FOXN4 and COVID-19: Compared to the female patients with critical COVID-19, men with critical COVID-19 have elevated abundances across five epithelial cell types: ciliated-differentiating (ciliated-diff; p < 2.0 × 10−16, Fisher’s exact test), FOXN4-positive cells (FOXN4+; p = 6.1 × 10−5), secretory (p < 2.0 × 10−16), secretory-differentiating (secretory-diff; p < 2.0 × 10−16), and squamous cells (p < 2.0 × 10−16).