims described in this proposal will determine whether: 1) the prevalence of dual immunoglobulin-expressing B cells depends on autoantigen avidity; 2) dual immunoglobulin-expressing autoreactive B cells are generated through receptor editing in wild type animals; 3) antigen stimulation of dual immunoglobulin-expressing autoreactive B cells can drive autoantibody production. The influence of antigen avidity and autoreactive B cell clonal frequency on the extent of receptor editing and on the development of dual antibody-expressing autoreactive B cells will be analyzed by using bone marrow chimeras of anti-MHC I immunoglobulin knock-in cells in various congenic wild type mouse strains. Receptor editing will be inhibited in vivo to determine whether this tolerance mechanism underlies the presence of dual antibody-expressing B cells. The capacity of dual-immunoglobulin expressing B cells to mount an immune response will be defined in vitro and in adoptive cell transfer in vivo systems.