In murine experimental acute pneumonia induced by S. aureus infection, the expression of airway mucus component bactericidal/permeability-increasing protein (BPI) fold-containing family A member 1 (Bpifa1), a secretory protein from the respiratory tract that has antimicrobial and anti-biofilm properties to regulate mucociliary clearance,55 was significantly intensified in Clca1−/− mice compared to that from WT mice at 24 hours post-infection.56 The gene discussed is BPIFA1; the disease is pneumonia.