Mediator release from the airway mucosa.

Mediator release from the bronchial mucosa depends largely on the distribution of target cells in it. While there have been few quantitative studies of these cells, the available data suggest that mast cells increase in concentration from the epithelial lumen to the cartilage and from the trachea to the peripheral airways. As the mucosa is relatively impermeable, it seems likely that mediator release at the luminal surface is an important event. Release at this location is amplified by the fact that the mediators can stimulate the irritant receptors causing reflex bronchoconstriction and render the epithelium more permeable so that more of the antigen can penetrate to the large population of mast cells in the submucosa.