MAL and COVID-19: To further explore whether TLR4 receptor is actually activated in COVID-19, in a subgroup of patients and controls, we measured the intracellular TIRAP, also known as Mal (MyD88 adaptor-like), which participates in TLR4 signal transduction where it acts as an adapter for MyD88 recruitment (19); thus, tyrosine phosphorylation of TIRAP is required for adapter signaling and regulates TIRAP interaction with TLR4 and receptor signaling (12).