TLR4 and acute respiratory distress syndrome: Some TLR4-activated danger-associated molecular pattern (DAMP) signals, including oxidized 1-palmitoyl-2-arachidonoyl-phosphatidylcholine (OxPAPC) and high-mobility group box 1 (HMGB1), are increased in the acute lung injury (ALI) caused by respiratory viruses such as the influenza virus (125, 126).