Environmental/genetic Risk Factors and Pathogenesis of Autoimmune Disease

多学科研究——包括临床、免疫学、病理学、流行病学和分子遗传学研究——被用来补充每个领域的研究结果，并克服每种方法固有的局限性。目前的研究重点是：探索可能的环境风险和保护因素；通过候选基因和全基因组SNP分析确定遗传风险和保护因素；确定自身免疫性疾病的临床、实验室和免疫学特征之间的关联，以用于诊断、预后和致病目的；并了解疾病不一致的同卵双胞胎之间表观遗传学、基因表达和蛋白质组模式的差异。目前正在通过一项针对系统性自身免疫性疾病不一致的双胞胎和近亲兄弟姐妹的研究，对接触二氧化硅、有机溶剂、紫外线、疫苗、选定药物和膳食补充剂、激素和怀孕、烟草烟雾、压力生活事件和传染源对系统性自身免疫性疾病发展的影响进行评估。 一组我们知之甚少、危及生命的自身免疫性肌肉疾病，称为肌炎综合征，其特征是慢性肌肉炎症和无力，并与特定的自身抗体相关。肌炎的主要形式是多发性肌炎（多块肌肉受到炎症影响）和皮肌炎（患者还会出现皮肤炎症）。然而，根据临床表现、病理学和自身抗体，似乎还有其他类型的肌炎。我们的全球研究表明，紫外线辐射可能会调节不同人群中肌炎的临床和免疫表达，今年美国的研究也证明了类似的发现。紫外线辐射暴露与皮肌炎的患病率以及针对 SNF2/RAD54 解旋酶家族 220 KD 成员的相关抗 Mi-2 自身抗体密切相关，该家族是核小体重塑和组蛋白脱乙酰酶 (NuRD) 复合物的主要组成部分。正在进行研究以了解紫外线辐射和雌激素对 Mi-2 靶标自身抗原的表达和功能的分子影响。 由于研究表明紫外线 (UV) 辐射可调节肌炎表型和 Mi-2 自身抗原表达，因此我们进行了一项回顾性调查，以确定紫外线辐射是否可能影响美国皮肌炎和抗 Mi-2 自身抗体的相对患病率。我们评估了转诊中心肌炎患者发病时居住状态的表面紫外线辐射强度与皮肌炎和肌炎自身抗体相对患病率之间的关系。我们发现紫外线辐射强度与皮肌炎患者的相对比例以及表达抗 Mi-2 自身抗体的患者比例相关。这些数据的建模表明，这些关联仅限于女性，并表明性别会影响紫外线辐射对自身免疫性疾病的影响。这项针对美国肌炎表型分布和紫外线辐射暴露的首次研究表明，紫外线辐射可能会调节女性自身免疫性疾病的临床和免疫学表达。对产生这些作用的机制的进一步研究可能会深入了解发病机制并提出治疗或预防策略。 我们还在评估某些导致不良临床结果的疾病特征的发病机制。例如，皮下组织炎症（称为脂膜炎）和皮下组织脂肪损失（称为脂肪营养不良）是一些肌炎患者（尤其是儿童）的主要问题。为了了解其发展的可能风险因素，我们对患有这些疾病的受试者进行了广泛的临床、实验室和遗传评估。脂膜炎与局灶性脂肪萎缩相关，而抗 p155 自身抗体（一种新描述的肌炎相关自身抗体）更常见与全身性脂肪营养不良相关。代谢研究揭示了全身性和部分性脂肪营养不良患者存在胰岛素抵抗和高甘油三酯血症。我们的结论是，脂肪营养不良是幼年皮肌炎的一种未被充分认识的并发症，某些具有严重、长期临床病程和高频率皮下钙质沉着的患者似乎更有可能出现该问题。 关于我们的遗传学研究，我们已经确定了成人和儿童肌炎的新遗传风险和保护因素。为了研究肿瘤坏死因子α（TNFα）和白细胞介素-1（IL-1）细胞因子多态性作为可能的危险因素和保护因素，确定它们的相对重要性，并检查它们作为青少年皮肌炎（DM）患者的严重程度因素，我们在白人青少年DM患者中进行了TNFα和IL-1细胞因子多态性分型，并将结果与​​种族匹配的健康志愿者的结果进行比较。我们发现 TNFα 和 IL-1 基因多态性有助于青少年 DM 的发展，也可能是疾病严重程度的指标。 我们将这些研究扩展到免疫球蛋白γ重链和κ轻链编码区域（分别位于染色体14q32.33和2p12上的GM和KM位点）的基因的多态性决定因素，这些基因与多种传染性和自身免疫性疾病的不同免疫反应相关。在欧洲美洲皮肌炎患者中，GM 3 23 5,13 表型是成人和儿童的危险因素。在肌炎自身抗体组中，GM 3 23 5,13 是具有抗 Jo-1 自身抗体的成人的危险因素，而 GM 3 同种异型对具有抗苏氨酰-tRNA 合成酶或抗 RNP 自身抗体的成人具有保护作用。相比之下，GM 6 是具有信号识别颗粒自身抗体的非裔美国成年人的危险因素。 这些数据综合起来表明，MHC 基因、促炎细胞因子以及免疫球蛋白基因的 GM 和 KM 位点的多态性等位基因与按年龄、种族、临床特征和自身抗体定义的肌炎亚组存在差异相关，并扩大了可能在肌炎发病机制中重要的免疫反应基因列表。我们的研究结果是从迄今为止研究的最大的肌炎患者群体中获得的，为以下假设提供了额外的支持：肌炎综合征包含多种不同的疾病实体，可能是由于不同的基因-环境相互作用导致不同的致病机制引起的。 在自身免疫性疾病中，环境驱动的表观遗传变化被认为是导致其病因的原因。我们首次报道了 DNA 甲基化的高通量候选序列分析，以研究双胞胎自身免疫性疾病的不一致。我们使用了一组患有三种疾病不一致的同卵双胞胎，这些疾病的临床症状经常重叠。只有 SLE 不一致的同卵双胞胎才会出现大量基因 DNA 甲基化状态的广泛变化。基因本体分析揭示了与免疫功能相关的类别的丰富。我们的研究结果不仅确定了与 SLE 患者临床特征潜在相关的 DNA 甲基化标记物，而且支持表观遗传变化可能对自身免疫性疾病的临床表现至关重要的观点。

Multidisciplinary studies - including clinical, immunologic, pathologic, epidemiologic and molecular genetic investigations - are being used to complement findings in each area and overcome limitations inherent in each approach. Current studies are focusing on: exploring possible environmental risk and protective factors; identifying genetic risk and protective factors by candidate gene and whole genome SNP analyses; defining the associations among clinical, laboratory and immunologic features of autoimmune diseases for diagnostic, prognostic and pathogenic purposes; and understanding differences in epigenetics, gene expression and proteomic patterns between monozygotic twins discordant for disease. Evaluation of exposures to silica, organic solvents, ultraviolet light, vaccinations, selected drugs and dietary supplements, hormones and pregnancy, tobacco smoke, stressful life events and infectious agents in the development of systemic autoimmune diseases are being conducted via a study of twins and close siblings discordant for systemic autoimmune disease. A group of poorly-understood, life-threatening autoimmune muscle diseases called the myositis syndromes are defined by chronic muscle inflammation and weakness and associated with specific autoantibodies. The major forms of myositis are polymyositis, in which multiple muscles are affected by inflammation, and dermatomyositis, in which patients also develop skin inflammation. Yet there appear to be other types of myositis based on the clinical presentations, pathology and autoantibodies. Our worldwide studies suggested that ultraviolet radiation exposure may modulate the clinical and immunologic expression of myositis in different populations and studies in the United States this year demonstrated similar findings. Ultraviolet radiation exposure strongly correlated with the prevalence of dermatomyositis and the associated anti-Mi-2 autoantibodies directed against a 220 KD member of the SNF2/RAD54 helicase family, which is a major component of the nucleosome remodeling and histone deacetylase (NuRD) complex. Studies are ongoing to understand the molecular effects of ultraviolet radiation and estrogen on the expression and function of the Mi-2 target autoantigen. Because studies suggest that ultraviolet (UV) radiation modulates the myositis phenotype and Mi-2 autoantigen expression, we conducted a retrospective investigation to determine whether UV radiation may influence the relative prevalence of dermatomyositis and anti-Mi-2 autoantibodies in the US. We assessed the relationship between surface UV radiation intensity in the state of residence at the time of onset with the relative prevalence of dermatomyositis and myositis autoantibodies in patients with myositis from referral centers. We found that UV radiation intensity was associated with the relative proportion of patients with dermatomyositis and with the proportion of patients expressing anti-Mi-2 autoantibodies. Modeling of these data showed that these associations were confined to women and suggests that sex influences the effects of UV radiation on autoimmune disorders. This first study of the distribution of myositis phenotypes and UV radiation exposure in the US showed that UV radiation may modulate the clinical and immunologic expression of autoimmune disease in women. Further investigation of the mechanisms by which these effects are produced may provide insights into pathogenesis and suggest therapeutic or preventative strategies. We are also assessing the pathogenesis of certain disease features that result in poor clinical outcomes. For example, inflammation of subcutaneous tissue, called panniculitis, and the loss of fat in the subcutaneous tissue, called lipodystrophy, are major problems for some patients with myositis, especially children. To understand possible risk factors for their development, we performed extensive clinical, laboratory and genetic assessments on subjects with these disorders. Panniculitis was associated with focal lipoatrophy, while the anti-p155 autoantibody, a newly described myositis-associated autoantibody, was more commonly associated with generalized lipodystrophy. Metabolic studies revealed insulin resistance and hypertriglyceridemia in patients with generalized and partial lipodystrophy. We conclude that lipodystrophy is an under-recognized complication of juvenile dermatomyositis, and certain patients with a severe, prolonged clinical course and a high frequency of subcutaneous calcinosis appear to be at greater risk for the development of this problem. Regarding our genetic studies, we have defined new genetic risk and protective factors for myositis in adults and children. To study tumor necrosis factor alpha (TNFalpha) and interleukin-1 (IL-1) cytokine polymorphisms as possible risk and protective factors, define their relative importance, and examine these as severity factors in patients with juvenile dermatomyositis (DM), TNFalpha and IL-1 cytokine polymorphism typing were performed in Caucasian patients with juvenile DM, and the results were compared with those in ethnically matched healthy volunteers. We found that TNFalpha and IL-1 genetic polymorphisms contribute to the development of juvenile DM and may also be indicators of disease severity. We extended these studies to polymorphic determinants of genes encoding regions of immunoglobulin gamma heavy and kappa light chains (GM and KM loci on chromosomes 14q32.33 and 2p12, respectively), which have been associated with different immune responses in a variety of infectious and autoimmune diseases. In European American dermatomyositis patients the GM 3 23 5,13 phenotype was a risk factor for both adults and children. Among the myositis autoantibody groups, GM 3 23 5,13 was a risk factor for adults with anti-Jo-1 autoantibodies, while the GM 3 allotype was protective for adults with anti-threonyl-tRNA synthetase or anti-RNP autoantibodies. In contrast, GM 6 was a risk factor for African American adults with autoantibodies to the signal recognition particle. These data, taken together, suggest that polymorphic alleles of MHC genes, pro-inflammatory cytokines, as well as the GM and KM loci for immunoglobulin genes, are differentially associated with myositis subgroups defined by age, ethnicity, clinical features and autoantibodies, and expand the list of immune response genes possibly important in the pathogenesis of myositis. Our findings, obtained from the largest cohort of patients with myositis studied to date, add additional support to the hypothesis that the myositis syndromes comprise multiple, distinct disease entities, perhaps arising from divergent pathogenic mechanisms as a result of different gene-environment interactions. In autoimmune diseases, environmentally driven epigenetic changes are thought to contribute to their etiology. We reported the first high-throughput and candidate sequence analyses of DNA methylation to investigate discordance for autoimmune disease in twins. We used a cohort of MZ twins discordant for three diseases whose clinical signs often overlap. Only MZ twins discordant for SLE featured widespread changes in the DNA methylation status of a significant number of genes. Gene ontology analysis revealed enrichment in categories associated with immune function. Our findings not only identify potentially relevant DNA methylation markers for the clinical characterization of SLE patients but also support the notion that epigenetic changes may be critical in the clinical manifestations of autoimmune disease.