Following intranasal challenge with purified Der p 1, Gilt−/− animals accumulate on average 30% less total cellularity and eosinophilia in the BAL and exhibit decreased expression of mucin-5AC and the Th2 cytokines IL-5 and IL-13 in the lung, suggesting a reduced allergic airway response to Der p 1. The gene discussed is IL13; the disease is Increased total eosinophil count.