TLR2 and acute respiratory distress syndrome: Hyaluronic acid produced by tissue injury is mediated by TLR2/4, which contributes to the development of ARDS.8 Endotoxin release from Gram-negative bacteria is mediated by TLR4.9 In addition, TLR3 mediates hyperoxia-induced ARDS,10 whereas TLR2 mediates bleeding-induced ARDS.11 In addition to membrane-bound PRRs, the PRRs in the cytoplasm, such as the NLRP3 inflammasome, can recognize PAMPs and DAMPs indirectly.