Objective:To investigate the expression and the effects of CD40/CD40L in lung tissue of rabbits with hemorrhagic shock.Methods:18 healthy rabbits were randomly divided into control group(group A)

hemorrhagic shock 1 hour group(group B) and hemorrhagic shock 2 hours group(group C)

with 6 rabbits in each group.Except the rabbits in the control group

rest rabbits were made into hemorrhagic shock models with lung injury according to Wiggers modified method.TNF-α、IL-10 in plasma were measured by ELISA.Expressions of CD40 and CD40L in lung tissue were measured by immunohistohemistry.Water quantity and pathological change in the lung were observed.Results:The lung of group B and C displayed obvious injury

water quantity increased(P<0.05).Compared with group A

plasma concentration of TNF-α and IL-10 in group B and C increased obviously(P<0.01)

and the concentration of TNF-α at the 2nd hour of hemorrhagic shock increased obviously than at the 1st hour(P<0.01).The immunohistohemistry results revealed that CD40 and CD40L expressed in the lung tissue after hemorrhagic shock but not in the normal.Conclusion:The alteration of CD40 and CD40L expression may participate in the generation and development of lung injury during hemorrhagic shock.