Differences in the tumoricidal activation of rat and mouse macrophages by endotoxins.

Conventional and specific pathogen-free rat resident peritoneal macrophages were lytic to tumor cells in the presence of endotoxins even when not elicited or not stimulated in vivo or in vitro. In contrast, conventional mouse resident peritoneal macrophages were not cytolytic in the presence of endotoxins. The induction by endotoxins of rat macrophage-mediated cytolysis was only obtained after the binding of tumor cells by macrophages. Rat resident peritoneal macrophages bound faster and stronger to tumor cells than mouse resident peritoneal macrophages. These differences in binding could explain the species differences in the tumoricidal response to endotoxins.