Morphology of Pneumocystis carinii and activation of the plasmalemmal vesicular system in alveolar epithelial cells of the host. An ultrastructural study.

Lungs from rats with dexamethasone-induced Pneumocystis carinii pneumonia were examined. The ultrastructure of Pneumocystis carinii and their zone of attachment on type I alveolar epithelial cells are described. An activation of the plasmalemmal vesicular system of type I alveolar epithelial cells was observed and is described here for the first time. The significance of this observation is discussed.