Effect of Selenium Supplementation on Human Lymphocyte Tumor Cytotoxicity

This study examined the effect of dietary (200 μg/day for 8 weeks) supplementation with Se (as sodium selenite) on the ability of human peripheral blood lymphocytes to respond to stimulation with antigen, develop into cytotoxic lymphocytes, and to destroy tumor cells. Sixteen male and six female volunteers were matched by age (mean age = 26.2 years; range = 23–37), sex, weight, and nutritional habits, and given selenite or placebo tablets. Lymphocytes (2.5 × 106), isolated prior to and 8 weeks following supplementation, were activated by allogeneic stimulation with 8.3 × 105 mitomycin C-treated Ragi cells for 5 days. Lymphocyte mediated tumor cytotoxicity was evaluated using a 4h-51Cr release assay and effector: target cell ratios of 1.25–20:1. The results indicated that supplementation with selenite in humans results in a significant (118%) increase in the ability of a given lymphocyte population to destroy a fixed number of tumor cells, i.e., 45.57 ± 5.96 vs. 20.87 ± 2.62% cytotoxicity at 20:1 ratio. While the cytotoxic efficiency of both lymphocyte populations remained the same, the number of lymphocytes required to destroy 2×105 tumor cells decreased significantly after supplementation (1.53 × 106 ± 1.98 × 105 vs. 7.10 × 105 ± 1.49 × 105). The results indicate that supplementation with Se in humans results in a significant increase in the number of cytotoxic lymphocytes within a cell population.