Tolerance in polyclonal and oligoclonal immune systems

描述（由申请方提供）：自身反应性B细胞通常在离开骨髓前或到达外周淋巴器官后通过耐受机制消除。尽管如此，已知分泌自身抗体的B细胞存在于健康个体中，并且不仅是许多自身免疫性疾病的主要效应物，而且它们还与淋巴组织增生性疾病有关。本申请的长期目标是1）定义确定B细胞耐受性的几种可用机制中的哪一种用于审查自身反应性B细胞的参数; 2）这些机制如何失效并允许自身反应性B细胞迁移到外周;和3）一旦在外周中，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，已显示自身反应性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。罕见的双重免疫球蛋白表达的人B细胞也发现在健康和患病的个体，虽然它是不清楚这些细胞是否是病理条件的效应。该建议解决了双重免疫球蛋白表达B细胞作为自身免疫的可能介质的作用。 受体编辑是B细胞耐受性的主要机制，其在新产生的自身反应性B细胞内通过最常消除自身反应性的次级免疫球蛋白基因重排起作用。有趣的是，最近的证据表明，受体编辑也可能产生双重免疫球蛋白表达B细胞。本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自身反应性B细胞的潜力以及这些细胞产生自身抗体的能力。具体而言，本提案中描述的目的将确定：1）双重免疫球蛋白表达B细胞的流行是否取决于自身抗原亲合力; 2）双重免疫球蛋白表达自身反应性B细胞是否通过野生型动物中的受体编辑产生; 3）双重免疫球蛋白表达自身反应性B细胞的抗原刺激是否可以驱动自身抗体产生。抗原亲合力和自身反应性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细胞的发育的影响将通过在各种同源野生型小鼠品系中使用抗MHC I免疫球蛋白敲入细胞的骨髓嵌合体来分析。受体编辑将在体内被抑制，以确定这种耐受机制是否是表达双重抗体的B细胞存在的基础。表达双免疫球蛋白的B细胞产生免疫应答的能力将在体外和体内系统中的过继细胞转移中确定。

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.