Objective      To study the mechanism of galectin-9 in inducing immune tolerance of rats after liver transplantation by observing its role in an acute rejection model of rats.       Methods       An acute rejection model of Lewis-BN rats after liver transplantation was established. Thirty rats were randomly divided into transfection group

blank plasmid group

and control group (10 in each group). Rats in transfection group were injected with 2 ml recombinant Ad-galectin-9 through the portal vein

those in blank plasmid group were injected with 2 ml adenoviral vector

and those in control group were injected with 2 ml normal saline during the cold ischemia period. Five rats in each group were sacrificed on day 7 after operation. Survival time of the remaining rats was observed. Degree of acute graft rejection was assayed according to the Banff scale. Expression levels of galectin-9

T-bet and RORγt mRNA

and IFN-γ and IL-17 protein in liver tissue were measured by RT-PCR and Western blot

respectively.       Results      Seven days after operation

the Banff scale wasⅠ to Ⅱin transfection group and Ⅲ in blank plasmid group and control group

  the expression level of galectin-9 mRNA was significantly higher in transfection group than in blank plasmid group and control group (1.14±0.05 vs 0.46±0.03 and 0.49±0.07，P0.05)

while the expression level of T-bet and RORγt mRNA

and IFN-γ and IL-17 protein was significantly lower in transfection group than in blank plasmid group and control group （0.27±0.07 vs 1.26±0.12 and 1.31±0.08

0.57±0.13 vs 1.57±0.09 and 1.58±0.07; 0.39±0.06 vs 1.28±0.11 and 1.47±0.05

0.64±0.07 vs 1.52±0.05 and 1.67±0.04

P0.05).       Conclusion      Galectin-9 can induce immune tolerance of rats after liver transplantation by clearing Th1 and Th17 cells.