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。 公共卫生相关性：自身反应性B淋巴细胞对1型糖尿病的发展至关重要。这个项目的目标是了解由Bruton‘s酪氨酸激酶介导的B细胞信号如何支持这种疾病中发生的免疫耐受的破坏。这些发现将为针对自身反应性、致病性B细胞的特定靶点提供新的干预途径。

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. PUBLIC HEALTH RELEVANCE: Autoreactive B lymphocytes are essential to the development of type 1 diabetes. The goal of this project is to understand how B cell signaling, mediated by Bruton's tyrosine kinase, supports the breach of immunologic tolerance that occurs in this disease. These discoveries will provide new avenues of intervention for the specific targeting of autoreactive, pathogenic B cells.