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 inflam matory reactions in asthmatic airways. There is little information on the e arly events at 5 min and 4 h after allergen challenge with respect to the c ell influx and the chemokine interleukin-8 (IL-8). Methods: Seven mild to m oderate allergic asthmatics (AA group), 5 allergic nonasthmatics (ANA group ) and 5 nonallergic controls underwent segmental allergen challenge, with a llergen doses based upon skin reactivity. Bronchoalveolar ravage (BAL) samp les were obtained before, 5 min and 4 h postchallenge, and were analyzed fo r cell numbers and differential counts, eosinophil and neutrophil chemotact ic activity, and levels of IL-8. Results: At 5 min postchallenge, no change s 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 depen dent 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 co rrelated with the number of neutrophils and with the in vitro neutrophil ch emotactic activities in BAL fluid. Conclusions: Neutrophil chemotactic acti vity is increased in BAL fluid at 4 h after segmental allergen challenge. W e suggest that apart from IgE-mediated mast cell degranulation, additional local factors in the airways determine the degree of IL-8 increase and neut rophil influx.