There are two genes for interleukin-1 : IL-1 alpha and IL-1 beta. IL-1β precursor is cleaved by cytosolic caspase 1 (interleukin 1 beta convertase) to form mature IL-1β.   The multiple biologic activities that define IL1 are properties of a 15- to 18-kD protein that is derived from a 30- to 35-kD precursor. It is a pro-inflammatory cytokine against infection, playing an important role in the pathogenesis of cancers. It signals through various adaptor proteins and kinases that lead to activation of numerous downstream targets. The expression level of IL-1B is very low.