Background: Allergic asthma results from inappropriate T(H)2-mediated inflammation. Both IL-4 and IL-13 contribute to asthma pathogenesis, but IL-4 predominantly drives T(H)2 induction, whereas IL-13 is necessary and sufficient for allergen-induced airway hyperresponsiveness and goblet cell hyperplasia. Although these 2 cytokines share signaling components, the molecular mechanisms by which they mediate different phases of the allergic asthmatic response remain elusive.
Objective: We sought to clarify the role or roles of IL-4 and IL-13 in asthma-pathogenesis.
Methods: We used DNA Affymetrix microarrays to profile pulmonary gene expression in BALB/c mice inoculated intratracheally with ragweed pollen, house dust mite, IL-4, IL-13, or both cytokines. IL-13 dependence was confirmed by comparing pulmonary gene expression in house dust mite-inoculated wild-type and IL-13 knockout mice.
Results: A signature gene expression profile consisting of 23 genes was commonly induced by means of inoculation with house dust mite, ragweed pollen, or IL-4 plus IL-13. Although rIL-4 and rIL-13 treatment induced an overlapping set of genes, IL-4 uniquely induced 21 genes, half of which were interferon response genes and half of which were genes important in immunoregulation. IL-13 uniquely induced 8 genes, most of which encode proteins produced by epithelial cells.
Conclusions: IL-4 and IL-13 together account for most allergen-induced pulmonary genes. Selective IL-4 induction of IFN-gamma response genes and other genes that might negatively regulate allergic inflammation could partially explain the greater importance of IL-13 in the effector phase of allergic airway disease.