The interleukin-1 receptor antagonist (IL-1ra) inhibits the activity of IL-1 by binding to the IL-1 receptor but has no IL-1 like activity. IL-1ra has 4 isoforms produced by alternative splicing, only isoform 1 is secreted. The intracellular forms of IL-1ra are predominantly e, Xenopus/Amphibian,pressed in epithelial cells. Under the name Kineret (Amgen), IL-1ra is used to treat patients with moderate to severe case of active rheumatoid arthritis by slowing the progression of the structural damages. This antibody recognizes human IL-1ra in ELISA.