Figure 3. SARS-CoV-2 entry molecule proteins are highly present in fully differentiated multiciliated cells, but not in secretory or differentiating cells.

(A–C) Representative images showing subtypes of human nasal epithelial cells. White-dashed boxes in A are magnified in B and C. Scale bar in A: 100 μm. (B) Image showing KRT7^hi secretory- or differentiating-type cells (yellow arrowhead) and KRT5^lo/KRT7^lo fully differentiated multiciliated cells (white arrowhead). Scale bar: 50 μm. (C) Image showing KRT5^hi basal type cells (white arrow). Scale bar: 50 μm. (D) Donut plot showing subtype proportions in 1538 pooled smeared nasal epithelial cells of healthy volunteers (n = 3). (E–J) Representative images and comparisons of relative ACE2, TMPRSS2, and FURIN intensity in the smeared nasal cells, showing high in KRT7^lo fully differentiated multiciliated cells (yellow arrowheads) but very low in KRT7^hi secretory or differentiating cells (white arrowheads). Scale bars: 50 μm. (F, H, and J) Each dot indicates a value obtained from 1 smear sample in 3 volunteers (3 smeared slides per volunteer) from 2 independent experiments. Horizontal bars indicate the mean ± SD. P value versus ciliated cells was obtained by 2-tailed Mann-Whitney U test.