Biochemical definition of human tracheobronchial mucus

Tracheobronchial mucus is a heterogeneous milieu produced by several cell types. It has viscoelastic properties related to the organization of macromolecular components such as glycoproteins, proteins, lipids and nucleic acids. Proteins comprise components antigenically related to plasma proteins and secretory proteins such as kallicrein, lysozyme, amylase, bronchotransferrin, immunoglobulins A and proline-rich polypeptides. Tracheobronchial mucus also contains protease inhibitors and, in pathological conditions, important amounts of protease. Mucins, which are glycoproteins with a very rich carbohydrate content, represent another complex and major group of tracheobronchial molecules.