Levamisole(LMS) augmented the ability to inhibit specifically the growth of secondary Meth 1 tumors in Meth 1-bearing BALB/c mice. 2) When spleen cells of Meth 1-bearing mice were restimulated in vitro with MMC-treated Meth 1 cells, cytotoxicity became detected by 51 Cr release assay. Such cytotoxicity was augmented by in vivo treatment with LMS. The cytotoxicity was tumor-specific and completely abrogated by incubation with anti-thy 1.2 antibody and complement before the assay. 3) Cytostatic activity of peritoneal macrophages induced by i. p. inoculation with MMC-treated Meth 1 cells was augmented by LMS treatment of Meth 1-bearing mice but such an activity was not Meth 1-specific. 4) LMS did not augment the natural killer cell activity of the spleen cells of BALB/c mice or BALB/c nude mice. These results suggested that the growth-inhibitory effect of LMS against secondary tumors was mediated by cytotoxic T-cells.
