IL17A and periodontitis: Moutsopoulos and his group have comprehensively investigated the role of the microbiota and its metabolites in induction of the local immune cells of the oral mucosal immune system, focusing on the interleukin-17 (IL-17)/T helper 17 (TH17)-dependent pathways that control the two major oral infectious diseases, periodontitis and candidiasis [85,86].