Airway Mucins: “Aircraft Carriers” in the Apical Surface Fluid

Airway mucins, the major component of airway mucus or apical surface fluid that covers the entire surface of the airways, have been shown to possess multi-factorial functions that are necessary for first line defense, the major function of airway mucus. In this mini-review, I will provide some evidence, both theoretical and experimental, that the multi-factorial functions of airway mucins are most likely due to various bioactive proteins that are tightly associated with mucins. Thus, the first line defense of airway mucus requires both the mucociliary clearance and the activity of various bioactive proteins tightly associated with mucins, which depend on the quality and quantity of airway mucins.