092 Opsonization of the bullous pemphigoid antigen BP180 by complement component 3-derived fragments may precipitate autoimmune skin disease

Bullous pemphigoid (BP) is characterized by autoantibodies (abs) that bind to BP180, promoting complement (C) fixation, inflammation, and blister formation. In contrast the rather detailed understanding of effector phase, mechanisms enabling emergence self-directed abs remain less understood. Insights into these early steps in immunopathogenesis may identify new avenues for treatment this fragile patient group. Incubating recombinant BP180-NC16A antigen (ag) with a C source we performed IP SDS-PAGE. This resulted appearance novel bands were subjected mass spectrometry, identifying C3b alpha' bound ag. Our results point toward direct opsonization autoag activated component 3 (C3) fragments, absence abs. To investigate conditions foster spontaneous activation deposition C3, incubated 3D-cultured keratinocytes various stimuli (TNF alpha, IL-6, S. aureus) assessed gene expression pathways proteins qPCR. We found upregulation mRNA most genes, mainly MASP1, C1r, C1s, C2, C3 and, importantly, factor B alternative pathway, which drives auto-hydrolysis, opsonization. Against well-documented immunogenicity-boosting effect C3-derived fragments (when protein ags), interpret our findings represent previously underexplored key step BP. During local inflammatory or infective episodes, genetic age-related reasons, processes lead covalent binding (the first opsonizing fragment C3) autoags. increase normally low immunogenic potential BP180 vivo, possibly where tolerance cannot be maintained, leading