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外源性物质。汞也是一种有效的免疫调节剂 在动物模型和人类中，它被认为是导致自身免疫性疾病的一个因素。一 最近的流行病学研究令人信服地表明，在其他方面健康的人中， 通过典型的环境来源暴露于低水平的汞， 水平和出现在血液中的抗体双链DNA，自身免疫生物标志物。这 研究结果表明，在适当的条件下，环境汞暴露可促进自身免疫， 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， 根据克隆选择理论，在B细胞发育的正常过程中， 必须产生产生免疫球蛋白不成熟B细胞，所述免疫球蛋白对许多自身抗原（自身 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 被统称为公差的过程阻止成熟。自身免疫性疾病发生时， 促进耐受性的机制被破坏。对于B细胞，已经确定耐受性 在很大程度上依赖于由未成熟B细胞中的B细胞受体（BCR）产生的信号。我们 初步和最近发表的研究表明，汞干扰BCR的信号产生， 不成熟的B细胞，通过可能涉及酪氨酸激酶林恩，酪氨酸磷酸酶 SHP-1和CD45以及细胞骨架的元件。我们的总体假设是， 与未接触汞的动物相比，汞干扰了接触汞的动物的BCR信号，导致B的干扰 暴露动物的细胞耐受性。这反过来又会导致过度成熟的自动驾驶汽车的出现， 汞暴露动物体内的反应性B细胞有可能导致自身免疫性疾病。我们建议 通过产生抗鸡蛋溶菌酶（HEL）/鸡蛋溶菌酶双转基因小鼠来检验这一假设 它们被设计成通常耐受HEL，并且它们暴露于或不暴露于Hg，以便破坏 HEL耐受性（目标1）。我们将扩大我们的初步数据，以进一步阐明分子机制 使汞能够干扰BCR信号。我们将利用不同基因的小鼠品系， 直接研究汞如何干扰酪氨酸的功能 激酶林恩和酪氨酸磷酸酶SHP-1和CD 45在BCR信号传导过程中的影响 不同的遗传背景（目标2）。我们将使用互补蛋白质组学和荧光磷酸流 细胞计数方法，以确定汞如何与细胞骨架的元素相互作用，从而减弱 BCR信号传导（Aim 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).