IFN-gamma (interferon, gamma) is an antiviral and antiparasitic agent produced by CD4+/CD8+ lymphocytes and natural killer cells that undergo activation by antigens, mitogens or alloantigens. It is a pleiotropic cytokine involved in the regulation of nearly all phases of immune and inflammatory responses, including the activation, growth and differentiation of T cell, B cells, macrophages, NK cells and other cell types such as endothelial cells and fibroblasts. The active form of IFN-G is a homodimer with each subunit containing six helices. The dimeric structure of human IFN-G is stabilized by non-covalent interactions through the interface of the helices. IFN-G translated precursor is 166 amino acids, including the 23 amino acid secretory sequence. It is upregulated by IL2, FGF basic, EGF and downregulated by vitamin D3 or DMN. Multiple forms exist due to variable glycosylation and under non-denaturing conditions due to dimers and tetramers.