IL17C and periodontitis: IL-17A is the most extensively studied IL-17 cytokine in periodontitis, followed by IL-17F.35 IL-17RE specifically binds IL-17C, influencing Th17 cell function and enhancing adaptive immunity against pathogens.36 This is also essential in host mucosal defense against infection by enhancing innate barriers.36 IL-17C stimulates expression of epithelial host defense mechanisms, including hBD2 (DEFB4A), S100A8, CCL20, and the CXCL family,37 all of which were downregulated in our study (Supplementary Table 1).