IL17A and chronic obstructive pulmonary disease: Wang et al. reported that COPD patients had higher levels of circulating Th17 cells, serum IL-1β, IL-6, IL-17A, IL-21, IL-22, IL-23, and TGF-β, but lower levels of Tregs and IL-10, which accounted for the dramatically higher ratio of Th17 to Tregs than that in HCs.