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 (By similarity). 270 Interleukin-1 alpha IL1A_HORSE IL1A MAKVPDLFEDLKNCYSENEDYSSEIDHLSLTQKSFYDASYDPLPEDCMDTFMSLSTSETSKTSKLNFKESVVLVAANGKTLKKRRLSLNQFITNDDLEAIANDPEEGIIRPRSVHYNFQSNTKYNFMRIVNHQCTLNDALNQSVIRDTSGQYLATAALNNLDDAVKFDMGAYTSEEDSQLPVTLRISKTRLFVSAQNEDEPVLLKEMPDTPKTIKDETNLLFFWERHGSKNYFKSVAHPKLFIATKQGKLVHMARGQPSITDFQILDNQF