Inflammation is part of your body's immune system response to something harmful or irritating, such as germs or damaged cells. White blood cells, blood, and fluids rush to the affected site to destroy the irritant and flush it from the body, often causing swelling, redness, and heat in that area. In the lungs, an immune response causes swelling that narrows the airways and makes it harder to breathe. An increased cough is often a sign of inflammation.
When the lungs are infected with bacteria, white blood cells release enzymes, called proteases, to break down the structural proteins in bacteria and eliminate the threat. Once the infection is gone, other chemicals signal the white blood cells to stop the attack. However, in people with cystic fibrosis, these chemical signals often are not released or are not plentiful enough to reverse the inflammatory response and prevent the destruction of healthy lung tissue.