Inflammation amplifies the antitumor cytostasis by human peritoneal macrophages

The effect of an inflammatory environment on the antitumor cytostatic ability of human macrophages was examined. Peritoneal macrophages of patients on continuous ambulatory peritoneal dialysis (CAPD) were collected, when CAPD was without complication, during an intercurrent infectious inflammation and after recovery. Inhibition of³H-thymicline uptake served as a measure of cytostasis by macrophages co-cultured with target murine cells MOPC-315 plasmacytoma, WEHI-3B rnyelomonocytic leukemia and L929 transformed fibroblasts. Macrophages from inflammatory peritoneum expressed a markedly enhanced cytostasis, irrespective of the nature of the tumor cell. Endotoxin (LPS) challenge of inflammatory macrophages failed to further reinforce the cytostasis towards MOPC-315 plasmacytoma, but reinforced the cytostasis towards WEHI-3B leukemia (sensitive to inhibition by IL-1) and towards L929 (sensitive to TNFα). Cytostasis by supernatants of human peritoneal macrophages against L929 was markedly inhibited by anti-rHuTNFa and against WEHI-3B by anti-rHuIL-lβ. The results suggest a link between inflammatory function and antitumor cytostasis by macrophages. This link is constituted by mediators involved in the activation process of macrophages.