IL17A and chronic rhinosinusitis with nasal polyps: In summary, although Th17 cells were increased in CRSwNP polyps and not in the periphery, Th17 cells producing IL-17A, IL-17F, IL21, and IL22 were significantly increased in CRSwNP patient polyps and peripheral blood suggesting an altered activation status of those cells both locally and systemically in CRSwNP patients.