Interleukin-4 and interleukin-4 soluble receptor alpha levels in bronchoalveolar lavage from children with asthma.

BACKGROUND: In asthma there is increased expression of the Th2-type cytokine interleukin-4 (IL-4). IL-4 is important in immunoglobulin isotype switching to immunoglobulin E and adhesion of eosinophils to endothelium. OBJECTIVE: We hypothesized that levels of IL-4 in bronchoalveolar lavage (BAL) fluid would be increased in stable, atopic asthmatic children compared with controls and that levels of its physiologic inhibitor IL-4 soluble receptor alpha (IL-4sR alpha) would be correspondingly decreased. METHODS: One hundred sixteen children attending a children's hospital for elective surgery were recruited. A nonbronchoscopic BAL was performed, and IL-4 and IL-4sR alpha were measured in the BAL supernatants. RESULTS: There was no significant difference in IL-4 concentrations between atopic asthmatic children, atopic normal controls, and nonatopic normal controls 0.13 pg/mL (0.13 to 0.87) vs 0.13 pg/mL (0.13 to 0.41) vs 0.13 pg/mL (0.13 to 0.5), P = 0.65]. IL-4sR alpha levels were significantly increased in asthmatic patients compared with atopic controls 6.4 pg/mL (5.0 to 25.5) vs 5.0 pg/mL (5.0 to 9.9), P = 0.018], but not when compared with the nonatopic controls 5.2 pg/mL (5.0 to 10.6), P = 0.19]. CONCLUSIONS: Contrary to expectation, IL-4sR alpha levels are increased in BAL from stable asthmatic children compared with nonatopic controls, and we speculate that IL-4sR alpha is released by inflammatory cells in the airways to limit the proinflammatory effects of IL-4.