These results are partly supported by our very recent infection studies in mice haboring a conventional intestinal microbiota, given that colonic IL-22 mRNA were down-regulated in infected conventional IL-23p19-/- mice and vice versa (i.e. colonic IL-23p19 mRNA down-regulated in infected conventional IL-22-/- mice) (Heimesaat et al., Gut Pathogens, in press). This evidence concerns the gene IL23A and infection.