Characterization of the human syncytiotrophoblast plasma membrane associated components.

A purification procedure of synctiotrophoblast plasma membrane (STPM) has previously been described. We now report a further characterization of their associated components. By immunochemical analysis two groups of proteins were found. The first fraction solubilized by chaotrope treatment was made up with a complex of IgG, albumin, transferrin and alpha-fetoprotein. The second fraction, insolubilized by KCl-treatment but by detergents, did not react with antisera to human proteins; it contained human chorionic gonadotropin and placental lactogen. The amino acid, carbohydrate and lipid content of STPM were determined. High galactosyl- and sialyl-transferase activities were found in purified STPM. The role of these various components on the acceptance of the fetal allograft is discussed.