Paternal and maternal major histocompatibility complex class I antigens are expressed co-dominantly by equine trophoblast.

Invasive equine trophoblast cells of the chorionic girdle express high levels of paternally inherited Major Histocompatibility Complex (MHC) class I antigens prior to migration into the endometrium to form the so-called endometrial cups. Three groups of experiments were performed to determine if maternally inherited MHC class I antigens are expressed on chorionic girdle cells. Results indicated that maternally and paternally inherited MHC class I antigens are co-dominantly expressed by cells of the invasive equine trophoblast, and therefore, that the expression of polymorphic equine MHC class I genes does not appear to be affected by genomic imprinting in this tissue.