Background The aim of this study was to investigate the potential relationship between the dynamic expression of Toll-like receptor 2 and 4 (TLR2/4) in peripheral blood mononuclear cells as well as changes in serum concentration of inflammatory factors and acute lung injury (ALl) in patients after orthotopic liver transplantation (OLT).Methods The peripheral blood samples of 27 patients (23 men and 4 women with ASA Ⅲ to Ⅳ) who received OLT were collected for measurement of TLR2/4 at T1 (after induction of anesthesia), T2 (25 minutes after anhepatic phase), T3 (3 hours after graft reperfusion) and T4 (24 hours after graft reperfusion). The expression of TLR2/4 in mononuclear cells was measured by flow cytometry. The serum concentrations of tumor necrosis factor (TNF)-a, intedeukin (IL)-113 and IL-8 were measured by enzyme-linked munosorbent assay (ELISA). Twenty-seven patients were assigned to ALI group (n=9) and non-ALI group (n=18) according to the diagnostic criteria of ALI. The expression of TLR2/4 in the ALl group or non-ALI group was analyzed.Results Compared to the non-ALI group, the volumes of blood loss, ascites, total output and transfused red blood cells were higher in the ALI group, and the anhepallc phase lasted longer (P<0.05, P<0.01). The expression of TLR2/4 in mononuclear cells increased significantly at T3 and T4, and serum concentrations of TNF-α, IL-1β and IL-8 increased significantly too. There was no significant difference in Child-Turcotte-Pugh (CTP) scores between the ALI group and non-ALl group (P>0.05). The expression of TLR2/4 in mononuclear cells increased significantly at T3 and 14 in the ALI group (P<0.05, P<0.01). A positive correlation was noted between the expression of TLR4 in mononuclear cells and the serum concentrations of TNF-α, IL-1β (P=0.041, P=0.046) in the ALl group. In the non-ALI group, statistical results showed that the expression level of TLR2/4 in mononuclear cells was not significantly different during the peri-operative period of OLT (besides TLR4 expression at T4). Compared to the non-ALI group, the increasing amplitude of TLR2/4 expression in mononuclear cells was more significant in the ALI group. The patients whose TLR2/4 expression in mononuclear cells exceeded that at T1 by one time were more likely to suffer from ALI (P=0.013), with a relative risk of 16.