ACE2 and chronic obstructive pulmonary disease: IL-4 and IL-13, which are cytokines highly produced in Th2/eosinophilic asthma, can downregulate ACE2 expression in airway epithelial cells (Kimura et al., 2020; Song et al., 2020), whereas, TNF, IL-12, and IL-17A, which are cytokines highly produced in Th17/neutrophilic asthma and COPD (Alcorn et al., 2009), can upregulate ACE2 expression in in vitro BEAS-2B cells (Song et al., 2020).