140 IMMUNOLOCALIZATION OF INDOLEAMINE 2,3-DIOXYGENASE IN PLACENTA FROM BOVINE CLONED CONCEPTUS PREGNANCY

Abstract

The catabolism of tryptophan by indoleamine 2,3-dioxygenase (IDO) activity is strongly correlated to maternal-fetal tolerance in hemochorial placentation. Several studies have been conducted on the role of IDO on maternal-fetal tolerance in human and mice placental tissue. Changes in IDO expression and activity are related to fertility problems in humans and lower IDO activity was found in women who had recurrent abortions. In mice, IDO was localized in blastocyst, cytotrophoblast, placental macrophages, stromal cells and invasive trophoblast cells, but not in the syncytiotrophoblast. Also, IDO staining was detected on villous trophoblast cells; probably due to the fact that this is the site where fetal antigen is most exposed to the maternal immune system during pregnancy. Our previous studies in bovine showed that IDO activity is present throughout pregnancy, increasing as it develops. IDO staining can be observed at the maternal-fetal interface, in the trophoblast, especially in giant cells where it increases as gestation progresses. IDO staining in the uterine epithelium remained constant during gestation and absent in the fetal mesenchyma. This study aimed to qualitatively immunolocalize IDO staining in placenta from bovine cloned conceptuses at term. Fibroblasts originated from one bull were cultured and fused with enucleated oocytes to produced clone embryos. Placentomes were collected from four cloned conceptuses and 10 normal conceptuses (control) at parturition. Samples were fixed in 10% buffered formalin and embedded in paraffin. Sections were made and processed for immunohistochemistry using a commercial monoclonal antibody against IDO. Placenta from two cloned conceptuses showed IDO staining on fetal mesenchyma, differing from normal pregnancy where the staining of this enzyme was absent in all control samples. IDO staining was absent at the fetomaternal interface in one sample from cloned placenta and present in all normal pregnancy animals. It was difficult to establish a staining profile for giant and binucleate cells in cloned placenta, since IDO staining varied greatly among individuals. IDO immunolocalization in placenta from cloned conceptus was altered in all animals studied. It may raise the question that cloning could interfere in maternal immune modulation during pregnancy and IDO misexpression in fetomaternal tolerance could be involved in a decreased maintenance of cloned pregnancies.