Interleukin-1 beta (IL-1 beta) is released from an inactive precursor by a proteolytic cleavage. A monocytic protease has been identified that appears to be involved in the physiological activation of this cytokine. Two situations have been found in which precursor IL-1 beta exists without the monocytic processing enzyme, and in these cases other proteases, such as neutrophil elastase, cathepsin G and cathepsin L, may be involved in generating the active cytokine.