Abstract： Objective To investigate the expression of macrophage migration inhibitory factor (MIF) and CD_(74), the receptor of MIF, in preeclamptic placenta and its correlation with the pathogenesis of preeclampsia.Methods From March 2008 to November 2008,69 preeclamptic women who delivered in the Department of Obstetrics, Affiliated Hospital of Qingdao University Medical College,were recruited,including 33 women with mild preeclampsia (MPE group) and 36 women with severe preeclampsia (SPE group).Another 43 healthy pregnant women were taken as control group.Immunoturbidimetry was applied to measure the concentrations of C-reactive protein (CRP) in maternal blood.The expressions of MIF and CD_(74) in placenta were tested with immunohistochemistry and the expressions of MIF mRNA and CD_(74) mRNA were detected by semiquantitative RT-PCR.The relationship between maternal blood level of CRP and MIF mRNA and CD_(74) mRNA in placenta was analyzed in the MPE and SPE group.Results (1) MIF and CD_(74) were expressed in the placenta of all pregnant women in the 3 groups, as shown in brown-yellow color, and significantly higher expression was found in the MPE and SPE group.(2) The expression of MIF mRNA and CD_(74) mRNA in the MPE group (0.70±0.13 and 0.96±0.16), SPE group (0.88 ± 0.12 and 1.08 ± 0.15) were significantly higher than in the control group (0.67 ± 0.11 and 0.83 ± 0.14) (P < 0.01), and statistical significance was also found between the MPE and SPE group (P <0.01).(3)The maternal blood concentrations of CRP in the MPE and SPE group were significantly higher than in the control group [(15.3±7.0) mg/L and (21.6±9.1)mg/L vs (4.8 ± 1.8) mg/L, P <0.01] , and significant difference was also found between the MPE and SPE group (P <0.01).(4) In the two preeclamptic groups, the blood concentrations of CRP were positively correlated with the expression of both MIF mRNA(r =0.67 ,P <0.01)and CD_(74) mRNA(r =0.83 ,P <0.01) in placenta.Positive correlation was also found between the levels of MIF mRNA and CD_(74) mRNA in placenta (r =0.93 ,P < 0.01).Conclusions Overexpression of MIF and CD_(74) in the placenta may up-regulate the CRP level in maternal blood, resulting in systemic inflammatory reaction and vascular endothelium damage which may be involved in the pathogenesis of preeclampsia.