Macrophages

Alveolar macrophages play a critical role in innate and acquired immunity, in the defense of the respiratory tract against pathogens, and in the clearance of inhaled particles. They also play an important role in the inflammatory response and there is increasing evidence that they play a pivotal role in the pathophysiology of COPD. Because of the extraordinary diversity of macrophage responses they can account for most of the known features of COPD (1-5) (Fig. 1).