Transcytosis of IgG anti-D by human term trophoblast cells in culture.

Placental trophoblast cells were cultured on filters that allow access to medium bathing the apical and basal surfaces of cells. Purified human IgG was added to either the apical or the basal chambers and sampled at intervals of up to 100min for determination of IgG concentration by ELISA. Using this experimental system, transport of IgG1 and IgG3 monoclonal anti-D, affinity-purified polyclonal anti-D and human polyclonal IgG were shown to occur primarily in the apical to basal (i.e. maternal to fetal) direction. The overall transport of monoclonal and polyclonal anti-D was less than 10% in 45 min, several times lower than that of IgG. There was no difference in the rate or percentage of transport between IgG1 (BRAD-5) and IgG3 (BRAD-3) monoclonal anti-D. The possibility that the Fc receptor mediating transcytosis of IgG anti-D through human trophoblast cells in culture is the placental hFcRn is proposed.