Studies of antigenic components of the human syncytiotrophoblast membrane.

In order to initiate characterization of potentially immunogenic moieties on the human trophoblast membrane, antisera to native and detergent-solubilized normal trophoblast membranes were prepared in rabbits. By indirect immunofluorescence, these antisera reacted strongly with all villous structures in normal placentae and also with a panel of normal adult human tissues. Specificities to normal human serum components were then removed by solid-phase immunoabsorption. However, the resultant antisera still reacted weakly with differentiated, normal adult tissues, and additional absorption with normal adult liver homogenate was necessary to remove cross-reactivity completely. Such absorbed antisera gave undiminished and specific fluorescence of the syncytiotrophoblast plasma membrane, and specifically precipitated two protein species with approximate relative molecular masses of 148,000 and 62,000. However, they also reacted with PHA-activated peripheral blood lymphocytes, in addition to Chang liver and HeLa cell lines. These results indicate that, even after extensive absorption, trophoblast membrane antisera may retain reactivity for determinants shared with normal and transformed adult cells.