SUPPLEMENTATION WITH SELENIUM AND HUMAN IMMUNE CELL FUNCTIONS .2. EFFECT ON CYTOTOXIC LYMPHOCYTES AND NATURAL-KILLER-CELLS

This study examined the effect of dietary (200 mu g/d for 8 wk) supple mentation with selenium (as sodium selenite) on the ability of human p eripheral blood lymphocytes to respond to stimulation with alloantigen , develop into cytotoxic lymphocytes, and to destroy tumor cells, and on the activity of natural killer cells. The participants in the study were randomized for age, sex, weight, height, and nutritional habits and given selenite or placebo tablets; all participants had a selenium replete status as indicated by their plasma Se levels prior to supple mentation. The data indicated that the supplementation regimen resulte d in 118% increase in cytotoxic lymphocyte-mediated tumor cytotoxicity and 82.3% increase in natural killer cell activity as compared to bas eline values. This apparently was related to the ability of the nutrie nt to enhance the expression of receptors for the growth regulatory ly mphokine interleukin-2 and consequently, the rate of cell proliferatio n and differentiation into cytotoxic cells. The supplementation regime n did not produce significant changes in the plasma Se levels of the p articipants. The results indicated that the immunoenhancing effects of selenium in humans require supplementation above the replete levels p roduced by normal dietary intake.