TLR4 and fibrosis: The concept that signaling of HMW HA via TLRs may initiate repair-promoting inflammatory processes in the lung that maintain epithelial cell integrity upon acute injury has recently been supported by a study showing that HMW HA and TLR4 are both expressed on AECII cells and cooperate in promoting the renewal of these cells thereby preventing severe BLM-induced fibrosis in mice [187].