HDAC4 and pulmonary emphysema: The miR-22-HDAC4-Th17 axis has been previously studied by Corry et al., who showed that exposure to smoking caused a down-regulation of miRNA 22, with a decrease in HDAC4 and an increase in TH17 immune response, which caused an increase in IL-6 and TNF and resulted in the disruption of the alveolar walls, and the formation of emphysema [13].