C. jejuni infection, however, resulted in down-regulation of colonic IL-22 expression in WT animals only, whereas neither IL-23p19 (as well-known master regulator of mucosal immune responses [52]) nor IL-18 (amplifying IL-22 production during intestinal inflammation [50]), were affected upon infection, which is well in line with our very recent results derived in C. jejuni infected conventional mice as well [30]. Here, IL23A is linked to infection.