Upregulatory Effects of Interleukin-4 and Interleukin-13 but Not Interleukin-10 on Granulocyte/Macrophage Colony-Stimulating Factor Production by Human Bronchial Epithelial Cells

Airway epithelial cells are known to produce a granulocyte/macrophage colony-stimulating factor (GM-CSF), which induces eosinophilic inflammation in bronchial asthma. Interleukin-4 (IL-4), IL-10, and IL-13 produced by Th2 cells are involved in the pathogenesis of bronchial asthma. To assess their contributions to airway inflammation, we examined their effects on GM-CSF production by bronchial epithelial cells. Human bronchial epithelial cells were obtained under bronchoscopy from 21 patients with various respiratory diseases and incubated with or without IL-4, IL-10, or IL-13. Then the GM-CSF concentrations in the cell-free supernatants were measured by enzyme-linked immunosorbent assay. Results showed that IL-4 and IL-13 stimulated GM-CSF production by the epithelial cells dose-dependently, whereas IL-10 did not. The eosinophil survival-stimulating activity in the culture supernatants was closely correlated with GM-CSF concentration and was neutralized by anti-GM-CSF antibody. Thus, IL-4 and IL-13 may contribute to airway inflammation by upregulating GM-CSF production by bronchial epithelial cells.