Abstract: Objective：To investigate the expressions of IDO and Foxp3 genes in the peripheral blood mononuclear cells（PBMCs) of patients with recurrent implantation failure during midluteal phase. Methods：Fifty patients with recurrent implantation failure（group 1）, 50 women with normal fertility（group 2） and 50 women with IVF-ET and pregnancy in their first cycle（group 3） were recruited with consent. Samples of 2 mL peripheral blood were got at their midluteal phase, and mononuclear cells were isolated. Expressions of Foxp3 and IDO mRNA were detected by real-time quantitative-PCR. Results：There was significant difference in expressions of Foxp3 mRNA and IDO mRNA among three groups（P＜0.05）. Expressions of Foxp3 mRNA and IDO mRNA in group 2 and group 3 were significantly higher than those in group 1（P=0.000），while expressions of two genes in group 2 were significantly higher than those in group 3（P＜0.05）. Conclusions：The lowered expressions of Foxp3 mRNA and IDO mRNA in PBMCs of patients during phase may be related with their recurrent implantation failure.

Key words: Embryo implantation, Dioxygenases, Forkhead transcription factors, RNA, messenger, Luteal phase