Enhancement of NK-cell activity in normal and tumor-bearing mice after administration of aclacinomycin.

Aclacinomycin (ACM) a new cytotoxic antibiotic employed in cancer chemotherapy, can either enhance or inhibit the NK-cell activity of the immune system, depending on the dose administered. A single intraperitoneal injection of 2-4 mg/kg of ACM augments the cytolytic activity by spleen and peritoneal exudate cells of normal mice and spleen cells depleted of nylon-adherent cells and peritoneal exudate cells of tumor-bearing mice. In contrast to the stimulatory effect of NK-cell activity by low doses of ACM, a single injection of 8 mg/kg of this agent leads to depression in the level of NK-cell activity in both normal and tumor-bearing animals. We suggest that the mechanism through which the ACM enhances NK-cell activity may be through the deletion of a suppressor cell population acting on the NK cells.