BEHAVIOR OF 2 IGG SUBCLASSES IN TRANSPORT OF IMMUNOGLOBULIN ACROSS THE HUMAN PLACENTA

The human IgG subclasses are a family of highly related yet distinct m olecules. Each of these four subclasses performs a discrete function w ithin the human immune system. Previous studies have shown that one of these molecules, hIgG2, may be discriminated against in transport acr oss the human placenta. We have aimed to elucidate the mechanism of th is discrimination in order to gain a more comprehensive understanding of the process of transport of immunoglobulin across the human placent a. We have used a combination of immunocytochemical localisation and b iochemical analysis to detail the behaviour of hIgG2. Confocal laser s canning microscopy was used to compare the localisation of hIgG1 (chos en as representative of the efficiently transported subclasses) and hI gG2 in term and first trimester chorionic villi. Complementary evidenc e was provided from immunoblot analysis of isolated placental coated v esicles. The data presented here suggest that hIgG2 is transported int o the syncytiotrophoblast and appears to accumulate in the stroma of t he villi. This leads us to the hypothesis that the fetal capillary end othelium is the cellular impediment to the transport of hIgG2 into the fetal circulation.