Indoleamine 2,3-dioxygenase (IDO) is expressed at feto-placental unit throughout mouse gestation: An immunohisto chemical study

Introduction: The cells expressing Indoleamine 2, 3-dioxygenase (IDO) in fetomaternalinterface mediate tryptophan catabolism, hence protect allogeneic fetus fromlethal rejection by maternal immune responses. In this study, we report immunolocalizationof IDO+ cells in murine reproductive tract and placenta throughout mousepregnancy by immunohistochemistry.Materials and Methods: Syngeneic pregnant mice were examined for vaginal plug todiscover about their state of pregnancy. A total of three pregnant mice were examinedat each stage.The examination was further confirmed by the detection of sperm invaginal smear. On the gestational days of 2nd, 12th and 18th, the uterus and oviductwere removed and expression of IDO was investigated in the endometrium, placentaand oviduct by immunohistochemistry.Results: Our results showed that IDO is expressed consistently in feto-maternalinterface throughout pregnancy. In endometrium, expression of IDO was predominantlyconfined to luminal and glandular epithelial cells. Cells at junctional andlabyrinth zones of placenta showed strong IDO immunoreactivity as well.Conclusion: Expression of IDO at the protein level in reproductive tract of pregnantmice during entire periods of gestation points to its potential protective role inmaintenance of pregnancy. In our knowledge this is the first report of expression ofIDO in feto-maternal phase during murine pregnancy.