IFNAR1 and listeriosis: High levels of interferon-β (IFN-β) have been demonstrated to be associated with host susceptibility to Listeria infection and mice deficient for IFN-β signalling components such as the type I interferon receptor (Ifnar) gene or the interferon regulatory factor 3 (Irf3) gene are more resistant to lethal L. monocytogenes infection [20-25].