Phagocytosis of Cryptococcus neoformans by alveolar macrophages.

Guinea pig pulmonary macrophages phagocytized but did not kill nonencapsulated cells of Cryptococcus neoformans. The phagocytic process was inhibited by cryptococcal capsular polysaccharide. Pulmonary macrophages, activated by preinjecting heat-killed bacteria into intact animals, did not kill the engulfed yeast cells. Labeled cells of C. neoformans were neither killed nor cleared from guinea pig lungs 6 h postexposure. The results of our experiments indicate that during the first few hours after the lung is exposed to the infectious particle of C. neoformans the pulmonary macrophage does not function primarily to kill engulfed yeast cells. We believe that a rapid yet transient acute inflammatory response probably plays a major role in this process during the first few hours after C. neoformans enters the lung.