Effect of pyran copolymer on activation of murine macrophages: evidence for incomplete activation by use of functional markers.

The degree of activation of peritoneal macrophages elicited by pyran copolymer (MVE-2) was studied in C57BL/6J mice. When cytotoxicity was examined under endotoxin-free culture conditions, the pyran-elicited macrophages could not complete cytolysis of tumor target cells. The macrophages, however, completed cytolysis when pulsed with endotoxin. These results were obtained when either the interval between injection of the pyran copolymer and harvest of the macrophage or the dose of pyran was varied. The pyran-elicited macrophages expressed five markers considered to be typical of inflammatory macrophages, and bound tumor cells to an augmented degree. The pyran-elicited macrophages were capable of secreting a potent cytolytic proteinase when pulsed with endotoxin, but did not secrete cytolytic proteinase spontaneously. The pyran-elicited macrophages, in contrast to inflammatory macrophages, could effect cytostasis of tumor cells; their cytostatic potential was also augmented by addition of endotoxin. Taken together, the results indicated that pyran copolymer elicits primed but not fully activated murine macrophages.