IL17A and chronic rhinosinusitis with nasal polyps: This signalling pathway mainly produces a neutrophil recruitment, and according to the study by Cheng et al. [66], NPDF, upon stimulation by TNF-α, are able to produce increased levels of IL-17A via the PI3K/Akt pathway, thus indicating that NPDF may participate in some way in the T3 inflammatory pathway by recruiting neutrophils in cases of CRSwNP without eosinophilia.