Pathogenesis of chronic bronchitis.

Inflammation of the central airways is a prominent feature in subjects with chronic bronchitis. The pathology of chronic bronchitis includes an inflammatory mononuclear cell infiltrate in the airway wall and a neutrophil influx into the airway lumen. The molecular events that produce the inflammation and its pathogenetic role in causing mucus hypersecretion are beginning to be elucidated. The inflammatory cell recruitment to the airways likely involves chemotactic agents derived not only from tissue fluid and invading microbes but also generated by the diseased bronchial epithelium. For example, bronchial epithelial cells synthesize interleukin (IL-8), a potent chemoattractant and activator of neutrophils and lymphocytes. Adhesion of infiltrating leukocytes to resident parenchymal cells in the bronchi and to extracellular matrix also is crucial for the development of airway inflammation. The resultant inflammation likely plays a direct role in the clinical features of the disorder. There is growing evidence incriminating neutrophil and lymphocytes constituents in the initiation and maintenance of cough and mucus expectoration that occurs in subjects with chronic bronchitis.