Anti-HLA G Antibody [MEM-G/1] (A86276)

In early pregnancy, trophoblasts and the fetus experience hypoxic and low-nutrient conditions; nevertheless, trophoblasts invade the uterine myometrium up to one third of its depth and migrate along the lumina of spiral arterioles, replacing the maternal endothelial lining. Here, we showed that autophagy, an intracellular bulk degradation system, occurred in extravillous trophoblast (EVT) cells under hypoxia in vitro and in vivo. An enhancement of autophagy was observed in EVTs in early placental tissues, which suffer from physiological hypoxia. The invasion and vascular remodeling under hypoxia were significantly reduced in autophagy-deficient EVT cells compared with wild-type EVT cells. Interestingly, soluble endoglin (sENG), which increased in sera in preeclamptic cases, suppressed EVT invasion by inhibiting autophagy. The sENG-inhibited EVT invasion was recovered by TGFB1 treatment in a dose-dependent manner. A high dose of sENG inhibited the vascular construction by EVT cells and human umbilical vein endothelial cells (HUVECs), meanwhile a low dose of sENG inhibited the replacement of HUVECs by EVT cells. A protein selectively degraded by autophagy, SQSTM1, accumulated in EVT cells in preeclamptic placental biopsy samples showing impaired autophagy. This is the first report showing that impaired autophagy in EVT contributes to the pathophysiology of preeclampsia.

B virus of the family Herpesviridae is endemic to rhesus macaques but results in 80% fatality in untreated humans who are zoonotically infected. Downregulation of major histocompatibility complex (MHC) class I in order to evade CD8(+) T-cell activation is characteristic of most herpesviruses. Here we examined the cell surface presence and total protein expression of MHC class I molecules in B virus-infected human foreskin fibroblast cells and macaque kidney epithelial cells in culture, which are representative of foreign and natural host initial target cells of B virus. Our results show <20% downregulation of surface MHC class I molecules in either type of host cells infected with B virus, which is statistically insignificantly different from that observed in uninfected cells. We also examined the surface expression of MHC class Ib molecules, HLA-E and HLA-G, involved in NK cell inhibition. Our results showed significant upregulation of HLA-E and HLA-G in host cells infected with B virus relative to the amounts observed in other herpesvirus-infected cells. These results suggest that B virus-infected cell surfaces maintain normal levels of MHC class Ia molecules, a finding unique among simplex viruses. This is a unique divergence in immune evasion for B virus, which, unlike human simplex viruses, does not inhibit the transport of peptides for loading onto MHC class Ia molecules because B virus ICP47 lacks a transporter-associated protein binding domain. The fact that MHC class Ib molecules were significantly upregulated has additional implications for host-pathogen interactions.

Gestational choriocarcinoma is a malignant trophoblastic tumor. The development of novel molecular-targeted therapies is needed to reduce the toxicity of current multiagent chemotherapy and to treat successfully the chemoresistant cases. The molecular mechanisms underlying choriocarcinoma tumorigenesis remain uncharacterized, however, and appropriate choriocarcinoma animal models have not yet been developed. In this study, we established a choriocarcinoma model by inoculating mice with induced-choriocarcinoma cell-1 (iC³-1) cells, generated from HTR8/SVneo human trophoblastic cells retrovirally transduced with activated H-RAS (HRASV12). The iC³-1 cells exhibited constitutive activation of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways and developed into lethal tumors in all inoculated mice. Histopathological analysis revealed that the tumors consisted of two distinct types of cells, reminiscent of syncytiotrophoblasts and cytotrophoblasts, as seen in the human choriocarcinoma. The tumors expressed HLA-G and cytokeratin (trophoblast markers) and hCG (a choriocarcinoma marker). Comparative analysis of gene expression profiles between iC³-1 cells and parental HTR8/SVneo cells revealed that iC³-1 cells expressed matrix metalloproteinases, epithelial-mesenchymal transition-related genes, and SOX3 at higher levels than parental trophoblastic cells. Administration of SOX3-specific short-hairpin RNA decreased SOX3 expression and attenuated the tumorigenic activity of iC³-1 cells, suggesting that SOX3 overexpression might be critically involved in the pathogenesis of choriocarcinoma. Our murine model represents a potent new tool for studying the pathogenesis and treatment of choriocarcinoma.

Decidual artery remodeling is essential for a healthy pregnancy. This process involves loss of vascular smooth muscle cells and endothelium, which are replaced by endovascular trophoblasts (vEVTs) embedded in fibrinoid. Remodeling is impaired during pre-eclampsia, a disease of pregnancy that results in maternal and fetal mortality and morbidity. Early vascular changes occur in the absence of vEVTs, suggesting that another cell type is involved; evidence from animal models indicates that decidual leukocytes play a role. We hypothesized that leukocytes participate in remodeling through the triggering of apoptosis or extracellular matrix degradation. Decidua basalis samples (8 to 12 weeks gestation) were examined by immunohistochemistry to elucidate associations between leukocytes, vEVTs, and key remodeling events. Trophoblast-independent and -dependent phases of remodeling were identified. Based on a combination of morphological attributes, vessel profiles were classified into a putative temporal series of four stages. In early stages of remodeling, vascular smooth muscle cells showed dramatic disruption and disorganization before vEVT presence. Leukocytes (identified as uterine natural killer cells and macrophages) were apparent infiltrating vascular smooth muscle cells layers and were matrix metalloproteinase-7 and -9 immunopositive. A proportion of vascular smooth muscle cells and endothelial cells were terminal deoxynucleotidyl transferase dUTP nick-end labeling positive, suggesting remodeling involves apoptosis. We thus confirm that vascular remodeling occurs in distinct trophoblast-independent and -dependent stages and provide the first evidence of decidual leukocyte involvement in trophoblast-independent stages.

Human leucocyte antigen G (HLA-G) is a tolerogenic molecule that protects the fetus from maternal immune attack, may favour tumoral immunoescape and is up-regulated in viral and inflammatory diseases. The aim of this work was to discover if nitric oxide (NO) could affect HLA-G expression or function because NO is an important modulator of innate and adaptive immunity. For this purpose HLA-G expression and function were analysed following treatment with a NO donor or a peroxynitrite donor in various cell lines expressing HLA-G either spontaneously or upon transfection. Results showed NO-dependent nitration of both cellular and soluble HLA-G protein, but not all HLA-G moieties underwent nitration. Endogenous biosynthesis of NO by both U-937-HLA-G1 and M8-HLA-G5 stable transfectants also caused HLA-G nitration. The NO decreased total HLA-G cellular protein content and expression on the cell surface, while increasing HLA-G shedding into the culture medium. This effect was post-transcriptional and the result of metalloprotease activity. By contrast, NO pretreatment did not affect HLA-G capability to suppress NK cytotoxicity and lymphocyte proliferation. Our studies show that NO regulates the availability of HLA-G molecules without modifying their biological activities.

HLA-G is a nonclassical class I MHC molecule with an unknown function and with unusual characteristics that distinguish it from other class I MHC molecules. Here, we demonstrate that HLA-G forms disulfide-linked dimers that are present on the cell surface. Immunoprecipitation of HLA-G from surface biotinylated transfectants using the anti-beta2-microglobulin mAb BBM.1 revealed the presence of an approximately equal 78-kDa form of HLA-G heavy chain that was reduced by using DTT to a 39-kDa form. Mutation of Cys-42 to a serine completely abrogated dimerization of HLA-G, suggesting that the disulfide linkage formed exclusively through this residue. A possible interaction between the HLA-G monomer or dimer and the KIR2DL4 receptor was also investigated, but no interaction between these molecules could be detected through several approaches. The cell-surface expression of dimerized HLA-G molecules may have implications for HLA-Greceptor interactions and for the search for specific receptors that bind HLA-G.

The MHC class Ib molecule HLA-G has previously been reported to be the ligand for the NK cell receptor killer Ig-like receptor (KIR)2DL4, but this remains controversial. In this study, we investigated IFN-γ production by freshly isolated NK cells in response to both soluble and solid-phase ligands, including anti-KIR2DL4 mAbs and rHLA-G. Although freshly isolated CD56(bright) NK cells produced IFN-γ in response to soluble HLA-G preparations, the response was found to be absolutely dependent on the presence of small numbers of contaminating CD56(-), CD14(-), CD11c(+) myeloid dendritic cells (mDCs). HLA-G tetramers bound only to the contaminating mDCs in the NK preparations, and Abs to KIR2DL4 and HLA-G did not block NK cell IFN-γ production. NK cells did not respond to plate-bound HLA-G. Freshly isolated NK cells also produced IFN-γ in response to unpurified soluble anti-KIR2DL4 mAb but not to low endotoxin affinity-purified Ab. The data suggest that previous reports of functional interactions between KIR2DL4 and HLA-G may have resulted from the use of purified NK cells that were contaminated with mDCs and HLA-G preparations that were contaminated with material capable of stimulating mDCs to produce cytokines that stimulate NK cells to produce IFN-γ.

Failures in human extravillous trophoblast (EVT) development could be involved in the pathogenesis of pregnancy diseases. However, the underlying mechanisms have been poorly characterized. Here, we provide evidence that Notch signaling could represent a key regulatory pathway controlling trophoblast proliferation, motility, and differentiation. Immunofluorescence of first-trimester placental tissues revealed expression of Notch receptors (Notch2 and Notch3) and membrane-anchored ligands (delta-like ligand [DLL] 1 and -4 and Jagged [JAG] 1 and -2) in villous cytotrophoblasts (vCTBs), cell column trophoblasts (CCTs), and EVTs. Notch4 and Notch1 were exclusively expressed in vCTBs and in CCTs, respectively. Both proteins decreased in Western blot analyses of first-trimester, primary cytotrophoblasts (CTBs) differentiating on fibronectin. Luciferase reporter analyses suggested basal, canonical Notch activity in SGHPL-5 cells and primary cells that was increased upon seeding on DLL4-coated dishes and diminished in the presence of the Notch/γ-secretase inhibitors N-[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester (DAPT) or L-685,458. Bromodeoxyuridine labeling, cyclin D1 mRNA expression, and cell counting indicated that chemical inhibition of Notch signaling elevated proliferation in the different primary trophoblast model systems. Notch inhibition also increased motility of SGHPL-5 cells through uncoated and fibronectin-coated Transwells, motility of primary CTBs, as well as migration in villous explant cultures on collagen I. Accordingly, small interfering RNA-mediated gene silencing of Notch1 also elevated SGHPL-5 cell migration. In contrast, motility of primary cultures and SGHPL-5 cells was diminished in the presence of DLL4. Moreover, DAPT increased markers of differentiated EVT, ie, human leukocyte antigen G1, integrin α5, and T-cell factor 4, whereas DLL4 provoked the opposite. In summary, the data suggest that canonical Notch signaling impairs motility and differentiation of first-trimester CTBs.

In order to characterize the degree of immunosuppression in regional immunity in patients with melanoma, we used immunohistochemistry to analyze markers of T-cell subtype and polarity, costimulation, dendritic cell maturation, monocytes, lymphatic vasculature, and angiogenesis. Specifically, we analyzed expression of CD4, CD8, CD14, CD40, CD86, CD123, HLA-DR, IL-10, LYVE, VEGFR3, and VEGF-C in lymph nodes. We compared sentinel lymph nodes with and without metastasis from patients with melanoma with both infection inflamed (reactive) and dormant human lymph nodes. There were no differences demonstrated between sentinel lymph nodes with or without metastasis from patients with melanoma in any of the markers that were tested. Both groups of sentinel lymph nodes had fewer CD8(+) T cells than either set of control nodes. Whereas the infection inflamed lymph nodes demonstrated Th2 polarity, the dormant lymph nodes demonstrated Th1 polarity. In conclusion, changes in regional immunity appeared to precede metastasis in melanoma. Whether there was tumor present in sentinel lymph nodes or not, these nodes demonstrated a marked decrease in cytotoxic T cells compared with both sets of controls. Furthermore, the control lymph nodes used for comparison can significantly impact interpretation, as the dormant and reactive lymph nodes markedly varied in their immune profiles. These immunologic changes may explain the successful metastasis of melanoma in the midst of the immune environment of the sentinel lymph node, and lend insights into the mechanisms of lymphatic metastases in other solid malignancies.

Classical Hodgkin's lymphoma (cHL) is characterized by the presence of an abundant reactive infiltrate, lacking effective cytotoxic responses. Especially in Epstein-Barr virus (EBV)-negative cHL, the neoplastic Hodgkin-Reed-Sternberg (HRS) cells have lost protein expression of major histocompatibility complex (MHC) class I, enabling escape from cytotoxic T lymphocyte (CTL) responses. However, downregulation of MHC class I generally induces natural killer (NK) cell activation. The paucity of NK cells in the reactive infiltrate of cHL and the systemic NK cell deficiency observed in cHL patients led us to investigate the expression of human leukocyte antigen (HLA)-G, which is known to inhibit NK-cell- and CTL-mediated cytotoxicity. By immunohistochemistry, HLA-G protein was expressed by HRS cells in 54% (95/175) of cHL cases. This expression was associated with absence of MHC class I on the cell surface of HRS cells (P < 0.001) and EBV-negative status (P < 0.001). Previously, genetic markers located in the proximity of the HLA-A and HLA-G genes had been shown to be associated with susceptibility to EBV-positive cHL. In the present study, these markers associated with MHC class I protein expression but not with presence of HLA-G. Our results suggest that induction of HLA-G protein expression in HRS cells contributes to the modulation of immune responses observed in cHL.

Human trophoblast is composed of a heterogeneous population of cells, which give rise to a variety of trophoblastic tumors and tumor-like lesions. In this report, we analyzed the expression pattern of the p63 gene, a transcription factor belonging to the p53 family, in different trophoblastic subpopulations and in trophoblastic lesions. p63 has various isoforms that are classified into two groups designated TA and DeltaNp63 isoforms. The TA isoforms have a p53-like suppressor function, whereas the DeltaNp63 isoforms exert an oncogenic effect. Based on immunohistochemistry and RT-PCR, it appears that cytotrophoblast expresses the DeltaNp63 isoform whereas chorionic-type intermediate trophoblast in the fetal membranes, placental site nodules, and epithelioid trophoblastic tumors expresses the TAp63 isoform. Intermediate trophoblast in the implantation site and placental site trophoblastic tumors does not express p63. Based on the expression patterns of p63 and the previously described expression patterns of other trophoblastic markers, including HLA-G, cytokeratin 18, hPL, and Ki-67, we developed an immunohistochemical algorithm to diagnose trophoblastic lesions. A validation set of 22 trophoblastic lesions and 34 nontrophoblastic tumors were classified correctly using this algorithm. In conclusion, the findings in this study demonstrate that different trophoblastic subpopulations and their related trophoblastic lesions are characterized by distinctive patterns of p63 expression. Recognizing these distinctive expression patterns helps to further elucidate the biology of trophoblast and can also provide a useful tool for the differential diagnosis of trophoblastic lesions.

HLA-G is an effective ligand of natural killer (NK) inhibitory receptors, HLA-G transcripts have been detected in several human tumors, and cytokines like gamma interferon (IFN) enable HLA-G molecules to be expressed. These findings are particularly upsetting in case of melanomas: IFN treatment is frequently included in melanoma therapeutic protocols, and downregulation of classical class I molecules occurs in nearly half of these tumors. Therefore, a melanoma cell downregulating classical class I and de novo expressing HLA-G, either constitutively or upon IFN treatment, is probably a stealthy target for the immune system, having inhibited both the cytotoxic T lymphocyte (CTL) and the NK activity. To elucidate this point we have investigated the expression of HLA-G molecules in 45 melanoma cell lines before and after gammaIFN treatment. Analysis was performed by immunofluorescence and flow cytometry, using the anti-HLA-G MoAbs 87G and G233, by Western blot, using the anti-HLA-G MEM/G1 MoAb and PAG1 antiserum, and by RT-PCR analysis. In addition, 8 melanoma tissues from patients free from therapy and 6 nevi were studied by immunohistochemistry using the 87G MoAb. No evidence was gathered of HLA-G expression, neither constitutive nor, in cell lines, after gammaIFN treatment. We therefore conclude that HLA-G expression is an uncommon event in melanomas, and that a therapy including IFNs cannot harm the patient by inducing the de novo expression of HLA-G molecules at least in its G1 isoform.

Different HLA-G monoclonal antibodies (mAbs) were first evaluated for their capability to identify soluble HLA-G (sHLA-G) in ELISA. Three of them, namely 87G, BFL.1 and MEM-G/9, when used as coating mAbs together with W6/32 capture mAb, identified beta2-microglobulin (beta2m)-associated-sHLA-G but not soluble HLA-B7 (sHLA-B7) in cell culture supernatants from transfected cells. By comparison, the anti-HLA class I mAb 90 did recognize both sHLA-G and sHLA-B7. By using these HLA-G mAbs, sHLA-G was identified in amniotic fluids as well as in culture supernatants of first trimester and term placental explants but not in cord blood. Intron 4-retaining sHLA-G isoforms were identified in some amniotic fluids by the use of an intron 4-specific mAb (16G1). Reactivity of these different HLA-G mAbs was then compared to determine their respective binding sites on soluble and membrane-bound HLA-G. Using both ELISA and flow cytometry analysis, we showed that they did not compete with each other, which suggested that they did not recognize the same determinants. Finally, we report that two mAbs directed against the alpha1 domain of HLA class I heavy chain (mAb 90 and YTH 862) did compete with 87G, therefore demonstrating that this latter mAb recognized an epitope localized on this external domain of HLA-G.

BACKGROUND:

Soluble human leucocyte antigen-G (sHLA-G) is secreted by extravillous trophoblast (EVT) and has roles in regulating immune cells within the decidua. HLA-G expression on EVT increases as they approach uterine spiral arteries and we have suggested that sHLA-G may be important in the remodelling of these vessels. The autocrine role of sHLA-G in regulating trophoblast function at this critical phase has not been studied. We aimed to investigate the effects of sHLA-G on trophoblast motility, invasion and survival.

METHODS:

The human EVT line, SGHPL-4, was stably transfected to over-express sHLA-G (SGHPL-4sG1). Motility and apoptosis were assessed by time-lapse microscopy. Cells were cultured on microcarrier beads embedded in fibrin gels to assess invasion. The effect of sHLA-G expression on motility, invasion and apoptosis in response to stimulation with either hepatocyte growth factor (HGF) or epidermal growth factor (EGF) was determined.

RESULTS:

There was no difference in the motility of either SGHPL-4 cells or SGHPL-4sG1 cells in the absence of stimulation. However, sHLA-G inhibited HGF-induced EVT motility. HGF- and EGF-induced invasions were significantly inhibited in SGHPL-4sG1 compared with SGHPL-4 cells. Increased expression of HLA-G had no significant effect on tumour necrosis factor (TNF)-alpha/actinomycin-induced apoptosis.

CONCLUSIONS:

Growth factor-stimulated trophoblast motility and invasion are regulated by sHLA-G, indicating a novel autocrine role. The inhibition of trophoblast invasion at the spiral artery may be important to allow interactions leading to vascular remodelling.