Neutrophil influx and migration in rabbit airways in response to staphylococcal enterotoxin-A

Single-cycle lavages performed on the lungs of rabbits 7 hours after they received intravenous staphylococcal enterotoxin-A (SEA) showed that most of the neutrophils were found in the second of 5 fractions of fluid removed from the lungs. To determine whether this finding reflected an accumulation of neutrophils in the airways versus the alveolar regions of the lungs, we counted the neutrophils in histologic sections (20 microns) and estimated the concentration of neutrophils in the epithelial lining fluid of the airways versus the alveoli. Comparisons of the morphometric measurements and the lavage data showed a strong correlation between the 2 methods (r = .90, P < .001), but the lavage technique underestimated the morphometric value by a factor of 7. The histologic examination confirmed that the concentration of neutrophils in the airways was 3-4 times higher than in the alveoli. There were no differences between the alveoli and the airways with respect to the concentration of endogenous proteins and the chemoattractant, interleukin (IL)-8. Lavages performed in additional rabbits 4 and 18 hours after injection of SEA showed that neutrophils most likely entered the alveolar region in response to SEA and migrated into the airways. The single-cycle technique provides a reliable measure of the relative concentration of neutrophils in the airways versus the alveoli.