STAT1 and chronic obstructive pulmonary disease: When we compared expression levels for the smokers with or without COPD with those of healthy nonsmokers, we found that the referred group of smokers expressed the lowest average level of IL-10R2 (Figure 2E), IL-20R1 (Figure 2F), STAT1 (Figure 2G), and STAT3 (Figure 2H) genes.