Transfer von Immunglobulinen durch die menschliche Plazenta

Abstract

Immunoglobulin G (IgG) measurements in maternal blood and samples taken from the umbilical artery and umbilical vein at delivery during the third trimester have yielded evidence of transplacental transfer of IgG and its four subclasses. In all three patient subgroups (28–33, 34–36, 37–42 weeks) the concentration in the umbilical vein was consistently higher than that in the umbilical artery. There was an increase in transfer capacity with advancing gestational age during the third trimester. At term the level in the umbilical artery was higher than the maternal IgG, concentration, indicating a transfer against a concentration gradient across the placenta. The comparison of the IgG1 to IgG2 ratio in the maternal blood sample with that in samples from the umbilical artery and vein showed that the ratio was three times as high in the fetal blood, suggesting a preferential transfer of IgG1 over IgG2. In in vitro perfusion experiments in an isolated cotyledon of the human placenta, direct evidence for transfer of IgG was obtained. The in vitro data also suggested a more efficient transport system for IgG1 than for IgG2. In vivo and in vitro, the placental transfer of IgG is a slow process, and following changes in maternal IgG concentration a period of several weeks is required before equilibration with the levels in the fetal circulation is achieved.

Zusammenfassung

Es handelt sich bei dem IgG-Transport durch die menschliche Plazenta um einen spezifischen, durch Bindung an Fc-Rezeptoren im Trophoblasten vermittelten Transportmechanisms. Die Transportkapazität steigt im dritten Trimester deutlich an unter präferentieller Bindung und Transport der Subklasse IgG I. Am Ende der Schwangerschaft wird IgG I gegen ein Konzentrationsgefälle von der mütterlichen auf die fetale Seite transportiert.