Localization and purification of SBU-4--a pregnancy specific protein of the ovine uterus.

In order to elucidate the function of molecules of the ovine maternal-fetal interface a monoclonal antibody was produced to intact interplacentomal trophoblast membranes. Extensive immunohistological studies revealed that the monoclonal antibody recognizes a protein designated SBU-4 which originates in the intercaruncular regions of the gravid sheep uterus at about the time of implantation and increases in concentration throughout gestation. The data suggest that SBU-4 is produced by endometrial epithelial cells and that adjacent uninucleate cells of the trophoblast acquire the antigen by endocytosis. Initial biochemical analysis of the purified SBU-4 molecule prepared by monoclonal antibody immunoaffinity chromatography indicates that SBU-4 is high molecular weight glycoprotein complex comprising several sub-units.