Phagocytosis-induced injury of normal and activated alveolar macrophages.

The present study tested the hypothesis that BCG-activated macrophages become injured when they phagocytose certain particulates. The data indicate that alveolar macrophages obtained from Mycobacterium bovis BCG-sensitized animals were more susceptible to cell death after in vitro incubation with BCG or zymosan than were macrophages from normal animals. Increased susceptibility was dependent on phagocytosis, since incubation with cytochalasin B, a phagocytosis inhibitor, abrogated the effect. Catalase, cytochrome c, and ascorbic acid offered partial protection to the macrophage, suggesting the involvement of free radicals in the generation of cytotoxicity. Not all of the cells from the alveolar populations were equally susceptible to cell death, thus suggesting either heterogeneity in the cell population or a requirement of more than one cell type in the induction of necrosis or both.