HLA-G antigen and parturition: maternal serum, fetal serum and amniotic fluid levels during pregnancy.
OBJECTIVE
To determine whether soluble HLA-G1 (sHLA-G1) concentrations in maternal serum and in amniotic fluid are lower at term than in the second trimester.


METHODS
In this prospective study amniotic fluid and maternal serum samples were aspirated from 21 pregnant women during genetic amniocentesis at 16-20 weeks' gestation, and from 19 women undergoing a cesarean section at term. In the latter group arterial umbilical cord blood was aspirated as well. sHLA-G1 levels were determined using ELISA assay. This assay included the anti-HLA-G monoclonal antibodies 87G and 16G1, both as capture antibodies and horseradish-peroxidase-labeled rabbit anti-human beta(2)-microglobulin antibodies, as the detection antibody. The relative concentrations of sHLA-G1 were measured from the absorbancy of the blue product at 650 nm. Student's t test was used for statistical analysis.


RESULTS
sHLA-G1 levels in amniotic fluid were significantly lower at term than in the second trimester (0.160 +/- 0.05 vs. 0.272 +/- 0.150 OD units; p < 0.05). Levels of sHLA-G1 in maternal serum declined toward term, but the difference from the second trimester was not statistically significant (0.266 +/- 0.157 vs. 0.205 +/- 0.120 OD units; p = 0.193). There was a strong correlation of sHLA-G1 concentrations between cord serum and maternal serum (R(2) = 0.79; p < 0.001), but not between cord serum and amniotic fluid (R(2) = 0.00004) or amniotic fluid and maternal serum (R(2) = 0.02).


CONCLUSIONS
sHLA-G1 antigen expression is higher in amniotic fluid than in maternal-fetal compartments and significantly decreases toward term. We speculate that the declining amniotic fluid sHLA-G1 levels may stimulate a maternal immunological response against the fetus and contribute to the initiation of parturition.
Department of Obstetrics and Gynecology, Soroka University Medical Center, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel. rinatia@netvision.net.il
Rinat
R
Hackmon
Mordechai
M
Hallak
Margalit
M
Krup
Dahlia
D
Weitzman
Eyal
E
Sheiner
Boris
B
Kaplan
Yacob
Y
Weinstein
D000653:Amniotic Fluid / Q000276:immunology*; D005260:Female; D005312:Fetal Blood / Q000276:immunology*; D006680:HLA Antigens / Q000097:blood* / Q000378:metabolism*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000097:blood* / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D036801:Parturition / Q000097:blood / Q000276:immunology; D011247:Pregnancy; D012995:Solubility
D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I