The Biological Functions and Intestinal Inflammation Regulation of IL-21 in Grass Carp (Ctenopharyngodon idella) during Infection with Aeromonas hydrophila

Abstract

Interleukin (IL) 21 is a pleiotropic cytokine that plays an important role in regulating innate and adaptive immune responses. In fish, the biological functions and cell source of IL-21 remain largely unknown. In this study, we performed qRT-PCR, Western blotting and immunofluorescent microscopy to examine the expression of IL-21 at the mRNA and protein levels. We found that il21 expression was induced in the primary head kidney leukocytes of grass carp (Ctenopharyngodon idella) by heat-inactivated Aeromonas hydrophila (A. hydrophila) and LPS and in tissues after infection with A. hydrophila. Recombinant IL-21 protein produced in the CHO-S cells was effective in elevating the expression of antibacterial genes, including β-defensin and lysozyme, and, interestingly, inhibited the NF-κB signaling pathway. Furthermore, we investigated the response of the IL-21 expressing cells to A. hydrophila infection. Immunofluorescent assay showed that IL-21 protein was detected in the CD3γ/δ T cells and was markedly accumulated in the anterior, middle and posterior intestine. Collectively, the results indicate that IL-21 plays an important role in regulating the intestinal inflammation induced by bacterial infection in grass carp.

Vitamin C Alleviates Intestinal Inflammation Caused by Aeromonas hydrophila in Juvenile Blunt Snout Bream (Megalobrama amblycephala)

“…Fish pathogens typically enter the fish through the intestine, which serves as a crucial site for digestion, absorption of nutrients, and immunity. Various fish species, including grass carp (Ctenopharyngodon idella) [5] and silver carp (Hypophthalmichthys molitrix) [6], have been reported to experience intestinal damage and dysfunction due to A. hydrophila infection. Enhancing the intestinal health of fish through improved dietary formulations and immunostimulants has emerged as a promising strategy to bolster their resistance to A. hydrophila infections, thereby reducing the incidence of inflammation and diseases [7].…”