Several mediators that inhibit bronchoconstriction have been identified as products of airway epithelial cells. The airway hyperresponsiveness observed in asthma is associated with damage to this layer and, most likely, the phenomenon occurs because of decreased secretion of such epithelium-derived relaxing factors. In addition, the epithelial ciliary escalator, responsible for the clearance of mucus in the airway, may exhibit impaired efficiency.

This presentation will review these aspects of airway epithelial function and will consider the extent to which inhaled cotton and other organic dusts and their constituents may affect the respiratory tract by damaging these components of the lung's homeostatic mechanisms.