Intestinal CD11c+ mononuclear phagocytes (MNP) that comprise bona-fide dendritic cells (DC) as well as macrophages (MO) play an important role in the induction of innate and adaptive immune responses upon infection with C. rodentium. Production of IL-23 by MNP is crucial for both the early innate as well as the T cell-mediated host response, since it directly stimulates IL-22-production by ILC3 and also contributes to the development of Th17 cells in the gut [9, 12, 17–19]. Here, IL23A is linked to infection.