Using a novel knock-in mouse model for MyD88, we report here that MyD88 signaling in CD11c+ dendritic cells (DC) is sufficient to activate RORγt+ group 3 innate lymphoid cells (ILC3) as well as Th17/Th1 cells in response to infection with C. rodentium. In contrast, restricting functional MyD88 signaling to several other immune cell types, including macrophages (MO), T cells and ILC3 did not result in intestinal immunity, while expression of MyD88 in intestinal epithelial cells (IEC) mainly enhanced epithelial barrier integrity. This evidence concerns the gene MYD88 and infection.