| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
,
,§
Departments of
*
Stomatology,
Anatomy,
Pharmaceutical Chemistry, and
§
Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, CA 94143;
¶
The Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98104; and
||
Adeza Biomedical, Sunnyvale, CA 94089
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Early in human pregnancy, cytotrophoblast stem cells differentiate into distinct trophoblast populations that ultimately reside in different placental compartments; consequently, their interactions with maternal cells also differ (reviewed in Refs. 1 and 2). In one differentiation pathway, the cytotrophoblast stem cells fuse to form a multinucleate syncytium. These syncytiotrophoblasts cover the surface of floating chorionic villi, which are bathed in maternal blood. Their location is ideally suited to their function: gas, nutrient, and waste exchange. In another differentiation pathway, the stem cells differentiate into tumor-like cells that leave anchoring chorionic villi to aggressively invade the uterine wall and its vasculature. This subpopulation of extravillous cytotrophoblasts anchors the conceptus to the uterus and establishes the flow of maternal blood to the placenta. In this location, they come into direct contact with several types of maternal cells, including a unique population of NK cells that are abundant in the pregnant uterus (3, 4). Another subpopulation of extravillous cytotrophoblasts lies adjacent to the amniotic epithelium. Collectively, these chorionic cytotrophoblasts, the amniocytes, and the connective tissue with which they are associated are termed the amnion-chorion.
HLAs present peptides to immune cells and are, therefore, important determinants of alloreactivity. Thus, defining the trophoblast HLA repertoire is central to understanding the role of the placenta in immune interactions with maternal cells. None of the trophoblast populations expresses HLA-A, HLA-B, or class II (HLA-D) MHC molecules. Whether these cells express HLA-C is controversial (5, 6). But it is well established that cytotrophoblasts that invade the uterus express the full-length nonclassical (class Ib) HLA protein, HLA-G (7, 8, 9, 10, 11), and secrete a truncated form of this molecule (8). Although HLA-G mRNA has been detected in other adult and fetal tissues by reverse-transcriptase PCR analyses (for a review, see 12 , a subpopulation of thymic epithelia are the only other cells that are known to express the protein (13).
Like the extensively studied class Ia genes, HLA-G contains eight exons
that encode three extracellular domains, a transmembrane region, and a
cytoplasmic tail. The single N-linked glycosylation site
(Asn86) present in all class I molecules is conserved, as
are the structurally important cysteines in the 
2 and 3 domains
(14). However, studies at the mRNA level suggest a high degree of
complexity. To date, six different alternatively spliced HLA-G mRNAs
have been reported. In addition to the full-length (G1) form,
transcripts lacking exon 3 (G2), exons 3 and 4 (G3), or exon 4 (G4)
have been described (15, 16). These mRNAs encode proteins that lack
either the 2, 2 and 3, or 3 domains. Additionally, cDNAs
that potentially encode soluble molecules have been reported (17, 18).
Thus, protein products of the HLA-G gene could vary widely in both m.w.
and function.
Determining which of these mRNAs is translated into protein has been
difficult due to the lack of suitable reagents. In this work, we report
the generation of mAbs that detect HLA-G via an 1 domain epitope
that is present in all of the potential forms of HLA-G proteins
described to date. We used this Ab to study HLA-G expression in the
placenta, amnion-chorion, and amniotic fluid. In tissue sections, the
Ab reacted with invasive cytotrophoblasts, chorionic cytotrophoblasts,
and amniocytes. Immunoblot analyses showed heterodisperse bands
(Mr 35,000–50,000) that resolved into
two major species after enzymatic N-deglycosylation. Cell
samples contained primarily an Mr 37,000–42,000
band, most likely the plasma membrane form of the protein. Conditioned
medium and amniotic fluid contained a slightly smaller protein, most
likely the secreted form. These results suggest that the m.w.
heterogeneity of HLA-G observed at the protein level is due to an
unusual type of glycosylation, rather than to the translation of
alternatively spliced mRNAs.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The initial stages of mAb production were performed essentially
as described (11). Briefly, BALB/c mice (Charles River, Wilmington, MA)
were immunized with a peptide corresponding to amino acids 61 to 83 of
the 1 domain of HLA-G (EEETRNTKAHAQTDRMNLQTLRG) coupled to
keyhole limpet hemocyanin. Splenocytes were fused according to standard
methods. Hybridomas that secreted Abs reactive with the peptide
immunogen were identified by ELISA.
In this study, lines that produced anti-peptide Abs were tested in a secondary screen for their ability to react with the HLA-G heavy chain in cytotrophoblast and JEG-3 cell lysates by immunoblotting. Those that did were tested in a tertiary screen for their ability to react with invasive cytotrophoblasts in tissue sections of the maternal-fetal interface, as previously described (11). Several promising lines were chosen and cloned by limiting dilution. One clone (4H84) was chosen for its superior properties and used in all additional experiments.
mAb 16G1 was produced by using a synthetic peptide immunogen corresponding to the amino acid sequence encoded by intron 4 in an HLA-G mRNA interrupted by this intron (17). Details of the methodology were published previously (19).
Tissue and amniotic fluid collection
Informed consent was obtained from all patients from whom tissue, fluid, and blood samples were collected. Placentas and amnion-chorion were obtained from elective pregnancy terminations. Leukocytes were isolated from blood by centrifugation through Ficoll-Hypaque 1027 (Sigma, St. Louis, MO).
Amniotic fluid samples collected during weeks 16 to 18 of pregnancy were obtained from the UCSF Cytogenetics Laboratory (San Francisco, CA). Amniotic fluid samples collected during the third trimester of pregnancy were obtained after amniocentesis for fetal lung maturity assessment. Fluids were stored at 4°C before centrifugation to remove cells, then stored at -20°C until analyzed.
Cervicovaginal fluid samples were obtained from women in labor at term. Cotton swabs were used to collect fluid samples from the cervical os and posterior fornix of women undergoing speculum examination for assessment of membrane integrity and the progress of labor. The status of their membranes was then determined using the ferning and nitrazine tests. The swabs were stored at -20°C until extraction with SDS-PAGE sample buffer, then analyzed by immunoblot.
Immunofluorescence
Immunofluorescence was performed as previously described on frozen sections of either first trimester placental bed samples or second trimester amnion-chorion (11). Hybridoma 4H84-conditioned medium was diluted 1/100. All sections were double stained with 4H84 and anti-cytokeratin (7D3).
Preparation of cell lysate and conditioned medium samples
Highly purified cytotrophoblasts were isolated from first, second, and third trimester chorionic villi, as previously described (20, 21). Cells (1 x 106) were plated in 35-mm culture wells coated with the extracellular matrix preparation Matrigel (Collaborative Research, Bedford, MA) in 2 ml MEM (UCSF Cell Culture Facility) containing 2% Nutridoma (Boehringer Mannheim, Indianapolis, IN). After 36 to 48 h, the conditioned medium was centrifuged to remove any cellular debris, aliquoted, and frozen at -80°C until analysis. The cells were collected in cold lysis buffer containing 150 mM NaCl, 10 mM Tris (pH 8), 0.5% Nonidet P-40 (Sigma), and protease inhibitors (1 mM PMSF, 5 mM EDTA, and 5 µg/ml aprotinin). Lysates were clarified by centrifugation at 16,000 x g for 15 min at 4°C.
Anchoring chorionic villi were dissected from placentas and cultured for 12 to 36 h, as previously described (22), before the cells and conditioned medium were processed as described for cytotrophoblasts. JEG-3 cells were cultured in MEM (UCSF Cell Culture Facility) supplemented with 10% FBS (HyClone, Logan, UT) and processed as for the cytotrophoblasts and their conditioned medium. PBL lysates were also prepared as described above for the cytotrophoblasts.
Immunoblotting
Samples were resolved in 10% SDS-PAGE gels and electroblotted to nitrocellulose membranes (Schleicher & Schuell, Keene, NH), according to published methods (23). Membranes were blocked in PBS containing 0.1% Tween-20 (Sigma) and 5% Carnation nonfat dry milk (T-blotto) for 1 h at room temperature, and then incubated with mAb 4H84 (hybridoma supernatant diluted 1/100 in T-Blotto) for 1 h at room temperature. Next, membranes were washed (3 x 10 min) with PBS-Tween and incubated with horseradish peroxidase-conjugated goat anti-mouse IgG (Jackson ImmunoResearch, West Grove, PA) diluted 1/2000 in T-blotto for 30 min at room temperature. Membranes were then processed for chemiluminescence, according to the manufacturer’s instructions (ECL; Amersham, Buckinghamshire, England), and exposed to autoradiography film (Hyperfilm; Amersham).
Glycosidase treatments
Peptide-N-glycosidase F (peptide N4-[N-acetyl-ß-glycosaminyl] asparagine amidase F; PNGase F3) was obtained from Boehringer Mannheim. Before N-deglycosylation, cell lysates, conditioned media, amniotic fluid, and cervical swab samples were boiled for 5 min in 20 mM NaPO4, pH 7.2, 50 mM EDTA, 10 mM sodium azide, and 0.05% SDS. PNGase was then added (8 U/ml), and the samples were incubated overnight at 37°C. Endo-ß-D-galactosidase was obtained from V-Labs (Covington, LA). Digestions with this enzyme (overnight at 37°C) were conducted in 50 mM sodium acetate, pH 5.5. Following glycosidase treatment, samples were boiled in SDS-PAGE sample buffer and either electrophoresed immediately or stored at -80°C for later analyses.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
In a previous study, we used Abs directed against a peptide that
corresponds to amino acids 61–83 of the HLA-G 1 domain to
show, by immunolocalization on tissue sections, that invasive
cytotrophoblasts express this Ib molecule in vivo (11). Since it was
not possible to use these IgM mAbs for immunoblotting, we used the same
immunogen to produce a second generation of anti-HLA-G (IgG) mAbs
that could be used for both immunocytochemistry and immunoblotting.
Several clones from this fusion had the desired properties. We
routinely used an IgG1 mAb produced by one of these clones (4H84)
because of its superior specificity and sensitivity.
First, we compared the staining properties of mAb 4H84 with the mAbs we
produced previously (1B8, 3F6) (11). Frozen sections of second
trimester placenta and placental bed samples were double stained with
an anti-cytokeratin Ab (7D3), which reacts with all trophoblast
cell types (Fig. 1
A),
and 4H84 (Fig. 1B). As we reported earlier,
extravillous invasive cytotrophoblasts in the uterine wall (placental
bed) stained strongly for HLA-G throughout pregnancy. No
immunoreactivity was detected in any cells of floating villi
(syncytiotrophoblast, villus cytotrophoblast, villus core, endothelium,
fetal blood cells). These results suggested that 4H84 had the same
staining characteristics as the anti-HLA-G Abs we originally
produced (11). In our previous study, we did not examine HLA-G
expression in extraembryonic membranes. In this study, we double
stained frozen sections of second trimester (18 wk) amnion-chorion with
7D3, to distinguish amniocytes and cytotrophoblasts (Fig. 1, C and E), and 4H84. All cells of the
amnion layer reacted with the mAb that specifically recognized HLA-G
(Fig. 1D). Many of the multilayered cytotrophoblasts
within the chorion also reacted with the Ab, but not all cells stained
with equal intensity, and some cells failed to demonstrate any
immunoreactivity (Fig. 1F). In addition, a few cells
that did not express cytokeratin reacted weakly with 4H84.
|
SDS-PAGE and immunoblotting of detergent extracts of early
gestation chorionic villi (12 wk) showed the HLA-G heavy chains as
heterodisperse immunoreactive bands smeared across a m.w. range from
approximately Mr 39,000–48,000 (Fig. 2). Conditioned medium from first
trimester (12 wk) placental villi cultured for 48 h contained
bands that spanned a similar m.w. range and also included isoforms of
slightly lower m.w. These results were typical of those we obtained
from early gestation samples, although some contained isoforms of even
higher m.w. Analysis of extracts prepared from term placental villi
showed that they contained less HLA-G per milligram of protein, and
that the bands detected were less heterodisperse. We then investigated
whether a cytotrophoblast cell line (JEG-3) that produces HLA-G makes a
similar array of heavy chain proteins. 4H84 reacted with an
Mr 40,000–43,000 protein in extracts prepared
from JEG cells (Fig. 2). In contrast, the major band identified in
conditioned medium from these cells was an Mr
37,000–40,000 protein. Both of these bands displayed much less m.w.
heterogeneity than those detected in placenta-derived samples. We also
investigated the nature of the HLA-G heavy chains produced by primary
cultures of purified first trimester cytotrophoblasts that were allowed
to differentiate along the invasive pathway in vitro. Both cell
extracts (Fig. 4) and CM samples (data not shown) contained
heterodisperse immunoreactive bands that resembled those detected in
samples of placental villi rather than the HLA-G produced by JEG
cells.
|
|
). PBLs from at least 20 other
individuals were analyzed with identical results (data not shown). In
addition, we have used this mAb for immunolocalization on tissue
sections prepared from at least 30 different placental samples and have
never seen cross-reactivity with other class I (Ia) molecules on
maternal and nontrophoblast fetal cells within these specimens. Thus,
although it is not technically feasible to test this mAb for
cross-reactivity against all alleles, 4H84 does not appear to
cross-react with the commonly expressed classical class I
molecules. Placental HLA-G does not contain epitopes encoded by intron 4
Previous reports suggested that soluble HLA-G is the product of an
alternatively spliced mRNA that contains intron 4. This mRNA has a stop
codon 21 amino acids after the 3 domain, thus excluding the
transmembrane region. LCL.221 cells transfected with a construct that
expresses this mRNA released the corresponding protein,
Gsol (17). To determine whether the Gsol
molecule contributed to the m.w. heterogeneity of the placental HLA-G
heavy chains, we analyzed placental cell extracts and conditioned
medium by immunoblotting with mAb 16G1 (Fig. 3). This mAb was raised against a
synthetic peptide corresponding to a portion of the intron 4 sequence
(17). As a positive control we included a recombinant Gsol
sample, and as a negative control we analyzed PBL extracts. The mAb
16G1 reacted strongly with the recombinant protein, but failed to react
with cell extracts or conditioned medium from placental villi, purified
cytotrophoblasts, or JEG-3 cells.
|
The broad m.w. range of the HLA-G-immunoreactive bands in
placental villi and cytotrophoblast samples could be due to the
presence of other splice variants of the molecule or to heterogeneous
glycosylation. To assess the role of glycosylation, we treated
cytotrophoblast and JEG-3 cell lysates with PNGase F, an asparagine
amidase that releases N-linked oligosaccharide chains, and
then analyzed the products by immunoblotting with 4H84. The results are
shown in Figure 4A. After
N-deglycosylation, the Ab primarily reacted with a more
discrete band (Mr 37,000–42,000) in
cytotrophoblast extracts; a great deal of the smearing previously
observed was eliminated. This band had an electrophoretic mobility that
was similar to HLA-G in JEG cell extracts that had also been treated
with PNGase F. Likewise, enzymatic N-deglycosylation of
HLA-G in extracts of early gestation chorionic villi resulted in a
single major band of Mr 37,000–39,000 band
(Fig. 4B). PNGase F treatment of
conditioned medium from villus explant cultures revealed a prominent
band that comigrated with cell-associated HLA-G. One slightly lower
m.w. band, presumably the soluble form of the molecule, was
consistently detected. In some samples, this band migrated as a doublet
(Fig. 4B). Thus, N-deglycosylation
resolved the HLA-G isoforms into more discrete bands, indicating that
the m.w. heterogeneity observed before treatment was primarily due to
N-linked glycosylation, which could add
Mr 10,000 to the estimated m.w. of the
molecule.
Our previous work shows that trophoblasts add polylactosamine
carbohydrate chains (repeating units of either Galß1,3GlcNAc (type 1)
or Galß1,4GlcNAc (type 2)) to fibronectin and certain integrin
receptors, molecules that carry simple bi- and triantennary chains when
they are isolated from other cellular sources (24, 25). The
4H84-immunoreactive bands observed in the chorionic villus and
cytotrophoblast samples had a ladder-like appearance that was
reminiscent of the polylactosaminylated placental glycoproteins we
described previously (24). This suggested that HLA-G from placental
sources may carry this unusual modification. To test this hypothesis,
we treated cytotrophoblast samples with
endo-ß-D-galactosidase (V-Labs), an enzyme that
hydrolyzes polylactosamine oligosaccharide units, but leaves the rest
of the saccharide core intact. This treatment increased the mobility of
placental HLA-G and decreased the molecular mass heterogeneity and
ladder-like appearance of the bands (Fig. 4A). As
expected from treating the samples with this enzyme, which only
partially deglycosylates the molecule, the
endo-ß-D-galactosidase-treated HLA-G was intermediate in
mobility between untreated and PNGase-treated samples. The mobility of
JEG-3 HLA-G was unaffected by treatment with this enzyme, indicating
that this cell line does not add polylactosamine units to the
oligosaccharides it carries.
HLA-G isoforms are detected in amniotic fluid
We have been very interested in the possibility that biologic
fluids of either maternal or fetal origin contain HLA-G. Given the
pattern of HLA-G protein expression in the amnion-chorion, it seemed
likely that this molecule might be detected in amniotic fluid. To test
this hypothesis, 30 samples were collected from women undergoing
amniocentesis for prenatal genetic testing at 16 to 18 wk of pregnancy;
10 samples were obtained from women undergoing amniocentesis for fetal
maturity assessment in the third trimester of pregnancy. By immunoblot
analysis, we detected HLA-G in every sample. Representative results are
shown in Figure 5. 4H84 reacted with
bands of varying intensity that had different degrees of m.w.
heterogeneity in all of these samples. These differences did not
correlate with gestational age. Treatment of the samples with PNGase F
collapsed the broad bands detected in the untreated samples into a
prominent Mr 35,000–36,000 band corresponding
to the estimated m.w. of the secreted form of HLA-G detected in
placental villus conditioned medium. A much less intense band,
corresponding to the mobility of the cell-associated form of the
molecule (Mr 38,000), was also detected in
most of these samples. The faint Mr 47,000 band
in the enzyme-treated samples was due to nonspecific reactivity of the
secondary Ab used in this experiment. As with the placental samples,
endo-ß-D-galactosidase treatment of amniotic fluid
resulted in a significant reduction in m.w. heterogeneity of the
immunoreactive bands (data not shown).
|
. We readily detected HLA-G in the
cervicovaginal fluid of six of seven women with ruptured membranes. In
all cases, the bands had less m.w. heterogeneity than was observed in
the amniotic fluid samples. HLA-G was not detected in three samples
from women with intact membranes.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Another layer of complexity is added to the interpretation of the immunolocalization data by the fact that whereas cytotrophoblasts are found in three different locations, in only two of these sites do they express HLA-G. With regard to the first location, our previous immunolocalization study with an anti-HLA-G IgM Ab showed that cytotrophoblast stem cells anchored to the basement membranes of chorionic villi do not express this class Ib molecule. But extravillous cytotrophoblasts that detach from this basement membrane and migrate through the columns that connect the placenta to the uterus up-regulate HLA-G expression. Expression in this second location is maintained once the cells have reached their final destination: either the interstitium of the uterine wall or the maternal vessels that traverse this region (11). Our findings have since been confirmed by a different group using yet another anti-HLA-G Ab (26). The fact that the new IgG Ab described in this work (4H84) failed to react with cytotrophoblast stem cells, but stained the extravillous population, suggests that it has the same specificity as the previously described Abs.
Much less is known about cytotrophoblast expression of HLA-G in the third location, the amnion-chorion. The possibility that this subpopulation of cells expresses HLA-G was first suggested by the work of Ellis et al. (7), who found, by using Northern hybridization, that cytotrophoblasts isolated from the amnion-chorion expressed HLA-G mRNA. Subsequently, other studies confirmed this finding (9) and showed that amniotic epithelia also express this mRNA (27). To our knowledge, the present study is the first report of the results of immunolocalization experiments using an HLA-G-specific Ab to study expression of this Ag in the amnion-chorion. In accordance with the mRNA data, we found that both cytotrophoblasts and amniocytes stained brightly with mAb 4H84. This prompted us to consider whether HLA-G, produced by either cell type, may also be a component of amniotic fluid. Immunoblot analyses, performed with the same Ab, confirmed this hypothesis. Taken together, our studies of HLA-G expression in various locations within the placenta and the amnion-chorion suggest that cytotrophoblasts that are in direct contact with maternal tissues express this class Ib molecule. In addition, we now know that the fetus is also surrounded by cells (i.e., amniocytes) that express, and fluid that contains, HLA-G.
We are interested in using the 4H84 mAb and the results of the studies reported in this work to design experiments to understand how HLA-G affects the maternal, and possibly the fetal, immune response during pregnancy. In this regard, our immunoblotting data suggest that the biologic activity of this molecule resides in either the full-length protein or a previously described truncated form (8), the exact origin of which remains elusive. We found no evidence that placental cells produce a soluble protein encoded by an HLA-G mRNA species that contains intron 4. Likewise, we failed to detect any immunoreactive bands corresponding to the predicted m.w. of the proteins that would be encoded by the other alternatively spliced mRNAs that have been described (G2, Mr 26,000; G3, Mr 15,000; G4, Mr 25,000; intron 4 HLA-G, Mr 31,000). In support of this conclusion, extensive Northern hybridization experiments conducted in our laboratory and by other investigators failed to detect transcripts that correspond to the predicted size of these splice variants (8, 10, 11, 28, 29). Thus, it seems likely that the alternatively spliced mRNAs that are frequently detected using reverse-transcriptase PCR (reviewed in 12 are not translated into protein.
A number of recent studies have focused on the role that HLA-G plays in regulating the maternal immune response to the fetus. In vivo, cytotrophoblasts in two locations could be involved in this phenomenon. Whereas little is known about maternal leukocyte interactions with fetal cells in the amnion-chorion, a great deal of evidence suggests that the HLA-G-positive cytotrophoblasts within the uterine wall are in direct contact with the unusual maternal NK cells that reside in this location. Cell-cell interactions within the uterine wall have been simulated in vitro by coculturing LCL.221 cells that overexpress HLA-G with peripheral or decidual NK clones. Using this approach, several groups have identified HLA-G-specific inhibitory receptors on NK cells (30, 31, 32, 33). For example, Soderstrom and colleagues recently showed that HLA-G expressed on target cells inhibits decidual NK cell killing by interacting with the CD94/NKG2 inhibitory receptor.
This inhibitory receptor is a lectin-type molecule, raising the possibility that the types of carbohydrate chains HLA-G carries might be relevant to its biologic activity. Thus, it is interesting to note that HLA-G carries an unusual type of glycosylation. Like all other human class I molecules, it contains a single N-linked glycosylation site (Asn86). But here the similarities end. Whereas the MHC class Ia molecules carry simple biantennary structures (34), HLA-G oligosaccharides are modified by the addition of numerous polylactosamine units. We hypothesize that such a modification could increase the stability of the molecule in the proteinase-rich environment of the uterus. This appears to be one function of the polylactosaminylated saccharides carried by placental fibronectins (24). Additionally, we are intrigued by the possibility that the unusual glycosylation HLA-G carries might enhance its ability to interact with the CD94/NKG2 inhibitory receptor.
The finding that HLA-G, produced by chorionic cytotrophoblasts and amniocytes, is easily detected in amniotic fluid raises the additional possibility that this class Ib molecule could function during development of the fetal immune system. In this regard, it is interesting to note that, beginning in early pregnancy, the fetus swallows amniotic fluid. Oral exposure is known to have efficacy in reestablishing tolerance to Ags that are implicated in autoimmune diseases, such as multiple sclerosis (35) and diabetes (36). Whether this route of exposure could explain how tolerance to HLA-G is established remains to be determined.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Susan J. Fisher, HSW 604, University of California, San Francisco, CA 94143-0512. E-mail address:
3 Abbreviations used in this paper: PNGase F, peptide-N-glycosidase F.
Received for publication December 5, 1997. Accepted for publication February 10, 1998.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
1 domain of HLA-G1 and HLA-G2 inhibits cytotoxicity induced by natural killer cells: is HLA-G the public ligand for natural killer cell inhibitory receptors?. Proc. Natl. Acad. Sci. USA 94:5249.This article has been cited by other articles:
|
|
 |
|
  M. Gauster, A. Blaschitz, and G. Dohr Monoclonal antibody HC10 does not bind HLA-G Rheumatology, May 1, 2007; 46(5): 892 - 893. [Full Text] [PDF]
|
|
|
|
 |
|
 A. van der Meer, H.G.M. Lukassen, B. van Cranenbroek, E.H. Weiss, D.D.M. Braat, M.J. van Lierop, and I. Joosten Soluble HLA-G promotes Th1-type cytokine production by cytokine-activated uterine and peripheral natural killer cells Mol. Hum. Reprod., February 1, 2007; 13(2): 123 - 133. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. Cirulli, J. Zalatan, M. McMaster, R. Prinsen, D. R. Salomon, C. Ricordi, B. E. Torbett, P. Meda, and L. Crisa The Class I HLA Repertoire of Pancreatic Islets Comprises the Nonclassical Class Ib Antigen HLA-G. Diabetes, May 1, 2006; 55(5): 1214 - 1222. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Le Rond, C. Azema, I. Krawice-Radanne, A. Durrbach, C. Guettier, E. D. Carosella, and N. Rouas-Freiss Evidence to Support the Role of HLA-G5 in Allograft Acceptance through Induction of Immunosuppressive/ Regulatory T Cells. J. Immunol., March 1, 2006; 176(5): 3266 - 3276. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Blaschitz, H. Juch, A. Volz, H. Hutter, C. Daxboeck, G. Desoye, and G. Dohr The soluble pool of HLA-G produced by human trophoblasts does not include detectable levels of the intron 4-containing HLA-G5 and HLA-G6 isoforms Mol. Hum. Reprod., October 1, 2005; 11(10): 699 - 710. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Blaschitz, H. Juch, A. Volz, H. Hutter, and G. Dohr Soluble HLA-G, the discussion is going on! Mol. Hum. Reprod., October 1, 2005; 11(10): 723 - 727. [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kobel, G. Pohl, W. D. Schmitt, S. Hauptmann, T.-L. Wang, and I.-M. Shih Activation of Mitogen-Activated Protein Kinase Is Required for Migration and Invasion of Placental Site Trophoblastic Tumor Am. J. Pathol., September 1, 2005; 167(3): 879 - 885. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Le Discorde, C. Le Danff, P. Moreau, N. Rouas-Freiss, and E. D. Carosella HLA-G*0105N Null Allele Encodes Functional HLA-G Isoforms Biol Reprod, August 1, 2005; 73(2): 280 - 288. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. E. Hiby, J. J. Walker, K. M. O'Shaughnessy, C. W.G. Redman, M. Carrington, J. Trowsdale, and A. Moffett Combinations of Maternal KIR and Fetal HLA-C Genes Influence the Risk of Preeclampsia and Reproductive Success J. Exp. Med., October 18, 2004; 200(8): 957 - 965. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. I. Torres, M. Le Discorde, P. Lorite, A. Rios, M. A. Gassull, A. Gil, J. Maldonado, J. Dausset, and E. D. Carosella Expression of HLA-G in inflammatory bowel disease provides a potential way to distinguish between ulcerative colitis and Crohn's disease Int. Immunol., April 1, 2004; 16(4): 579 - 583. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Bilban, N. Ghaffari-Tabrizi, E. Hintermann, S. Bauer, S. Molzer, C. Zoratti, R. Malli, A. Sharabi, U. Hiden, W. Graier, et al. Kisspeptin-10, a KiSS-1/metastin-derived decapeptide, is a physiological invasion inhibitor of primary human trophoblasts J. Cell Sci., March 15, 2004; 117(8): 1319 - 1328. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.S. Hunt, J.L. Pace, P.J. Morales, and C. Ober Immunogenicity of the soluble isoforms of HLA-G Mol. Hum. Reprod., November 1, 2003; 9(11): 729 - 735. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Singer, V. Rebmann, Y.-C. Chen, H.-T. Liu, S. Z. Ali, J. Reinsberg, M. T. McMaster, K. Pfeiffer, D. W. Chan, E. Wardelmann, et al. HLA-G Is a Potential Tumor Marker in Malignant Ascites Clin. Cancer Res., October 1, 2003; 9(12): 4460 - 4464. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. N. Patel, K. C. Quack, J. A. Hill, and D. J. Schust Expression of membrane-bound HLA-G at the maternal-fetal interface is not associated with pregnancy maintenance among patients with idiopathic recurrent pregnancy loss Mol. Hum. Reprod., September 1, 2003; 9(9): 551 - 557. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. C. Ibrahim, Y. Allory, F. Commo, B. Gattegno, P. Callard, and P. Paul Altered Pattern of Major Histocompatibility Complex Expression in Renal Carcinoma: Tumor-Specific Expression of the Nonclassical Human Leukocyte Antigen-G Molecule Is Restricted to Clear Cell Carcinoma While Up-Regulation of Other Major Histocompatibility Complex Antigens Is Primarily Distributed in All Subtypes of Renal Carcinoma Am. J. Pathol., February 1, 2003; 162(2): 501 - 508. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. K. Langat and J. S. Hunt Do Nonhuman Primates Comprise Appropriate Experimental Models for Studying the Function of Human Leukocyte Antigen-G? Biol Reprod, November 1, 2002; 67(5): 1367 - 1374. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. M. Emmer, E. A.P. Steegers, H. M.J. Kerstens, J. Bulten, W. L.D.M. Nelen, K. Boer, and I. Joosten Altered phenotype of HLA-G expressing trophoblast and decidual natural killer cells in pathological pregnancies Hum. Reprod., April 1, 2002; 17(4): 1072 - 1080. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. C. Ibrahim, N. Guerra, M.-J. T. Lacombe, E. Angevin, S. Chouaib, E. D. Carosella, A. Caignard, and P. Paul Tumor-specific Up-Regulation of the Nonclassical Class I HLA-G Antigen Expression in Renal Carcinoma Cancer Res., September 1, 2001; 61(18): 6838 - 6845. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Riteau, N. Rouas-Freiss, C. Menier, P. Paul, J. Dausset, and E. D. Carosella HLA-G2, -G3, and -G4 Isoforms Expressed as Nonmature Cell Surface Glycoproteins Inhibit NK and Antigen-Specific CTL Cytolysis J. Immunol., April 15, 2001; 166(8): 5018 - 5026. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Fisher, O. Genbacev, E. Maidji, and L. Pereira Human Cytomegalovirus Infection of Placental Cytotrophoblasts In Vitro and In Utero: Implications for Transmission and Pathogenesis J. Virol., August 1, 2000; 74(15): 6808 - 6820. [Abstract] [Full Text]
|
|
|
|
|
|
S. Fournel, M. Aguerre-Girr, X. Huc, F. Lenfant, A. Alam, A. Toubert, A. Bensussan, and P. Le Bouteiller Cutting Edge: Soluble HLA-G1 Triggers CD95/CD95 Ligand-Mediated Apoptosis in Activated CD8+ Cells by Interacting with CD8 J. Immunol., June 15, 2000; 164(12): 6100 - 6104. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Copeman, R. N.N. Han, I. Caniggia, M. McMaster, S. J. Fisher, and J. C. Cross Posttranscriptional Regulation of Human Leukocyte Antigen G During Human Extravillous Cytotrophoblast Differentiation Biol Reprod, June 1, 2000; 62(6): 1543 - 1550. [Abstract] [Full Text]
|
|
|
|
|
|
B. A. Kilburn, J. Wang, Z. M. Duniec-Dmuchkowski, R. E. Leach, R. Romero, and D. R. Armant Extracellular Matrix Composition and Hypoxia Regulate the Expression of HLA-G and Integrins in a Human Trophoblast Cell Line Biol Reprod, March 1, 2000; 62(3): 739 - 747. [Abstract] [Full Text]
|
|
|
|
 |
|
 M. Janatpour, M. McMaster, O Genbacev, Y Zhou, J Dong, J. Cross, M. Israel, and S. Fisher Id-2 regulates critical aspects of human cytotrophoblast differentiation, invasion and migration Development, January 2, 2000; 127(3): 549 - 558. [Abstract] [PDF]
|
|
|
|
|
|
S. D. Wainwright, P. A. Biro, and C. H. Holmes HLA-F Is a Predominantly Empty, Intracellular, TAP-Associated MHC Class Ib Protein with a Restricted Expression Pattern J. Immunol., January 1, 2000; 164(1): 319 - 328. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Mallet, A. Blaschitz, L. Crisa, C. Schmitt, S. Fournel, A. King, Y. W. Loke, G. Dohr, and P. Le Bouteiller HLA-G in the human thymus: a subpopulation of medullary epithelial but not CD83+ dendritic cells expresses HLA-G as a membrane-bound and soluble protein Int. Immunol., June 1, 1999; 11(6): 889 - 898. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
