Moreover, two studies in broncho-alveolar lavage fluid of COPD patients who were former smokers showed that smoking cessation did not prevent the rates of apoptotic T cells from increasing (49), and, even after 5 years, the percentage of CD8+CD25+ T cells in former smokers remained increased in comparison to never smokers (50), further suggesting a persistent inflammation of the airways after quitting smoking. This evidence concerns the gene CD8A and chronic obstructive pulmonary disease.