Insights into teleost interferon-gamma biology: An update

15 pages, 3 tables, 3 figuresInterferon-gamma (IFN-ϒ) is probably one of the most relevant cytokines orchestrating the immune response in vertebrates. Although the activities mediated by this molecule are well known in mammals, several aspects of the IFN-ϒ system in teleosts remain a riddle to scientists. Numerous studies support a potentially similar role of the fish IFN-ϒ signalling pathway in some well-described immunological processes induced by this cytokine in mammals. Nevertheless, the existence in some teleost species of duplicated ifng genes and an additional gene derived from ifng known as interferon-γ-related (ifngrel), among other things, raises new interesting questions about the mode of action of these various molecules in fish. Moreover, certain IFN-ϒ-mediated activities recently observed in mammals are still fully unknown in fish. Another attractive but mainly unexplored curious property of IFN-ϒ in vertebrates is its potential dual role depending on the type of pathogen. In addition, some aspects mediated by this molecule could favour the resolution of a bacterial infection but be harmful in the context of a viral disease, and vice versa. This review collects old and new aspects of IFN-ϒ research in teleosts and discusses new questions and pathways of investigation based on recent discoveries in mammalsThis work was funded by the project BIO2017-82851-C3-1-R from the Spanish Ministerio de Economía y Competitividad and IN607B 2016/12 from Consellería de Economía, Emprego e Industria (GAIN), Xunta de Galicia. Patricia Pereiro wishes to thank the Axencia Galega de Innovación (GAIN, Xunta de Galicia) for her postdoctoral contract (IN606B-2018/010)Peer reviewe