Studies on the mechanism of phagocytosis. II. The interaction of macrophages with anti-immunoglobulin IgG-coated bone marrow-derived lymphocytes

We have examined the effect of the distribution of anti-immunoglobulin IgG molecules on the surface of bone marrow-derived lymphocytes upon the interaction of these cells with macrophages. Lymphocytes which were diffusely coated with antibodies to surface immunoglogulin were ingested by macrophages. Lymphocytes which had the same number of anti- immunoglobulin IgG molecules redistributed to one pole of the surface bound to the macrophages' Fc receptors but were not ingested. These results confirm our previous hypothesis that ingestion of an immunologically coated particle requires the sequential, circumferential binding of specific receptors on the plasma membrane of a phagocytic cell to immunologic ligands distributed over the entire particle surface. Macrophages which had bound capped lymphocytes by the macrophages' Fc receptors removed the immune complex caps from the lymphocyte surface without destroying the lymphocytes. These lymphocytes remained attached to the macrophage surface. The finding that macrophages can phagocytize immune complexes from the surface of a cell without destroying the cell to which these complexes are attached may be important in understanding the effects of antigens and antibodies on cells participating in a humoral immune response, in identifying the mechanisms by which chronic viral infections are established, and in defining the roles of blocking antibodies in tumor immunity.