Bruton's Tyrosine Kinase and Immune Tolerance in Type 1 Diabetes

描述(申请人提供)：1型糖尿病(T1D)由一系列复杂的事件引起，破坏免疫耐受，最终导致胰岛2细胞破坏。B淋巴细胞(B细胞)在疾病发展中起关键作用，可能是通过向致病T细胞呈递抗原来实现的。B细胞在糖尿病发展中的作用取决于多种因素，包括对自身抗原的耐受性丧失。这种耐受性是通过B细胞受体(BCR)对抗原结合的细胞反应介导的。Bruton‘s酪氨酸激酶(BTK)是BCR触发的信号通路的中心组成部分。了解B细胞驱动的糖尿病发展背后的细胞信号成分将推动该领域朝着致病B细胞的特定靶点发展。我们将BTK缺乏引入到非肥胖糖尿病(NOD)小鼠的T1D模型中，并发现这对糖尿病的发展具有显著的保护作用。此外，BTK缺乏干扰了B细胞相关的免疫耐受破坏，表现为野生型NOD小鼠胰岛素特异性免疫球蛋白自身抗体的丢失，以及转基因抗胰岛素BCR模型中胰岛素结合B细胞的减少。支持这一建议的特定假设是，BTK介导的BCR信号的传播有助于1)自身反应性B淋巴细胞的选择和存活，以及2)这些B细胞的促病功能特性。为了了解BTK在打破B淋巴细胞耐受性和促进自身免疫性糖尿病疾病中的作用机制，我们建议：1)使用包括条件性B细胞特异性BTK基因敲除模型和小分子BTK抑制剂在内的新工具，发现BTK如何参与自身反应性B淋巴细胞的选择和保留；2)通过系统地恢复负责激酶和连接功能的独立成分，确定BTK分子的哪些结构域负责自身反应性B淋巴细胞的选择和功能；以及3)通过检测对B细胞亚群、抗原呈递结果和调节参数的影响，研究BTK缺乏在预防T1D中的作用机制。该项目对于了解BCR信号如何支持T1D中自身反应性B细胞的选择、存活和功能具有直接的临床意义，这是开发治疗干预措施的必要步骤。

DESCRIPTION (provided by applicant): Type 1 diabetes (T1D) results from a complex cascade of events that breaks immune tolerance and culminates in the destruction of islet 2 cells. B lymphocytes (B cells) play a critical role in disease development, probably via antigen-presentation to pathogenic T cells. B cell contribution to the development of diabetes depends upon multiple factors, including loss of tolerance to self antigen. This tolerance is mediated by cellular 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. Understanding cell signaling components underlying B cell-driven diabetes development will advance the field toward specific targeting of pathogenic B cells. We have introgressed btk-deficiency onto the nonobese diabetic (NOD) mouse model of T1D, and found that this results in significant protection against the development of diabetes. In addition, btk-deficiency interferes with B cell related breaches of immune tolerance, as evidenced by the loss of insulin-specific IgG autoantibodies in wild type NOD mice, and reduction of insulin-binding B cells in a transgenic anti-insulin BCR model. The specific hypothesis underlying this proposal is that BTK-mediated propagation of BCR signals contributes to 1) selection and survival of autoreactive B lymphocytes, and 2) disease- promoting functional properties of these B cells. To understand the mechanisms of action of BTK in breaking B lymphocyte tolerance and promoting disease in autoimmune diabetes, we propose to: 1) discover how BTK participates in the selection and retention of autoreactive B lymphocytes, using use new tools that include a conditional, B cell-specific BTK knockout model and small molecule BTK- inhibitors, 2) determine which domains of the BTK molecule are responsible for autoreactive B lymphocyte selection and function, by systematically restoring independent components responsible for the kinase and linking functions, and 3) investigate the mechanisms of btk-deficiency in preventing T1D by examining effects on B cell subsets, antigen-presenting outcomes, and regulatory parameters. This project has direct clinical importance in understanding how BCR-signaling supports the selection, survival and function of autoreactive B cells in T1D, as a necessary step in developing therapeutic interventions.