Vectorial transcytosis of immunoglobulin G by human term trophoblast cells in culture.

Trophoblast cells were grown on filters that allow access to apical and basal surfaces of cells. Using this experimental system, IgG transport was shown to be specific and to occur primarily in the apical to basal direction. This transport was time- and temperature-dependent, with approximately 10% of added IgG appearing on the basal side within a 60-min incubation at 37 degrees C. Other substances such as heparin were transported only minimally, whereas horseradish peroxidase was transported to the same degree in both directions. Greater than 90% of the transported IgG was precipitable by trichloroacetic acid and 81% was capable of binding to protein G. Such a rapid transport of large amounts of IgG in trophoblast cells is consistent with a receptor-mediated process of transcytosis.