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Amberjack Seriola dumerili interleukin-10 negatively suppresses host cell-mediated immunity

Megumi Matsumoto, Mahumoud Tanekey Amer, Kyosuke Araki, Atsushi Nishitani, Kazuma Hayashi, Yutaka Takeuchi, Kazuhiro Shiozaki, Atsushi Yamamoto
Fisheries science 2018 v.84 no.5 pp. 857-867
CD4-positive T-lymphocytes, Nocardia seriolae, Seriola dumerili, antibacterial properties, cell-mediated immunity, dose response, fish, genes, in vitro culture, interleukin-10, pathogens, recombinant proteins, spleen
Interleukin-10 (IL-10) is an anti-inflammatory cytokine and negatively regulates cell-mediated immunity (CMI) induction by inhibiting cytokine production in type 1 T helper cells. IL-10 genes have been isolated from several fish, and inflammatory cytokine inhibition by IL-10 has been well examined. However, a CMI regulator of IL-10 in fish has not yet been identified. In this study, we cloned the IL-10 gene in amberjack Seriola dumerili and analyzed its function using its recombinant protein (rIL-10). In an in vitro culture experiment, gene expression of inflammatory cytokines was suppressed in leukocytes incubated with rIL-10 compared with cells that only received Nocardia seriolae stimulation. This result suggests amberjack IL-10 has conserved function as an inflammatory cytokine inhibitor. Bactericidal activity of amberjack cells against intracellular pathogen stimulation was decreased in a rIL-10 dose-dependent manner. Furthermore, a significant reduction in the T-bet/GATA-3 ratio was observed in N. seriolae living cell (LC) + rIL-10-injected fish. Taken together, these results suggest amberjack rIL-10 suppresses CMI induction both in vitro and in vivo. In addition, the number of IgM⁺ cells among spleen leukocytes in N. seriolae + rIL-10-injected fish was higher than in only N. seriolae LC, suggesting that Th2-dominant immunity was induced by adding rIL-10.