Preparation and characterization of monoclonal antibodies against placental alkaline phosphatase and other human trophoblast-associated determinants.

We have prepared monoclonal antibodies by immunizing BALB/c mice with purified human term placental plasma membranes. The antibodies were selected to show predominant specificity for trophoblast and trophoblast derivatives. Four of these antibodies have been found to recognize the placenta-specific isozyme of alkaline phosphatase (EC 3.1.3.1), and to cross-react with the closely related testis form of this enzyme. One antibody recognized transferrin, a serum protein with an abundant placental receptor. The specificities of the other antibodies, whose target antigens are unknown, are described. Their reactivity with some human tumour-derived epithelial cell lines suggests that they may provide useful markers of human trophectoderm differentiation, as well as for properties selected for during tumour progression.