Leukocytic response to inhaled bacteria.

Using histologic techniques, we have quantified the amount of infiltration of bronchi and alveoli by polymorphonuclear leukocytes during the 4 hours after an aerosol inoculation of mice with bacteria. Although the lungs of animals challenged with Staphylococcus aureus differed little from those of animals exposed only to a water aerosol, the lungs of animals exposed to Klebsiella pneumoniae or to Escherichia coli demonstrated significantly greater polymorphonuclear leukocyte infiltrations in bronchi and alveoli 2 and 4 hours afer exposure. These results suggest that the polymorphonuclear leukocyte may contribute to the early defense of the lung against some bacteria.