In Vitro Studies of the Foamy Macrophage of Postobstructive Endogenous Lipoid Pneumonia in Man

Alveolar macrophages were washed from lung parenchyma distal to a bronchus obstructed by a tumor and were isolated by glass adherence. Control cells were obtained similarly from resected lungs of patients with nonobstructive endobronchial tumors. The cells from the patients with obstructive tumor were larger than normal and contained large lipid-filled vacuoles, giving them a foamy appearance; they also contained inclusions similar to those seen in normal alveolar macrophages. The cells that adhered to glass had a normal phagocytic rate for their size. Like normal alveolar macrophages, their phagocytic rate was depressed by low oxygen tension but not by high carbon dioxide tension. After the foamy macrophages from 5 patients were cultured in vitro for 4 hours, a white precipitate formed in the medium. The material was removed by centrifugation, and the lipid discharged into the cell culture medium from the cells of 2 of the patients with endobronchial obstruction was analyzed. It contained a high percentage of dipalmitoyl lecithin, the major surface-active component of the lung-lining layer. This finding is compatible with the suggestion that lung macrophages have a role in surfactant metabolism in patients with obstructed bronchi. No similar material could be separated by centrifuging medium from normal macrophages. The histories of the patients, the course of their illness, and the histologic appearance of the surgical specimens suggested that infection is not essential to the accumulation of foamy macrophages.