IL17A and chronic obstructive pulmonary disease: The expression of both IL-17A (2.4 ± 0.6 fold increase, P < 0.05) and F (3.7 ± 0.7 fold increase, P < 0.05) in the tissue from non-COPD subjects was significantly increased after exposure to 5% of CSE at 3 h, which returned to baseline by 6 h (Figure 1A).