Interleukin 1 (IL-1) is a name that designates two proteins, IL-1α and IL-1β, that are the products of distinct genes, but recognize the same
cell surface receptors. IL-1α and IL-1β are structurally related polypeptides that show approximately 25% homology at the
amino acid level. Both proteins are produced by a wide variety of cells in response to stimuli such as those produced by inflammatory
agents, infections, or microbial endotoxins. The proteins are synthezied as 31 kDa precursors that are subsequently cleaved into proteins
with molecular weights of approximately 17.5 kDa. The specific protease responsible for the processing of IL-1β, designated interleukin
1β-converting enzyme (ICE), has been described.