ObjectiveTo determine whether endotoxin-stimulated alveolar macrophages would attract neutrophils and whether exogenous surfactant treatment would modulate this chemoattraction.DesignAlveolar macrophages were harvested from bronchoalveolar lavage fluid and neutrophils from the blood of anesthetized guinea pigs.SubjectsHartley guinea pigs.InterventionsAlveolar macrophages were suspended in RPMI 1640 and stimulated with 1 [micro sign]g/mL of lipopolysaccharide (LPS), the supernatant removed and the alveolar macrophages were incubated in either RPMI or RPMI with surfactant at two different doses (292 [micro sign]g/mL or 875 [micro sign]g/mL) for 16 hrs.Measurements and Main ResultsThe supernatant was extracted from the alveolar macrophages and placed in a chemotaxis plate and the migration of neutrophils was measured. Chemotaxis of all cell types to be tested was measured by a change of absorbance on a microplate reader set at 492 nm. Results were compared with alveolar macrophages not stimulated with LPS, RPMI alone, and N formyl-methionyl-leucyl-phenylalanine (FMLP).The supernatant of the stimulated alveolar macrophages increased neutrophil chemotaxis as compared with unstimulated alveolar macrophages, and RPMI (p < .05). Surfactant treatment with 292 [micro sign]g/mL significantly decreased LPS-stimulated alveolar macrophages induced neutrophil chemotaxis. Treatment with 875 [micro sign]g/mL of surfactant did not alter neutrophil chemotaxis.ConclusionsAlveolar macrophages stimulation with LPS increased the chemotaxis of neutrophils. Treatment with surfactant at a concentration of 875 [micro sign]g/mL did not alter neutrophil migration; however, treatment with 292 [micro sign]g/mL significantly decreased neutrophil chemotaxis suggesting that at low concentrations, surfactant inhibits chemokine release and may reduce pulmonary neutrophil sequestration in vivo. (Crit Care Med 1998; 26:1414-1418)