A significantly higher percentage of BPIFA1-positive respiratory epithelial cells per 100 μm basement membrane was observed at 48 h after infection in Clca1−/− mice compared to WT mice in the distal trachea with 22.6 and 14.5% BPIFA1-expressing epithelial cells, respectively (p < 0.05; Fig. 7b). The gene discussed is CLCA1; the disease is infection.