Ex vivo human placenta models: transport of immunoglobulin G and its subclasses.

The comparison between fetal and maternal levels of immunoglobulins indicate that the human placenta during pregnancy develops a specific transport mechanism for IgG in the maternal to fetal direction. There are differences for the four subclasses, with preferential transfer of IgG(1) while the slowest transfer is seen for IgG(2). Under in vitro perfusion conditions of human term placenta IgG, when compared to other proteins, showed a significantly higher transfer rate of its subclasses from the maternal to the fetal side, indicating a specific transport mechanism. There is a preferential transfer rate, highest for IgG(1) and lowest for IgG(2), similar to those observed under in vivo conditions. The similarity in transfer of anti-TT-IgG and tetanus antigen, which was observed under in vivo and in vitro conditions, may suggest the transport as antibody-antigen complex.