Interleukin-1 (IL-1), originally described as lymphocyte activating factor (LAF) for its effects on thymocytes(1), is a polypeptide cytokine with two molecular forms. The two distinct molecular forms of IL-1 are thought to be derived from two genes(2,3). After transcription, as 31kD precursor polypeptide is cleaved to give rise to mostly cell membrane associated IL-1? and secreted IL-1?. Both have the same molecular weight of 15kD but have different isoelectric points of 5 and 7, respectively.

Despite sequence homology of only 20%, both forms are thought to bind to the same receptor(4). IL-1 inhibitors that vary only in their degree of glycosylation have been described to bind to the IL-1 receptor(5). These inhibitors are structurally related to IL-1β and may be important in regulation of IL-1? action(6).

IL-1? is produced primarily by monocytes and macrophages (7) but also by astrocytes, oligodendroglia, adrenal cortical cells, NK cells, endothelial cells, keratinocytes, megakaryocytes, platelets, neurons, neutrophils, osteoblasts, Schwann cells, trophoblasts, T cells, and fibroblasts. IL-1 has multiple immunological functions including enhancement of IL-2 production by T cells and activation of B-cells (BAF) and thymocytes(8-10). A true pleiotrope, IL-1 may have tumoricidal activity via its release of IL-2 and Interferon gamma and indirectly antiviral by stimulating to release interferon beta(11).

Low levels of IL-1? have been reported in normal serum(12). It is thought that IL-1 genes are induced to respond to tissue damage or in infection. Elevated levels have been reported in a number of infectious disease conditions and in noninfectious inflammatory conditions such as Crohn