Immunostimulatory effects of fermented vegetable product on the non-specific immunity of Japanese flounder Paralichthys olivaceus

The stimulatory effect of fermented vegetable product (FVP) upon the phagocytic and superoxide generation of leukocytes was studied in the Japanese flounder Paralichthys olivaceus. The phagocytic activity of casein-induced, intraperitoneal leukocytes was investigated and quantified, that is the activity significantly increased (P < 0.05 or < 0.01) by the addition of FVP beyond 3 mg/kg body weight. Further analysis investigated the effect of FVP on superoxide generation in leukocytes. Established in vitro cytochrome c reduction assay was used to measure superoxide generation; reduced levels of FVP in assay samples had a profound effect on superoxide generation. FVP was also incorporated in commercial diets and fed to Japanese flounder for 4 weeks. The phagocytic activities and superoxide generation of peritoneal induced leukocytes were significantly higher (P < 0.05, < 0.01) in fish fed the FVP supplemented diet than fish fed the control diet. FVP feeding in fish had a significantly higher (P< 0.05) activity of lysozyme than in the control fish.