Interleukin-1 (IL-1) is a cytokine produced by activated macrophages. IL-1 stimulates thymocyte proliferation by inducing IL-2 release, B-cell maturation and proliferation, and fibroblast growth factor activity.
IL-1 is involved in the inflammatory response as endogenous pyrogens, and are reported to stimulate the release of prostaglandin and collagenase from synovial cells.