IL17A and chronic obstructive pulmonary disease: Grumelli et al. found that emphysema‐related pathological changes in patients with COPD were strongly correlated with Th1‐related immunity,43 whereas the Th17 cell population and its related cytokines, IL‐17 and IL‐22, were strongly associated with the generation and exacerbation of COPD.66, 92, 93