Interferon-gamma or IFN-g is a dimerized soluble cytokine which is a Type II Interferon. In contrast to interferon-alpha and interferon-beta which can be expressed by all cells, IFN-g is secreted by T lymphocytes and NK cells only.

IFN-g has antiviral, immunoregulatory and anti-tumour properties. It alters transcription in up to 30 genes producing a variety of physiological and cellular responses. Activation by IFN-g is achieved via a heterodimer receptor consisting of IFNGR1 & IFNGR2 (interferon gamma receptor). IFN-g binding to the receptor activates the JAK-STAT pathway

IFN-g activates APCs and promotes Th1 differentiation by upregulating the transcription factor T-bet.

Interferons are used to treat infectious diseases, but can also precipitate autoimmunity (in up to 19% people treated with these cytokines).