MECHANISMS THAT REGULATE B CELL TOLERANCE

调节 B 细胞耐受性的机制

• 批准号: 6626346
• 负责人: TIMOTHY W. BEHRENS
• 金额: $ 29.52万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-01-15 至 2005-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6626346
• 关键词: B cell receptor; B lymphocyte; CD5 molecule; T cell receptor; T lymphocyte; autoantibody; autoimmunity; calcium flux; cell proliferation; gene targeting; genetically modified animals; immune tolerance /unresponsiveness; interleukin 7; laboratory mouse; passive immunization; systemic lupus erythematosus

DESCRIPTION: The mechanisms, which are thought to be important for the maintenance of B cell tolerance, include deletion of self-reactive cells both in the bone marrow and the periphery, immunoglobulin receptor editing, and the induction of clonal anergy. This laboratory has recently shown that anergic B cells express significant surface levels of CD5, a molecule normally found on T cells and a subset of B-1 cells. Breeding of the en egg lysozyme (HEL) transgenic model for B cell anergy onto the CD5 null background resulted in a spontaneous loss of B cell tolerance in vivo. Evidence for this included elevated levels of anti-HEL IgM antibodies in the serum of CD5-/- mice transgenic for both a HEL-specific B cell receptor (BCR) and soluble lysozyme. "Anergic" B cells lacking CD5 also showed enhanced proliferative responses in vitro and elevate intracellular Ca++ levels at rest and following IgM crosslinking. These data sup ort the hypothesis that CD5 negatively regulates immunoglobulin receptor signaling in anergic B cells and functions to inhibit autoimmune B cell responses. Additional preliminary experiments suggest a role for CD5 in regulating B cell receptor signaling in antigen naive B cells. Also, we have begun to characterize CD5-/- HEL-Ig/sHEL mice that develop a profound loss of tolerance. In these mice we hypothesize that autoantibody secretion effectively titrates self-antigen leading to a reversal of the anergic B cell phenotype. The experiments described here will focus n these in vivo models, and are designed to further characterize the nature of he in vivo tolerance defects observed in HEL-Ig/sHEL double transgenic mice lacking CD5, and to fully evaluate CD5-/-Ig/sHEL mice that exhibit the very highest levels of serum antibody. Next the CD5 knockout alleles will be bred onto lupus-prone sle2 congenic and sle1/sle3 bi-congenic mice to determine whether CD5 deficiency will enhance autoimmunity in these models for systemic lupus erythematosus (SLE). Finally, the influence of CD5 on receptor editing and induction into the B-1 compartment will be explored. Together, the experiments proposed should significantly advance understanding of the role that CD5 plays in regulating immune responses. In addition, these experiments are likely to provide interesting new insights into the mechanisms that lead to autoimmunity, with potential therapeutic implications for patients with antibody-mediated autoimmune diseases such as SLE.

描述：这些机制被认为对于 维持 B 细胞耐受性，包括删除自身反应性细胞 在骨髓和外周，免疫球蛋白受体编辑，以及 诱导克隆无能。该实验室最近表明，无能 B 细胞表面表达显着水平的 CD5，这是一种通常在 T 上发现的分子 细胞和 B-1 细胞的子集。鸡蛋溶菌酶 (HEL) 的育种 CD5 无效背景上的 B 细胞无反应性转基因模型产生了 体内 B 细胞耐受性自发丧失。这方面的证据包括 CD5-/- 小鼠血清中抗 HEL IgM 抗体水平升高 HEL 特异性 B 细胞受体 (BCR) 和可溶性溶菌酶的转基因。 缺乏 CD5 的“无能”B 细胞也表现出增强的增殖反应 在静息和 IgM 后进行体外培养并提高细胞内 Ca++ 水平 交联。这些数据支持 CD5 负调节的假设 无反应性 B 细胞中的免疫球蛋白受体信号传导及其抑制功能 自身免疫 B 细胞反应。额外的初步实验表明了一个作用 CD5 在抗原幼稚 B 细胞中调节 B 细胞受体信号传导。还， 我们已经开始表征 CD5-/- HEL-Ig/sHEL 小鼠，这些小鼠发展出深刻的 失去耐受性。在这些小鼠中，我们假设自身抗体分泌 有效滴定自身抗原，导致无能 B 细胞逆转 表型。这里描述的实验将集中在这些体内模型上， 并旨在进一步表征体内耐受性的性质 在缺乏 CD5 的 HEL-Ig/sHEL 双转基因小鼠中观察到的缺陷 全面评估表现出最高血清水平的 CD5-/-Ig/sHEL 小鼠 抗体。接下来，CD5 敲除等位基因将被培育到易患狼疮的 sle2 上 同源和 sle1/sle3 双同源小鼠以确定是否 CD5 缺陷 将增强这些系统性红斑狼疮模型的自身免疫能力 （系统性红斑狼疮）。最后，CD5对受体编辑和诱导的影响 B-1隔间将被探索。总之，所提出的实验应该 显着促进对 CD5 在调节中的作用的理解 免疫反应。此外，这些实验可能会提供 对导致自身免疫的机制提出有趣的新见解 对抗体介导的患者的潜在治疗意义 自身免疫性疾病，如系统性红斑狼疮 (SLE)。