Figure 3. ACE2 protein in human lower airways.
a) Large airways (trachea and bronchi) exhibited rare ACE2 protein on the apical surface of ciliated cells. b-d) Small airways (bronchioles) exhibited uncommon to localized apical ACE2 protein in ciliated cells (c, #1 in b) while the adjacent bronchioles (d, #2 in b) lacked protein. Bar = 35 (a), 140 (b), and 70 μm (c, d).