Functional expression and characterization of grass carp IL-10: An essential mediator of TGF-β1 immune regulation in peripheral blood lymphocytes

► Recombinant grass carp IL-10 (rgcIL-10) has been purified. ► Both rgcIL-10 and TGF-β1 induced the cell activation of peripheral blood lymphocytes. ► Removal of endogenous IL-10 could abolish TGF-β1-induced cell activity. ► TGF-β1 enhanced gcIL-10 mRNA expression and protein secretion in the same cell model. ► TGF-β1 may function through its effect on IL-10 production in fish immunity.