Fig. 7.

Coexpression of ACE2 and TMPRSS2 on type II pneumocytes. (A) The amount of Tmprss2 transcript in the indicated organs was quantified by PCR, employing GUSB as a housekeeping reference. The averages of three independent experiments are shown; error bars indicate standard deviations (std err). No specific signal was measured for brain in three out of three experiments. A specific signal was measured for heart in one out of three independent experiments. (B, i) Hematoxylin-and-eosin-stained section of normal lung showing several alveolar spaces, in which alveolar macrophages (M), type I pneumocytes (P1), and type II pneumocytes (P2) are labeled. Scale bar, 20 μm. (ii) Serial section of frame i immunostained for TMPRSS2 using the peroxidase technique (brown) shows strong positive staining in type II pneumocytes and alveolar macrophages. (iii) Serial section of frame ii immunostained for ACE-2 shows strong positive staining in type II pneumocytes and alveolar macrophages. (iv) Serial section of frame iii immunostained with an irrelevant mouse primary antibody (melan-A), as a negative control for frame ii, shows no immunostaining. Alveolar macrophages show a faint brown tint, due to the presence of carbon, but not the strong brown staining of macrophages seen in frame ii. (v) Serial section of frame iv immunostained using goat polyclonal serum as a primary antibody, as a negative control for frame iii. Alveolar macrophages show a faint brown tint, due to the presence of carbon, but not the strong brown staining of macrophages seen in frames ii and iii.