IFN2

IFN2 is a designation that has appeared in some literature to refer to interferon type II, commonly known as interferon gamma (IFN-γ). In contemporary practice, IFN-γ is the standard name; IFN-2 is less commonly used and may reflect historical nomenclature. IFN-γ is a cytokine essential for innate and adaptive immunity and is produced mainly by natural killer cells and T helper 1 cells upon infection or immune activation.

In humans, the IFNG gene encodes IFN-γ. The protein is secreted primarily as a homodimer and acts in autocrine and paracrine fashion to coordinate immune responses. IFN-γ signals through a receptor complex composed of IFNGR1 and IFNGR2, activating the JAK1 and JAK2 kinases, which phosphorylate STAT1. Phosphorylated STAT1 dimerizes and translocates to the nucleus to induce transcription of interferon-stimulated genes that shape the immune response.

Biological roles of IFN-γ include antiviral and antimicrobial activities, especially against intracellular pathogens. It enhances macrophage activation, increases antigen presentation by upregulating MHC class II molecules, and promotes differentiation of naive T cells toward a Th1 phenotype, supporting cytotoxic T cell responses. IFN-γ also modulates inflammation and influences other cytokine networks.

Clinical relevance centers on its critical role in immunity. Disruptions in IFN-γ signaling can predispose individuals to enhanced susceptibility to certain infections. Recombinant IFN-γ (IFN-γ1b) has been developed for therapeutic use in select conditions, such as chronic granulomatous disease, with adverse effects including flu-like symptoms and injection-site reactions. The term IFN-2 reflects historical usage; current nomenclature standardizes on IFN-γ.

See also: Interferon, IFN-α, IFN-β, IFN-γ receptor, JAK-STAT signaling.