Cytokine responses in the common carp, Cyprinus carpio L. treated with baker's yeast extract

Cytokines are important regulators of the immune system and investigation of their functions may prove useful for the development of vaccines and immunostimulants for aquaculture. We therefore investigated the cytokine [interleukin (IL)-1β, IL-10, IL-12 p35 and p40, tumor necrosis factor (TNF)-α, CXC‐chemokine and interferon (IFN)-α and γ] responses of the common carp, Cyprinus carpio L., upon treatment with a commercial baker's yeast extract (CW-I) that contained nucleotides and β-glucan. Additionally, to confirm that the CW-I-induced cytokines were functional, we also assessed the effect of CW-I administration on superoxide anion production and phagocytic activities of head kidney leucocytes and resistance to Aeromonas hydrophila infection in the common carp. Our results demonstrate that baker's yeast extract-treated fish displayed a significant up-regulation of pro-inflammatory cytokine (IL-1β, IL-12 p35 and p40, TNF-α, CXC-chemokine, IFN-γ2) gene expression and a down-regulation of anti-inflammatory cytokine (IL-10) gene expression. Furthermore, significantly increased phagocytic activity and superoxide anion production in kidney cells, and resistance to a bacterial pathogen, were observed in the yeast extract-treated fish compared to non-treated fish. The current study indicates the immunostimulatory effects of a baker's yeast extract rich in nucleotides and β-glucan on the carp immune system and supports its potential use in aquaculture.

► Baker's yeast extract contained nucleotides and β-glucan as major components.
► Yeast extract-treated fish had up-regulation of cytokine genes expression.
► Treated fish showed increased phagocytosis, NBT reduction and pathogen resistance.
► Baker's yeast extract had immunostimulatory effects on common carp immune system.
► It may be used as a potential immunostimulant in carp aquaculture.