AHR and asthma: To determine the significance of epithelial AhR in cockroach allergen–induced asthma, we deleted AhR selectively from type II alveolar airway epithelium (AT2) by crossing floxed AhR mice (AhRf/f) with Sftpc-cre mice that express the Cre recombinase in AT2 cells from the endogenous promoter/enhancer elements of the surfactant protein C (Sftpc) locus (Sftpc-Cre; AhRf/f, Figure 1A).