Isolation of the phagocytosis-inducing IgG-binding antigen on senescent somatic cells.
To remove senescent red blood cells (RBCs) from the circulation, macrophages must distinguish them from mature RBCs. That is achieved by a specific recognition system. An antigen that develops on the surface of a senescing RBC is recognized and bound by the Fab region of an IgG autoantibody in the serum. Subsequently the Fc region of the autoantibody is recognized and bound by a macrophage, which proceeds to phagocytose the RBC. The antigenic molecule can be extracted from senescent but not young RBCs with Triton X-100 (ref. 4), although 10--30% as much antigen can be extracted from middle-aged as from senescent RBCs. I have now used IgG autoantibodies eluted from senescent RBCs to isolate and purify the IgG-binding antigen on senescent RBCs, and to detect the antigen on other somatic cells. The antigen is a congruent to 62,000-Mr protein which is present on stored platelets, lymphocytes and neutrophils, and on cultured human adult liver and embryonic kidney cells, as well as senescent RBCs.
D000954:Antigens, Surface / Q000302:isolation & purification*; D001323:Autoantibodies; D001792:Blood Platelets / Q000276:immunology; D002470:Cell Survival; D002478:Cells, Cultured / Q000276:immunology; D004905:Erythrocyte Aging; D006801:Humans; D007668:Kidney / Q000276:immunology; D008099:Liver / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology; D008970:Molecular Weight; D009504:Neutrophils / Q000276:immunology; D010587:Phagocytosis
D000954:Antigens, Surface; D001323:Autoantibodies