Role of natural killer cells in reproductive failure

Abstract

Reproductive losses are quite frequent in the modern world. They include: infertility, infertility of unknown etiology, multiple losses when IVF, recurrent implantation failure, miscarriage, recurrent miscarriage, both in the natural cycle and after ART management. It is important to note that the classification of some of these categories are not established yet. The etiology of reproductive losses is extremely diverse. Successful development of pregnancy at early terms is determined by genetic and immunological factors. Among the reproductive failures of unclear etiology, immunological causes are 50-80%. Over the past 20 years there are already known many different immunological factors that play role in the processes of fertilization. In this case, the evidence base on the role of each of them in the pathogenesis of reproductive failures is only being formed. Currently, the immunological relationship between mother and fetus is considered as a two-way communication process: the presentation of fetal antigens on the one hand, and on the other – the recognition and response to these antigens of the maternal immune system. Implantation of the embryo is accompanied by an increase in the production of proinflammatory cytokines followed by a sharp change in the cellular composition in the decidualizing endometrium, and the main population is NK cells. That is why this type of cells have a significant role in the normal development of pregnancy. The properties of NK cells in the uterus and peripheral blood are significantly different. To predict the onset and prolongation of pregnancy, peripheral blood NK (activity and quantity) is used. Evaluation of endometrial NK is often performed for the diagnosis of chronic endometritis. Currently, the definition of NK cells in peripheral blood in many clinics is proposed as a useful diagnostic test to address the issue of further appointment of immunoglobulins and evaluating the effectiveness of this therapy in patients with reproductive losses.