Opsonization of Early Apoptotic Cells by IgG from Lupus Nephritis Amplifies Activation of Early Complement Components and Promotes Inflammatory Phagocytosis

Background SSA/Ro 60 has been reported to be exposed on the surface of early apoptotic cells and recognized by autoantibodies from lupus. The aim of this study was to explore the subsequent effects of the binding of IgG from anti-SSA positive LN patients on the fate of early apoptotic cells. Results IgG which have been confirmed with extensive binding to early apoptotic cells were purified from three anti-SSA positive LN patients. Opsonization of early apoptotic cells by IgG from LN augmented C3c deposition without influence on the assembly of the terminal complement components or cell lysis. IgG from LN enhanced opsonization and phagocytosis of early apoptotic cells by macrophages directly or dependent on complement activation, with massive TNF-a and IL-1β secretions. Conclusions IgG from anti-SSA positive LN facilitates early apoptotic cell clearance by macrophages and triggers proinflammatory cytokines release, possibly exacerbating underlying pathogenic mechanisms in lupus nephritis.