Abstract: Objective:To investigate the signal transduction and expression of STAT4 and STAT6 in placenta of preeclampsia patients and its significance.Methods:The expressions and location of STAT4 and STAT6 in placenta of 30 normal late pregnant women(control group) and 50 preeclampsia patients(including 22 mild cases and 28 severe cases) were observed using Western blot and immunohistochemistry,respectively.Results:The expressions of STAT4 and STAT6 located mainly in the cytoplasm of villous trophoblast cell,the most nucleus were no clear coloring.The expressions of STAT4 and STAT6 were significantly higher and lower than those of control group,respectively(P<0.01).The differences of the expressions between STAT4 and STAT6 in placenta of mild and severe preeclampsia patients were statistically significant(P<0.01).The expressions of STAT4 in the cytoplasm of villous trophoblast cell in two groups were negative correlation with the level of STAT6(r=-0.509,r=-0.617;P<0.01).Conclusions:Both STAT4 and STAT6 paticipate the pathogenic process of preeclampsia,and are related to the severe degree of disease.The high expression of STAT4 and low expression of STAT6 in the villous trophoblast cell of preeclampsia patients can lead to Th1/Th2 imbalance,which may lead to the preeclampsia.