ACE2 and asthma: In the context of SARS-CoV-2 infection, a significant reduction in angiotensin-converting enzyme 2 (ACE2) expression and an increase in transmembrane protease serine 2 (TMPRSS2) expression have been observed not only in the lower airway epithelial cells but also in the nasal epithelial cells of patients with asthma and AR.