The effects of α-tocopherol on the immune response and non-specific resistance factors of rainbow trout ( Salmo gairdneri Richardson)

The effects of α-tocopherol on the specific immunity and non-specific resistance of fish were studied. Rainbow trout ( Salmo gairdneri) were maintained on a control diet and an α-tocopherol deficient diet for 12–17 weeks. Fish in both experimental groups continued to grow, suffered no mortalities and showed no gross or histopathological signs of disease throughout the experiment. The specific immune response to sheep red blood cells (SRBC) and Yersinia ruckeri was monitored. Both T-cell (migration inhibition factor, MIF) and B-cell (plaque-forming cell, PFC) responses were assayed. Humoral immunity was measured by hemagglutination, hemolysin and bacterial agglutination. The non-specific factors assayed were total serum protein, serum globulin and the phagocytic index of peritoneal macrophages. Fish fed the α-tocopherol deficient diet had significantly reduced responses in almost all assays. Possible mechanisms for these effects as well as the ramifications of marginal α-tocopherol deficiencies to fish health are discussed. The possibility of immunopotentiation by vitamin E is also addressed.