Effects of selenium in vitro on human T-lymphocyte functions and K-562 tumor cell growth

In vitro E-rosette formation, lymphocyte mitogenesis, and natural killer (NK) cell activity of human blood lymphocytes were strongly inhibited by high concentrations (10^-4 M) of sodium selenite, sodium selenate, and selenium dioxide. Lower concentrations (10^-5 or 10^-7 M) also inhibited E-rosette formation and natural killer cell activity against K-562 tumor cells. Lymphocyte transformation induced by concanavalin A (con A) or pokeweed mitogen (PWM) was also inhibited by all selenium compounds tested, but only at the highest concentrations (10^-5 and 10^-4 M). There was depression of the total number of viable lymphocytes following incubation with selenium dioxide only at a high concentration (10^-4 M). Interferon production was enhanced at lower levels (10^-9 to 10^-6 M) of selenium dioxide while a higher concentration (10^-5 and 10^-4 M) appeared to inhibit its production. The mechanism of inhibition by selenium compounds (10^-4 M) is due, in part, to the decrease of viable lymphocytes. It is unclear how other and lower concentrations (10^-7 or 10^-9 M) of selenium compounds inhibit E-rosette formation, NK activity, or K-562 tumor cell growth.