Asthma was induced as in Materials and Methods. Anti-IL-13 (0.5, 2, 8, or 200 μg/injection), or Rat IgG2a (200μg/injection) was administered i.p. 48 hours before, and 48 hours after each HDM exposure. (A) methacholine-induced AHR was measured by Flexivent. BALF was collected, and the number of macrophages (B), eosinophils (C), neutrophils (D), and lymphocytes (E) were assessed. Data are mean ± SEM of n = 6–12 mice from 2 independent experiments. **p < 0.01, ***p < 0.001, and **** p < 0.0001 versus PBS. † < 0.05 versus isotype.