The IgG autoantibody binding determinant appearing on senescent membranes residues on a 62000 MW peptide

Mechanisms by which macrophages recognize and remove senescent red blood cells (RBC) were investigated. Present evidence indicates that the antigen binding portion of immunoglobulin G (IgG) autoantibodies in normal serum selectively binds to senescent RBC in situ and initiates their removal by mononuclear phagocytes. IgG autoantibodies eluted from senescent RBC were conjugated to cyanogen bromide activated Sepharose 4B, and used to isolate and purify the IgG binding receptor. Sialoglycoprotein mixtures were processed with the senescent cell IgG affinity column. Gel electrophoresis of the bound material eluted from the column revealed a single band migrating with a molecular weight of approximately equal to 62000. This isolated peptide, but not the sialoglycoprotein mixture from which it was isolated, absorbed the phagocytosis inducing ability of IgG. Thus, the senescent cell antigen to which IgG binds, is a 62000 Dalton glycopeptide.