Interleukin-1 beta （IL-1β） 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. IL-1β is a member of the interleukin 1 family of cytokines. This cytokine is produced by activated macrophages as a proprotein, which is proteolytically processed to its active form by caspase 1 （CASP1/ICE）. This cytokine is an important mediator of the inflammatory response, and is involved in a variety of cellular activities, including cell proliferation, differentiation, and apoptosis. The induction of cyclooxygenase-2 （PTGS2/COX2） by this cytokine in the central nervous system （CNS） is found to contribute to inflammatory pain hypersensitivity. Increased production of IL-1β causes a number of different autoinflammatory syndromes, most notably the monogenic conditions referred to as Cryopyrin-Associated Periodic Syndromes （CAPS）, due to mutations in the inflammasome receptor NLRP3 which triggers processing of IL-1B.