Influx of neutrophils into the airway lumen at 4 h after segmental allergen challenge in asthma

Background: Segmental allergen challenge is a powerful tool to study inflammatory reactions in asthmatic airways. There is little information on the early events at 5 min and 4 h after allergen challenge with respect to the cell influx and the chemokine interleukin-8 (IL-8). Methods: Seven mild to moderate allergic asthmatics (AA group), 5 allergic nonasthmatics (ANA group) and 5 nonallergic controls underwent segmental allergen challenge, with allergen doses based upon skin reactivity. Bronchoalveolar ravage (BAL) samples were obtained before, 5 min and 4 h postchallenge, and were analyzed for cell numbers and differential counts, eosinophil and neutrophil chemotactic activity, and levels of IL-8. Results: At 5 min postchallenge, no changes were observed compared to baseline. At 4 h postchallenge, an increase was found in the number of neutrophils and the levels of IL-8, which was dependent on the dose of allergen in the AA and ANA group. At the same allergen dose, the increases in neutrophils and levels of IL-8 were calculated to be 91 and 67 times higher, respectively, in AA than in ANA. Levels of IL-8 correlated with the number of neutrophils and with the in vitro neutrophil chemotactic activities in BAL fluid. Conclusions: Neutrophil chemotactic activity is increased in BAL fluid at 4 h after segmental allergen challenge. We suggest that apart from IgE-mediated mast cell degranulation, additional local factors in the airways determine the degree of IL-8 increase and neutrophil influx.