Lung cell reactions after inhalation of bacterial lipopolysaccharides

Cells in airway lavage fluid were studied in guinea pigs exposed to an aerosol of bacterial lipopolysaccharide (LPS). The major response after a single exposure was a large increase in the number of macrophages and neutrophils. The neutrophil response decreased markedly after repeated exposure. De-complementation of the animals did not affect the response to a single exposure, nor did exposure to zymosan produce a neutrophil increase. It is suggested that other factors than serum complement activation initiate the neutrophil increase after LPS inhalation. One conceivable mechanism is the activation of pulmonary macrophages.