Natural killer cell – Wikipedia, Summary answer: The NK cell receptor (NKR) expression profile in pre-pregnancy endometrium appears to have a unique tissue-specific phenotype, different from that found in NK cells in peripheral blood, suggesting that these cells are finely tuned towards the reception of an allogeneic fetus.
Uterine natural killer (NK) cells provide immune-modulation at the interface between maternal decidua and the trophoblast. The aim of this study to evaluate whether there was a significant difference in the number of endometrial CD56+ NK between women with a history of recurrent implantation failure and women who had a live birth.