Role and mechanisms of the PI3K pathway in B cell tolerance

项目总结 B细胞耐受性是发展对自身耐受的免疫系统的关键，但其机制 强制执行这一过程尚不清楚。我们研究的首要目标是阐明 调节B细胞选择的分子途径在未成熟和发育检查点之间 过渡细胞阶段，促进自身反应性骨髓B细胞的耐受过程 非自身反应性细胞的分化及其骨髓的存在。通过研究免疫球蛋白敲入小鼠模型 在中央B细胞耐受性方面，我们记录了RAS、ERK和PI3K信号分子，它们是 在非自身反应性疾病中，GTP酶、MAP激酶和脂蛋白激酶分别处于较高的基础水平 而不是自身反应性未成熟B细胞。我们的研究发现，虽然ERK和PI3K对于 未成熟B细胞体外分化为过渡性B细胞，体内仅激活B细胞中PI3K 细胞，但不是ERK 1)取消中央B细胞耐受，包括受体编辑和克隆性删除，2) 支持自身反应性B细胞从骨髓中退出，以及3)促进其进一步成熟和 激活。综上所述，这些发现证实了PI3K通路可以覆盖中枢和早期 小鼠自身反应性B细胞的外周耐受性，即使这些细胞对自身... 抗原。这项拨款的目标是定义PI3K控制B中心检查点的机制 小鼠的细胞选择以及它在人类B细胞中是否具有类似的功能。AIMS 1和AIMS中描述的实验 2将利用小鼠耐受模型来研究FOXO1、CXCR4和ERK是否以及如何翻译 PI3K在未成熟的B细胞中发挥作用。非自身反应性B细胞和自身反应性B细胞的RNAseq分析 打破或建立容忍将有助于在这一过程中发现更多的PI3K介体。患有疾病的患者 最近发现了PI3K的功能获得突变，它们经常表现出自身抗体和 其他自身免疫表现。目标3中的实验将利用两种互补的新方法 目的：确定PI3K功能增益突变打破人类B细胞中枢耐受的能力。 总体而言，这些研究具有重要意义，因为它们将产生对如何 主要的B细胞谱系是形成的，以及B细胞的耐受性如何在发展过程中被打破 自身反应B细胞，提高初级B细胞库的自身反应能力，因此， 有自体免疫的风险。

PROJECT SUMMARY B cell tolerance is key to the development of an immune system tolerant to self, but the mechanisms that enforce this process are not yet clearly understood. The overarching goal of our studies is to elucidate the molecular pathways that regulate B cell selection at the developmental checkpoint between the immature and transitional cell stages, enforcing the process of tolerance in autoreactive bone marrow B cells while promoting the differentiation of nonautoreactive cells and their bone marrow exit. By studying Ig knock-in mouse models of central B cell tolerance we documented that the RAS, ERK, and PI3K signaling molecules, which are GTPases, MAP kinases, and lipid kinases respectively, are active to a higher basal level in nonautoreactive than autoreactive immature B cells. Our studies have found that while both ERK and PI3K are necessary for the in vitro differentiation of immature B cells into transitional B cells, only the in vivo activation of PI3K in B cells, but not that of ERK 1) abrogates central B cell tolerance, including receptor editing and clonal deletion, 2) supports the exit of autoreactive B cells from the bone marrow, and 3) promotes their further maturation and activation. Taken together, these findings establish that the PI3K pathway can override central and early peripheral tolerance in mouse autoreactive B cells, even when these cells possess high avidity for the self- antigen. The goal of this grant is to define the mechanisms by which PI3K controls this central checkpoint of B cell selection in mice and whether it similarly functions in human B cells. Experiments described in Aims 1 and 2 will utilize mouse models of tolerance to investigate whether and how FOXO1, CXCR4, and ERK translate PI3K function in immature B cells. RNAseq analyses of nonautoreactive B cells and of autoreactive B cells that either break or make tolerance will aid the discovery of additional PI3K mediators in this process. Patients with gain-of-function mutations in PI3K have been recently discovered, and they often exhibit autoantibodies and other autoimmune manifestations. Experiments in Aim 3 will utilize two complementary and novel approaches to determine the ability of gain-of-function mutations in PI3K to break central tolerance in human B cells. Overall, these studies are significant because they will generate a deeper mechanistic understanding of how the primary B cell repertoire is formed and how B cell tolerance can be breached during the development of autoreactive B cells, raising the autoreactive capacity of the primary B cell repertoire and, consequently, the risk for autoimmunity.