Objective        To investigate the expression  of CD200/CD200R in septic acute lung injury in rats.       Methods       Thirty-six Wistar rats were randomly divided into the sepsis group and sham-operation control group. Sepsis was induced by cecal ligation and perforation. Rats of the 2 groups were respectively sacrificed in 8

16

and 24 h respectively after model establishment. Blood samples were collected from the abdominal artery of rats for blood gas analysis. Tissues from lung of rats were embedded for histological analysis

and wet/dry weight. The serum level of IL-4 were determined by ELISA. The expression of CD200/CD200R in the lung tissue at mRNA and protein levels was measured by RT-PCR and Western blotting.       Results      CD200/CD200R expression at mRNA and protein levels was significantly lower in septic acute lung injury group than in control group in 8 and 16 h after injury (P0.05)

but not in 24 h (P0.05). In septic acute lung injury group

the levels were highest in 24 h

followed by those in 16 h and in 8 h (both P0.05). The highest levels in 24 h were then decreased gradually to the levels of sham-operation control. Arterial blood gas analysis showed there was no significant in partial pressure of oxygen in 8 h between the 2 groups. The pressures in 16 and 24 h were respectively higher in septic acute lung injury group than in control group (P0.05). As the disease progressed

the pressure of oxygen was reduced gradually in septic acute lung injury group. There was no significant difference in IL-4 level at 8 h between septic acute lung injury group and control group. IL-4 level was higher in 16 and 24 h in septic acute lung injury group than control group  (P0.05)

which became higher with progress of the disease. There was no significant difference in lung wet/dry weight ratio in 8 h between septic acute lung injury group and control group. ratio was higher in 16 and 24 h in septic acute lung injury group than control group (P0.05)

which was increased with the progression of the disease (P0.05). The pathological damage of septic acute lung injury group became severe with the disease progression

but no such change was found in the control group.       Conclusion      Expression of CD200/CD200R at mRNA and protein levels is decreased in the lung in rats at early stage of septic acute lung injury

and then restore to the levels of control group. CD200/CD200R is involved in the progression of septic acute lung injury.