Interactions of NK Cells and Trophoblast Cells. Methodological Aspects

Characteristics of Natural Killer Cell Interaction with Trophoblast Cells During Pregnancy

BACKGROUND

Maternal natural killer cells (NK cells) are a prevailing leukocyte population in the uteroplacental bed. Current descriptions of the effect of cytokines from the placental microenvironment on the expression of receptors by trophoblast and NK cells are inadequate and contradictory. There is insufficient information about the ability of NK cells to migrate through trophoblast cells.

OBJECTIVE

To assess the impact of conditioned media obtained during culturing of placentas from the first and the third trimesters of healthy pregnancies on the phenotype of trophoblast and NK cells and impact on adhesion and transmigration of NK cells through trophoblast cell layer.

RESULTS

We established that conditioned media obtained from both first and third trimester placentas increased the intensity of CD106, CD49e, CD49a, CD31, CD51/61, and integrin β6 expression by trophoblast cells. Conditioned media obtained from first trimester placentas increased the intensity of CD11a, CD29, CD49d, CD58, CD29 expression by NK cells. The presence of conditioned media from third trimester placentas resulted in more intense CD29, CD49d, CD11a, CD29, CD49d, and CD58 expression by NK cells. Migration of NK cells through trophoblast cells in the presence of conditioned media from first trimester placentas was increased compared with the migration level in the presence of conditioned media from third trimester placentas. This may be associated with increased expression of CD18 by NK cells.

CONCLUSION

First trimester placental secretory products increase adhesion receptor expression by both trophoblast and NK cells. Under these conditions, trophoblast is capable of ensuring NK cell adhesion and transmigration.

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.