[Experimental study on levamisole modulation of antitumor immunity--1].

Experimental studies on modulation of antitumor immunity by administration of levamisole (LMS) were performed using a metastasizing rat's mammary tumor (MRMT-1) which was routinely inoculated subcutaneously at one back side of the Slc-SD rat. Experiment 1: The optimal ip dose of LMS for getting antitumor effects was found to be 2.5 mg/kg/day, administered every other day for 7 times. Administration at doses between 0.5 mg/kg and 2.5 mg/kg tended to cause tumor suppression and the doses over 10 mg/kg tended to cause tumor progression. Experiment 2: Optimal timing of starting LMS administration was found to be on day 2 of tumor inoculation. Starting LMS on day 14 of inoculation caused a tendency of transient tumor progression. Experiment 3: A slight tumor suppression was observed when splenectomy was done on day 14 of inoculation. However, when LMS was, given simultaneously, the tumor suppressive effect of splenectomy was cancelled. Experiment 4: According to immunological parameters with whole lymphocyte of peripheral blood, spleen cells and thymus cells, the mechanism of modulation of antitumor immunity by LMS administration was suggested to be an increase in immunocompetency of peripheral lymphocytes and augmentation of specific cytotoxicity. Immunocompetency of NK cells was found to be reduced. LMS was found to have some effects also on spleen and thymus cell functions.