Pulmonary immunology.

The lower respiratory tract of normal healthy individuals is kept sterile and disease-free by formidable local and systemic immune system defenses. In patients with AIDS, these defenses are severely compromised. Undoubtedly, alterations in both local and systemic forces make the host vulnerable to infection by opportunistic organisms. Indeed, substantial evidence suggests that at least a small percentage of macrophages, which normally function alone and in concert with other immune components, can be and are infected with HIV, and do not function normally. Abnormalities with lymphocytes in the lung may contribute to macrophage defective function. Further investigations into the role of lung macrophages and other lower respiratory tract defenses are needed if we are to comprehend fully the mechanisms that lie behind the multitude of pulmonary complications associated with AIDS.