Maintain sterility by producing mucus containing antimicrobial compounds.[23] Mucus contains glycoproteins, e.g., mucins, lactoferrin,[24] lysozyme, lactoperoxidase.[25][26] We find also on the epithelium Dual oxidase 2[27][28][29] proteins generating hydrogen peroxide, useful for hypothiocyanite endogenous antimicrobial synthesis. Function not in place in cystic fibrosis patient lungs.