B Lymphocytes in Autoimmune Disease

 描述（由申请人提供）： 类风湿性关节炎是由一系列复杂的事件引起的，这些事件破坏了免疫耐受性，最终导致滑液组织的破坏。B淋巴细胞（B细胞）在疾病发展中起关键作用，产生触发这种疾病的自身抗体。B细胞对关节炎的作用取决于多种因素，首先是B细胞对自身抗原耐受性的丧失， 其发生在T细胞相互作用之前的骨髓中B细胞发育的不成熟阶段。这种耐受性是由B细胞通过B细胞受体（BCR）对抗原结合的信号传导应答介导的。布鲁顿酪氨酸激酶（BTK）是BCR触发的信号传导途径的中心组分。这种蛋白质不存在于T细胞中，因此提供了研究B细胞对这种疾病失去耐受性的贡献的机会。了解支持关节炎发展的B细胞信号成分将推动该领域朝着特异性靶向致病性B细胞的方向发展。我们使用btk缺陷来测试BTK在自发性自身免疫性关节炎的K/BxN模型中的作用，并发现显著的疾病保护，伴随着自身抗体的损失，总IgG相对较少。这些发现补充了我们以前的工作，表明自身反应性B细胞比正常细胞对BTK的丢失更敏感。因此，与一般B细胞靶向药物如利妥昔单抗提供的全面B细胞免疫抑制不同，这些发现表明，有可能在免疫抑制剂中靶向B细胞信号传导。 这种方法可以优先消除自身反应性细胞，而不会诱导全身性B细胞免疫缺陷。该提议背后的具体假设是，自身反应性B细胞比正常B细胞更依赖于BTK介导的信号放大。为了理解BTK在促进自身免疫性关节炎中的作用机制，我们将使用我们新开发的小鼠模型，其包括1）允许定时缺失BTK的诱导型模型，以模拟药理学抑制而没有脱靶结合的混杂效应，2）条件性、B细胞特异性和树突细胞特异性BTK敲除模型，以测试BTK的细胞特异性贡献，和3）btk缺陷模型作为测试小分子BTK抑制剂的对照，以确定药物特异性和剂量如何与遗传缺陷相比，以增强未来的药物设计。该项目在理解BCR信号如何支持自身反应性B细胞在自身免疫性关节炎中的功能方面具有直接的临床重要性，作为开发治疗干预的必要步骤。

 DESCRIPTION (provided by applicant): Rheumatoid arthritis results from a complex cascade of events that breaks immune tolerance and culminates in the destruction of synovial tissue. B lymphocytes (B cells) play a critical role n disease development, producing the autoantibodies that trigger this disease. B cell contributions to arthritis depend upon multiple factors, beginning with loss of B cell tolerance to self-antigen, which occurs at immature stages of B cell development in the bone marrow, prior to T cell interactions. This tolerance is mediated by B cell signaling responses to antigen-binding via the B cell receptor (BCR). Bruton's tyrosine kinase (BTK) is a central component of the BCR- triggered signaling pathway. This protein is not present in T cells, so offers the opportunity to study B cell contributions to lost tolerance in this disease. Understanding B cell signaling components that support arthritis development will advance the field toward specific targeting of pathogenic B cells. We used btk-deficiency to test the role of BTK in the K/BxN model of spontaneous autoimmune arthritis, and found significant disease protection, accompanied by loss of autoantibodies, with relative sparing of total IgG. These findings complement our previous work showing that autoreactive B cells are more sensitive to loss of BTK than normal cells are. Therefore, unlike global B cell immunosuppression offered by general B cell-targeting drugs such as rituximab, these findings suggest that it is possible to target B cell signaling in a way that would preferentially eliminate autoreactive cells without inducing generalized B cell immunodeficiency. The specific hypothesis underlying this proposal is that autoreactive B cells are more dependent on BTK-mediated signal amplification than normal B cells. To understand the mechanisms of action of BTK in promoting autoimmune arthritis, we will use our newly developed mouse models that include 1) an inducible model that allows timed deletion of BTK, to simulate pharmacologic inhibition without the confounding effect of off-target binding, 2) conditional, B cell-specific and dendritic cell-specific BTK knockout models to test cell-specific contributions of BTK, and 3) btk-deficent models as controls for testing of small molecule BTK inhibitors to determine how drug specificity and dosing compare with genetic deficiency, to enhance future drug design. This project has direct clinical importance in understanding how BCR-signaling supports the function of autoreactive B cells in autoimmune arthritis, as a necessary step in developing therapeutic interventions.