During adherent-invasive E. coli (AIEC) infection, systemic administration of IL-18 corrects compromised T-cell IFNγ production and restores Lysozyme+ Paneth cells in Il-22−/− mice, but IL-22 administration fails to restore these parameters in Il-18−/− mice, thereby placing IL-22-Stat3 signalling upstream of the IL-18-mediated barrier defence function. The gene discussed is IL18; the disease is escherichia coli infection.