Human interleukin-1α (IL-1α) or IL-1F1, also known as hematopoietin-1, is a glycosylated 30.6 kDa protein. It is produced by activated macrophages and is an endogenous pyrogen. Along with IL-1β it stimulates thymocyte proliferation by inducing IL-2 release. IL-1α has multiple receptors. Along with IL-1β, IL-1α binds directly to IL-1 RI, which is then associated with IL-1 R accessory protein (IL-1RAcP) to form a high-affinity receptor complex for signal transduction. IL-1 RII has high affinity for IL-1α, but it is a negative regulator of IL-1α activity. IL-1 receptor antagonist (IL-1ra) interacts with IL-1 RI preventing it from binding IL-1α and IL-1β. IL-1α is associated with a number of disorders such as cerebral amyloid angiopathy-related hemorrhage, periodontal disease, and silicosis. The Human IL-1α Kit provides assay-specific components for the quantitative determination of endogenous IL-1α in human urine, serum, plasma, and cell culture supernatants.