IL-1a is produced by activated macrophages, stimulates thymocyte proliferation by inducing IL-2 release, B-cell maturation and proliferation, and fibroblast growth factor activity. This protein is involved in the inflammatory response, being identified as endogenous pyrogens, and are reported to stimulate the release of prostaglandin and collagenase from synovial cells. Recombinant mouse IL1a protein, fused to His-tag at N-terminus, was expressed in E.coli.