As shown in Figure 2 and Additional file 1, mice immunized and challenged with OVA showed significantly increased AHR following methacholine exposure compared with the control animals (PBS group), which received only the i.n. OVA challenge but were not pre-sensitized by OVA immunization, indicating that the OVA-immunized/challenged mice developed symptoms of allergic asthma. This evidence concerns the gene AHR and allergic asthma.