Bronchial epithelium and asthma.

The bronchial epithelium has a number of mechanical functions, including mucociliary clearance and protection against noxious agents. It may also modulate the function of the underlying smooth muscle by metabolism and regulation of mediators and the production of relaxant or constrictor substances, and regulate the activation and differentiation of lymphocytes and mast cells by releasing chemotactic factors and cytokines. It is possible that epithelial structural and functional abnormalities may lead via several mechanisms to increased bronchial responsiveness in asthmatic subjects.