Leukocyte recruitment after local endobronchial allergen challenge in asthma. Relationship to procedure and to airway interleukin-8 release

Abstract

We have investigated the profile of cellular recruitment into asthmatic airways after allergen and saline exposure and its relationship to interleukin-8 (IL-8) release. Fiberoptic bronchoscopy was used to instill allergen into the middle lobe while the right upper lobe received a sham saline challenge. Bronchoalveolar lavage (BAL) of both sites was performed either 4 or 24 h later. Neutrophil numbers in BAL fluid obtained 4 and 24 h after challenge were 17 and 48 times higher than prechallenge numbers (p < or = 0.001), but there was no statistically significant difference between the numbers of neutrophils at the two sites. In contrast, eosinophil numbers were increased by 6- and 20-fold, respectively, at 4 and 24 h at allergen-challenged as compared with saline-challenged sites (p < 0.005 and p < 0.02, respectively). Baseline concentrations of IL-8 in BAL fluid were undetectable in most cases. Four hours after allergen or saline exposure, BAL fluid IL-8 concentrations were: median, 200 pg/ml; range, 20 to 750 pg/ml and median, 123 pg/ml; range, < 20 to 800 pg/ml, respectively. These declined to 23 pg/ml (range, < 20 to 126 pg/ml) and 43 pg/ml (range < 20 to 130 pg/ml), respectively, 24 h after exposure. There was a significant correlation between neutrophil numbers and IL-8 concentrations 4 h after saline exposure. These findings indicate that neutrophil infiltration is a nonspecific response to the procedure of bronchoscopy and lavage, in contrast to eosinophil recruitment, which is an allergen-specific phenomenon, and it suggests that IL-8 release may be involved in neutrophil recruitment.