Interleukin-1 receptor antagonist (IL-1ra) encoded by the IL1RN gene is a member of the interleukin 1 cytokine family. IL-1ra is secreted by various types of cells including immune cells, epithelial cells, and adipocytes, and is a natural inhibitor of the pro-inflammatory effect of IL-1β. This protein inhibits the activities of IL-1α and IL-1β, and modulates a variety of IL-1 related immune and inflammatory responses. Mutations in the IL1RN gene results in a rare disease called deficiency of the interleukin-1–receptor antagonist (DIRA). Variants of the IL1RN gene is also associated with risk of schizophrenia. Elevated levels of IL1RN has been found in serum of schizophrenia patients. IL-1ra is used in the treatment of rheumatoid arthritis, an autoimmune disease in which IL-1 plays a key role.