Clarification of pathophysiological mechanisms of autoimmune skin disease, pemphigus

寻常天疱疮（PV）是由针对桥粒中的桥粒糖蛋白（Dsg）的IgG自身抗体引起的自身免疫性起泡疾病，所述桥粒糖蛋白是钙粘蛋白型细胞-细胞粘附分子。本研究从天疱疮模型小鼠的分析和皮肤感染与自身免疫的接触点两个方面探讨了自身免疫性疾病的免疫学机制，取得了以下进展：1）从PV模型小鼠中分离出8株致病性和非致病性AK系列抗Dsg 3单克隆抗体，并显示表位是决定致病性的关键因素，（2）建立了AK 7单抗可变区cDNA转基因B细胞小鼠，并分析了自身反应性B细胞的命运;（3）从Dsg 3-/-小鼠中建立了几个Dsg 3反应性T细胞克隆，并分析了它们在致病性抗Dsg 3抗体产生中的作用;（4）阐明了脱落毒素诱导Dsg 3抗体产生的分子机制结论：1）SSSS和大疱性脓疱病的致病菌金黄色葡萄球菌（S.aureus）产生的ETA、ETB和ETD是Dsg 1特异性的丝氨酸蛋白酶，5）证实部分SSSS患者产生了低滴度的抗Dsg 1 IgG自身抗体。6）通过显示通过注射致病性AK 23 mAb从外周淋巴器官消除Dsg 3特异性B细胞，发现了潜在的新的外周B细胞耐受机制，7）证明了天疱疮患者亚群中针对新桥粒芯糖蛋白同种型Dsg 4的自身免疫反应，为更好地理解自身免疫性疾病（包括自身免疫性脱发）的发病提供了一个新的框架。我们建立了一个独特的器官-通过使用PV模型小鼠、Dsg 3特异性B细胞转基因小鼠以及在不久的将来Dsg 3特异性T细胞转基因小鼠，我们的目的是建立一个新的标准实验系统，以揭示自身免疫和对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.