Caspase-5, a 47kD cysteine protease, otherwise known as ICH-3. Caspase-5 has been shown to be expressed at higher levels in the colon, lung, spleen, small intestine and by peripheral blood lymphocytes. Caspase-5 is a member of a growing number of inflammatory caspases belonging to the Caspase-1 (ICE­type) subfamily, which require proteolytic processing of their inactive precursor into smaller active subunits. Unlike Caspase-1, Caspase-5 is not directly responsible for the activation of IL-1Beta from the pro-IL-1Beta precursor, but the presence of Caspase-5 does appear to enhance the processing of IL-1Beta. The in vivo expression of Caspase-5 is elevated by Lipopolysaccharide (LPS) and gene expression is also increased by Interferon gamma (IFNg). In vitro studies have shown cleavage of Caspase-5 by the serine protease Granzyme B, which plays a major role in Cytotoxic T lymphocyte (CTL)-induced apoptosis (1).