Interleukin-5 and interleukin-8 in relation to eosinophils and neutrophils in nasal fluids from school children with seasonal allergic rhinitis

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Abstract
The objectives of this study were to measure interleukins 5 and 8 (IL-5 and IL-8) in relation to eosinophils and neutrophils, in nasal lavage fluids from 60 school children with allergic rhinitis, and to determine the influence of treatment with a topical steroid (budesonide) on the levels of the two cytokines. Highly sensitive enzyme immunoassays were used to analyze IL-5 and IL-8. IL-5 levels and relative eosinophil counts in nasal lavage fluid increased significantly in patients with allergic rhinitis during the pollen season, compared with values obtained before the start of the season, and decreased significantly after treatment with budesonide. By contrast, no significant changes in IL-8 or neutrophils were found during the pollen season, nor did they decrease following treatment. In the untreated patients, IL-5 levels correlated significantly with eosinophil counts but not with neutrophil counts, whereas IL-8 levels correlated with neutrophil counts but not with eosinophil counts. After budesonide treatment, the correlation between IL-8 and neutrophils remained, and a correlation between IL-8 and eosinophils emerged. These findings support the concepts that IL-5 has a key role in regulating eosinophils and that IL-8 is important for the regulation of neutrophils. Whereas IL-5 and relative eosinophil counts are profoundly affected by topical steroid treatment, IL-8 and neutrophils are not demonstrably affected by such treatment. It is possible that neutrophils, through the release of IL-8, could be chemotactic for eosinophils in steroid-treated patients.