Selection & Regulation of B Lymphocytes in IDDM

描述(申请人提供)：本项目的目标是了解自身反应性B淋巴细胞在1A型或胰岛素依赖型糖尿病(IDDM)中的选择和调节。从长远来看，这些信息将被用来确定诊断和治疗这种疾病的新靶点。临床和实验数据表明，IDDM是由于自身耐受性的丧失和随后产生胰岛素的β细胞的自身免疫破坏所致。尽管抗胰岛素、GAD和其他胰岛抗原的自身抗体被认为是免疫耐受丧失的早期指标，但大多数研究集中在T淋巴细胞在疾病中的作用。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淋巴细胞是唯一能够呈递一些关键的β细胞抗原的细胞，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，建立了表达抗胰岛素单抗125的免疫球蛋白转基因(TG)的NOD小鼠。虽然携带抗胰岛素转基因的B淋巴细胞在正常的B6小鼠中功能上是沉默的，但同样的转基因在NOD中表达时表现出耐受性的破坏。此外，当NOD小鼠被设计为只携带mab125(VH 125Tg)的重链(HC)TG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小鼠表达的转基因基因(VH281)在其他方面相同，只有两种胰岛素结合所需的氨基酸不同，可以预防糖尿病。当检测这些HC-TG结节的胰岛素结合B细胞时，观察到来自VH125-TG结节的B细胞受体(BCR)与内源性轻链结合，产生一个异质性的胰岛素结合B细胞群体，其中一些与胰岛素具有高亲和力。追踪VH125Tg NOD中的抗胰岛素B细胞表明，BCR对胰岛素亲和力的变化与糖尿病的进展相一致。这些观察表明，在IDDM的背景下，HC-TG小鼠提供了一种独特的手段来追踪通常埋藏在大型多克隆谱系中的抗胰岛素B细胞的命运和功能。将在以下特定目标中研究将B细胞活动与IDDM联系起来的细胞和分子机制：1.表征伴随NOD小鼠进行性β细胞破坏的B细胞胰岛素谱系的结构和功能的变化。了解T1 DM病程中侵袭胰岛的B淋巴细胞的多样性和功能。确定在T1 DM的情况下，B淋巴细胞在启动T细胞对胰岛素和胰岛素原反应中的需求。研究受体识别β细胞自身抗原的B细胞的抗原提呈功能。

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.