Expression of MHC I Isoforms in Bovine Placentomes: Impact of Cloning

As observed in other species during pregnancy, bovine placentomes are assumed to suppress classical MHC I antigens, whereas overexpress non-classical MHC I to be recognized but not rejected by maternal immune system. However, in cloned bovine classical antigens were overexpress early in the pregnancy instead of non-classical ones. Then, MHC I antigens were investigated by immunohistochemistry (N=23) and RT-qPCR (N=16) in control and cloned bovine placentomes in early gestation and near term. In controls, IL-A88 staining was present in all stages, majorly in maternal tissues, whereas Qa-2 reacted only near term. Clones had an opposite pattern. Trophoblast giant cells near the uterine epithelium were weakly stained. By PCR, especially the non-classical isoform BoLA-NC3 resulted in significant higher expression in early gestation and down-regulation near term in controls compared to clones, as stain produced by Qa-2 antibody. The presence of MHC I in the placentomes indicated that bovine epitheliochorial placentas followed similar principles than that known for other species. Controls and clones reacted differently to the applied antibodies and differ partly in gene expression, which may explain pregnancy problems.