A 72 kD trophoblast glycoprotein defined by a monoclonal antibody.

A novel trophoblast cell surface antigen has been defined by a monoclonal antibody 5T4, raised following immunisation with wheat germ agglutinin (WGA) purified glycoproteins from deoxycholate (DOC) solubilised human syncytiotrophoblast plasma membrane (StMPM). The distribution of the antigen was determined by indirect immunoperoxidase staining of sections of normal organ and placental tissues as well as immunofluorescence and radiobinding assays with a wide variety of cell lines representing differing normal and tumour cell types. In frozen sections of normal full term placenta, 5T4 is strongly expressed only by the syncytiotrophoblast, some extravillous cytotrophoblast and the amniotic epithelium. The 5T4 antigen is apparently not expressed by any maternal component of the placenta nor is it detected in adult liver, lung, bronchus, heart, testis, ovary, brain, or muscle. The antigen is apparently expressed by several specialised epithelia. Immunoprecipitation of radiolabelled StMPM indicated that 5T4 molecules are glycoproteins of mol. wt of approximately 72 kD on SDS-PAGE. 5T4 antigen is selectively expressed by diverse tumour cell lines, including those of developmental origin. The molecular characteristics, relatively restricted normal tissue distribution and expression by certain tumour cell types make this antigen worthy of future study for use as a diagnostic marker of malignancy.