TUMOR-CYTOTOXICITY OF NITRIC-OXIDE PRODUCED FROM ALVEOLAR MACROPHAGESDIRECTLY STIMULATED WITH TUMOR-CELLS

Macrophages activated by lipopolysaccharide or interferon-gamma have b een shown to be cytotoxic to tumor cells by releasing nitric oxide. He re, we report that unstimulated rat alveolar macrophages cultured with certain tumor cells produce nitric oxide and are cytotoxic to these t umor cells. Alveolar macrophages were taken from BUF/Mna rats, which w ere known to produce spontaneous thymoma, and cultured with syngeneic BUF/Mna-derived thymoma cells. They were killed by syngeneic or alloge neic alveolar macrophages and this killing was partially abolished by addition of N(G)-monomethyl-L-arginine. X-ray irradiated, mitomycin C- treated or membranous fragments of BUF/Mna-derived thymoma cells direc tly stimulated rat alveolar macrophages to produce nitric oxide.