1. MSCs mitigate airway hyperresponsiveness (AHR) and reduce airway resistance and neutrophil counts in acute AAI.2. MSCs reduce IL-17a and IL-6 in airway fluid during acute AAI.3. MSCs show limited effects in recurrent AAI.4. Effects may involve suppression of Th17 pathways. Here, IL6 is linked to airway hyperresponsiveness.