TLR4 and COVID-19: To evaluate the functionality of the innate immune cells in COVID-19, we performed ex vivo stimulation of whole blood with different pathogen-associated molecular patterns (PAMPs): bacterial LPS, a TLR4 ligand; R848, a synthetic ligand for TLR7/8; and Pam3CSK4 (PAM), a synthetic ligand for TLR1/2.