DEFECT OF A COMPLEMENT RECEPTOR-3 EPITOPE IN A PATIENT WITH SYSTEMIC LUPUS-ERYTHEMATOSUS

Complement receptor 3 (CR3) is expressed on cells of the reticuloendot helial system and involved in the clearance of immune complexes. In th is article a patient with a deficiency of the C3bi binding site of thi s receptor is described. Clinically this patient exhibited predominant ly cutaneous manifestations of a systemic lupus erythematosus with an immune vasculitis and panniculitis. The deficiency of the CR3 epitope was demonstrated using flow cytometry. The functional relevance of thi s defect was demonstrated in a rosetting assay with C3bi-loaded erythr ocytes. C3bi binding was found to be significantly decreased. Furtherm ore, there was an impairment of phagocytosis of opsonized Escherichia coli. The CR3 defect is not due to an autoantibody but is assumed to h ave a genetic basis. These data suggest that the defect of the CR3 may be involved in the pathogenesis of the immune vasculitis in this pati ent.