This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for IL-1b has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any IL-1b present is bound by the immobilized antibody. Following incubation unbound samples are removed during a wash step, and then a detection antibody specific for IL-1βis added to the wells and binds to the combination of capture antibody-IL-1βin sample. Following a wash to remove any unbound combination, and enzyme conjugate is added to the wells. Following incubation and wash steps a substrate is added. A colored product is formed in proportion to the amount of IL-1β present in the sample. The reaction is terminated by addition of acid and absorbance is measured at 450nm. A standard curve is prepared from seven IL-1β standard dilutions and IL-1β sample concentration determined. Sample Types: serum, plasma, cell culture. Range: 7.8 - 250 pg/ml. Sensitivity: 2 pg/ml. Time: 3.5 hours ? 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-1a and secreted IL-1b. Both have the same molecular weight of 15kD but have different isoelectric points of 5 and 7, respectively.