The lower respiratory tract is repetitively inoculated with oropharyngeal bacteria and yet
pneumonia is an infrequent event. Efficient mechanisms of antibacterial defense are present
in the respiratory tract that eliminate microbes before their presence or multiplication leads to
disease in the majority of instances. Resident pulmonary defenses consist of aerodynamic
defenses, the mucociliary apparatus, alveolar macrophages, complement, and surfactant.
These resident defenses can be augmented by the development of an inflammatory …