BPIFA1 and chronic rhinosinusitis with nasal polyps: As CLU and SLPI were both found to be localized in the mucous cells of submucosal glands, it is possible that the decreased number of submucosal glands may be an important reason for the reduced expression of AMPs seen in the present study, as well as that indicated by the study on BPIFA1 in CRSwNP [44].