How IgG traverses the human placenta from mother to fetus is unknown, although recently a candidate for the transporter was suggested: the cDNA for the human homologue of FcRn, the MHC Class I homologue that binds IgG with pH dependent affinity, was cloned by Simister et al from a placenta cDNA library. Pursuing this lead, we have purified from human placenta a heterodimer of 46 kD and 14 kD by IgG affinity at acid pH. The smaller molecule is beta2-microglobulin by immunoblot analysis. The larger, characterized by amino acid sequence and by immunoblot, is the human homologue of FcRn (hFcRn). Immunohistochemical analysis of placenta sections with anti-hFcRn peptide antibodies indicated extensive expression of hFcRn in the syncytiotrophoblast and traces in the endothelium and other unidentified cellular elements of the villus stroma. By Northern analysis the message is found in all tissues except brain, the only tissue of the body free of IgG. We suggest that hFcRn not only transports IgG across the human placenta but serves a wider function, likely salvaging IgG from catabolism as was hypothesized by Brambell thirty years ago.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology