Defining the Role of Thymic Tolerance in the Pathogenesis of the COPA syndrome

项目总结： 我们的实验室最近共同发现了COPA综合征，这是一种由显性 表现为炎症性关节炎和间质性病变的辅酶A亚单位(COPA)基因突变 肺部疾病(ILD)。COPA编码外壳蛋白复合体I(COPI)的COPA亚单位。Copi从事的是 蛋白质从高尔基体到内质网的逆行运动，是细胞运输的重要组成部分 机械设备。COPA综合征患者出现高滴度抗核或抗中性粒细胞胞浆 自身抗体、免疫介导的肾脏疾病和CD4+T辅助17(Th17)细胞的增加，以及 免疫细胞亚群与自身免疫有关。一些患者的发现与类风湿一致 关节炎类风湿性关节炎，包括类风湿因子或对环瓜氨酸肽的自身抗体。ALL COPA综合征 患者最终会患上间质性肺病(ILD)，并伴有关节炎。泛化 免疫抑制药物如霉酚酸酯已被用于治疗患者，但效果有限， 尽管ILD通常在治疗上取得进展，并导致终末期肺纤维化。 我们产生了一只生殖系点突变敲入小鼠，携带着与 COPA综合征患者。初步数据显示，CopaE241K/+小鼠自发发育 单核细胞肺浸润性病变和外周淋巴组织检查显示 效应器记忆T细胞。对发育中的胸腺细胞的详细研究表明，成熟的CD8+显著增加 和CD4+单一阳性(SP)细胞群，这些发现表明胸腺细胞发育或 选择。培育成T细胞受体转基因小鼠系统的CopaE241K/+小鼠表现出阴性缺陷 CD4+T细胞的选择。有趣的是，相互的骨髓嵌合体实验描绘了选择缺陷 E241K CopA在胸腺间质中的表达。因此，我们假设，自身免疫的一个关键先兆 COPA综合征中的疾病是由突变的COPA表达引起的胸腺细胞选择异常 胸腺上皮。我们建议通过1)确定突变的CopA在阳性中的作用来进一步探讨这一假说 以及CD4+和CD8+T细胞的阴性选择2)确定胸腺基质对胸腺细胞的作用 CopaE241K/+小鼠的发展及3)确定其自身免疫特性 综合症受试者。 通过我们的研究，我们试图确定胸腺耐受在老年糖尿病的病理生理学中的作用。 建立CopaE241K/+小鼠作为该病的临床前模型。因为美洲杯 综合征与其他炎症性关节疾病有相同的特征，我们的研究可能为我们提供新的见解 囊泡转运受损通过改变负性改变参与了关节炎和ILD的发病 选择自身反应性T细胞并导致中枢免疫耐受缺陷。

PROJECT SUMMARY: Our lab recently co-discovered the COPA syndrome, an autoimmune disease caused by dominant mutations in the Coatomer subunit alpha (COPA) gene that manifests as inflammatory arthritis and interstitial lung disease (ILD). COPA encodes the COPA subunit of coat protein complex I (COPI). COPI is engaged in the retrograde movement of proteins from the Golgi to the ER and is a vital component of a cell's trafficking machinery. Patients with the COPA syndrome develop high-titer antinuclear or anti-neutrophil cytoplasmic autoantibodies, immune-mediated kidney disease and an increase in CD4+ T helper 17 (Th17) cells, an immune cell subset implicated in autoimmunity. Some patients have findings consistent with rheumatoid arthritis RA including rheumatoid factors or autoantibodies to cyclic citrullinated peptides. All COPA syndrome patients eventually develop interstitial lung disease (ILD) in combination with their arthritis. Generalized immunosuppressive drugs such as mycophenolate have been used to treat patients with limited success, although the ILD typically progresses on treatment and leads to end stage lung fibrosis. We generated a germline point mutant knock-in mouse bearing the exact same E241K mutation as COPA syndrome patients. Preliminary data demonstrates that CopaE241K/+ mice spontaneously develop mononuclear lung infiltrates and an examination of peripheral lymphoid tissues reveals a significant increase in effector memory T cells. Detailed study of developing thymocytes shows a significant increase in mature CD8+ and CD4+ single positive (SP) cell populations, findings that suggest alterations in thymocyte development or selection. CopaE241K/+ mice bred to a T cell receptor transgenic mouse system revealed a defect in the negative selection of CD4+ T cells. Interestingly, reciprocal bone marrow chimera experiments map the selection defect to E241K COPA expression in the thymic stroma. Thus, we hypothesize that a critical precursor to autoimmune disease in the COPA syndrome is aberrant thymocyte selection caused by mutant COPA expression in the thymic epithelium. We propose to pursue this hypothesis by 1) Determining the role of mutant COPA in positive and negative selection of CD4+ and CD8+ T cells 2) Defining the role of the thymic stroma on thymocyte development in CopaE241K/+ mice and 3) Defining the autoimmune features of CopaE241K/+ mice and COPA syndrome subjects. Through our study we seek to determine the role of thymic tolerance in the pathophysiology of the COPA syndrome and establish CopaE241K/+ mice as a preclinical model for the disease. Because the COPA syndrome shares features with other inflammatory joint disorders, our study may provide novel insight into how impaired vesicular trafficking contributes to the pathogenesis of arthritis and ILD by altering the negative selection of autoreactive T cells and causing a defect in central immune tolerance.