Autoimmunity is the third most common category of disease in the United States, and its incidence is rising. Pemphigus vulgaris (PV) is a debilitating autoimmune disease characterized by blistering of the skin and mucous membranes. The disease is caused by serum autoantibodies (autoAbs) against desmoglein 3 (Dsg3), a protein that mediates keratinocyte cell adhesion. Currently, it is unknown why or how autoimmunity occurs in PV. A deeper understanding of how B cells become autoreactive to a peripheral antigen in a model human autoimmune disease such as PV, in which the disease autoantigen is well- characterized, is essential to understand the pathophysiology of disease and optimal treatment strategies. In order to differentiate into an antibody-secreting cell, all B cells must first randomly rearrange certain gene segments to express a receptor that can bind foreign antigens, a process called V(D)J recombination. Upon interacting with antigen, a B cell can acquire additional somatic mutations that increase affinity for antigen, thus maturing the immune response. However, these stochastic processes of B cell development are likely to produce B cells that bind self, requiring elimination of these autoreactive cells to prevent autoimmunity. In PV, a defect in B cell development occurs such that Dsg3-reactive B cells are not eliminated from the repertoire, resulting in the expression of anti-Dsg3 Abs and the development of disease. Our laboratory has previously shown that anti-Dsg3 Abs in PV patients use a limited number of variable region sequences, with shared variable region gene usage among different patients, implying common mechanisms of disease development. We have shown that a subset of these Abs bind Dsg3 even in the absence of somatic mutation, implying autoreactivity of the naive B cell repertoire. Intriguingly, these same variable region sequences have been described in the immune response to rotavirus, HIV, and influenza. The goals of the current research proposal are two-fold: 1) to identify pathologic B cell subsets in PV, defined as those that exhibit Dsg3-binding B cells in PV patients but not unaffected individuals; and 2) to determine whether Abs that recognize Dsg3 also bind foreign antigens, thereby explaining their persistence in the repertoire. Flow cytometry, single B cell PCR and ELISPOT utilizing patients' whole blood will reveal B cell subsets that are enriched for Dsg3-reactive B cells in comparison to unaffected individuals. Multiple approaches will be used to identify anti-Dsg3 Abs that are cross-reactive to foreign antigen, including directed immunochemical assays and high-throughput hybridoma and phage display screening techniques. Through the proposed research plan, we may validate novel therapeutic targets for PV that may more safely or effectively capture the disease-relevant B cell populations, via targeting of certain VH Ab families or more specific B cell subsets. Furthermore, we will gain a much better understanding of how autoAbs arise in PV, and therefore a deeper understanding of the pathogenesis of autoimmune disease as a whole.
Autoimmune diseases are caused by immune cells producing antibodies against the body's own components rather than foreign bacteria or viruses. In pemphigus vulgaris, a potentially fatal autoimmune skin disease, a defect in B cell development allows autoreactive cells to persist in the body and escape elimination. The proposed research plan will extend our knowledge of this developmental defect and the origins of these autoreactive cells, which may ultimately improve current therapies to treat disease.
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| Cho, Michael Jeffrey; Ellebrecht, Christoph T; Payne, Aimee S (2015) The dual nature of interleukin-10 in pemphigus vulgaris. Cytokine 73:335-41 |
