Immunological regulation of trophoblast invasion.

In investigating the immunological regulation of trophoblast invasion, emphasis is frequently placed on the constitution of the implantation site and its specific characteristics. However trophoblast cells are able of invading into not only the uterine tissue, but in the case of ectopic pregnancies also invade into other tissues, where they are actively involved in the creation of a beneficial local environment by expressing a range of membrane bound and soluble factors. The similarities and differences in trophoblast invasion in uterine and tubal pregnancies concerning trophoblast cells and maternal leukocytes and their interaction with each other are discussed in this review.