IL-4 induces IL-13–independent allergic airway inflammation

BackgroundThe related TH2 cytokines IL-4 and IL-13 are produced during allergic responses, signal through receptors that contain IL-4 receptor (IL-4R) α, and promote allergic inflammation by activating signal transducer and activator of transcription 6. IL-4 promotes TH2 response induction, and IL-13 is necessary and sufficient to induce airways hyperresponsiveness (AHR) and goblet cell hyperplasia in some mouse models of asthma. The nonredundant role of IL-13 could reflect unique IL-13 activation of a signaling pathway, inhibitory effects induced by IL-4 but not IL-13, or greater production-potency of IL-13 than IL-4.ObjectivesWe sought to distinguish among these possibilities by determining whether IL-4 inhalation can induce acute allergic airways disease in the absence of IL-13.MethodsMice were inoculated intratracheally with IL-13 or a long-acting formulation of IL-4. Responses of IL-13–deficient and IL-13–sufficient mice were compared, as were responses in mice treated with a potent IL-13 antagonist, anti–IL-4Rα antibody, or control reagents.ResultsIL-4 inhalation stimulated bronchoalveolar lavage fluid eosinophilia, AHR, and goblet cell hyperplasia. These responses were similar in IL-13–deficient and IL-13–sufficient mice and were not inhibited by an IL-13 antagonist but were blocked by anti–IL-4Rα antibody.ConclusionIL-4 can induce IL-13–independent AHR and goblet cell hyperplasia. Thus the greater role for IL-13 than IL-4 in the induction of these acute allergy-related changes reflects increased production, potency, or both of IL-13 relative to IL-4 rather than a unique IL-13–signaling pathway or a suppressive effect of IL-4.Clinical implicationsDual IL-4/IL-13 inhibition might be more effective than selective IL-13 inhibition at suppressing allergic inflammation in some circumstances.