Selection & Regulation of B Lymphocytes in IDDM

描述（由申请人提供）：本项目旨在了解自身反应性B淋巴细胞在1A型或胰岛素依赖型糖尿病（IDDM）中的选择和调控。从长远来看，这些信息将用于确定诊断和治疗这种疾病的新目标。临床和实验数据表明，IDDM是由自身耐受性丧失和随后产生胰岛素的β细胞的自身免疫破坏引起的。虽然针对胰岛素、GAD和其他胰岛抗原的自身抗体被认为是免疫耐受性丧失的早期指标，但大多数研究都集中在T淋巴细胞在疾病中的作用上。最近的一些研究表明，B淋巴细胞在IDDM中也起着关键作用。NOD小鼠是IDDM的一种高度相关的动物模型，当B淋巴细胞被阻断或消除时，NOD小鼠可以免受疾病过程的影响。此外，数据表明B淋巴细胞能够独特地呈递一些关键的β细胞抗原，其抗原呈递功能包括控制T细胞分化的能力。为了更好地了解B淋巴细胞在IDDM中的作用，我们制造了表达抗胰岛素mab125免疫球蛋白转基因（Tg）的NOD小鼠。虽然携带抗胰岛素转基因的B淋巴细胞在正常B6小鼠中功能沉默，但相同的转基因在NOD中表达时显示出耐受性的破坏。此外，当NOD小鼠只携带来自mab125的重链（HC） Tg （VH 125Tg）时，这些动物患糖尿病的速度明显快于非Tg对照组。相比之下，NOD小鼠表达一种其他方面相同的转基因（VH281），仅在胰岛素结合所需的两个氨基酸上存在差异，可保护其不患糖尿病。当检测这些HC-Tg NOD的胰岛素结合B细胞的表达时，观察到VH125-Tg NOD的B细胞受体（BCR）与内源性轻链结合产生异质的胰岛素结合B细胞群，其中一些高亲和力地结合胰岛素。对VH125Tg NOD中抗胰岛素B细胞的追踪表明，BCR对胰岛素的渴望度的变化与糖尿病发展的进展是一致的。这些观察结果表明，在IDDM的背景下，HC-Tg小鼠提供了一种独特的方法来追踪抗胰岛素B细胞的命运和功能，这些细胞通常埋藏在大量的多克隆库中。将B细胞作用与IDDM联系起来的细胞和分子机制将在以下具体目标中进行研究：1 .描述NOD小鼠中伴随进行性β细胞破坏的B细胞库中胰岛素的结构和功能的变化。2。了解T1DM过程中浸润胰岛的B淋巴细胞的多样性和功能。3。在T1DM的情况下，确定B淋巴细胞对胰岛素和胰岛素原启动T细胞反应的需求。表征受体识别β细胞自身抗原的B细胞的抗原呈递功能。

DESCRIPTION (provided by applicant): The goal of this project is to understand the selection and regulation of autoreactive B lymphocytes in Type 1A or insulin dependent diabetes mellitus (IDDM). In the long term this information will be used to identify new targets for the diagnosis and treatment of the disorder. Clinical and experimental data indicate that IDDM results from loss of self-tolerance and subsequent autoimmune destruction of insulin producing beta cells. Although autoantibodies to insulin, GAD and other islet antigens are recognized as early indicators of loss of immunological tolerance, most studies focus on the role of T lymphocytes in the disease. Several recent studies indicate that B lymphocytes also play a critical role in IDDM. NOD mice, a highly relevant animal model of IDDM, are protected from the disease process when B lymphocytes are blocked or eliminated. Further, data indicate that B lymphocytes are uniquely able to present some key beta cell antigens, and their antigen presenting function includes the ability to govern T cell differentiation. To better understand the role of B lymphocytes in IDDM, NOD mice were produced that express immunoglobulin transgenes (Tg) from anti-insulin mab125. While B lymphocytes that carry anti-insulin transgenes are functionally silenced in normal B6 mice, the same transgenes demonstrate breaches of tolerance when expressed in NOD. In addition, when NOD mice are engineered to harbor only the heavy chain (HC) Tg from mab125 (VH 125Tg), these animals develop diabetes at a significantly faster rate than non-Tg controls. In contrast, NOD mice expressing an otherwise identical transgene (VH281) that differs in only two amino acids that are required for insulin binding are protected from developing diabetes. When these HC-Tg NOD were examined for expression of insulin binding B cells, B cell receptors (BCR) from VH125-Tg NOD were observed to combine with endogenous light chains to produce a heterogeneous population of insulin-binding B cells, some of which bind insulin with high affinity. Tracking anti-insulin B cells in VH125Tg NOD shows that changes in BCR avidity for insulin occurs in concert with progression to diabetes development. These observations indicate that in the context of IDDM, HC-Tg mice provide a unique means to track the fate and function of anti-insulin B cells that are usually buried in a large polyclonal repertoire. The cellular and molecular mechanisms that connect B cell actions to IDDM will be examined in the following specific aims: I. To characterize the shifts in structure and function of a B cell repertoire for insulin that accompanies progressive beta cell destruction in NOD mice. II. To understand the diversity and function of B lymphocytes that invade pancreatic islets in the course of T1DM. III. To determine the requirement for B lymphocytes in the initiation of T cell responses to insulin and proinsulin in the context of T1DM. IV. To characterize the antigen presenting function of B cells whose receptors recognize a beta cell autoantigen.