Immunochemical identification of human trophoblast membrane antigens using monoclonal antibodies.

Human trophoblast membrane antigens recognised by monoclonal antibodies (H310, H315, H316 and H317) have been identified using combinations of radioimmunoprecipitation, SDS-PAGE, electroblotting, chromatographic and ELISA-type techniques. H317 is known to identify heat-stable placental-type alkaline phosphatase and accordingly was shown to react with a protein of subunit Mr of 68 000. H310 and H316 both recognise an antigen with a subunit Mr of 34 000 under reducing conditions. In non-reducing conditions, the H310/316 antigen gave oligomers of a component of Mr 62 000. It is unknown whether this 62 000 dalton component is a dimer of the 34 000 dalton protein with either itself or a second protein chain of presumed Mr around 28 000. H315 recognises an antigen with subunit Mr of 36 000; in non-reducing conditions this component readily associates to oligomeric structures. The epitope recognised by H315 may be sensitive to SDS. The two proteins recognised by H310/316 and H315 have been termed the p34 and p36 trophoblast membrane proteins, respectively.