Mechanisms of DNA-Specific Autoimmunity in Systemic Lupus Erythematosus

摘要 系统性红斑狼疮（SLE）的标志是产生抗核抗体， 抗原如核糖核蛋白和DNA，产生的免疫复合物引起全身性免疫反应。 免疫激活和组织炎症。针对双链DNA的高亲和力IgG抗体 双链DNA（dsDNA）是特别致病的，并且与组织损伤的严重性相关。的 对自身DNA的耐受机制及其在SLE中的分解机制知之甚少。我们有 通过关注DNASE1L3研究了这些机制，DNASE1L3是一种分泌型DNA酶，在几种 2例早发性家族性SLE。我们发现，DNASE1L3缺陷小鼠产生了大量的抗- dsDNA抗体应答，而对其他抗原的应答不存在或延迟。这 免疫应答以及随后的免疫激活和组织损伤需要先天免疫信号传导 通过衔接蛋白MyD88 DNASE1L3缺陷小鼠和人类患者显示， 在循环凋亡微粒内的基因组DNA的积累，并且该DNA是 以DNASE1L3敏感的方式被自身抗体识别。因此，DNASE1L3维持 通过消化凋亡微粒中潜在的抗原性细胞外DNA来耐受自身DNA。 拟议的工作将应用新开发的概念框架和实验工具， 分析抗DNA免疫反应的基本机制及其与人类的相关性 SLE。在目标1中，我们将使用DNASE1L3缺陷小鼠作为主要抗dsDNA反应性的模型， 表征DNA反应性B细胞的性质和调节。在目标2中，我们将描述先天 抗DNA抗体应答的免疫机制，特别是MyD88依赖性 感知路径在目标3中，我们将把我们的发现转化为人类SLE患者，研究SLE患者的免疫功能。 抗体对微粒上的DNASE1L3敏感染色质的应答。总的来说，这些研究 将提供对SLE中致病性抗DNA反应的起源和机制的深入了解， 并促进其治疗阻断的靶向方法。

ABSTRACT The hallmark of systemic lupus erythematosus (SLE) is the production of antibodies to nuclear antigens such as ribonucleoproteins and DNA, with the resulting immune complexes causing systemic immune activation and tissue inflammation. High-affinity IgG antibodies to double-stranded DNA (dsDNA) are particularly pathogenic and associate with the severity of tissue damage. The mechanisms of tolerance to self-DNA and of its breakdown in SLE are poorly understood. We have studied these mechanisms by focusing on DNASE1L3, a secreted DNase that is mutated in several cases of early-onset familial SLE. We found that DNASE1L3-deficient mice develop a massive anti- dsDNA antibody response, whereas the response to other antigens was absent or delayed. This response and the ensuing immune activation and tissue damage required innate immune signaling through the adaptor protein MyD88. DNASE1L3-deficient mice and human patients showed the accumulation of genomic DNA within circulating apoptotic microparticles, and this DNA was recognized by autoantibodies in a DNASE1L3-sensitive manner. Thus, DNASE1L3 maintains tolerance to self-DNA by digesting potentially antigenic cell-extrinsic DNA in apoptotic microparticles. The proposed work will apply the newly developed conceptual framework and experimental tools to analyze the fundamental mechanisms of anti-DNA immune responses and their relevance to human SLE. In Aim 1, we will use DNASE1L3-deficient mice as a model of primary anti-dsDNA reactivity to characterize the nature and regulation of DNA-reactive B cells. In Aim 2, we will characterize innate immune mechanisms of anti-DNA antibody response, particularly the identity of MyD88-dependent sensing pathways. In Aim 3, we will translate our findings to human SLE patients, studying the antibody response to DNASE1L3-sensitive chromatin on microparticles. Collectively, these studies would provide insights into the origin and mechanisms of the pathogenic anti-DNA responses in SLE, and facilitate targeted approaches towards their therapeutic blockade.