Immune modifications
For a successful pregnancy outcome, the maternal immune system must tolerate the fetus. Placental trophoblast cells, there fore,not only provide aphysical barrier but also secretea variety of cytokines and hormones, including several immunomodulatory molecules. These secretions induce detectable immune changes, including enhanced regulatory T cell function10,11 (Table 1), which have great importance for many autoimmune diseases. The result is a general improvement in autoimmune intolerance during gestation.12 In addition, takingadvantageofthisimmunosuppressivecondition,fetalcells cross the placental barrier and survive maternal intolerance