[Effects of selenium deficiency and supplementation on tumor immune response in mice]

DBA/2 mice were fed for 16 weeks with Torula yeast-based synthetic diet containing various concentrations of selenium (Se). At 13th week, the mice were immunized with syngenetic L5178 Y lymphoma cells and their specific and non-specific tumor immune responses were examined 3 weeks after immunization. The results indicated that in mice fed with a diet containing 0.007 ppm Se, the serum Se level was extremely low (0.02 micrograms/ml). These Se-deficient mice were unable to elicit normal tumor-specific immune responses. Both the specific proliferation of T cells in MLTC and tumoricidal activity of CTL were very much depressed. In addition, these mice also showed impaired NK and LAK cell activity. The effects of Se supplementation varied depending on the amount of Se given. When 0.170 ppm Se was added to the low Se diet, all the immune parameters examined were restored to the normal level. When 0.567 ppm Se was added, however, the tumor immune responses remained as low as those in Se-deficient mice. This study implies that the prevalence of primary hepatocellular carcinoma in areas where Se is deficient has a profound immunological basis. Se supplementation is obviously indicated for cancer prevention in these areas but the amount of Se supplied is crucial.