The human placental immunoglobulin G receptor and immunoglobulin G transport.
OBJECTIVE
The objective of this study was to quantitatively determine an immunoglobulin G receptor, placental alkaline phosphatase, and its ligand immunoglobulin G in maternal and fetal blood and to study the transport capacity of the receptor.


METHODS
Venous blood samples from 66 term pregnant women and cord samples from their fetuses were obtained, together with the corresponding placentas.


RESULTS
Mean placental alkaline phosphatase levels were determined to be 23.7 ng/ml and 1.2 ng/ml in maternal and fetal blood, respectively. Mean immunoglobulin G level of the fetal samples was significantly higher than that of the maternal samples (12.6 vs 9.5 gm/L, p < 0.0001). The placental alkaline phosphatase phenotype S had a larger dissociation constant to immunoglobulin G than did type F and was found to have mean fetal immunoglobulin G levels higher than those of the F type (13.3 vs 9.7 gm/L).


CONCLUSIONS
The placental immunoglobulin G receptor placental alkaline phosphatase is found in the fetal circulation. The placental alkaline phosphatase phenotype was found to be related to the levels of its ligand immunoglobulin G in fetal blood, although the mechanism for this remains to be established. Immunoglobulin G is actively transported to fetal blood to reach higher levels than in the maternal circulation.
Department of Obstetrics and Gynecology, University of Umeå, Sweden.
B E
BE
Fridén
R
R
Makiya
B M
BM
Nilsson
S
S
Holm
T I
TI
Stigbrand
D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood* / Q000235:genetics; D001692:Biological Transport; D005260:Female; D005312:Fetal Blood / Q000201:enzymology* / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000378:metabolism; D007527:Isoenzymes / Q000097:blood; D010641:Phenotype; D010920:Placenta / Q000201:enzymology* / Q000276:immunology; D011247:Pregnancy / Q000097:blood* / Q000276:immunology; D017452:Receptors, IgG / Q000032:analysis
D007074:Immunoglobulin G; D007527:Isoenzymes; D017452:Receptors, IgG; D000469:Alkaline Phosphatase