Tolerance in Polyclonal and Oligoclonal Immune Systems

描述（由申请人提供）：等位基因和同型（单倍型）排除确定每个B细胞仅表达一个免疫球蛋白重链和轻链对，因此表现出单一特异性。然而，在健康个体和野生型小鼠中存在表达两条重链或两条轻链（包括单倍型）的B细胞，其频率估计约为B细胞群的2-10%。对免疫球蛋白转基因小鼠的分析表明，自身反应性B细胞有时可以通过共表达非自身反应性抗原受体来绕过中枢耐受机制。这些包含单倍型的细胞共同表达自身反应性和非自身反应性抗原受体，并在成熟的B细胞群中发现。由于大多数初级免疫球蛋白基因重排编码自身反应性特异性，我们提出野生型含单倍型的B细胞比含单倍型的（单表达ab的）B细胞有更高的自反应性机会。本研究的目的是了解小鼠单倍型B细胞的性质和调控，并确定这些细胞是否与自身免疫有关。为了实现这一目标，我们概述了三个特定目标，这些目标将表征具有野生型抗体库的小鼠中表达双免疫球蛋白轻链的B细胞，确定这些B细胞是否有助于自身免疫易感性小鼠的自身免疫过程，并了解包含单倍型的B细胞如何受到生理调节。包括单倍型在内的自身反应性B细胞将在体外和体内进行评估，使用各种小鼠模型和各种技术，包括B细胞杂交瘤的产生和表征以及细胞过继转移的使用。由于自身免疫是一个重要的健康问题，具有多种病因学基础，迄今为止，知之甚少，因此有必要对包含单倍型的B淋巴细胞进行分子和细胞分析。特别是，我们预测包含单倍型的B细胞是独特的，因为它们表达的自身抗体有可能与自身抗原表现出高度的相互作用，并产生同时结合外来和自身抗原的抗体。

DESCRIPTION (provided by applicant): Allelic and isotypic (haplotype) exclusion establishes that each B cell expresses only one immunoglobulin heavy and light chain pair and, consequently, exhibits a single specificity. Nevertheless, B cells expressing either two heavy or two light chains (haplotype-included) exist in healthy individuals and wild-type mice at a frequency estimated to be approximately 2-10% of the B cell population. Analyses of immunoglobulin transgenic mice have demonstrated that autoreactive B cells can sometimes bypass mechanisms of central tolerance by co-expressing non-autoreactive antigen receptors. These haplotype-included cells co-express autoreactive and non-autoreactive antigen receptors and are found in the mature B cell population. Because the majority of primary immunoglobulin gene rearrangements encode autoreactive specificities, we propose that wild-type haplotype-included B cells have higher chances of being autoreactive than haplotype-included (single Ab-expressing) B cells. The goal of this proposal is to understand the nature and regulation of haplotype-included B cells in mice and to determine if these cells are associated with autoimmunity. To accomplish this we outline three Specific Aims that will characterize dual immunoglobulin light chain- expressing B cells in mice with a wild-type antibody repertoire, determine whether these B cells contribute to the autoimmune process of autoimmune-prone mice, and understand how haplotype- included B cells are physiologically regulated. Haplotype-included autoreactive B cells will be evaluated both in vitro and in vivo using various mouse models and a variety of techniques that include the generation and characterization of B cell hybridomas and the use of cell adoptive transfer. Because autoimmunity is a significant health issue that has multiple, as of yet, poorly understood etiological bases, a molecular and cellular analysis of haplotype-included B lymphocytes is warranted. In particular, we predict haplotype-included B cells to be unique in that the autoantibody they express have the potential to exhibit a high avidity interaction with autoantigen and produce antibodies that simultaneously bind foreign as well as self-antigens. Project Narrative: Systemic autoimmune diseases such as lupus erythematosus and rheumatoid arthritis are complex disorders caused by defects in B and other blood cell types and that continue to cause significant morbidity and mortality. Although significant knowledge on these conditions has been achieved, substantial work remains to be done to fully understand the etiology and pathogenesis of these diseases. Some B cells in autoimmunity secrete autoantibodies that bind to molecules produced by the organism. It is still vastly unclear why these cells are generated and why they are activated to secrete autoantibodies. Our studies aim at characterizing a small population of B cells in mice that express two types of antibodies to determine whether these cells are progenitors of autoantibody-secreting cells and pathogenic players of autoimmunity.