Dissecting self and microbial dual clonal IgA and IgG B cell reactivity in pediatric lupus 2823

Abstract Description Systemic lupus erythematosus (SLE) is a clinically heterogeneous autoimmune disease characterized by B cell dysregulation and autoantibody production to nuclear antigens. Pediatric SLE (pSLE) represents 10-20% of all SLE cases and is associated with a more severe disease course, underscoring the need to dissect pSLE pathogenesis. SLE patients have been shown to have increased levels of anti-nuclear IgA and IgG antibodies compared to healthy controls. Presence of the IgA isotype suggests mucosal involvement in the breakdown of peripheral tolerance, the mechanisms of which remain poorly understood. Thus, we hypothesize that a mucosal trigger in genetically susceptible individuals leads to an IgA response that later transforms into an IgG response in the clinical phase of the disease. To this end, we constructed and validated nuclear-antigen specific B cell tetramers to isolate antigen specific B cells using flow cytometry. We observe a higher frequency of these cells in pSLE patients relative to healthy controls and B-cell depleted pSLE patients. We sorted and cultured these antigen specific B cells to verify their antigen specificity and frequency by probing for lupus antibodies. In future work, we will VDJ sequence, filter IgG and IgA dual clonal B cells, and express their sequences as monoclonal antibodies to assess bacterial cross reactivity in stool samples from the same patients. This will shed light on mucosal involvement in the breakdown of peripheral tolerance in pSLE. Funding Sources Supported by the Center for Mucosal Immunology and Rheumatic Disease Pathogenesis (CMIR) at the University of Colorado Anschutz Medical Campus. Topic Categories Mucosal and Regional Immunology (MUC)