As their name implies, a primary role for members of the Inhibitors of Apoptosis (IAP) family lies in their ability to suppress apoptosis. This occurs through the inhibition of pro-apoptotic members of the Caspase family. IAP proteins are characterized structurally by the presence of at least one BIR (baculoviral IAP repeat) domain. Binding of the BIR domain of IAPs to active caspases inhibits caspase activity. Eight IAPs have been identified in humans including Apollon/BRUCE, cIAP-1, cIAP-2, ILP-2, Livin, NAIP, Survivin, and XIAP.