Effect of alveolar lining material on phagocytic and bactericidal activity of lung macrophages against Staphylococcus...

Unstimulated rabbits were sacrificed and their lungs washed with heparinized saline. After alveolar macrophages were harvested, the cell-free lavage fluid was centrifuged at 47,000 X g to recover a small, whitish, surface-active pellet (F fraction.) The supernatant was concentrated 15-fold by vacuum dialysis (P fraction). Alveolar macrophages in a serum-free system were challenged with radiolabeled (32P) Staphylococcus aureus preincubated in either balanced salt solution or F or P fraction. A small increase in alveolar macrophage bacterial uptake occurred with P fraction-treated staphylococci. P fraction from locally immunized animals further enhanced phagocytosis. In bactericidial experiments, alveolar macrophages were allowed to phagocytize staphylococci preincubated in either balanced salt solution or F fraction. Intracellular bactericidal activity of alveolar macrophages was quantitated by lysotaphin lysis of extracellular bacteria and quantitation of viable intracellular bacteria. Enhanced lung macrophage bactericidal activity against F fraction-incubated staphylococci was noted.