Interleukin 1 alpha (IL-1α), a pro-inflammatory cytokine of 271 amino acids, is mainly produced by activated macrophages, as well as neutrophils, epithelial cells, and endothelial cells. Both the 31 kDa precursor form of IL-1α and its 18 kDa mature form are biologically active. The IL-1α precursor is released upon cell death as occurs in ischemic diseases such as myocardial infarction, stroke, acute renal failure, and tumor necrosis. IL-1α, mediator of inflammatory reactions, is produced in minute quantities and is active in very low concentrations in serum and plasma.