Use of a Macrophage Cytotoxicity System to Show Macrophage Activation by Listeria monocytogenes Cell Wall Fraction

Abstract

A partially purified Listeria cell wall fraction may stimulate macrophages to high levels of activation. To detect activation of macrophages, a macrophage-mediated cytotoxicity system was established. Listeria cell wall components can activate thioglycollate-induced adherent peritoneal exudate cells [PEC] to be cytotoxic for 51Cr-labeled target tumor cells. The Listeria fraction is as effective as bacterial lipopolysaccharide in inducing cytotoxicity. The Listeria fraction can induce PEC from congenitally thymusless nude mice to become cytotoxic. Mature T [thymus-derived] cells are not required. Thioglycollate-induced adherent PEC from mice hyperimmunized to live Listeria organisms are already stimulated to be cytotoxic for tumor cells and do not need to be activated in vitro. Additional data are presented which characterize the system. A critical concentration of adherent peritoneal cells is required for in vitro activation. Only peritoneal cells induced with aged batches of thioglycollate and not uninduced peritoneal cells or those induced with fresh thioglycollate or with protease peptone can be activated in vitro to kill tumor cells. The cytotoxic cell may be a macrophage.