Tolerance in polyclonal and oligoclonal immune systems

描述（由申请人提供）：B细胞是自身免疫的重要致病成分。然而，我们目前对这些疾病中致病B细胞表型的了解仍然有限，需要更多的研究来进一步表征这些细胞，揭示其独特的特征和作用方式。B细胞只表达一种抗体，对一种抗原有特异性。然而，罕见的共表达两种不同抗体的B细胞（即双反应性B细胞）存在于小鼠和人类中。我们的目标是了解双反应性B细胞是否在自身免疫中代表一个相关的B细胞亚群。我们的新发现表明，自身免疫小鼠比非自身免疫小鼠更频繁地产生双反应性未成熟和成熟B细胞。这些细胞中的大多数与自身抗原反应，表明它们逃避了负选择机制。双反应性B细胞比单反应性B细胞更频繁地产生自身抗体，并且在自身免疫小鼠的抗原活化B细胞亚群中高度富集。最后，我们已经确定了非自反应性未成熟B细胞阳性选择的分子途径，我们建议该途径也用于产生双自反应性B细胞。在之前的资助周期中，我们通过创建突变小鼠和方法建立了拟议研究的基础，这些方法用于在自身免疫性和非自身免疫性小鼠中跟踪双反应性B细胞的发育和选择。因此，我们有独特的条件来进行拟议的研究。我们的创新假设是，双反应性B细胞可以逃避B细胞耐受机制，成为自身免疫性疾病的重要组成部分。本研究的目的是加深我们对小鼠双反应性B细胞与自身免疫之间关系的理解。我们将研究导致自身免疫易感性小鼠双反应性B细胞增加产生、选择和富集的机制，以及这些B细胞是否有助于自身免疫的发展。我们还将通过检查自身免疫个体中双反应性B细胞的患病率来翻译我们的小鼠研究。为了实现我们的目标，我们将发展以下具体目标：1)确定强直性B细胞受体信号是否抑制双自反应性未成熟B细胞中的受体编辑并通过Ras-Erk途径促进其分化；2)建立自身免疫小鼠抗原介导的双反应性B细胞选择和活化的一些机制；3)确定双反应性B细胞是否参与自身免疫并在自身免疫患者中富集。本文提出的研究将确定双反应性B细胞是否是自身免疫的诊断性和/或致病性B细胞亚群，并将对开发识别和靶向这些B细胞的方法具有价值。总的来说，这些研究对于理解B细胞介导的自身免疫发展机制和发现自身免疫干预的新靶点是重要的。

DESCRIPTION (provided by applicant): B cells are an important pathogenic component of autoimmunity. However, our current knowledge of the phenotype of pathogenic B cells in these diseases is still limited and more studies are needed to further characterize these cells and uncover their unique characteristics and mode of action. B cells are known to express only one type of antibody and be specific for one antigen. However, rare B cells co-expressing two different antibodies (i.e., dual-reactive B cells) exist in mice and are present in humans. Our goal is to understand whether dual-reactive B cells represent a relevant B cell subset in autoimmunity. Our novel findings demonstrate that autoimmune mice generate dual-reactive immature and mature B cells more frequently than nonautoimmune mice. The majority of these cells react with self-antigens indicating that they evade mechanisms of negative selection. Dual-reactive B cells generate autoantibodies more frequently than single-reactive B cells and are highly enriched in the antigen-activated B cell subsets of autoimmune mice. Finally, we have identified a molecular pathway for the positive selection of nonautoreactive immature B cells that we propose is used for the generation of dual-autoreactive B cells as well. In the previous grant cycle, we have established the bases for the proposed research by creating the mutant mice and methodologies with which to follow development and selection of dual-reactive B cells in autoimmune and nonautoimmune mice. Therefore, we are uniquely posed to carry out the proposed studies. Our innovative hypothesis is that dual-reactive B cells can evade mechanisms of B cell tolerance to become an important component of autoimmune diseases. The goal of the proposed research is to deepen our understanding of the relationship between dual-reactive B cells and autoimmunity in mice. We will investigate the mechanisms that cause increased generation, selection and enrichment of dual-reactive B cells in autoimmune-prone mice and whether these B cells contribute to the development of autoimmunity. We will also translate our mouse studies by examining the prevalence of dual-reactive B cells in individuals with autoimmunity. To achieve our goals we will develop the following specific aims: 1) To determine whether tonic B cell receptor signaling inhibits receptor editing in dual-autoreactive immature B cells and promotes their differentiation via the Ras-Erk pathway; 2) To establish some of the mechanisms of antigen-mediated selection and activation of dual-reactive B cells in autoimmune mice; 3) To determine whether dual-reactive B cells contribute to autoimmunity and are enriched in autoimmune patients. The studies proposed here will establish whether dual-reactive B cells are a diagnostic and/or pathogenic B cell subset in autoimmunity and will be of value for the development of methods to identify and target these B cells. Overall, these studies are important for understanding B cell-mediated mechanisms of autoimmune development and to uncover novel targets for autoimmune intervention.