Role of fish IFNγ‐related gene in immune system

Unlike mammals, two type II interferons, IFNγ and fish intrinsic IFNγ‐related (IFNγrel), have been isolated in several fish species so far. Both IFNγ and IFNγrel are structurally similar to human and mouse IFNγ. Here we report the identification and characterization of two IFNγrel genes, IFNγrel 1 and IFNγrel 2 with distinct IFNγ motif from the ginbuna crucian carp, Carassius auratus langsdorfii , focusing on their antiviral activities, the gene expression and its receptor. Recombinant IFNγrel 1 and IFNγrel 2 proteins produced in animal cells showed the high antiviral activities of the two IFNγrel proteins against highly‐virulent crucian carp hematopoietic necrosis virus. Furthermore, we found the translocation of IFNγrel 1 from cytosol into nucleus, while IFNγrel 1 did not interact with previously reported IFNγ receptors such as IFNγ receptor alpha chain (IFNGR1) isoforms, IFNGR1‐1 and IFNGR1‐2. Chemical cross‐linking study implied the existence of other receptor. These results suggest that both IFNγrel 1 and IFNγrel 2 are functional, but bind to other specific receptor than previously reported receptors. Identification and characterization of the receptor with its signal transduction pathway is in progress.