TLR3 and COVID-19: We determined whether TLR3 mediated the immune response to COVID-19 plasma exosomes by treating PBMC with the dsRNA/TLR3 small molecular inhibitor, a competitive inhibitor of dsRNA binding to TLR3 with high affinity and specificity17,45, followed by stimulation with COVID-19 or non-COVID-19 control plasma exosomes and flow cytometry.