A special interaction is established during pregnancy between the maternal immune
system and fetal cells to allow the survival and the normal growth of the fetus.
Fetal cells expressing paternal alloantigens are not recognized as foreign by the
mother because of an efficient anatomic barrier and a local immunosuppression
determined by the interplay of locally produced cytokines, biologically active
molecules and hormones. A special balance between TH1 and TH2 lymphocytes has
also been observed at the feto-maternal barrier that contribute to control the
immune response at this level. An important role is played by trophoblast cells
that act as a physical barrier forming a continuous layer and exert
immunomodulatory function. Trophoblast cells have also been shown to express
regulators of the complement system and to downregulate the expression of HLA
antigens. Dysfunction of these cells leads to morphological and functional
alterations of the feto-maternal barrier as well as to hormonal and immune
imbalance and may contribute to the development of pathologic conditions of
pregnancy, such as recurrent spontaneous abortions. Efforts are still needed to
better understand the physiology of the feto-maternal interaction and the
pathogenetic mechanisms responsible for tissue damage in pathologic conditions of
pregnancy.
