Clarification of pathophysiological mechanisms of autoimmune skin disease, pemphigus

寻常型天疱疮（Pemphigus vulgaris， PV）是一种自身免疫性水疱疾病，由IgG自身抗体直接针对桥粒蛋白（Dsg）引起，桥粒蛋白是在桥粒中发现的钙粘蛋白型细胞粘附分子。本研究的目的是通过两种独特的方法来阐明自身免疫性疾病的免疫学机制；分析天疱疮模型小鼠，探讨皮肤感染与自身免疫的接触点。我们取得了以下进展：1)从PV模型小鼠中分离到8个致病性和非致病性ak -系列抗Dsg3单抗克隆，发现其表位是决定致病性的关键因素；2)从AK7单抗可变区cDNA中获得B细胞转基因小鼠，分析其自身反应性B细胞的命运；3)从Dsg3-/-小鼠中获得多个Dsg3反应性T细胞克隆，分析其在致病性抗Dsg3单抗产生中的作用。4)阐明了引起SSSS和大疱性脓疱疮的金黄色葡萄球菌产生的剥脱性毒素（ETA、ETB和ETD）是dsg1特异性丝氨酸蛋白酶的分子机制；5)表明部分SSSS患者出现低滴度的抗dsg1 IgG自身抗体。我们进一步取得了以下意想不到的进展：6)发现了一种潜在的新的外周B细胞耐受机制，通过注射致病性AK23单抗消除了外周淋巴器官中dsg3特异性B细胞；7)在天疱疮患者亚群中发现了针对一种新的桥蛋白异型Dsg4的自身免疫反应，为更好地理解包括自身免疫性脱发在内的自身免疫性疾病的发病提供了新的框架。我们已经通过PV模型小鼠、dsg3特异性B细胞转基因小鼠，以及在不久的将来dsg3特异性T细胞转基因小鼠，建立了独特的器官特异性自身免疫性疾病生理系统。我们旨在建立一个新的标准实验系统来揭示自身免疫和外周抗原耐受的奥秘。

Pemphigus vulgaris (PV) is an autoimmune blistering disease caused by IgG autoantibodies directed against desmogleins (Dsg), cadherin-type cell-cell adhesion molecules found in desmosomes. The goal of this study is to clarify the immunological mechanisms of autoimmune diseases by taking two unique approaches ; analyzing pemphigus model mice and investigating the contact points of skin infection and autoimmunity.We have achieved the following progresses ; 1)isolated 8 clones for pathogenic and non-pathogenic AK-series anti-Dsg3 mAbs from PV model mice and showed the epitope is a critical factor determining the pathogenicity, 2)developed B cell transgenic mice from cDNA for the variable regions of AK7 mAb and analyzed the fate of the autoreactive B cells, 3)developed several Dsg3-reactive T cell clones from Dsg3-/- mice and analyzed their roles in the production of pathogenic anti-Dsg3 Abs, 4)clarified the molecular mechanisms that exfoliative toxins (ETA,ETB, and ETD) produced by S.aureus, which causes SSSS and bullous impetigo, are Dsg1-specific serine proteases, 5)demonstrated that some patients with SSSS developed low titers of anti-Dsg1 IgG autoantibodies.We further achieved the following unexpected progresses ; 6)found a potentially new peripheral B cell tolerance mechanism by showing the elimination of Dsg3-specific B cells from peripheral lymphoid organs by injection of pathogenic AK23 mAb, 7)demonstrated the autoimmune reaction against a novel desmoglein isoform, Dsg4, in subsets of pemphigus patients, providing a new framework for better understanding the onset of autoimmune diseases including autoimmune alopecia.We have established a unique physiological system for organ-specific autoimmune diseases by using PV model mice, Dsg3-specific B cell transgenic mice, and, in the near future, Dsg3-specific T cell transgenic mice. We aimed to establish a novel standard experimental system to uncover the mysteries of autoimmunity and tolerance to peripheral antigens.