Representing a family of glycoproteins derived from human cells which normally have a role in fighting viral infections by preventing virus multiplication in cells.

They are secreted by vertebrate cells in response to a wide variety of inducers and confer resistance against many different viruses, inhibit proliferation of normal and malignant cells, impede multiplication of intracellular parasites, enhance macrophage and granulocyte phagocytosis, augment natural killer cell activity, and show several other immunomodulatory functions.

Interferon-alpha is made by leucocytes and interferon-gamma by fibroblasts after viral infection.

Interferon-alpha and interferon-beta are also called type I interferons, interferon-gamma as type II interferons, and they are more normally classified as cytokines.