The etiological role of allogeneic fetal rejection in pre-eclampsia

Problem: It has been demonstrated that allogeneic fetal rejection in normal pregnancy is prevented by placental indoleamine 2,3-dioxygenase (IDO). Further, an immunological etiology has been implicated in pre-eclampsia. Method of study: We examined the differences in placental IDO activity between normal and pre-eclamptic pregnancies. Results: IDO mRNA expression and enzyme activity levels in the placenta were low in patients with severe pre-eclampsia. The enzyme activity also inversely correlates with the blood pressure of the patients. In the placentas from severe pre-eclampsia, IDO immunoreactivity was low, whereas regional T-cell infiltration was observed reciprocally proportional to the IDO activity. Conclusion: Our findings implicate a potential role for IDO activity and a maternal immunological reaction against an allogeneic fetus in the etiology of pre-eclampsia.