Role of CD56 and CD57 Uterine Natural Killer Cells and E-cadherin in Either Successful Implantation or Recurrent Abortion

Introduction Women with recurrent early pregnancy loss may have impaired receptor expression in natural killer cells, which regulate implantation through receptor–ligand interactions. Unexplained miscarriages have immunological background whenever decidual tissue is formed; natural killer cells are invariably present, which may have a role in implantation. This process might lead to downregulation of adhesion molecule involved in cell–cell interactions. Aim of the study The aim of this study was to investigate the role of uterine natural killer cells and E-cadherin in human endometrium of nonpregnant women and of those with recurrent abortion to find out their role in implantation or recurrent abortion. Materials and methods Sixty-five samples were collected from Egyptian women (in the first trimester with unexplained repeated spontaneous abortion and endometrial biopsies from nonpregnant fertile state). Sections were immunostained by CD56, CD57, and E-cadherin. Results We found that CD57+ natural killer cells may have a role in the normal fertile cycle. However, CD56+ natural killer cells are highly expressed in women with recurrent abortion. Conclusion There is switching of receptors on natural killer cells, which may downregulate E-cadherin expression at chorionic trophoblasts and which may affect the adhesion to the placental bed, thereby interfering with embryo implantation and pregnancy.