The ability to ward off bacterial or viral infection is impaired in Il6 knockout mice (Kopf et al., 1994)Genetically disrupting Il6 in mice impairs liver regeneration and causes liver failure (Cressman et al., 1996)Transgenic mice overexpressing human IL6 are substantially smaller and have reduced levels of circulating Igf1 (De Benedetti et al., 1997). Here, IL6 is linked to viral infectious disease.