The eosinophil and the lung.

Current concepts regarding the morphology, constituents, distribution, and kinetics of the eosinophil allow an expanded understanding of the eosinophil's function in health and disease. In particular, certain eosinophil constituents may have beneficial effects (modulation of mast cell-dependent reactions and helminthotoxic properties), while others may produce detrimental effects (tissue destruction). Eosinophils may be clinically important in obstructive and infiltrative pulmonary diseases. In obstructive disease, a peripheral eosinophilia indicates reversibility, and the magnitude of the peripheral eosinophil count correlates with the severity of the reversible obstruction. Concerning infiltrative pulmonary disease, an updated classification of pulmonary infiltrates with eosinophilia, which is based on recognizable causes and syndromes, is presented, and allergic bronchopulmonary aspergillosis, chronic eosinophilic pneumonia, drug reactions, the hypereosinophilic syndrome, parasitic infestations, and the Churg-Strauss syndrome are specifically considered.