IL-1β, IL-6, IL-17A, and RORγT protein expression, but IL-10 was significantly decreased and there were no changes in IL-21 and IL-22 between the COPD patients and non-smoking controls (4 out of 6 enrolled samples were randomly selected for western blot tests from control and COPD group respectively, Fig. 1B–G). Here, IL21 is linked to chronic obstructive pulmonary disease.