IL17A and bacterial infectious disease: Therefore, IL-17 seemingly promotes an amplification loop of the inflammatory response upon infection, as previously reported in EAE.52 Importantly, we observed very high susceptibility of Il17−/− and Tcrδ–/− mice to high (4 × 103 CFU) doses of L. monocytogenes, which firmly establishes the protective role of mucosal γδ17 cells against bacterial infection in situ.