Selective recognition in erythrophagocytosis by mouse peritoneal macrophages: Isolation and purification of a possible self-marker from mouse erythrocyte membranes

Abstract

Rabbit anti-mouse red blood cells (RBC) antibody stimulated the phagocytosis of mouse RBC by isologous macrophages in two ways; mouse RBC pretreated with the antibody are susceptible to phagocytosis by isologous macrophages, while mouse macrophages pretreated with the antibody actively phagocytize even normal mouse RBC. The activity of the antibody to stimulate phagocytosis of isologous RBC, which can be called the opsonin activity, is specific for mouse and rat cells, since it was shown that the antibody could be absorbed on both mouse and rat cells, but not on sheep or rabbit cells. Non-immune rabbit serum did not show any opsonin activity. These results indicate that an antigen common to mouse and rat cells is responsible for preventing these cells from phagocytosis by mouse macrophages. The surface antigen of mouse RBC membranes was isolated and purified using the opsonininhibitor activity against mouse macrophages as a criterion of the self-marker of mouse cell. The opsonin-inhibitor activity of mouse RBC membranes was recovered as a lipoprotein in a fraction insoluble in 0.4 N-acetate, but soluble in 75% ethanol. This lipoprotein contained 81% lipid and 15% protein on a dry weight basis. Both the lipid and protein were indispensable for the activity of the opsonin-inhibitor. The opsonin-inhibitor activity against mouse macrophages was found only in fractions from mouse and rat RBC, not in similar fractions from sheep or rabbit RBC. This species-specificity seems to be due to the protein moiety, not the lipid moiety, since the latter was exchangeable with those of heterologous RBC fractions while the protein moiety was not.