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 r eceived intravenous staphylococcal enterotoxin-A (SEA) showed that most of the neutrophils were found in the second of 5 fractions of fluid removed fr om the lungs. To determine whether this finding reflected an accumulation o f neutrophils in the airways versus the alveolar regions of the lungs, we c ounted the neutrophils in histologic sections (20 microns) and estimated th e concentration of neutrophils in the epithelial lining fluid of the airway s 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 f actor 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 inject ion of SEA showed that neutrophils most likely Entered the alveolar region in response to SEA and migrated into the airways. The single-cycle techniqu e provides a reliable measure of the relative concentration of neutrophils in the airways versus the alveoli.