Caspases are a family of cysteine proteases that can be divided into the apoptotic and inflammatory caspase subfamilies. Unlike the apoptotic caspases, members of the inflammatory subfamily are generally not involved in cell death but are associated with the immune response to microbial pathogens. Members of this subfamily include caspase-1, -4, -5, and -12 and can activate proinflammatory cytokines such as IL-1β and IL-18. Caspase-1 was initially identified as an IL-1β-converting enzyme; later experiments revealed it to be a mammalian homolog of the C. elegans cell death gene ced-3 whose overexpression can induce apoptosis in fibroblasts.