As shown in Fig. 2A, the COVID-19 patient–derived EVs-induced NETs formation was suppressed completely in the presence of the vacuolar type H+-ATPase inhibitor bafilomycin A1 (BafA1, 100 nM), suggesting that endolysosomal TLRs such as TLR3, TLR7, TLR8 and TLR9 mediate NETs formation. Here, TLR9 is linked to COVID-19.