Immunologic Processes at the Feto-Maternal Interphase

Maternal immune cells join the conceptus from fertilization until birth. The non-pregnant endometrium is rich in immune cells, mostly natural killer (NK) cells, which, instead of attacking the embryo, are required for successful implantation and placentation. They have low cytotoxicity and high cytokine production. Disorders of uterine NK cell numbers and functions may disturb this process. In early pregnancy NK cells may be involved in angiogenesis. T cells are comparatively rare in endometrium and early decidua and display mainly regulatory phenotypes, such as Treg cells, Th2 cells or gamma/delta T cells. Decidual T helper cells increase towards end of pregnancy. Also other immune cells, such as macrophages, dendritic cells or B cells are present and underly dynamical changes during the course of pregnancy. In the non-pregnant uterus mainly female factors regulate immune cell composition and functions.In the pregnant uterus trophoblast cells interact with local and circulating maternal immune cells by manifold matters. One of the most recently described is the interaction via trophoblast derived extracellular microvesicles. Dysfunctions of the immune balance in pregnancy may be invoved in numerous pathologies.