Effect of cisplatin, lipopolysaccharide, muramyl dipeptide and recombinant interferon-gamma on murine macrophages in vitro. I. Macrophage-mediated tumor cell lysis

Murine macrophage monolayers treated with cisplatin, lipopolysaccharide (LPS), muramyl dipeptide (MDP) or recombinant interferon-gamma (rIFN gamma) were observed to have significantly increased tumoricidal activity. rIFN gamma had synergistic effects with cisplatin, LPS or MDP in activating macrophages. However, MDP showed much more pronounced synergism with cisplatin and LPS than with rIFN gamma. Supernatants collected from these activated macrophage monolayers also showed increased tumoricidal activity. Tumor cell lysis mediated by cisplatin-treated macrophages did not require priming with rIFN gamma though it may be necessary as a first signal for the increased macrophage activation with LPS and MDP.