IL17A and airway hyperresponsiveness: Both age groups showed potent inflammatory/allergic responses to HDM, but only older HDM-exposed mice had lower lung compliance and increased airway hyperresponsiveness compared with age-matched controls, increases in tissue bronchiolitis, perivasculitis, and BALF neutrophilia relative to their younger counterparts, and a higher extent of immunostaining for IL-4, IL-13, IL-17A and IFN-γ compared with the other groups.