Effects of inactivated streptococci (OK-432) on macrophage functions in mice.

The effects of inactivated streptococci (OK-432) on murine macrophage functions were investigated. In vivo treatment of peritoneal macrophages with OK-432 augmented the direct cytotoxic activity against TU5 tumor cells in a 48 h tritiated thymidine release assay. OK-432 also stimulated the rapid (6 h, 51Cr release) macrophage-mediated killing of Actinomycin D-sensitized WEHI 164 sarcoma cells. Moreover, the expression of la antigens on peritoneal macrophages was found to be greatly enhanced after in vivo treatment with OK-432. The immunomodulatory effects of OK-432 on macrophages functions may contribute to the antitumor activity of inactivated streptococci.