Indoleamine 2,3 Dioxygenase-Dependent T Cell Suppression and Pregnancy.

Viviparity remains an immunological paradox despite increased knowledge of immuno-logical processes that occur during mammalian pregnancy. The maternal immune system protects both mother and fetus from invading pathogens during gestation, but also has to maintain immunological tolerance towards the fetus. Medawar proposed three ways in which this paradox might be resolved: physical segregation of maternal and fetal tissues, immunologic immaturity of fetal tissues, and immunological anergy (tolerance) of the maternal immune system towards fetal alloantigens.1 [ABSTRACT FROM AUTHOR]