Pregnancy process

Factors expressed or produced by uNK cells




Prokinetincin1 (a marker of receptive endometrium) secreted by uNK cells

Facilitating the embryo to implant into the endometrium by regulating implantation factor like leukemia inhibitory factor, IL-11, and prostaglandins

[50] [51] .

High expression of KIR2DL4

Activating a pro-inflammatory/proangiogenic response by binding with its ligand HLAG on trophoblastic cells; this step is beneficial to the establishment of receptive endometrium



IL-25 secreted by dNK cells

Promotes the proliferation of DSCs and of the regulation of decasualization


Killer immunoglobulin-like receptors

Control NK cell activity and cytotoxicity



IL-8 and INF-γ inducible protein, IP10

Increasing MMP-9 secretion, which reduces the apoptosis of extra villus trophoblastic cells (EVT)


TNF-α, TGF-β and IFN-γ

Down-regulate the harmful excessive EVT invasion

[62] [63]

Spiral arteries remodeling

IL-8, TGF-β, angiopoietin-1/2 (Ang1/2), and VEGF-C

Contribute to increase the calibers diameter of spiral arteries to maintain satisfactory blood flow to the growing Festus

[60] [66] [67]

Fetal development

dNK cells secrete growth-promoting factors like pleiotrophin (PTN)and osteoglycin (OGN)

Promote the growth and development of the fetus