LAUSR

Abstract In mammals, interleukin (IL)-4 and IL-13 are important cytokines involved in the immune response of the host defence against pathogens and play critical roles in the polarization of monocytes/macrophages (MO/Mϕs). However, in teleost fish, the role of IL-4/13 homologues in the polarization of MO/Mϕ remains unknown. In this paper, we identified a second isoform of IL-4/13 (CiIL-4/13A) from grass carp (Ctenopharyngodon idella) in addition to the IL-4/13 homologue previously reported and comparatively studied their expression profiles and functions. The two CiIL-4/13 transcripts were constitutively expressed in tissues but displayed distinct expression patterns. Infection with Flavobacterium columnare or grass carp reovirus II (GCRV-Ⅱ) resulted in the alteration of expression levels of both IL-4/13 isoforms. Furthermore, in the primary head kidney cells, the recombinant CiIL-4/13A and B could up-regulate the expression of IL-10, inducible nitric oxide synthase (iNOS) and M2 macrophage marker gene (KLF4, kruppel like factor 4), whilst down-regulate the expression of IL-1β and M1 macrophage marker gene (MARCO, macrophage receptor with collagenous structure). The results suggest that the CiIL-4/13A and B play similar roles in regulating inflammation and differentiation of MO/Mϕs in grass carp.