Understanding the connection between exposure to mercury, auto-immunity and tolerance in B cells.

摘要 汞 (Hg) 是一种广泛存在于环境中的异生物质。汞也是一种有效的免疫调节剂 这被认为是导致动物模型和人类自身免疫性疾病的一个因素。一个 最近的流行病学研究令人信服地表明，在其他健康的个体中，仅 通过典型的环境来源暴露于低水平的汞，血液汞与 血液中双链 DNA（一种自身免疫生物标志物）抗体的水平和出现。这个 研究结果表明，在适当的情况下，暴露于环境汞会促进自身免疫， 自身免疫性疾病的前兆。自从发现 B 细胞以来，免疫学家已经认识到，在 根据克隆选择理论，在 B 细胞发育的正常过程中，大量 必须产生未成熟的 B 细胞，其产生对许多自身抗原（自身抗原）有反应的免疫球蛋白。 抗体）。然而，在正常发育过程中，绝大多数未成熟的自身反应性B细胞 通过统称为耐受性的过程来阻止成熟。自身免疫性疾病发生在以下情况： 促进耐受性的机制被破坏。对于 B 细胞来说，已经确定耐受性 很大程度上取决于未成熟 B 细胞中 B 细胞受体 (BCR) 产生的信号。我们的 初步和最近发表的研究表明，汞会干扰 BCR 的信号生成 未成熟的 B 细胞，通过可能涉及酪氨酸激酶 Lyn（酪氨酸磷酸酶）的机制 SHP-1 和 CD45 以及细胞骨架的元件。我们的总体假设是，环境暴露 与未接触汞的动物相比，汞会破坏接触汞的动物的 BCR 信号传导，从而导致 B 暴露动物的细胞耐受性。这反过来又会导致出现过多的成熟汽车 暴露于汞的动物中的反应性 B 细胞有可能引起自身免疫性疾病。我们建议 通过生成抗鸡蛋溶菌酶（HEL）/鸡蛋溶菌酶双转基因小鼠来检验这一假设 它们被设计为通常能够耐受 HEL，并且它们是否将其暴露于 Hg，以破坏 HEL 耐受性（目标 1）。我们将扩展我们的初步数据以进一步阐明分子机制 使汞能够干扰 BCR 信号传导。我们将利用具有不同遗传基因的小鼠品系 对汞中毒的敏感性，以直接研究汞如何干扰酪氨酸的功能 激酶 Lyn 以及酪氨酸磷酸酶 SHP-1 和 CD45 在 BCR 信号传导过程中的影响 不同的遗传背景（目标 2）。我们将使用互补的蛋白质组学和多色 phosphflow 细胞计数方法确定汞如何与细胞骨架元素相互作用，从而减弱 BCR 信号传导（目标 3）。

ABSTRACT Mercury (Hg) is a xenobiotic that is widespread in the environment. Mercury is also a potent immunomodulator that has been implicated as a factor contributing to autoimmune disease in animal models and humans. A recent epidemiological study has now convincingly shown that, in otherwise healthy individuals who were only exposed to low levels of Hg through typical environmental sources, there is a correlation between blood Hg levels and the appearance in the blood of antibodies to double-stranded DNA, an autoimmune biomarker. This finding indicates that under the proper circumstances, exposure to environmental Hg promotes autoimmunity, a precursor to autoimmune disease. Since the discovery of B cells, immunologists have appreciated that, in light of the Clonal Selection Theory, during the normal course of B cell development, large numbers of immature B cells must be generated that produce immunoglobulin that is reactive to many self-antigens (auto- antibodies). However, in the course of normal development, the vast majority of immature auto-reactive B cells are prevented from maturing by processes collectively known as tolerance. Autoimmune disease arises when the mechanisms that promote tolerance are disrupted. For B cells, it is firmly established that tolerance depends to a large extent on signals generated by the B cell receptor (BCR) in immature B cells. Our preliminary and recently published studies have shown that Hg interferes with signal generation by the BCR in immature B cells, through mechanisms that likely involve the tyrosine kinase Lyn, the tyrosine phosphatases SHP-1 and CD45 and elements of the cytoskeleton. Our overall hypothesis is that environmental exposure to Hg disrupts BCR signaling in Hg-exposed compared with non-exposed animals, resulting in the disruption of B cell tolerance in exposed animals. This in turn should lead to the appearance of an excess of mature auto- reactive B cells in Hg-exposed animals that have the potential to cause autoimmune disease. We propose to test this hypothesis by generating anti-hen egg lysozyme (HEL)/hen egg lysozyme double transgenic mice which are designed to be normally tolerant to HEL, and them exposing them or not to Hg, in order to break HEL tolerance (Aim 1). We will expand on our preliminary data to further elucidate the molecular mechanisms that enable Hg to interfere with BCR signaling. We will utilize mouse strains with different genetic susceptibilities to Hg intoxication to directly investigate how Hg interferes with the function of the tyrosine kinase Lyn and the tyrosine phosphatases SHP-1 and CD45 during BCR signaling under the influence of different genetic backgrounds (Aim 2). We will use complementary proteomic and multicolor phosphoflow cytometric approaches to determine how Hg interacts with elements of the cytoskeleton, so as to attenuate BCR signaling (Aim 3).