Cytokine which binds to interferon gamma receptor 1-like (ifngr1l) (PubMed:18831986, PubMed:19577303, PubMed:20507977). Has activating effects on primary macrophages and neutrophils (PubMed:18831986, PubMed:20507977). Induces nitric oxide production and phagocytic responses in macrophages (PubMed:18831986, PubMed:20507977). Primes macrophages and neutrophils for production of reactive oxygen intermediates (ROI) (PubMed:18831986, PubMed:20507977). Stimulates phosphorylation and nuclear localization of the JAK/STAT signal transducer stat1 (PubMed:20507977). Promotes increased expression of a number of genes important for macrophage activity, including the interferon regulatory factors irf1, irf2, irf8 and irf9 (PubMed:18831986, PubMed:20507977). Homodimer. Highly expressed in spleen. Also detected at lower levels in brain, gill, kidney, heart, intestine and muscle. In immune cell populations, has highest expression in peripheral blood leukocytes and splenocytes. Detected in kidney-derived monocytes, neutrophils, macrophages and leukocytes. Strongly up-regulated in kidney leukocytes in response to phytohaemagglutinin (PHA). Also up-regulated to a lesser extent by polyinosinic:polycytidylic acid (poly(I:C)). Belongs to the type II (or gamma) interferon family.