• Chronic bacterial infections occur because thick secretions are not well removed from the lung. Alterations in the lung airway surface liquid (ASL) affect the body’s natural antibacterial defenses.

• Inflammation causes continuing injury to the lung that leads to scarring and loss of function. This process is exaggerated because CF cells produce inflammatory chemicals called mediators, even in the absence of infection.

The primary site of lung injury is within small airways called bronchioles. Think of the anatomy of the human airway as an inverted tree -- the trachea is the hollow trunk and the bronchioles the smallest stems before the leaves. The outer wall of the ‘trunk’ is comprised of connective tissue and muscle that gives shape and structure, but is flexible to allow coughing. The inside layer is covered by epithelial cells containing CFTR and other ion channels, cells with cilia and cells that secrete components of the ASL. In CF, the ASL is abnormally thick and viscous because it contains thick mucus, bacteria, neutrophils - white blood cells attempting to kill the bacteria - and cell debris like DNA remnants from white blood cells. The blockages in the smaller airways caused by thickened secretions can be made worse by swelling of the lining of the airways from constant inflammation.

Select from the menu above to compare the normal lung airway to the lung airway with CF and bacterial infection or with CF and inflammation.