The role of TLR4 in the pathogenesis of indirect acute lung injury.

Indirect acute lung injury (IALI) manifests as rapid-onset respiratory failure following secondary clinical events to the parenchyma or lung vasculature, such as hemorrhage shock, extra-pulmonary sepsis, trauma, ischemia-reperfusion, and burn injury. Accumulating evidence demonstrates the pivotal role of pattern recognition receptors (PRRs) in the innate immune system of lung diseases. Toll like receptor 4 (TLR4), one of the well characterized PRRs, recognizes not only the lipopolysaccharide (LPS) of Gram-negative bacteria, but also the endogenous ligands in IALI. In this review, we summarize a variety of reports concerning the role of TLR4 and IALI pathogenesis.