The effects of pregnancy on autoimmune diseases.

Despite a now reasonable large body of developed information, critical gaps are apparent. Pregnancy is the only naturally occurring event in which an individual is exposed to nonself HLA. How the HLA mismatched fetus escapes rejection remains a biologic enigma. More definitive evidence is needed to determine if TH2 bias occurs in normal human pregnancy and how this impacts on established autoimmune diseases. With regard to specific autoantibody-associated placental and fetal disease, why aren't all pregnancies affected when the putative maternal antibodies are present? Future studies of maternal-fetal immunology, inclusive of information on cytokine regulation, should yield insights not only into the maintenance of normal pregnancy but also into the disproportionate increase of autoimmune diseases in females and the variable course of these diseases during pregnancy.