Specific binding of an antigen-antibody complex to apoptotic human neutrophils

Examination of apoptotic cell surface molecules has so far failed to reveal cell type-specific membrane alterations that serve as a signal for phagocytosis. In the present study we have identified a novel murine monoclonal antibody, BOB93, which bound to the surface of apoptotic neutrophils but not to apoptotic lymphocytes. BOB93 binding to apoptotic neutrophils was dependent on the presence of the sialoglycoprotein fetuin, a constituent of bovine serum. We demonstrate that fetuin is the antigen for BOB93, and that BOB93 and fetuin form a complex in solution that is necessary and sufficient for binding to apoptotic neutrophils. Individuals who were homozygous for an adenine nucleotide at position 519 of the gene for the immune complex receptor Fc gamma RIIA exhibited markedly reduced binding of BOB93/fetuin. This report is the first to provide evidence that antigen-antibody complexes bind specifically to apoptotic neutrophils and implicates apoptosis-associated changes in Fc gamma receptor function.