Decidual natural killer cells in recurrent spontaneous abortions

A repeated or habitual miscarriage (PSP) is defined as three or more consecutive losses of pregnancy. In the first three months of pregnancy, habitual miscarriages occur in about 1% of pregnant women, out of which 50% are of an unknown etiology. It is believed that among them, the greatest number is the consequence of an inadequate alloimmune response of a women to the pregnancy. The endocrine and immune systems are in a close interaction during the implantation and maintaining of pregnancy. This communication is the most obvious on endometrium of pregnancy decidua. The aim of the study was to identify the number and the subpopulation distribution of the decidual NK cells in the decidua by using an immunohistochemical method. The research included a group of 30 women who had had two spontaneous miscarriages consecutively in the first three months of their pregnancy, while the curettage after the third spontaneous abortion was histopathologically and immunohistochemically analyzed. The control group consisted of 20 women without a problematic reproductive anamnesis, who had had their pregnancy terminated for social reasons. The criteria for the eliminating from the research were the diagnosed uterus anomalies, positive screening on thrombophilia, as well as women suffering from diabetes melitus and the ones with the thyroid gland function disorder. The number and the phenotype structure of the uterus NK cells were significantly different between the decidua of a normal pregnancy and that in PSP. In the decidua in PSP, there were much more NK cells with the phenotype of the peripheral circulation CD57 and CD56dim, while in the decidua of the control group the dominant cells were the typical uNK cell subpopulation CD56bright. The above mentioned results show that the disregulation of the immunocompetent cells of the decidua, by creating an inadequate cytokine milieu, is one of the mechanism of rejecting the semiallogeneic blastocyst.