TLR7 and COVID-19: Moreover, increased cytosolic ROS levels were revealed in the neutrophils after being treated with COVID-19 patient–derived EVs (Fig. 2G) and this effect was inhibited in the presence of the NADPH oxidase inhibitor diphenyleneiodonium (DPI, 25 μM), TLR7-specific inhibitor IRS661 (10 μM), or TLR8-specific inhibitor Cu-CPT9a (10 μM).