Interleukin-1 beta (IL-1ß) also known as '"leukocytic pyrogen"', "'leukocytic endogenous mediator'", "'mononuclear cell factor'", "'lymphocyte activating factor'" and other names, is a
cytokine protein that in humans is encoded by the
IL1B gene. There are two genes for Interleukin-1 (IL-1):
IL-1 alpha and IL-1 beta (this gene). IL-1ß precursor is cleaved by cytosolic
caspase 1 (interleukin 1 beta convertase) to form mature IL-1ß.