Genomics of fish IL-17 ligand and receptors: A review

Interleukin-17 (IL-17) is a cytokine family composed of six ligands (A–F). Especially, the IL-17A and IL-17F are best characterized cytokines of IL-17 family cytokine. These are produced by Th17 cells and induce the expression of many mediators of inflammation properties. In addition, the five member of IL-17 receptor family (RA-RE) have been identified in mammals. Although the research on fish IL-17 is a little to date, this review discusses some of the recent advances in research on IL-17 ligand and receptor genes in fish. IL-17 family member was chosen from the fish genome database, and its structure and phylogeny is analyzed in detail. Moreover, invertebrate IL-17 genes are also discussed, and the isolation and current status of fish IL-17 receptor genes are summarized. Comparative genomic analysis of the IL-17 family among mammals, teleost and invertebrates provided new insights. Novel IL-17 ligand (IL-17N) was identified from teleost, moreover it was suggested that IL-17N may be a teleost specific ligand by synteny and phylogenetic analysis. On the other hand, IL-17 receptors are well conserved between mammal and teleost, the five member of IL-17 receptor family: IL-17RA-RE were found on the teleost genome. In addition, the IL-17RA gene was duplicated in tandem on the stickleback and medaka genome. Knowledge about the IL-17 ligand/receptor in fish is very limited. Therefore this review will hopefully encourage future studies of IL-17 in fish.