Fish oil and tocopherol-induced changes in natural killer cell-mediated cytotoxicity and PGE2 synthesis in young and old mice.

Natural killer cell (NK) activity decreases and prostaglandin E2 (PGE2) level increases in aged mice. Because PGE2 is involved in control of NK activity this study was conducted to investigate whether or not decreasing PGE2 level by changing the type of dietary fat or increasing the level of vitamin E (vit. E) modulates NK activity of young and old mice. Mice were fed either a corn oil (CO) or a fish oil (FO) diet supplemented with 30 or 500 mg/kg diet of vit. E for 6 wk. To study the effect of vit. E during active immune response and oxidative stress, groups of old mice fed CO and either 30 or 500 mg/kg diet of vit. E were injected with sheep red blood cells (SRBC) prior to assessment of their NK activity. As reported by others regarding mice fed a nonpurified diet, the old mice in all dietary groups had significantly less NK activity and tended to synthesize more PGE2 than young mice. FO-fed mice synthesized less PGE2 than CO-fed mice; however, their NK activity was not higher than that of CO-fed mice. By contrast young mice fed FO had a moderately lower NK activity than those fed CO. Vit. E supplementation did not change NK activity in nonimmunized mice but was effective in preventing SRBC-induced decrease in NK activity of old mice.