Smokers with chronic obstructive pulmonary disease (COPD) had higher number of CD8 T cells in both lung parenchyma and pulmonary arteries compared with asymptomatic smokers and nonsmokers [61].This may be related to the enhanced expansion of CTLs by nicotine (Fig. 2A) and/or to biased migration [62]. Here, CD8A is linked to chronic obstructive pulmonary disease.