Interleukin 1 (IL-1) is a name that designates two proteins, IL-1α?and IL-1β, which are the products of distinct genes, but which recognize the same cell surface receptors. With the exception of skin keratinocytes, some epithelial cells, and certain cells of the central nervous system, IL-1 is not produced by the cells of healthy individuals. However, in response to stimuli such as those produced by inflammatory agents, infections, or microbial endotoxins, a dramatic increase in the production of IL-1 by macrophages and various other cell types is seen(1-3).

IL-1α ?and IL-1β are structurally related polypeptides that show approximately 25% homology at the amino acid level (2). Both are synthesized as 31 kDa precursors that are subsequently cleaved into proteins with molecular weights of approximately 17.5 kDa (4, 5).

Intracellular IL-1βconsists exclusively of the 31 kDa precursor form (6). Extracellular IL-1βconsists of a mixture of both unprocessed and mature IL-1β. These results indicate that processing takes place subsequently to secretion and is not tightly coupled to secretion(7). The specific protease apparently responsible for the processing of IL-1β, designated interleukin-1β-converting enzyme (ICE), has been described (7).

IL-1 possesses a wide variety of biological activities. IL-1 also plays an important role in immune functions, having effects on macrophages/ onocytes, Tlymphocytes, B lymphocytes, NK cells, and LAK cells. It acts on macrophages/ monocytes, inducing its own synthesis as well as the production of TNF and IL-6 (8,9). It activates T cells, resulting in IL-2 production and expression of IL-2 receptors (10). IL-1 also induces the production of GM-CSF and IL-4 from activated T cells (11). It induces B cell proliferation and maturation and increased immunoglobulin synthesis (12, 13).