Two forms of IL-1 have been isolated: Il-1α and IL-1β. They represent the products of two distinct genes and exert their effects by binding to two distinct IL-1 receptor types each with different binding affinities. The production of IL-1β is one of the most effective mediators of inflammatory reactions primarily produced by activated monocytes and macrophages. Cell wall fragments and toxins from gram-positive organisms can induce TNFa and IL-1β production. A large number of cell types, in addition to monocytes and macrophages, have been shown to produce IL-1, such as Langerhans cells, NK cells, B cell lines, endothelial cells and dendritic cells.

Activities of IL-1 include T cell activation, IL-2 receptor induction, stimulation of pre-B cells and augmentation of IL-1 and IFN-induced activation of NK-mediated cytotoxicity. IL-1 has also been shown to accelerate wound healing, possibly due to its ability to induce angiogenesis, and fibroblast activation. Since IL-1 is a primary inflammatory mediator, the use of IL-1 antagonists, such as IL-1ra or soluble IL-1 receptors is being investigated as a potential treatment for chronic inflammatory diseases.