TLR9 and COVID-19: MicroBeads selected CD4+ T cells, CD8+ T cells, and CD14+ monocytes from PBMCs were treated with plasma exosomes from early-stage COVID-19 patients and non-COVID donors for 16 h at 37 °C, followed by flow cytometry for expression of TLR3, TLR7, TLR8, and TLR9 gating on live cells.