[Study of anti-macrophage serum and of its effect on antibody formation]

A specific anti-macrophage serum (AMS) has been obtained by immunizing rabbits with mouse peritoneal exudate cells and after repeated absorption with mouse erythrocytes, thymocytes and splenic lymphocytes. A comparative study of the cytotoxic activities of this serum on macrophages, thymocytes and lymph node cells, before and after absorption, showed that macrophage posses antigens which are common to both thymic and lymph node lymphocytes, and other antigens which are in common with lymph node lymphocytes but absent on thymocytes, as well as antigens being particular to macrophages. The absorbed sera had a definite cytotoxic effect on macrophages in vitro. This effect was observed when complement was added immediately or 4 hours after incubation with serum. It was lost after 24 hours. An inhibitory effects of AMS on phagocytosis in vivo has also been observed, which disappeared after one day. Antibody production in vivo was only moderately affected by a pretreatment with AMS. However, addition of AMS to spleen cell cultures stimulated with sheep red blood cells inhibited the appearance of hemolytic plaque forming cells.