In vitro activation of tumoricidal properties of rat peritoneal macrophages using lipopolysaccharide.

The peritoneal macrophages from normal Lewis rats were characterized by their capacity to phagocytose, by the presence of nonspecific esterase and Fc receptors. In vitro, these macrophages were maintained in culture 7 and/or 21 days, respectively, and for the last 24 h (activation period) were cultured with 0.1-4.0 micrograms/ml of lipopolysaccharide (LPS) and were found tumoricidal against different rat fibrosarcomas, at a ratio of 50:1 (BP6-Tu2, MC-1 and B77). Macrophage-mediated tumor cytolysis was determined using 51Cr-release assay. The sensitivity of used tumors to macrophage-mediated cyto-toxicity was different. In vivo the transfer of the activated macrophages together with the mentioned tumor cells to rats inhibited the growth of tumors. The adoptive transfer of macrophages activated with "activators" might lead to a new kind of immunotherapy of neoplastic diseases.