Lysis of primitive teratocarcinoma cells by non-activated macrophages

The capacity of non-activated murine thioglycollate-elicited macrophages and bone marrow-derived macrophages to lyse primitive F9 teratocarcinoma cells lacking H-2 antigens was investigated. Both populations of non-activated macrophages killed F9 cells efficiently whereas they were not cytolytic against murine fibrosarcoma targets. In vitro activation by lipopolysaccharide induced the macrophages to lyse fibrosarcoma cells but did not significantly increase the level of cytolysis against F9. These results are consistent with the hypothesis that the absence of H-2 expression on target cells may serve as a signal for macrophage "foreign" recognition and cytolysis.