Role of autoantibody isotype in pemphigus pathogenesis

描述(申请人提供)：天疱疮是一组潜在的致命水泡性疾病，其特征是抗桥粒芯糖蛋白(DSG)细胞黏附蛋白的自身抗体。目前的治疗方法需要全面的免疫抑制，这有可能导致致命的感染和继发性癌症。自身免疫研究的一个主要前沿是只针对致病抗体。我们的总体目标是更好地确定天疱疮中的致病抗体群体，长期目标是设计合理的、有针对性的治疗方法。我们率先在天疱疮中使用抗体克隆技术来识别导致疾病的患者自身抗体可变区和恒定区的特征。我们已经确定了致病自身抗体的可变区基因使用模式，即使在不同的患者中也是如此。在定义了足以引起皮肤起泡的抗DSG可变区的子集之后，我们现在处于独特的位置来解决抗体恒定区(Fc)在天疱疮发病中的作用。我们推测，IgG4、IgA和IgE是天疱疮的关键致病亚型，涵盖了天疱疮的全部临床和组织学谱。在缓解期患者及其健康亲属中发现抗DSG IgG1抗体，而活动期患者则表现出IgG4自身抗体。在IgA天疱疮中，中性粒细胞皮肤脓肿是由抗DSG IgA与白细胞Fc受体结合引起的，类推抗DSG IgE可引起嗜酸性天疱疮。由于慢性抗原刺激促进了从IgG1到IgG4、IgA和IgE的类别转换，这些亚型可以作为临床标记物，将疾病特异性抗体与其他对提供对感染的免疫力更重要的IgG亚类区分开来。在目标1中，我们将从天疱疮患者中克隆抗DSG的IgG1和IgG4单抗，以确定是否在IgG1和IgG4中发现致病抗体，或者在这两种亚型中都发现致病抗体。如果在IgG1和IgG4中都发现抗DSG IgG4，我们将确定抗DSG IgG4是源于IgG1的类别转换，还是来自不同的B细胞群，从而有助于深入了解天疱疮中IgG4类别转换的机制。在AIMS 2和AIMS 3中，我们将分别克隆中性粒细胞和嗜酸性天疱疮患者的抗DSG IgA和IgE单抗。我们将评估抗DSG IgA和IgE在相关Fc受体人源化的小鼠中是否复制炎性水泡疾病，并通过用Fc效应功能抑制剂治疗小鼠来证明水泡和/或炎症的FC依赖性。通过系统地表征天疱疮mAb亚型可变区和恒定区的致病性，我们可以确定哪些结构特征导致疾病。这些研究将创建一个合理的框架来预测不同形式的天疱疮对治疗的反应，描述用于评估FC介导的疾病的新的小鼠模型，并可能确定新的治疗策略，如同型特异性靶向。由于类天疱疮、获得性大疱性表皮松解症和其他慢性自身免疫性疾病也存在相似的同型特征，我们的研究可能对广泛的自身抗体介导的疾病具有治疗意义。 公共卫生相关性：我们建议使用抗体克隆技术作为一种新的方法来识别患者自身抗体中导致天疱疮的特征，天疱疮是一种潜在的致命自身免疫性水疱性皮肤病。我们推测，在天疱疮中，IgG4、IgA和IgE是关键的致病抗体亚型，因此可以作为临床标记物来区分疾病特异性抗体和其他免疫球蛋白亚类，这些亚类对于提供对感染的免疫力是重要的。我们的研究将创建一个合理的框架来预测不同形式的天疱疮对治疗的反应，描述用于评估疾病的新的小鼠模型，并可能建议新的和潜在的更安全的治疗策略，例如同型特异性靶向。

DESCRIPTION (provided by applicant): Pemphigus is a group of potentially fatal blistering diseases characterized by autoantibodies against desmoglein (Dsg) cell adhesion proteins. Current therapy requires general immune suppression, which risks fatal infection and secondary cancers. A major frontier for autoimmunity research is to target only disease- causing antibodies. Our overall aim is to better define this pathogenic antibody population in pemphigus, with the long term goal of designing rational, targeted therapies. We have pioneered the use of antibody cloning technology in pemphigus to identify features of variable and constant regions of patient autoantibodies that cause disease. We have identified a pattern of variable region gene usage for pathogenic autoantibodies, which is shared even among different patients. Having defined a subset of anti-Dsg variable regions sufficient for skin blistering, we are now uniquely situated to address the role of the antibody constant region (Fc) in pemphigus pathogenesis. We hypothesize that IgG4, IgA and IgE are the critical pathogenic isotypes in pemphigus, accounting for the full clinical and histologic spectrum of disease. Anti-Dsg IgG1 is found in patients in remission and their healthy relatives, while patients with active disease exhibit IgG4 autoantibodies. In IgA pemphigus, neutrophilic skin abscesses are caused by anti-Dsg IgA binding to leukocyte Fc receptors, and anti-Dsg IgE may cause eosinophilic forms of pemphigus by analogy. Because chronic antigen stimulation promotes class switching from IgG1 to IgG4, IgA, and IgE, these isotypes may serve as clinical markers to distinguish disease-specific antibodies from the other IgG subclasses that are more important for providing immunity from infection. In Aim 1 we will clone IgG1 and IgG4 anti-Dsg monoclonal antibodies (mAbs) from pemphigus patients to determine whether pathogenic antibodies are found in IgG1, IgG4, or both isotypes. If found in both IgG1 and IgG4, we will determine whether anti-Dsg IgG4 result from class switching from IgG1 or arise from separate B cell populations, lending insight into mechanisms of IgG4 class switching in pemphigus. In Aims 2 and 3 we will clone anti-Dsg IgA and IgE mAbs from patients with neutrophilic and eosinophilic forms of pemphigus, respectively. We will evaluate whether anti-Dsg IgA and IgE reproduce inflammatory blistering disease in mice humanized for the relevant Fc receptor and demonstrate the Fc-dependence of blistering and/or inflammation by treating mice with inhibitors of Fc effector function. By systematically characterizing the pathogenicity of the variable and constant regions of pemphigus mAb isotypes, we can define which structural features cause disease. These studies will create a rational framework for predicting the response of different forms of pemphigus to therapy, describe novel mouse models for evaluating Fc-mediated disease, and may identify novel therapeutic strategies, such as isotype-specific targeting. As similar isotype profiles occur in pemphigoid, epidermolysis bullosa acquisita, and other chronic autoimmune conditions, our studies may have therapeutic relevance for a broad range of autoantibody-mediated diseases. PUBLIC HEALTH RELEVANCE: We propose to use antibody cloning technology as a novel approach to identify features within patient autoantibodies that cause pemphigus, a potentially fatal autoimmune blistering skin disorder. We hypothesize that IgG4, IgA, and IgE are the critical pathogenic antibody isotypes in pemphigus, and as such may serve as clinical markers to distinguish disease-specific antibodies from the other IgG subclasses that are important for providing immunity from infection. Our studies will create a rational framework for predicting the response of different forms of pemphigus to therapy, describe novel mouse models for evaluating disease, and may suggest novel and potentially safer therapeutic strategies, such as isotype-specific targeting.