Interleukin-1 alpha (IL-1α), is produced in a variety of cells including monocytes, tissue macrophages, keratinocytes and other epithelial cells. Both IL-1alpha and IL-1beta bind to the same receptor and have similar if not identical biological properties. These cytokines have a broad range of activities including stimulation of thymocyte proliferation via IL-2 release, B-cell maturation and proliferation, mitogenic FGF-like activity, and the ability to stimulate the release of prostaglandin and collagenase from synovial cells. However, whereas IL-1beta is a secreted cytokine, IL-1alpha is predominantly a cell-associated cytokine.