Protective effect of vitamin E on lymphocyte growth capacity during incubation in vitro

Vitamin E, an essential lipid-soluble micronutrient, plays an important role in the immune system and serves as an immunostimulant in geriatric subjects. Using an in vitro incubation to simulate aging processes, we find that vitamin E mitigates loss of growth capacity in lymphocytes. Vitamin E presence during in vitro incubation did not affect significantly the level of peroxidation, the effects of exogenous IL-2, PGE2, or indomethacin, nor levels of IL-2 production. Thus, the preservative effect on lymphocyte growth by vitamin E is not due primarily to its antioxidant function or to interleukin-2 or prostaglandin effects. The decreased growth capacity generated by in vitro incubation is accompanied by a variety of cellular alterations, including decreased CD5 surface antigen, enhanced suppression by adherent cells, and impaired communication between lymphocytes and adherent cells. The decrease in CD5 surface antigen correlates inversely with the cell density required for maximal cell proliferation, and the diminished CD5 levels were unaltered by vitamin E presence during the aging process. In contrast, protection of T-cell proliferative capacity by vitamin E in vitro correlates with diminished suppression by adherent cells and normalized interaction between lymphocytes and adherent cells.