The Role of Cytokines in Maintaining the Dynamics of Cell-Cell Interaction between Natural Killer Cells and Trophoblast Cells.

We analyzed the effect of individual cytokines that are secretory products of placenta typical of the uteroplacental bed. The proinflammatory cytokines IL-6, IFNγ, and IL-1ß increased the expression of TGFßR2 molecule by trophoblast cells, while VEGF and PLGF increased the expression of CD45, CD29, and CD54 adhesion molecule by trophoblast cells. The antiinflammatory cytokine IL-4 increased LeptinR expression by trophoblast cells. PMA and TNFα also enhanced the adhesion of NK cells to trophoblast cells. Our findings suggest that NK cells involved CD11a, CD11b, and CD18 molecules during their transmigration through trophoblast, as well as during their transendothelial migration.

Trophoblast cell influence on peripheral blood natural killer cell proliferation and phenotype in non-pregnant women and women in early pregnancy.

Natural killer (NK) cells are the main population of leukocytes in decidua during the first trimester of pregnancy. NK cells can have contact with trophoblast cells during pregnancy, which raises the possibility of mutual influence. This research aimed to evaluate the proliferation and phenotype of peripheral blood NK cells in the presence of trophoblast cells of the JEG-3 cell line. We showed that trophoblast cells of the JEG-3 cell line (American Type Culture Collection (ATCC), USA) produced TGFß. However, co-culturing of NK and trophoblast cells did not change the SMAD2/3 to pSMAD2/3 ratio within NK cells. These data indicate that the canonical signaling pathway from TGFß is not activated, but do not preclude activation of SMAD-independent signaling pathways through the effect of TGFß and/or other cytokines. We established that trophoblast cells inhibited both constitutive and IL-2-induced expression of Ki-67 proliferation marker by NK cells in vitro in both pregnant and non-pregnant women. Constitutive and induced Ki-67 expression by peripheral blood NK cells was increased in pregnant women compared with non-pregnant women. The influence of trophoblast cells on Ki-67 expression by NK cells was more pronounced in the presence of other mononuclear cells than in their absence. In the presence of trophoblast cells and IL-2, the number of NK cells with the CD16+CD57- phenotype in peripheral blood mononuclear cells (PBMCs) was increased in pregnant and non-pregnant women, compared with culturing with IL-2 only. This might reflect a decrease in the number of NK cells at the terminal stage of differentiation. We also revealed the increased content of NK cells with the CD16-CD56bright phenotype in PBMCs of pregnant women when incubated with trophoblast cells and IL-2, compared with culturing with trophoblast cells only. Our results suggest that NK cells need contact interactions with trophoblast cells and additional cytokine stimulation (IL-2, cytokines of other mononuclear cells) to acquire the CD56bright phenotype.

Changes in expression of Ki-67, CD16 and CD56 by natural killer cells from peripheral blood mononuclear cells in the setting of recurrent miscarriage after in vitro culturing in the presence of trophoblast cells and IL-2.

The aim of this research was to assess the proliferative activity of Natural Killer Cells (NK cells) from Peripheral Blood Mononuclear Cells (PBMCs) in the presence of trophoblast cells in women with a history of recurrent miscarriages. We examined the peripheral blood of women with recurrent miscarriage in the proliferative (n = 12) or secretory (n = 13) phase of their menstrual cycle, and pregnant women with a history of recurrent miscarriage at 6-7 weeks of their current pregnancy (n = 14). Controls were fertile non-pregnant women in the proliferative (n = 11) or secretory (n = 13) phase of their menstrual cycle, and pregnant women at 6-7 weeks of a physiologically normal pregnancy (n = 20). We used IL-2 as a factor maintaining PBMCs viability during long-term culturing. We established that culturing in the presence of IL-2 contributed to an increase in the number of CD56+CD16- NK cells and to a decrease in the number of CD56+CD16+ NK cells from PBMCs compared with these numbers before culturing in both healthy women and in women with recurrent miscarriage. After culturing of PBMCs in the presence of trophoblast cells and IL-2 (compared with culturing without trophoblast cells), the intensity of Ki-67 expression by NK cells was reduced in the whole NK cell population (CD3-CD56+), and in the CD56+CD16- and CD56+CD16+ populations of NK cells in women with recurrent miscarriage and in healthy controls. The intensity of CD56 expression was reduced in the presence of trophoblast cells and IL-2 in non-pregnant women with recurrent miscarriage in the secretory versus the proliferative phase of the menstrual cycle.

Cytotoxic Activity of Peripheral Blood NK Cells towards Trophoblast Cells during Pregnancy.

We evaluated cytotoxic activity of peripheral blood NK cells towards trophoblast cells. NK cells either isolated or in the composition of mononuclear cell fraction, caused death of trophoblast cells. In women with physiological pregnancy, the cytotoxic effect of NK cells present in mononuclear cell fraction preincubated with IL-2 was lower than in nonpregnant women, who had never been pregnant previously, and in fertile women. Cytotoxic activity of isolated NK cells preincubated with IL-2 in fertile women was lower than in nonpregnant women, who had never been pregnant previously.

Interactions of NK Cells and Trophoblast Cells. Methodological Aspects.

NK cells present in different organs differ by their functional characteristics, in particular, proliferative activity. For studying tissue-resident NK cells, tissue-specific microenvironment should be reproduced. In case of decidual NK cells, this microenvironment is created by trophoblast cells. We developed a method for evaluation of proliferative activity of peripheral blood NK cells in the presence of trophoblast cells. Proliferative activity of peripheral blood NK cells was evaluated by the expression of protein Ki-67 after culturing with JEG-3 trophoblast cells. This method allows evaluating the functional state of NK cells in microenvironment specific for the decidua.