Murine pulmonary alveolar macrophages: rates of bacterial ingestion, inactivation, and destruction.

The component processes of phagocytosis (ingestion, inactivation, and destruction of bacteria) were studied in mice by histological and microbiological techniques after aerosol infection with Staphylococcus aureus. Rates of bacterial ingestion and inactivation were (respectively): 0 hr, 37.7% and 0; 1 hr, 64.5% and 45.8%; 2 hr, 75.9% and 67.9%; 4 hr, 82.4% and 84.1%; and 8 hr, 90.7% and 94.8%. Bacterial destruction began 2-4 hr after aerosol infection and affected 80% of the bacteria by 8 hr. Comparison of these processes indicated that bacterial ingestion occurred before inactivation and was 76% complete at 2 hr. Inactivation resulted in death of 84% of the bacteria at 4 hr, and 80% of the bacteria were at least partially destroyed by 8 hr. The mechanism of X-irradiation-induced depression of pulmonary bacterial inactivation was studied in syngeneic mice protected from lethal effects of X-irradiation by chest and pelvic shields or by transplantation of 2 times 10(6) bone marrow cells. Impairments in bacterial inactivation resulted from diminished ingestion of bacteria by macrophages.