Allergen exposure increases airway hyper-responsiveness and lung inflammation. (A) Timeline of the study design. The rats received 2 intraperitoneal injections of saline or OVA-Al(OH)3 [1 mg OVA (Grade III; Sigma) and 100 mg Al(OH)3, in 1 ml saline] on day 0 and day 7, and 14 inhalation exposures (for 30 min, every 2 days, from day 14 to day 40) with aerosols of saline or OVA solution (2% wt/vol). (B) Hematoxylin and eosin (H&E) staining of lung sections to identify peribronchial inflammatory cell infiltration (Scale bar = 50 μm). (C) Airway hyper-responsiveness in response to increasing doses of methacholine. Data are presented as percent of baseline, expressed as mean ± SEM, and analyzed by repeated measures two-way ANOVA, with the Bonferroni post-hoc test, n = 7 per group. (D,E) Total BAL inflammatory cells and eosinophils, respectively. The horizontal bars represent mean values. Data were analyzed by t-test, n = 7 per group. *p < 0.05, ***p < 0.001 and ****p < 0.0001 compared to control. OVA, ovalbumin.