The appearance of transferrin receptors on cultured human cytotrophoblast and in vitro-formed syncytiotrophoblast.

Using trypsinization and Percoll gradient centrifugation, mononuclear cell populations were prepared from human term placentae. These populations consist mainly of cytotrophoblast, which probably lacks transferrin receptors. In vitro, transferrin receptors appear on these mononuclear cells and on syncytiotrophoblast formed in vitro, independently, of cellular fusion and proliferative state.