Functional properties of peripheral CD8+  T cells in patients with repeated implantation failure.

CD8+ T cells are the main candidates to recognize and respond to fetal HLA-C at the fetal-maternal interface, but data on the amount of peripheral CD8+ T cells and their functions during the window of implantation in recurrent implantation failure (RIF) patients are limited. Peripheral blood was obtained from 56 women with RIF and 16 fertile women in the mid-luteal phase of the menstrual cycle, and the CD8+ T cells were determined by FACS analysis. No statistical differences in the proportion of peripheral CD8+ T cells were observed among the women with RIF and the control group. However, the levels of IFN-γ+ and TNF-α+ CD8+ T cells in the RIF group were significantly higher than those in the control group. The cytolytic activity and regulatory proportion of CD8+ T cells in RIF were similar to that in the control group. Our data indicated that the elevated expression levels of IFN-γ and TNF-α in peripheral CD8+ T cells may contribute to an impaired immune tolerance in women with RIF.