Identification and bioactivities of IFN-gamma in rainbow trout Oncorhynchus mykiss: The First Th1-Type Cytokine Characterized Functionally in Fish

Jun Zou, Allison Christina Carrington, Bertrand Collet, J M Dijkstra, Y Yoshiura, N Bols, Christopher John Secombes

Research output: Contribution to journalArticlepeer-review


IFN-gamma is one of the key cytokines in defining Th1 immune responses. In this study, an IFN-gamma homologue has been identified in rainbow trout Oncorhynchus mykiss, and its biological activities have been characterized. The trout IFN-gamma cDNA is 1034 bp in length and translates into a 180-aa protein. The first intron of the trout IFN-gamma gene contains highly polymorphic GACA minisatellites and 44-bp DNA repeats, giving rise to at least six alleles. IFN-gamma is structurally conserved among vertebrates, and a signature motif has been identified. A nuclear localization sequence known to be crucial for IFN-gamma biological activities is also present in the C-terminal region of the trout IFN-,y. The IFN-gamma expression was induced in head kidney leukocytes by stimulation with PHA or poly(I:Q and in kidney and spleen of fish injected with poly(I:C). rIFN-,y produced in Escherichia coli significantly stimulated gene expression of IFN-gamma-inducible protein 10 (gamma IP-10), MHC class II beta-chain, and STAT1, and enhanced respiratory burst activity in macrophages. Deletion of 29-aa residues from the C terminus containing the nuclear localization sequence motif resulted in loss of activity with respect to induction of gamma IP-10 in RTS-11 cells. Moreover, IFN-gamma-induced gamma IP-10 expression was completely abolished by the protein kinase C inhibitor staurosporine, and partially reduced by U0126, a specific inhibitor for ERKs. Taken together, the present study has demonstrated for the first time a functional IFN-gamma homologue in a fish species, strongly suggesting a conserved Th1 immune response is most likely present in lower vertebrates.

Original languageEnglish
Pages (from-to)2484-2494
Number of pages11
JournalThe Journal of Immunology
Issue number4
Publication statusPublished - 15 Aug 2005


  • human interferon-GAMMA
  • protein-kinase-C
  • nuclear-localization sequence
  • salmo-gairdneri leukocytes
  • gene
  • expression
  • polymorphism
  • cloning
  • terminus
  • promoter

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