TRANSFER OF ANTI‐D ANTIBODIES ACROSS THE ISOLATED PERFUSED HUMAN PLACENTAL LOBULE AND INHIBITION BY HIGH‐DOSE INTRAVENOUS IMMUNOGLOBULIN: A POSSIBLE MECHANISM OF ACTION

Using an in vitro perfusion model, therapeutic intravenous immunoglobulin (IVIgG) and IgG anti‐D have been shown to cross the placenta from the maternal circuit to the fetal circuit. The transfer of all IgG species was linear with respect to time, and the amount of IgG transferred was proportional to the concentration of IgG in the maternal circuit ([IgG]m), but reached saturation at upper limits. With total [IgG]m at 6.5 g/l, 11.1 g/l or 26.2 g/l the increase in the fetal concentration of total IgG was 4.6 mg/l/h, 8.9 mg/l/h and 9.9 mg/l/h respectively. The rate of transfer of specific anti‐D antibody to the fetal circuit was 0.026 IU/ml/h at a concentration of 38 IU/ml in the maternal circuit ([anti‐D]m). High‐dose therapeutic IVIgG added to the maternal circuit (total [IgG]m 29.2 g/l) significantly inhibited (P