2Oropharyngeal candidiasis (OPC) is an opportunistic infection of the oral mucosa caused by the 3 commensal fungus C. albicans. IL-17 receptor signaling is essential to prevent OPC in mice and 4 humans, but the individual roles of its ligands, IL-17A, IL-17F and IL-17AF, are less clear. A 5 homozygous IL-17F deficiency in mice does not cause OPC susceptibility, whereas mice lacking 6 IL-17A are moderately susceptible. In humans, a rare heterozygous mutation in IL-17F (IL-7 17F.S65L) was identified that causes chronic mucocutaneous candidiasis, suggesting the existence 8 of essential antifungal pathways mediated by IL-17F and/or IL-17AF. To investigate the role of 9