SUPPLEMENTATION WITH SELENIUM RESTORES AGE-RELATED DECLINE IN IMMUNE CELL-FUNCTION

This study examined the effect of dietary (2.00 ppm for 8 weeks) suppl ementation with selenium (as sodium selenite) on the ability of lympho cytes from aged (24-month-old), male, C57BL/6JNIA mice to respond to: (i) stimulation with mitogen (phytohemagglutinin) or alloantigen; (ii) develop into cytotoxic effector cells; and (iii) destroy tumor cells, Supplementation with selenium resulted in a significant increase in t he ability of spleen lymphocytes from aged animals to undergo blastoge nesis, as indicated by significantly higher amounts of nuclear incorpo ration of H-3-thymidine after stimulation with mitogen. The dietary re gimen restored the age-related deficiency of the cells to respond to s timulation by nuclear DNA synthesis and cell proliferation, at least, to the level of cells from unsupplemented young adult animals, Further more, populations of in vivo, alloantigen-activated lymphocytes from S e-supplemented aged animals contained significantly higher numbers of cytotoxic lymphocytes than those from Se-normal aged animals, which re sulted in an enhanced capacity to destroy tumor cells. The significant increase in the number of cytotoxic effector cells within these activ ated T-lymphocyte populations was probably the result of an enhanced c lonal proliferation of cytotoxic precursors cells, followed by the dif ferentiation of greater numbers of cytotoxic effector cells. This effe ct occurred in the absence of changes in the ability of the cells to p roduce IL-2, which confirmed our earlier observation that dietary supp lementation with selenium does not affect the production of IL-2. The data suggested that selenium restores the age-related defect in cell p roliferation through an increase in the number of high-affinity IL-2 r eceptors.