Allergen-induced airway inflammation and bronchial responsiveness in interleukin-5 receptor alpha chain-deficient mice

Objective: The role of IL-5 Receptor alpha chain (IL-5Ralpha) in the onset of bronchial hyperresponsiveness (BHR) to acetylcholine was investigated by testing IL-5Ralpha knockout (IL-5Ralpha KO) mice.

Methods: Mice were immunized with antigen at intervals of 12 days. Starting 10 days after the secondary immunization, mice were exposed to antigen three times every fourth day. Twenty-four hours after the last antigen challenge, bronchial responsiveness to acetylcholine was measured and bronchoalveolar lavage was carried out.

Results: Twenty-four hours after the last antigen inhalation, total and differential cells counts of bronchoalveolar lavage revealed a significant increase in eosinophils and lymphocytes in ovalbumin-exposed wild-type mice. In IL-5Ralpha KO mice, there was little increase of eosinophils in bronchoalveolar lavage fluid (BALF). The production of IL-5 in BALF increased in both mice after repeated antigen challenge, and there was no significant difference between wild-type and IL-5Ralpha KO mice. Similar to the BAL study, histological sections of lung tissue from ovalbumin-exposed wild-type mice exhibited airway eosinophilic inflammation, which was attenuated by the deficiency of IL-5Ralpha chain. There was no significant difference in serum antigen-specific IgE levels between wild-type and IL-5Ralpha KO mice after immunization nor antigen inhalation. Repeated antigen provocation caused BHR to acetylcholine in wild-type mice. In contrast, no BHR was observed in IL-5Ralpha KO mice after repeated inhalation of antigen.

Conclusion: These findings indicate that IL-5Ralpha plays an important role in the development of antigen-induced airway eosinophilia and BHR in mice.