Characteristics of peritoneal macrophages induced by asbestos injection

The effect of single intraperitoneal injections of UICC crocidolite, UICC chrysotile, and a latex control particulate on the induced murine peritoneal macrophage population was measured. Spreading, Fc receptor avidity, and phagocytosis were measured 3, 18, and 70 days after injection. When activation of the induced macrophage populations was found at all three times with asbestos, but not with latex, experiments were undertaken to determine whether the asbestos-activated macrophages had attained the full tumoricidally activated state. An in vitro assay measuring macrophage cytotoxicity to tumor cells revealed that the tumoricidal potential of asbestos-activated macrophages was low at 3 and 5 days and negligible by 35 days after injection. An in vivo assay measuring the effect of asbestos on tumor growth generally supported the contention that asbestos-activated macrophages were not tumoricidal, although one dose of UICC chrysotile did produce a small, significant reduction in growth of a concomitant tumor. It was concluded that a single intraperitoneal asbestos injection in mice induces activated macrophages which do not become fully tumoricidal.