Possible Mechanisms That Protect the Fetus from Maternal Rejection

There is no other foreign tissue transplant that has such a strongly parasitic relationship with its human host as the fetus. Although the fetus contains paternal genes, is completely tolerized by its maternal host in almost all pregnancies. This presents an immunological paradox and has generated a lot of attention from leading researchers in the reproductive and immunology fields. This paper reviews the leading explanations for this paradox; that it is attributed to a detailed mechanism of the maternal and fetal immune system in which tryptophan suppresses T-cells from attacking specific paternal cells, while maintaining a strong immune response against other foreign antigens during pregnancy. Other opinions contribute fetal tolerization to the maternal immune systems strong bias of Th2 cells and a decrease of Th1 cells. Researchers suspect that women suffering from recurrent miscarriages are unable to tolerize their fetus, and consequently, their immune system attacks the fetus several weeks after implantation and aborts the pregnancy. Other medical implications include preeclampsia, which is attributed to immunological issues. Doctors are now trying to understand how these mechanisms work to provide treatment for women who cannot naturally tolerize their fetus, and for patients suffering from preeclampsia