Yang et al. showed that in patients with moderate or severe COPD receiving treatment with 50/500 μg of salmeterol/fluticasone propionate twice a day for 12 weeks, the proportion of FOXP3+ Tregs in the total CD4+ T-cell population in the peripheral blood was drastically higher than that before treatment [29]. Here, FOXP3 is linked to chronic obstructive pulmonary disease.