TLR9 and COVID-19: The overall analysis of the TLR expression indicated significant upregulation of TLR3 (fold change = 2.78, P = 0.007), TLR7 (fold change = 2.25, P = 0.003), TLR8 (fold change = 2.14, P = 0.028), and TLR9 (fold change = 2.25, P = 0.009) in the epithelial cells from COVID-19 patients compared to the control subjects (Fig. 2).