Characterisation of IL-21 and IL-21Rα in grass carp: IL-21-producing cells are upregulated during Flavobacterium columnare infection

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

“…In 2005, the first fish il21 gene was sequenced in the Japanese puffer Fugu rubripesi [ 14 ]. Subsequently, il21 genes have been reported in spotted green pufferfish ( Tetraodon nigroviridis ) [ 15 ], zebrafish [ 16 ] ( Danio rerio ), rainbow trout ( Oncorhynchus mykiss ) [ 17 ], Japanese flounder ( Paralichthys olivaceus ) [ 18 ], grass carp ( Ctenopharyngodon idella ) [ 19 , 20 , 21 ] and snakehead ( Channa argus ) [ 22 ]. Similar to mammalian IL-21 counterparts, teleost IL-21 homologs consist of four α-helices and two pairs of conserved disulfide bonds [ 14 , 17 , 23 ].…”

“…The expression of fish il21 has been studied mostly at the transcriptional level. It has been shown that fish il21 genes are constitutively expressed in most tissues but more abundantly in the head kidney, gills and intestine [ 14 , 15 , 17 , 18 , 20 , 21 , 22 ]. The il21 expression can be modulated by immune stimuli and pathogenic infections.…”

“…The il21 expression can be modulated by immune stimuli and pathogenic infections. For instance, grass carp and rainbow trout il21 genes have been shown to be upregulated in the primary leukocytes (HKLs) by phytohemagglutinin (PHA) and phorbol myristate acetate (PMA), known to activate T cells, suggesting that il21 could be produced in activated T cells [ 17 , 21 ]. In grass carp, splicing variants of il21 were identified and could be induced by LPS and polyinosinic–polycytidylic acid (poly(I:C)) in the head kidney leukocytes (HKLs) [ 20 ].…”

“…In grass carp, splicing variants of il21 were identified and could be induced by LPS and polyinosinic–polycytidylic acid (poly(I:C)) in the head kidney leukocytes (HKLs) [ 20 ]. Moreover, remarkable increases of il21 expression have been detected in the immune tissues of fish infected with bacterial pathogens such as Yersinia ruckeri ( Y. ruckeri ), Edwardsiella tarda ( E. tarda ), Nocardia seriolae ( N. seriolae ), Aeromonas schubertii ( A. schubertii ) and Flavobacterium columnare ( F. columnare ) [ 17 , 18 , 21 , 22 ]. It has also been shown that il21 is induced by viral hemorrhagic septicemia virus in the kidney of rainbow trout at the early stage of infection [ 17 ].…”

“…It has also been shown that il21 is induced by viral hemorrhagic septicemia virus in the kidney of rainbow trout at the early stage of infection [ 17 ]. In our previous studies, we showed that the IL-21 protein was detected in the primary kidney leukocytes stimulated with PHA and in tissues of fish infected with F. columnare using a monoclonal antibody [ 21 ]. This study aims to investigate whether IL-21 is produced in T cells and, if so, whether the IL-21 producing T cells can be modulated after infection with bacterial pathogens.…”