Alternate roles for immune regulators: establishing endometrial receptivity for implantation.

Many immune regulators are now identified as having key roles at the embryo-maternal interface. Importantly, a cohort of cytokines, chemokines and growth factors are produced by the endometrial glands and secreted into the uterine cavity where they act both on the blastocyst and on the endometrial surface, changing adhesive capacity, modifying blastocyst development and outgrowth and providing chemoattraction, in addition to their previously known functions in immune regulation. As implantation progresses to highly controlled invasion of the trophoblast through the maternal decidua, similar factors produced by glands, decidual cells and cells of the innate immune system are critical for guiding the trophoblast to the maternal vasculature and establishing a functional placenta. Disturbance to production or action of such mediators can result in loss of uterine receptivity (manifesting as infertility) or disorders of early pregnancy including recurrent miscarriage and preeclampsia.