Figure 3.

dNK cells promote pregnancy success through surface receptor expression or cytokine secretion in early human pregnancy. (A) dNK cells are important in defense against microbial invasion at the maternal-fetal interface. dNK cells deliver GNLY through nanotubes into trophoblast cells infected with Listeria monocytogenes to kill the bacteria without damaging the trophoblast cells. In addition, the expression of various activating receptors or the acquisition of CD16 is involved in the process by which dNK cells kill other microbial infections. (B) dNK cells promote trophoblast invasion and participate in the remodeling process of uterine spiral arteries. The above functions are induced by the direct binding of activating or inhibitory receptors on the surface of dNK cells to ligands on the surface of trophoblast cells and may also be involved in promoting the secretion of various cytokines. (C) dNK cells promote embryonic growth and development by secreting growth-promoting factors. In addition, activation or inhibition of dNK cells severely affects embryonic growth. Co-expression of the activating receptor KIR2DS1 and the inhibitory receptor KIR2DL1 of dNK cells regulates the balance of embryonic growth, especially when the embryo inherits the paternal HLA-C2 gene. (D) Decreased expression of various activating receptors is one of the main mechanisms by which dNK cells maintain immune tolerance at the maternal-fetal interface. CD39 is highly expressed on dNK cells, which can bind to CD73 on the surface of epithelial glands and EVT cells to convert ATP to adenosine to maintain immune tolerance.