Submitted to: Fish and Shellfish Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/23/2014
Publication Date: 3/4/2014
Citation: Wang, X., Li, C., Thongda, W., Luo, Y., Beck, B.H., Peatman, E. 2014. Characterization and mucosal responses of interleukin 17 family ligand and receptor genes in channel catfish Ictalurus punctatus. Fish and Shellfish Immunology. 38:47-55. Interpretive Summary: Cytokines are a diverse group of chemical messengers that are important in the immune response to infectious microorganisms. One such family of cytokines is the interleukin-17 family, which has been linked to immune protection against certain diseases in humans. In the present study, we characterized the diversity and levels of IL-17 and IL-17 receptors in the tissues of healthy channel catfish, and after exposure to Edwardsiella ictaluri and Flavobacterium columnare, the two most costly and problematic pathogens of the United States farmed catfish industry. We found that channel catfish had seven different types of IL-17 genes and four unique IL-17 receptors, both of which varied by tissue type and changed very rapidly after infection. This initial description of the IL-17 family in channel catfish sets the stage for future studies examining the role of the IL-17 system in the defense against these important bacterial diseases of farm-raised channel catfish.
Technical Abstract: Interleukin (IL) 17 family cytokines are important mediators of mucosal immune responses, tightly regulated by signals from the complex milieu of pathogenic and commensal microbes, epithelial cells and innate and adaptive leukocytes found at tissue barriers. In mammals, IL17 ligand expression has been linked not only to protective immunity but also excessive tissue inflammation and damage in the gut and lungs. To better understand the scope and action of the IL17 family in channel catfish Ictalurus punctatus, we identified and characterized seven IL17 ligands and four IL17 receptor (IL17R) homologues from transcriptomic and genomic databases. To gain insight into the mucosal actions of the IL17A/Fs-associated pathway in inflammatory processes, the expression profiles of three IL17A/Fs and their putative receptors IL17RA and IL17RC in mucosal tissues of catfish following experimental challenge with Edwardsiella ictaluri and Flavobacterium columnare were investigated. Bacterial challenge induced higher expression of the catfish IL17A/Fs as early at 4 h post-infection, particularly in gill tissue. In contrast, in the catfish intestine, where IL17 function is best understood in mouse models, IL17A/F expression showed minimal early responses to E. ictaluri infection. Instead, a significant up-regulation of IL17 ligands and receptors was observed in the intestine at 7 d, highlighting species and tissue-specific regulation of the IL17 family.