A) Cell differentials of saline- and HDM-treated WT and Htr4−/− mice collected from BALF (n = 17/group). B) Histopathological scoring of HDM-treated WT and Htr4−/− mice for PVI (0–8), PBI (0–8), goblet cell hyperplasia (GC, 0–4), and the combined total (0–20; n = 17/group). C) Total serum IgE levels in saline- (n = 6/genotype) or HDM-treated WT and Htr4−/− mice (n = 18/genotype). D) Expression of Htr4−/− in whole lungs of WT mice after treatment with HDM (n = 6/12 for naïve/HDM). E) Assessment of MCH-induced AHR in saline- vs. HDM-treated WT and Htr4−/− mice. Whole lung resistance (R), Newtonian resistance (Rn), tissue resistance (G), compliance (C), elastance (E), and tissue elastance (H) were measured with flexiVent. Mean values per group with sem are plotted (n = 6/genotype for saline and n = 17/genotype for HDM, *P < 0.05).