Impact of SLE-Associated ITGAM Variants on Dendritic Cell Function

系统性红斑狼疮(SLE)是一种威胁生命的疾病，影响着约150万美国人，其中 自身抗体攻击身体，引发致残性和破坏性炎症。非特定 免疫抑制可降低系统性红斑狼疮的发病率和死亡率，但通常有严重的副作用。特效疗法 治疗SLE的副作用较少的药物正在开发中，但到目前为止只有一种药物获得FDA批准(Belimumab)。 在更好地了解系统性红斑狼疮的发病机制之前，对更具体的治疗方法的需求仍然很大，而且还没有得到满足。 目前已知有80多种不同的基因与系统性红斑狼疮的风险有统计上的联系，但对 这些变异改变基因表达或功能的机制以及它们如何影响SLE的发病机制。 我们提出的研究直接解决了这一知识鸿沟。中国人群中的单核苷酸多态(SNPs) 称为ITGAM的基因与系统性红斑狼疮的风险密切相关。ITGAM编码Mac-1受体的CD11b亚单位 主要由髓系细胞表达。Mac-1有大量的配体，通过将它们连接到 不同的细胞，这种受体可以调节多种不同的免疫功能。值得注意的是，Mac-1是一种 树突状细胞(DC)上的重要受体，一种细胞类型，其中Mac-1的表达与适当的DC有关 DC介导的T细胞完全激活的发展和抑制。长期以来，DCs一直被牵连到 系统性红斑狼疮的发生、发展和调控。我们的长期目标是了解ITGAM如何遗传 变异改变了髓系细胞上的Mac-1功能，从而推动了SLE的发生。这样做的两个目标 应用程序是迈向我们长期目标的重要一步，它是：(I)确定SLE与ITGAM 77His相关 变异体改变人外周血单核细胞来源的DC上的Mac-1生物学和(Ii)确定这种SLE 相关的ITGAM变异体在人源化小鼠体内改变DC介导的耐受。我们建议的研究是 基于我们可以将这种与SLE相关的基因变异与Mac-1介导的改变联系起来的基本原理 DC功能具有推动SLE的免疫学后果。因此，我们的中心假设是 77His突变扰乱了DC介导的T细胞介导的获得性免疫调节。在目标1中，我们将 使用人类DC来测试77His的存在以某种方式改变DC上的Mac-1功能的假设 足以干扰细胞触发正常T细胞反应的能力。对于目标2，我们已经生成了 表达SLE相关CD11b 77His变体的独特人源化小鼠。这些将被用来确定 77His对DC生物学的影响是否足以影响体内的外周免疫耐受。工作假说 这就是，表达SLE相关77His变体的小鼠将在DC介导的耐受中表现出缺陷 机械装置。这项工作的成功开展将为人类基因组学研究提供新的功能基因组学解释 确认这种ITGAM变异与系统性红斑狼疮的关联，这可能对人类健康产生积极影响。

Systemic lupus erythematosus (SLE) is a life threatening disease affecting ~1.5 million Americans, wherein autoantibodies attack the body and trigger disabling and destructive inflammation. Non-specific immunosuppression reduces SLE morbidity and mortality but often has severe side effects. Specific therapies for SLE with fewer side effects are being developed but so far only one has been FDA approved (belimumab). The need for more specific therapies will remain great and unmet until SLE pathogenesis is better understood. Over 80 different genes are known to be statistically linked with SLE risk, but little is known about the mechanisms by which these variants alter gene expression or function and how they affect SLE pathogenesis. Our proposed research directly addresses this knowledge gap. Single-nucleotide polymorphisms (SNPs) in a gene called ITGAM strongly associate with SLE risk. ITGAM encodes the CD11b subunit of Mac-1, a receptor expressed mainly by cells of the myeloid lineage. Mac-1 has numerous ligands and by engaging them on different cells, this receptor can regulate many and diverse immunological functions. Notably, Mac-1 is an important receptor on dendritic cells (DCs), a cell type wherein Mac-1 expression has been linked to proper DC development and inhibition of full DC-mediated T cell activation. DCs have long been implicated in the initiation, progression, and modulation of SLE. Our long-term goal is to understand how ITGAM genetic variation changes Mac-1 function on myeloid cells in a way that propels SLE. The two objectives of this application, a major step towards our long-term goal, are (i) to establish that an SLE associated ITGAM 77His variant alters Mac-1 biology on human peripheral blood monocyte-derived DCs and (ii) to determine if this SLE associated ITGAM variant alters DC mediated tolerance in vivo in humanized mice. Our proposed research is based on the rationale that we can link this SLE associated genetic variant with alterations in Mac-1 mediated DC functions that have immunological consequences that propel SLE. Accordingly, our central hypothesis is that the 77His variant perturbs DC-mediated regulation of T cell-mediated adaptive immunity. In Aim 1 we will use human DCs to test the hypothesis that presence of 77His alters Mac-1 function on DCs in a manner sufficient to interfere with the cells' ability to trigger a normal T-cell response. For Aim 2 we have generated unique humanized mice expressing the SLE associated CD11b 77His variant. These will be used to determine if the impact of 77His on DC biology is sufficient to affect peripheral tolerance in vivo. The working hypothesis here is that mice expressing the SLE associated 77His variant will show defects in DC-mediated tolerance mechanisms. Successful pursuit of this work will provide a new functional genomics interpretation for the recognized associations of this ITGAM variant with SLE, which could have a positive impact on human health.