Development and Function of Natural Autoreactive B Cells

描述（由申请人提供）：尽管广泛认为具有自身反应性的B细胞被删除或使其功能失活，但在健康动物的血清中可以发现称为“天然自身抗体”的自身反应性抗体。这种天然自身抗体是由一小部分B细胞产生的，其具有细胞表面糖蛋白CD 5的独特表达。这些CD 5+自身反应性B细胞比成人骨髓中的那些更频繁地从胎儿B细胞前体产生，作为“B-1”B细胞发育的一部分。我们的研究探讨了为什么这种天然的自身反应性B细胞应该存在，它们的发展机制，以及它们失调的潜力。通过建立和研究表达天然抗Thy-1自身抗体（ATA）的小鼠天然自身反应性B细胞模型，我们发现自身抗原对于CD 5 + ATA自身反应性B-1 B细胞积累具有重要作用，相对较高的B细胞受体（BCR）信号强度介导正选择过程。相反，在来自骨髓的脾中的常规B细胞发育（“B-2”）期间，表达相同BCR的细胞发生负选择。在这次更新中，我们将获得对B细胞亚群发育机制的全面了解。我们将首先研究传统的非自身反应性B-2 B细胞成熟的机制，特别是其他淋巴细胞提供的非BCR信号的意义。我们将评估T细胞和胎儿B-1 B细胞在成人B-2（滤泡B细胞）发育和免疫中的作用及其潜在的相互作用（目标1）。为了理解为什么自身反应性B-1阳性选择与胎儿B细胞发育相关，我们将鉴定“胎儿B-1特征”，我们假设其反映了与骨髓（B-2）发育相比决定BCR信号传导阈值差异的独特细胞机制。为了跟踪早期产生的B-1细胞的命运，我们将产生Lysmd 2-GFP报告小鼠，基于我们最近将该基因鉴定为胎儿B-1特征的成员（Aim 2）。完成所提出的工作将显着推进我们的理解自身反应性B-1阳性选择和B细胞的发展一般。我们假设，早期产生的天然自身反应性淋巴细胞发生的关键保护性原因，作为先天免疫系统的组成部分，以帮助发展的适应性免疫系统。7.与公共卫生的相关性 在某些自身免疫小鼠品系中，随着年龄的增长，CD 5 + B细胞可能会发生异常扩增， 和B淋巴瘤。在人类中，CD 5表达是晚期慢性B的标志 细胞白血病（B CLL），占美国成人白血病病例的三分之一， 西欧全面了解B细胞的发育、选择， 和成熟机制，并确定CD 5+天然自身反应性B细胞是如何 正常调节和功能，如本申请中所提出的，将是至关重要的 设计这种失调的CD 5 + B细胞的合理疗法。

DESCRIPTION (provided by applicant): Although it is widely accepted that B cells with self-reactivity are deleted or rendered functionally inactive, self-reactive antibodies, referred to as "natural autoantibodies" can be found in the serum of healthy animals. Such natural autoantibodies are produced by a small fraction of B cells with distinctive expression of the cell surface glycoprotein CD5. These CD5+ autoreactive B cells are more frequently generated from fetal B cell precursors as a part of "B-1" B cell development than those in the adult bone marrow. Our research explores why such natural autoreactive B cells should exist, the mechanism whereby they develop, and their potential for dysregulation. By establishing and investigating mouse natural autoreactive B cell models expressing natural anti-Thy-1 autoantibody (ATA), we found that self-antigen is important for CD5+ ATA autoreactive B-1 B cell accumulation with relatively higher B cell receptor (BCR) signal intensity mediating a positive selection process. In contrast, negative selection occurs for cells expressing the identical BCR during conventional B cell development ("B-2") in spleen from bone marrow. In this renewal, we will obtain a comprehensive understanding of the mechanism for B cell subset development. We will first investigate the mechanism of conventional non-autoreactive B-2 B cell maturation, in particular the significance of non-BCR signaling provided by other lymphocytes. We will assess the role of T cells and fetal B-1 B cells in adult B-2 (follicular B cell) development and immunity and their potential interaction (Aim 1). To understand why autoreactive B-1 positive selection occurs in relation to fetal B cell development, we will identify a "fetal B-1 signature" that we hypothesize reflects distinctive cellular machinery determining a difference in BCR signaling threshold, compared to bone marrow (B-2) development. To follow early-generated B-1 cell fate, we will produce Lysmd2-GFP reporter mice, based on our recent identification of this gene as a member of the fetal B-1 signature (Aim 2). Accomplishing the proposed work will significantly advance our understanding of autoreactive B-1 positive selection and B cell development in general. We hypothesize that early generation of natural autoreactive lymphocytes occurs for critical protective reasons, as a component of the innate immune system, to help development of the adaptive immune systems that follows. 7. Relevance to Public Health Abnormal expansions of CD5+ B cells can occur with age, in certain autoimmune mouse strains, and as B lymphomas. In humans, CD5 expression is a hallmark of late developing chronic B cell leukemia (B CLL), accounting for a third of adult leukemia cases in the United States and Western Europe. Arriving at a comprehensive understanding of B cell development, selection, and maturation mechanism(s), and establishing how CD5+ natural autoreactive B cell are normally regulated and function, as proposed in this application, will be critically important for designing rational therapies of such dysregulated CD5+ B cells.