An overview of pulmonary host defense

Abstract

In response to a constant barrage of inhaled and aspirated material, the lung has evolved a sophisticated multi-tiered system of defense. Components of this system include mechanical and biochemical barriers, phagocytic scavengers, and specific cellular and humoral immune responses. A breakdown of individual components of this system is frequently associated with the inability to maintain a sterile milieu and the consequent development of respiratory tract infection.