LAUSR

Abstract Interleukin 10 (IL-10) is a pleiotropic cytokine with important immune regulation function, not only participating in the differentiation of B cells, but also boosting B cell antibody production in mammals. In this study, OnIL-10 was successfully cloned and identified from Nile tilapia (Oreochromis niloticus). Its roles in response to bacterial challenge and promotion of IgM antibody production were investigated. The full-length cDNA of OnIL-10 was 1040 bp, of which the open reading frame was 549 bp, encoding 182 amino acids. Analysis showed that the structure of OnIL-10 was similar to that of humans by constructing 3D model, including homologous dimer molecules with six α-helix. In addition, at transcription level, OnIL-10 is widely expressed in various tissues of tilapia and highly expressed in immune tissues. Following the stimulation of Streptococcus agalactiae in vivo and in vitro, the mRNA levels of OnIL-10 were dramatically increased in head kidney and spleen. Further, the transcription level of IgM (sIgM and mIgM) were obviously increased (4-folds and 20.5-folds) following recombinant protein OnIL-10 ((r)OnIL-10) stimulation. Moreover, the increasing level of sIgM induced by (r)OnIL-10 was mostly shown in plasma-like B cells, while the mIgM mainly expressed in plasmablasts and activated B cells. Collectively, these results demonstrated that OnIL-10 participated in host defense against pathogens and promoted the IgM antibody production, which enriched the function study of IL-10 in teleosts.