Objective:To investigate the expression of a new cytokine,thymic stromal lymphopoietin (TSLP) and its receptor TSLPR in the villi of human first trimester gestation.Methods:Villi were collected from women who had undergone an artificial abortion at 7-11 weeks of normal gestation.The trophoblast cells (Tros) were isolated and cultured.The total RNA was extracted using TRIzol reagent,from both villi and the Percoll-gradient-isolated Tros,then the DNA fragments of hTSLP and hTSLPR were amplificated by RT-PCR.Villous tissues were detected for TSLP by immunohistochemistry (IHC) and Western blot.Immunocytochemistry (ICC) was carried out on cultured trophoblast cells for TSLP/TSLPR expression.Levels of TSLP in the supernatants were detected by ELISA.Results:Normal villi and the cultured Tros transcript were found to express TSLP/TSLPR mRNA and secreted TSLP protein.In addition,TSLP receptor was also expressed on trophoblasts.Conclusion:Both TSLP and its receptor are expressed on villi and trophoblast cells,which suggests that TSLP plays an important role in maternal-fetal immuno-tolerance in human early pregnancy.