Bachelor Thesis from the year 2007 in the subject Medicine - Gynecology, Andrology, grade: Excellent , Maastricht University, language: English, abstract: The main issue of this paper is the question how the placenta, in particular placental trophoblast cells, prevent a maternal allograft immune rejection by modulating the immune response in the uterine side of implantation.The attempt is done to give insights about special immunological interactions at the placental-uterine side of implantation that makes the fascinating event of pregnancy possible. Of main interest are interactions between trophoblast human leukocyte antigens (HLAs), natural killer (NK) cells as well as T lymphocytes, in questions of state of the art literature. Although a broad introduction is given to the development of the embryo until nidation; how the uterus is made up during implantation and the mechanisms of placentation.