TLR9 and COVID-19: Compared to TLR7 and TLR9, a dramatically elevated level of TLR8 was shown in neutrophils after treatment with COVID-19 patient–derived EVs (MFI, 92.97 ± 25.07 versus 24.48 ± 5.03, P < 0.005, Fig. 2C), and this effect was suppressed in the presence of the TLR8 specific inhibitor Cu-CPT9a (Fig. 2B).