PECULIARITIES OF NK CELLS DIFFERENTIATION: CD56dim AND CD56bright NK CELLS AT PREGNANCY AND IN NON-PREGNANT STATE

Natural killer (NK) cells represent a lymphocyte subpopulation which is capable of contact cytolysis of virus-infected cells and tumor cells, being a source of cytokines which stimulate other immunecells and promote immune response. NK cell differentiation is connected with a consequent acquisition of specific NK cell receptors by stem cells and formation of functional characteristics inherent to natural killer cells. The aim of this review was to describe the CD56dim and CD56bright populations of NK cells in the course of their differentiation. The authors describe NK surface receptors and expression of transcription factors at various steps of the NK differentiation. We present comparative characteristics of data concerning cytokines and cellular microenvironment influence upon NK cell differentiation, and examine a phenomenon of existing memory-like NK cells. Uterine NK cell differentiation is of special interest, since these cells represent a special NK cell population which prevails among decidual lymphocytes during pregnancy and participates in the process of placental formation and development. This review considers some features of uterine NK cell differentiation, taking into account a possibility of formation of this NK cell population from both peripheral blood NK pool, and in situ proliferation. Moreover, functional studies of the uterine NK cells allow to get closer to understanding the role of NK cells during pregnancy and abnormality of utero-placental bed regulation by NK cells in cases of pregnancy failure.