For implantation to occur, the endometrium must be receptive. That’s a process that depends on factors such as hormones and appropriate interaction between the embryo and the mother’s immune system.
Several types of immune cells contribute to a healthy endometrium. One type, called a uterine natural killer (NK) cell, has a vital role in implantation.
Natural killer cells destroy tumor cells. They can be toxic, but in the uterus, they secrete substances needed for a successful pregnancy.
Uterine NK cells trigger the growth of essential blood vessels and release growth factors that support implantation and help build a healthy placenta.