Impact of SLE-Associated ITGAM Variants on Dendritic Cell Function

系统性红斑狼疮（SLE）是影响约150万美国人的危及生命的疾病，其中 自身抗体攻击身体并引发致残性和破坏性炎症。非特异性 免疫抑制可降低SLE发病率和死亡率，但通常具有严重的副作用。特定疗法 正在开发副作用较少的治疗SLE的药物，但迄今为止只有一种药物（贝利木单抗）获得FDA批准。 在更好地了解SLE发病机制之前，对更特异性治疗的需求仍然很大且未得到满足。 已知超过80种不同的基因与SLE风险在统计学上相关，但对SLE风险的影响知之甚少。 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发病机制。 我们提出的研究直接解决了这一知识差距。单核苷酸多态性（SNPs）在 ITGAM基因与SLE风险密切相关。ITGAM编码Mac-1的CD 11b亚基，Mac-1是一种受体， 主要由髓系细胞表达。Mac-1有许多配体， 在不同的细胞中，这种受体可以调节许多不同的免疫功能。值得注意的是，Mac-1 树突状细胞（DC）上的重要受体，其中Mac-1表达已与适当的DC相关联 发展和抑制完全DC介导的T细胞活化。DC长期以来一直与 SLE的发生、发展和调节。我们的长期目标是了解ITGAM基因是如何 变异改变了Mac-1在髓样细胞上的功能，从而促进SLE。这两个目标 应用，朝着我们的长期目标迈出的重要一步，是（i）建立SLE相关的ITGAM 77 His 变体改变人外周血单核细胞衍生的DC上的Mac-1生物学和（ii）确定这种SLE是否 相关的ITGAM变体改变人源化小鼠体内DC介导的耐受性。我们的研究计划是 基于我们可以将这种SLE相关的遗传变异与Mac-1介导的 DC功能具有免疫学后果，推动SLE。因此，我们的中心假设是 77 His变体干扰DC介导的T细胞介导的适应性免疫调节。在目标1中， 使用人DC来检验77 His的存在以一种方式改变DC上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，我们生成了 表达SLE相关CD 11b 77 His变体的独特人源化小鼠。这些将用于确定 如果77 His对DC生物学的影响足以影响体内外周耐受性。工作假设 表达SLE相关77 His变体的小鼠将显示DC介导的耐受性缺陷， 机制等这项工作的成功进行将为人类的免疫功能提供一个新的功能基因组学解释。 该ITGAM变异体与SLE的关联已被公认，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.