LTF and chronic rhinosinusitis with nasal polyps: Since it has been described that submucosal glands [55], [56] and also certain antimicrobial proteins, most notably lactoferrin [57], [58], are diminished in CRSwNP, our results for the MUC5B and lactoferrin secretions could be indicating that there is a glandular phenotype in control NM ALI cultures, that may be not well developed during the mucociliar differentiation of NP epithelial cells.