Differentiation molecules of the equine trophoblast

Monoclonal antibodies raised against horse placenta were tested using an indirect immunoperoxidase-labelling technique for reactivity with a panel of tissues from adult horses and conceptuses of various gestational ages. The pattern of reactivity of 4 of the antibodies (F67.1, F71.3, F71.7, F71.14) on trophoblastic tissues described unique antigenic phenotypes for the non-invasive trophoblast of the allantochorion, the invasive trophoblast of the chorionic girdle, and the mature endometrial cup cells, which are derived from the chorionic girdle. Two of the monoclonal antibodies (F67.1 and F71.3) reacted only with chorionic girdle and the endometrial cups. Antibody F71.7 labelled strongly the non-invasive allantochorion from Day 29 of gestation to term. However, F71.7 failed to label mature endometrial cups and stained chorionic girdle only weakly, suggesting that the ability of the girdle cells to synthesize the molecule identified by F71.7 was gradually lost after development of the girdle. Antibody F71.14 reacted with trophoblastic tissues from all stages of gestation tested, with the exception of chorionic girdle. The other 3 anti-trophoblast monoclonal antibodies (F71.1, F71.2 and F71.8) labelled trophoblast-derived tissues from all stages tested. When the monoclonal antibodies were tested on cultured fetal and placental cells from Day 33 conceptuses recovered non-surgically from pregnant mares, the reactivities of the monoclonal antibodies on cultured cells were mostly identical to their reactivities in situ on tissue samples of similar gestational age; F67.1 and F71.3 were strong, specific markers for chorionic girdle cells, and F71.7 labelled allantochorion weakly in vitro, but failed to label chorionic girdle cells.(ABSTRACT TRUNCATED AT 250 WORDS)