Effect of serum on autologous cell recognition by macrophages

The non-immune mechanisms of recognition of self and non-self substances by macrophages has not yet been clarified. In this work, we report the ability of mouse peritoneal macrophages to attach to and phagocytize in vitro autologous and homologous erythrocytes in proportions as high as those for certain heterologous red blood cells. This ability was abrogated by autologous or homologous serum but not by heterologous serum or a serum-free supplement. This effect of serum was dose dependent and did not affect the phagocytosis of homologous "old" red cells. Procedures for the identification of this serum factor indicated that it was dialyzable (10 kD cut off) and was excluded by filtration in Sephadex G-25. We conclude that this finding supports the possibility that macrophages do not selectively phagocytize foreign particles or senescent cells but, rather, that they do phagocytize all particles or cells indiscriminately and this serum factor may prevent phagocytosis of normal self cells.