The naive airway hyperresponsiveness of the A/J mouse is Kit-mediated

There is a wide variation among humans and mice in airway hyperresponsiveness (AHR) in the absence of allergen sensitization, i.e., naive AHR. Because mast cell (MC) activation is thought to mediate AHR in atopic asthmatic subjects, we asked whether MCs mediate naive AHR in A/J mice. We generated an A/J congenic strain lacking c-Kit by introgression of the Wv mutation, which resulted in the elimination of MCs and the abrogation of naive AHR. Imatinib, which disrupts Kit signaling, also abrogated AHR in A/J mice. Remarkably, introduction of the Vga9 Mitf mutation into the A/J background resulted in the ablation of MCs but did not ameliorate AHR. These results indicate that c-Kit is required for development of AHR in an MC-independent fashion.