Human interleukin 1.

Interleukin 1 (IL-1), a product of stimulated monocytes or macrophages, is defined by its ability to enhance the response of thymocyte to mitogenic stimulation. Numerous studies attribute a multiplicity of other biological functions to IL-1 in immunological and inflammatory reactions. IL-1 also appears to be identical with endogenous pyrogen. Even though this mediator is produced in minute quantities and is active at very low concentrations, greatly complicating its purification, knowledge of its chemical structure and biochemical properties is rapidly increasing. The activity of human IL-1 is associated with multiple molecules of similar size, but subtly different compositions. Structure-function relations, most particularly the question of whether the functional diversity of IL-1 is a reflection of structural diversity or simply of diversity of target-cell responses to a single molecule can now be addressed, as the IL-1 components have been purified to homogeneity, on the one hand, and a precursor molecule, derived from a cloned cDNA sequence, has been obtained.