Fetus-Placenta-Newborn
Soluble HLA-G circulates in maternal blood during pregnancy,☆☆

https://doi.org/10.1067/mob.2000.106762Get rights and content

Abstract

Objective: Soluble isoforms of the HLA class Ib gene HLA-G have been identified at the maternal-fetal interface. Because soluble forms of other HLA class I antigens modulate T-cell reactivity and induce cellactivated apoptosis, our goal was to determine whether soluble HLA-G circulates in maternal or fetal blood and to identify the specific isoform. Study Design: Capture enzyme-linked immunosorbent assays with mouse monoclonal antibodies directed toward an epitope present on all isoforms of soluble HLA-G were constructed to identify soluble HLA-G in 44 serum samples from nonpregnant control subjects, 129 serum samples from pregnant women, and 10 samples of term cord blood. Distinguishing between soluble HLA-G1, which is composed of heavy chains complexed with light chains (β2-microglobulin), and soluble HLA-G2, which consists only of heavy chains, was achieved by substituting a monoclonal antibody that requires β2-microglobulin for binding (W6/32) in the capture phase of the enzyme-linked immunosorbent assay. Results: Capture enzyme-linked immunosorbent assays with mouse anti–soluble HLA-G showed that soluble HLA-G was present at all stages of gestation and that levels of soluble HLA-G were statistically significantly higher in serum samples from pregnant women than in serum samples from nonpregnant women. In contrast, W6/32 failed to detect soluble HLA-G in serum samples from pregnant women. Cord serum samples did not contain detectable soluble HLA-G. Conclusion: Collectively, the data indicate that pregnancy is characterized by the presence of soluble HLA-G circulating in maternal blood and strongly suggest that the major isoform is soluble HLA-G2. (Am J Obstet Gynecol 2000;183:682-8.)

Section snippets

Material and methods

Serum samples from nonpregnant female control subjects (n = 44) were obtained from the Community Blood Center of Greater Kansas City with the kind assistance of G. Tegtmeier, director of the Viral Testing Laboratory. Serum samples from pregnant women (n = 137) were collected between 1980 and 1985 from women with and without diabetes as described elsewhere.20 The samples were continuously maintained at –80°C and were shipped to the University of Kansas Medical Center on dry ice. The 137 samples

Results

The capture ELISA that used monoclonal and polyclonal antibodies directed toward an amino acid sequence derived from intron 4 specifically detected sHLA-G in serum, as determined by inclusion of positive and negative control preparations in each experiment. The positive control preparation consisted of undiluted supernatant culture medium from an HLA-G–transfected mouse fibroblast cell line, the S14/8 cells. The mean (±SEM) specific binding for S14/8 supernatants in 23 separate experiments was

Comment

The data presented in this report show for the first time that sHLA-G circulates in mothers during pregnancy. Multiple control preparations were used to verify the specificity and sensitivity of the capture ELISA. Supernatant culture media of the HLA-G–transfected mouse fibroblast cell line S14/8, which has been shown previously to transcribe messenger ribonucleic acid encoding for sHLA-G,12 was used as a positive control preparation. Values in supernatants were consistently 2-fold greater than

Acknowledgements

We appreciate the kind gifts by Drs G. Tegtmeier and P. Brown of serum samples from nonpregnant control subjects and cord blood, and we acknowledge the expert technical assistance of T. Phillips and S. Platt.

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  • Cited by (0)

    Supported by grants from the National Institutes of Health awarded to Joan S. Hunt, PhD (HD26429), Daniel E. Geraghty, PhD (AI31874), and Carole Ober, PhD (HD27626) and by core facilities of the Kansas Reproductive Science National Institutes of Health P30 Center (HD33994) and the Kansas Mental Retardation Research Center (HD02528). Wenjiang Chu, MD, PhD, was supported by a fellowship from the Kansas Health Foundation Training Program.

    ☆☆

    Reprint requests: Joan S. Hunt, PhD, Department of Anatomy and Cell Biology, University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160-7400.

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