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 proteins are involved in the inflammatory response, being identified as endogenous pyrogens, and are reported to stimulate the release of prostaglandin and collagenase from synovial cells. (www.uniprot.org) Produced in E.coli. Non-glycosylated polypeptide chain containing 153 amino acids. The ED50 as determined by the dose-dependant stimulation of murine D10S cells is less then 0.002 ng/ml, corresponding to a Specific Activity of 5 x109 IU/mg.