RESUMEN
OBJECTIVE: Overview of current placental findings from the point of view of immunology, tolerance and mesenchymal stem cells. TYPE OF STUDY: Review. SETTING: Medicínské centrum Praha. CONCLUSION: The placenta is an important organ that connects mother and developing fetus during pregnancy. For the uncomplicated course of pregnancy and fetal development the placental function is crucial. The placenta provides not only the replacement of breathing gases, nutrients and waste materials, but also creates an immunological interface between the mother and the fetus. Maternal tolerance towards the fetus carrying paternal antigens is induced at the fetomaternal interface due to the mutual molecular interactions. Immune tolerance at the interface between placenta and decidua is ensured mainly due to the expression of HLA-C, HLA-E, HLA-F, and HLA-G on trophoblasts and their interactions with receptors expressed on uterine NK cells. Regulatory T cells and DC-10 cells also play an important role at the fetomaternal interface on the mothers side of placenta. However, some fetal cells, such as Hofbauer cells or granulocytic myeloid-derived suppressor cells are also partially involved in inducement of maternal tolerance towards the fetus. Recently, considerable attention is also paid to mesenchymal stem cells derived from both placental and umbilical tissues. These mesenchymal stem cells play an important role in inducement of immune tolerance and exhibit better immunomodulatory properties than mesenchymal stem cells isolated from adult human tissues.