HLA-G: from biology to clinical benefits

HLA-G UTR haplotype conservation in the Malian population: association with soluble HLA-G

The HLA-G molecule plays an important role in immunomodulation. In a previous study carried out on a southern French population our team showed that HLA-G haplotypes, defined by SNPs in the coding region and specific SNPs located in 5'URR and 3'UTR regulatory regions, are associated with differential soluble HLA-G expression (sHLA-G). Furthermore, the structure of these HLA-G haplotypes appears to be conserved in geographically distant populations. The aim of our study is to confirm these expectations in a sub-Saharan African population and to explore additional factors, such as HLA-A alleles, that might influence sHLA-G expression. DNA and plasma samples were collected from 229 Malians; HLA-G and HLA-A genotyping were respectively performed by the Snap Shot® method and by Luminex™ technology. sHLA-G dosage was performed using an ELISA kit. HLA-G and HLA-A allelic and haplotypic frequencies were estimated using an EM algorithm from the Gene[Rate] program. Associations between genetic and non genetic parameters with sHLA-G were performed using a non-parametric test with GRAPH PAD Prism 5. Our results reveal a good conservation of the HLA-G UTR haplotype structure in populations with different origins and demographic histories. These UTR haplotypes appear to be involved in different sHLA-G expression patterns. Specifically, the UTR-2 haplotype was associated with low sHLA-G levels, displaying a dominant negative effect. Furthermore, an allelic effect of both HLA-G and HLA-A, as well as non genetic parameters, such as age and gender possibly linked to osteogenesis and sexual hormones, also seem to be involved in the modulation of sHLA-G. These data suggest that further investigation in larger cohorts and in populations from various ethnical backgrounds is necessary not only to detect new functional polymorphism in HLA-G regulatory regions, but also to reveal the extent of biological phenomena that influence sHLA-G secretion and this might therefore have an impact on transplantation practice.

The clinicopathologic significance of the expression of HLA-G in oral squamous cell carcinoma

OBJECTIVE

This study aimed to evaluate HLA-G expression in primary oral cavity squamous cell carcinoma (OCSCC) and potentially malignant lesions and to evaluate its relationship with clinicopathologic parameters.

STUDY DESIGN

HLA-G expression in samples from patients with metastatic and nonmetastatic OCSCC (n = 60), potentially malignant lesions (n = 15), and clinically and histologically normal oral mucosa (n = 10) was characterized by immunohistochemistry. The density of CD8, CD83, and CD68 cells and Ki-67(+) and bcl-2(+) neoplastic cells were analyzed.

RESULTS

HLA-G expression by neoplastic cells was significantly higher in metastatic OCSCC compared with nonmetastatic OCSCC (P = .01). Higher HLA-G expression was observed in OCSCC than in potentially malignant lesions (P = .006). Moreover, patients with lower HLA-G expression exhibited a tendency toward longer survival (22 months) compared with those with higher HLA-G expression (16 months).

CONCLUSIONS

Our findings suggest that increased HLA-G expression in metastatic OCSCC may represent a tumor escape mechanism, which portends an unfavorable clinical prognosis.

Mutated HLA-G3 localizes to the cell surface but does not inhibit cytotoxicity of natural killer cells

HLA-G plays an important role in the induction of immune tolerance. Various attempts to produce good manufacturing practice levels of HLA-G as a therapeutic molecule have failed to date partly due to the complicated structure of full-length HLA-G1. Truncated HLA-G3 is simpler and easier to produce than HLA-G1 and contains the expected functional epitope in its only α1 monomorphic domain. In this study, we engineered the ER retrieval and retention signal on HLA-G3's cytoplasmic tail by replacing its RKKSSD motif with RAASSD. We observed that mutated HLA-G3 was highly expressed on the cell surface of transduced K562 cells but did not inhibit cytotoxicity of natural killer cells.

Polymorphic sites at the 3' untranslated region of the HLA-G gene are associated with differential hla-g soluble levels in the Brazilian and French population

HLA-G molecule has well-recognized tolerogenic properties, and the encoding gene shows lower frequency of polymorphism at the coding region but higher variability at regulatory 5' and 3' untranslated (3'UTR) regions. At least three 3'UTR polymorphic sites have been associated with HLA-G mRNA regulation, including the 14 base pair (14bp) Insertion/Deletion, +3142C-G and +3187A-G. We studied the association of polymorphic sites at 3'UTR (sequencing analysis, encompassing the 14bp Ins-Del/+3003T-C/+3010C-G/+3027C-A/+3035C-T/+3142C-G/+3187A-G/+3196C-G polymorphic sites) with plasma soluble HLA-G levels (sHLA-G, detected by ELISA) in 187 French and 153 Brazilian healthy individuals. Allele and genotype frequencies were closely similar in both populations; however, Brazilians showed a higher HLA-G 3'UTR haplotype diversity. Considering sHLA-G levels in both populations altogether, individuals presenting 14bp Del/Del showed higher levels compared to 14bpIns/Ins genotype (P <0.05); those presenting +3010C/G showed higher levels compared to the +3010C-C genotype (P< 0.05); those presenting +3027C-C showed higher levels than the +3027A-A genotype (P< 0.05); and those bearing +3035C-C showed higher levels compared to the +3035C-T (P < 0.01) and +3035T-T (P < 0.05) genotypes. The analyses of 3'UTR haplotypes showed that UTR-1 (DelTGCCCGC) was associated with higher expression of sHLA-G, whereas UTR-5 (InsTCCTGAC) and UTR-7 (InsTCATGAC) with lower expression and other UTRs (UTR-2/3/4/6) exhibited intermediate levels. Since the differential expression of HLA-G may be beneficial or harmful depending on the underlying condition, the identification of individuals genetically programmed to differentially express HLA-G may help on defining novel strategies to control the immune response against the underlying disorder.

Genetic variants within the MHC region are associated with immune responsiveness to childhood vaccinations

The influence of genetic variability within the major histocompatibility complex (MHC) region on variations in immune responses to childhood vaccination was investigated. The study group consisted of 135 healthy infants who had been immunized with hepatitis B (HBV), 7-valent pneumococcal conjugate (PCV7), and diphtheria, tetanus, acellular pertussis (DTaP) vaccines according to standard childhood immunization schedules. Genotype analysis was performed on genomic DNA using Illumina Goldengate MHC panels (Mapping and Exon Centric). At the 1 year post vaccination check-up total, isotypic, and antigen-specific serum antibody levels were measured using multiplex immunoassays. A number of single nucleotide polymorphisms (SNPs) within MHC Class I and II genes were found to be associated with variations in the vaccine specific antibody responses and serum levels of immunoglobulins (IgG, IgM) and IgG isotypes (IgG1, IgG4) (all at p<0.001). Linkage disequilibrium patterns and functional annotations showed that significant SNPs were strongly correlated with other functional regulatory SNPs. These SNPs were found to regulate the expression of a group of genes involved in antigen processing and presentation including HLA-A, HLA-C, HLA-G, HLA-H, HLA-DRA, HLA-DRB1, HLA-DRB5, HLA-DQA1, HLA-DQB1, HLA-DOB, and TAP-2. The results suggest that genetic variations within particular MHC genes can influence immune response to common childhood vaccinations, which in turn may influence vaccine efficacy.

HLA-G 5' URR SNPs and 3' UTR 14-bp insertion/deletion polymorphism in an Afro-Brazilian population from Paraná State

The present study investigated 23 SNPs in the 5'URR promoter region and the 14 bp ins/del polymorphism at the 3'UTR region of the HLA-G gene in 150 individuals with Afro-Brazilian ancestry. Three haplotypes were found to be the most frequent. Comparing these polymorphisms in other samples, our data suggest that Afro-Brazilians are more similar to the Euro-Brazilians than to Hutterite population.

Synthetic HLA-G proteins for therapeutic use in transplantation

The human leukocyte antigen (HLA)-G is a tolerogenic molecule, whose expression by allografts is associated with better acceptance. An increasing interest in producing HLA-G as a clinical-grade molecule for therapy use is impaired by its complexity and limited stability. Our purpose was to engineer simpler and more stable HLA-G-derived molecules than the full-length HLA-G trimolecular complex that are also tolerogenic, functional as soluble molecules, and compatible with good manufacturing practice (GMP) production conditions. We present two synthetic molecules: (α3-L)x2 and (α1-α3)x2 polypeptides. We show their capability to bind the HLA-G receptor LILRB2 and their functions in vitro and in vivo. The (α1-α3)x2 polypeptide proved to be a potent tolerogenic molecule in vivo: One treatment of skin allograft recipient mice with (α1-α3)x2 was sufficient to significantly prolong graft survival, and four weekly treatments induced complete tolerance. Furthermore, (α1-α3)x2 was active as a soluble molecule and capable of inhibiting the proliferation of tumor cell lines, as does the full length HLA-G trimolecular complex. Thus, the synthetic (α1-α3)x2 polypeptide is a stable and simpler alternative to the full-length HLA-G molecule. It can be produced under GMP conditions, it functions as a soluble molecule, and it is at least as tolerogenic as HLA-G in vivo.

The expression of human leukocyte antigen G (HLA-G) is associated with sacroiliitis stages of ankylosing spondylitis

Recent studies have demonstrated that human leukocyte antigen G (HLA-G) may play an important role in autoimmune diseases. The present study is to investigate whether or not HLA-G is associated with sacroiliitis stages of ankylosing spondylitis (AS), a systemic autoimmune disease. Plasma levels of soluble HLA-G (sHLA-G) and HLA-G expression on the surface of peripheral blood mononuclear cells (PBMCs) were measured in 55 AS patients and 49 healthy controls by using a specific HLA-G ELISA and flow cytometric (FCM) analysis, respectively. Association of HLA-G expression with sacroiliitis stages of the patients was statistically analyzed. The plasma sHLA-G concentrations were noticeably lower in the AS patients when compared to the healthy controls while the mean fluorescence intensity (MFI) of the HLA-G expression on the surface of PBMCs was significantly higher in the AS patients than in the healthy controls (both P<0.0001). The HLA-G expression on the surface of PBMCs, plasma sHLA-G levels and HLA-B27 expression were significantly correlated to each other. Moreover, the plasma sHLA-G was inversely associated with the sacroiliitis stages (P=0.008), while the HLA-G expression on the surface of PBMCs increased from stage 0 to II but decreased in stage III (P=0.001). The significant association of HLA-G expressions with AS sacroiliitis stages suggests that HLA-G is possibly involved in the pathology of the disease. The detection of HLA-G expression may therefore be a useful laboratory test to reveal disease process in AS patients.

Elevation of human leukocyte antigen-G expression is associated with the severe encephalitis associated with neurogenic pulmonary edema caused by Enterovirus 71

Enterovirus 71 (EV71) infection can develop devastating clinical outcomes such as brain stem encephalitis (BE) and pulmonary edema (PE). Alteration of human leukocyte antigen-G (HLA-G) expression or cytokine production was considered playing important roles in virus-related pathogenesis. However, clinical relevance of HLA-G in EV71 infection remains unknown. In the current study, patients were stratified by disease severity as BE (n = 107) and PE (n = 18). HLA-G expression on peripheral blood monocytes from patients with BE (n = 15), patients with PE (n = 15) and control subjects (n = 31) was analyzed with flow cytometry. Plasma soluble HLA-G (sHLA-G) (in 67 BE, 18 PE and 120 control subjects), IL-6 and IL-10 (in 50 patients with BE, 18 patients with PE and 45 control subjects) were determined with enzyme-linked immunosorbent assay. Data showed that the percentage of HLA-G-positive monocytes (mean 7.76 vs 3.68 %, p < 0.001), levels for sHLA-G (median 129.2 vs 70.6 U/ml, p < 0.001), IL-10 (median 160.5 vs 29.5 pg/ml, p < 0.001) and IL-6 (median 20.50 vs 5.21 pg/ml, p = 0.002) was significantly higher in patients with PE than in patients with BE. Taken together, our findings indicated that elevation of HLA-G expression on monocytes, plasma sHLA-G, IL-10 and IL-6 levels was associated with PE in patients infected with EV71.

Network-guided sparse regression modeling for detection of gene-by-gene interactions

MOTIVATION

Genetic variants identified by genome-wide association studies to date explain only a small fraction of total heritability. Gene-by-gene interaction is one important potential source of unexplained total heritability. We propose a novel approach to detect such interactions that uses penalized regression and sparse estimation principles, and incorporates outside biological knowledge through a network-based penalty.

RESULTS

We tested our new method on simulated and real data. Simulation showed that with reasonable outside biological knowledge, our method performs noticeably better than stage-wise strategies (i.e. selecting main effects first, and interactions second, from those main effects selected) in finding true interactions, especially when the marginal strength of main effects is weak. We applied our method to Framingham Heart Study data on total plasma immunoglobulin E (IgE) concentrations and found a number of interactions among different classes of human leukocyte antigen genes that may interact to influence the risk of developing IgE dysregulation and allergy.

AVAILABILITY

The proposed method is implemented in R and available at http://math.bu.edu/people/kolaczyk/software.html.

CONTACT

chenlu@bu.edu

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

The 14bp-deletion allele in the HLA-G gene confers susceptibility to the development of hepatocellular carcinoma in the Brazilian population

Human leukocyte antigen-G (HLA-G) is a nonclassical HLA class I molecule involved in tumor escape mechanisms. Considering that the HLA-G 14bp insertion/deletion polymorphism is located at the 3' untranslated region (3'UTR) in exon 8, and since it has been associated with the magnitude of HLA-G production, we studied the association of 14bp insertion/deletion polymorphism with the risk of developing hepatocellular carcinoma (HCC). A total of 109 HCC patients followed at the University Hospital, Faculty of Medicine of Ribeirão Preto, São Paulo, Brazil, and 202 healthy controls from the same geographic area were genotyped for the 14bp insertion/deletion polymorphism using polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis. Compared to controls, the frequency of the 14bp deletion allele was overrepresented in HCC patients (65% versus 56%, respectively, P = 0.0326). The 14bp deletion conferred an odds ratio (OR) of 1.46 [95% confidence interval (CI): 1.04-2.05]. Similarly, the deletion/deletion genotype was marginally overrepresented in HCC patients (45% versus 35% in controls, P = 0.0871), conferring an OR of 1.54 (95% CI: 0.96-2.48). The frequencies of the deletion/insertion or insertion/insertion genotypes observed in patients were not statistically different from those observed in controls (P > 0.05). Our results suggest that the 14bp-deletion allele in HLA-G gene is associated with HCC susceptibility in a Brazilian population.

HLA-G 2012 conference: the 15-year milestone update

The non-classical human leukocyte antigen (HLA) Class I molecule HLA-G is best known for its tolerogenic function at the maternal-fetal interface, where it protects the fetus from destruction by the immune system of its mother. Yet, HLA-G has been the topic of intense investigations and its functions reach much further than originally believed. International conferences on HLA-G have taken place every 3 years since 1998, and the Sixth International Conference on HLA-G, that took place in Paris in July 2012. It counted 180 attendees from 28 countries, 35 speakers in plenary sessions, and 63 presentations of research in symposia and poster sessions, bringing new insight in HLA-G research. Here we summarize the major advances on the function and nature of HLA-G molecule that were reported, with particular interest on the findings in new mechanisms of action through regulatory cells, its relevance in cancer as well as in the molecular structure and functions of HLA-G, which are key for its clinical application.

HLA-G expression in acute lymphoblastic leukemia: a significant prognostic tumor biomarker

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility class Ib antigen with multiple immune regulatory functions including the induction of immune tolerance in malignancies. The goal of our study was to investigate the expression of membrane form of HLA-G in acute lymphoblastic leukemia (ALL) before and after therapy in a trial to evaluate its role as a tumor escape mechanism and prognosis. So we measured its expression by reverse transcription (RT)-PCR in peripheral blood mononuclear cells of 25 (ALL) patients and 15 healthy controls and correlated our findings with a variety of clinical and laboratory variables and two important cytokines, IL-10 and INF-γ, and with natural killer (NK) cells. Serum levels of IL-10 and INF-γ were measured by ELISA. NK cells were quantitated by flow cytometry. The best cutoff values for the investigated markers were determined by ROC curve. The current study showed that membrane-bound HLA-G expression levels and positivity rates above the cutoff value 0.37 were significantly higher in ALL patients at diagnosis compared to after therapy and both showed significant higher levels than in normal control group (P < 0.01). Moreover, IL-10 and INF-γ serum levels were significantly elevated in ALL patients at time of diagnosis compared to healthy controls with a significant reduction in their levels in ALL patients after receiving chemotherapy. Membrane HLA-G expression showed a significant positive correlation with lactate dehydrogenase, peripheral and bone marrow blast cells and with IL-10 and INF-γ. The positive correlation of membrane HLA-G expression with both IL-10 and INF-γ serum levels supports the speculation that both cytokines may be involved in the control of HLA-G expression. HLA-G showed a negative correlation with NK cells confirming its importance in tumor escape through down-regulation of NK cells. In conclusion, HLA-G expression could be used as a prognostic tumor marker to monitor disease state and improvement in ALL.

Human leukocyte antigen-G expression in differentiated human airway epithelial cells: lack of modulation by Th2-associated cytokines

Background

Human leukocyte antigen (HLA)-G is a nonclassical class I antigen with immunomodulatory roles including up-regulation of suppressor T regulatory lymphocytes. HLA-G was recently identified as an asthma susceptibility gene, and expression of a soluble isoform, HLA-G5, has been demonstrated in human airway epithelium. Increased presence of HLA-G5 has been demonstrated in bronchoalveolar lavage fluid recovered from patients with mild asthma; this suggests a role for this isoform in modulating airway inflammation though the mechanisms by which this occurs is unclear. Airway inflammation associated with Th2 cytokines such as IL-4 and IL-13 is a principal feature of asthma, but whether these cytokines elicit expression of HLA-G is not known.

Methods

We examined gene and protein expression of both soluble (G5) and membrane-bound (G1) HLA-G isoforms in primary differentiated human airway epithelial cells collected from normal lungs and grown in air-liquid interface culture. Cells were treated with up to 10 ng/ml of either IL-4, IL-5, or IL-13, or 100 ng/ml of the immunomodulatory cytokine IL-10, or 10,000 U/ml of the Th1-associated cytokine interferon-beta, for 24 hr, after which RNA was isolated for evaluation by quantitative PCR and protein was collected for Western blot analysis.

Results

HLA-G5 but not G1 was present in dAEC as demonstrated by quantitative PCR, western blot and confocal microscopy. Neither G5 nor G1 expression was increased by the Th2-associated cytokines IL-4, IL-5 or IL-13 over 24 hr, nor after treatment with IL-10, but was increased 4.5 ± 1.4 fold after treatment with 10,000 U/ml interferon-beta.

Conclusions

These data demonstrate the constitutive expression of a T lymphocyte regulatory molecule in differentiated human airway epithelial cells that is not modulated by Th2-associated cytokines.

The long-term immunosuppressive effects of disulfide-linked HLA-G dimer in mice with collagen-induced arthritis

HLA-G, a natural immunosuppressant present in the human placenta during pregnancy, prevents fetal destruction by the maternal immune system. The immunosuppressive effect of HLA-G is mediated by the immune cell inhibitory receptors, LILRB1 and LILRB2. HLA-G forms disulfide-linked dimers by natural oxidation, and the dimer associates with LILRB1/B2 much more strongly than the monomer. Furthermore, the dimer formation remarkably enhanced the LILRB-mediated signaling. In this report, we studied the in vivo immunosuppressive effect of the HLA-G dimer, using the collagen-induced arthritis model mouse. Mice were treated with the HLA-G monomer or dimer intracutaneously at the left foot joint, once or for 5 days, and the clinical severity was evaluated daily in a double-blind study. The HLA-G monomer and dimer both produced excellent anti-inflammatory effects with a single, local administration. Notably, as compared to the monomer, the dimer exhibited significant immunosuppressive effects at lower concentrations, which persisted for about two months. In accordance with this result, a binding study revealed that the HLA-G dimer binds PIR-B, the mouse homolog of the LILRBs, with higher affinity and avidity than the monomer. The HLA-G dimer is expected to be quite useful as an anti-rheumatoid arthritis agent, in small amounts with minimal side effects.

Can HLA-G polymorphisms predict the development of cardiac allograft vasculopathy?

A 14 bp insertion/deletion polymorphism in exon 8 of the HLA-G gene is associated with mRNA stability and HLA-G expression. In cardiac transplantation, the 14 bp deletion polymorphism plays an important role in the expression of HLA-G and is associated with fewer episodes of cellular rejection. We investigated the association between the 14 bp insertion/deletion HLA-G polymorphism and cardiac allograft vasculopathy (CAV) post heart transplantation. There were no statistically significant differences in the presence of the three HLA-G genotypes (-14 bp/-14 bp, +14 bp/-14 bp, +14 bp/+14 bp) between patients without CAV and patients with CAV at 1 year (p=0.61) or 5 years (p=0.76) post-transplant. We found no correlation between HLA-G genotypes and CAV progression from baseline to 5 years post-transplant (p=0.55). HLA-G polymorphism appears to play an important role as a genetic indicator for cellular rejection post-transplant; however, it is not a reliable marker to identify patients at risk of CAV.

Human leukocyte antigen-G is frequently expressed in glioblastoma and may be induced in vitro by combined 5-aza-2'-deoxycytidine and interferon-γ treatments: results from a multicentric study

Human leukocyte antigen-G (HLA-G) is a nonclassical major histocompatibility complex (MHC) class I molecule involved in immune tolerance processes, playing an important role in the maintenance of the semi-allogeneic fetus. Although HLA-G expression is restricted in normal tissues, it is broadly expressed in malignant tumors and may favor tumor immune escape. We analyzed HLA-G protein and mRNA expression in tumor samples from patients with glioblastoma collected in France, Denmark, and Brazil. We found HLA-G protein expression in 65 of 108 samples and mRNA in 20 of 21 samples. The absence of HLA-G protein expression was associated with a better long-term survival rate. The mechanisms underlying HLA-G gene expression were investigated in glioma cell lines U251MG, D247MG, and U138MG. Induction of HLA-G transcriptional activity was dependent of 5-aza-2'-deoxycytidine treatment and enhanced by interferon-γ. HLA-G protein expression was observed in U251MG cells only. These cells exhibited a permissive chromatin state at the HLA-G gene promoter and the highest levels of induced HLA-G transcriptional activity following 5-aza-2'-deoxycytidine treatment. Several antigen-presenting machinery components were up-regulated in U251MG cells after demethylating and IFN-γ treatments, suggesting an effect on the up-regulation of HLA-G cell surface expression. Therefore, because of its role in tumor tolerance, HLA-G found to be expressed in glioblastoma samples should be taken into consideration in clinical studies on the pathology and in the design of therapeutic strategies to prevent its expression in HLA-G-negative tumors.

Genotypes and haplotypes in the 3' untranslated region of the HLA-G gene and their association with clinical outcome of hematopoietic stem cell transplantation for beta-thalassemia

Polymorphisms in the 3' untranslated region (3'UTR) of HLA-G, an important player in immunological tolerance, could be involved in post-transcriptional expression control, and their association with different clinical immune-related conditions including autoimmunity and transplantation is of mounting interest. Most studies have focused on a 14 base pair (bp) insertion/deletion (ins/del), while additional single-nucleotide polymorphisms (SNPs) in the HLA-G 3'UTR have been described but not extensively investigated for their clinical relevance. Here we have comparatively studied the association between 3'UTR haplotypes of HLA-G, or the 14 bp ins/del, with clinical outcome of HLA-identical sibling hematopoietic stem cell transplantation (HSCT) in 147 Middle Eastern beta-thalassemia patients. Sequence based typing of 3'UTR HLA-G polymorphisms in the patients and in 102 healthy Italian blood donors showed strong linkage disequilibrium between the 14 bp ins/del and five 3'UTR SNPs, which together could be arranged into eight distinct haplotypes based on expectation-maximization studies, with four predominant haplotypes (UTRs1-4). After HSCT, we found a moderate though not significant association between the presence of UTR-2 in double dose and protection from acute graft versus host disease (hazard ratio (HR) 0.45, 95% confidence intervals (CI): 0.14-1.45; P = 0.18), an effect that was also seen when the corresponding 14 bp ins/ins genotype was considered alone (HR 0.42, 95% CI: 0.16-1.06; P = 0.07). No association was found with rejection or survival. Taken together, our data show that there is no apparent added value of considering entire 3'UTR HLA-G haplotypes for risk prediction after allogeneic HSCT for beta-thalassemia.

HLA-G1 and HLA-G5 active dimers are present in malignant cells and effusions: the influence of the tumor microenvironment

Dimers of the nonclassical HLA-G class I molecule have recently been shown to be active structures that mediate inhibition of NK-cell cytotoxic activity through interaction with the immunoglobulin-like transcript (ILT)-2 inhibitory receptor. However, this has only been proven in trophoblasts and HLA-G transfectants. Here, we document for the first time the existence of HLA-G dimers in cancer. Indeed, we identified both surface and soluble HLA-G dimers in tumor cells and malignant ascites respectively. Interestingly, factors from the tumor microenvironment, such as interferons, enhanced the formation of HLA-G dimers and increased the protection of tumors from NK cell-mediated lysis. These data emphasize the impact of HLA-G conformation on its efficiency at inhibiting the antitumor response and thus favoring tumor progression. In view of these results, the effect of the tumor microenvironment on upregulation of HLA-G function deserves particular attention when designing cancer immunotherapy protocols.

Importance of HLA-G expression and tumor infiltrating lymphocytes in molecular subtypes of breast cancer

This study is aimed at investigating whether or not human leukocyte antigen-G (HLA-G) expression is associated with breast cancer molecular subtypes. HLA-G expression was immunohistochemically investigated in 104 patients with invasive ductal breast carcinoma, in which 56 were luminal A, 17 were luminal B, 19 were HER-2, and 12 were basal-like/normal breast-like subtype classified according to immunohistochemical staining results of ER, HER-2, CK5/6, and EGFR. Host immune response status was assessed by estimating the density of tumor infiltrating lymphocytes (TIL). For comparison, other biomarkers such as Ki67, p53 and VEGF were also investigated. Associations of these biomarkers and TIL with molecular subtypes were statistically analyzed. We found that there were more cases with high expressions of HLA-G in non-luminal than in luminal subtypes (P=0.035). In contrast, more cases with high density of TIL was found in luminal than in non-luminal subtypes (P=0.023). Compared to all the biomarkers studied, only HLA-G expression was found to be inversely associated with the density of TIL (P=0.004). Furthermore, patients with HLA-G(high)/TIL(low) status had a higher risk of recurrence than those with HLA-G(low)/TIL(high) status, regardless of the molecular subtypes. Therefore, a combination of the status of HLA-G and TIL could improve the prognostic prediction for patients with various molecular subtypes of breast cancer.

Inflammatory bowel disease and pregnancy: overlapping pathways

Several studies have reported on the association between inflammatory bowel disease (IBD) and adverse pregnancy outcomes, such as preterm birth. The exact mechanisms of action are unclear; however, several pathways and processes are involved in both IBD and pregnancy that may help explain this. In this review, we discuss the immune system's T helper cells and human leukocyte antigens, inflammation, its function, and the role of Toll-like receptors (TLRs), NOD-like receptors (NLRs), and prostaglandins in the inflammatory response. For each of these topics, we consider their involvement in IBD and pregnancy, and we speculate as to how they can lead to preterm birth. Finally, we review briefly corticosteroids, biologic therapies, and immunosuppressants for the treatment of IBD, as well as their safety in use during pregnancy, with special focus on preterm birth.

Distribution of HLA-G 14-bp insertion/deletion polymorphism in six Chinese ethnic groups

Recently, a 14-bp insertion/deletion polymorphism (+14 bp/-14 bp) in exon 8 of the Human leucocyte antigen-G (HLA-G) gene has been studied extensively because this polymorphism has been associated with HLA-G mRNA stability and could influence HLA-G mRNA expression. We investigated the distribution of the 14-bp insertion/deletion polymorphism in six different Chinese ethnic groups (Bulang, Wa, Hani, Jinuo, Maonan and Zhuang), which originated from three major ancient tribes (Di-Qiang, Baipu and Baiyue) in China. Comparison of the 14-bp insertion frequency in the six groups with other Chinese groups showed marked variation among the three ancient tribes, Di-Qing (0.490-0.534), Baipu (0.470-0.609) and Baiyue (0.280-0.344). Furthermore, the frequencies of the 14-bp insertion were similar in groups that came from the same ancient tribe, which indicated that the individuals who share the 14-bp insertion have the most probably inherited the 14-bp element from a common ancestor. In addition, an intra-tribal comparison of the 14-bp insertion/deletion frequencies between the descendants of the ancient ancestral tribes suggests that population histories or some environmental effects, such as founder effect or isolation, might also influence the distribution.

Identification of a novel HLA-G+ regulatory population in blood: expansion after allogeneic transplantation and de novo HLA-G expression at graft-versus-host disease sites

BACKGROUND

The human leukocyte antigen-G (HLA-G) has been considered to be an important tolerogeneic molecule playing an essential role in maternal-fetal tolerance, which constitutes the perfect example of successful physiological immunotolerance of semi-allografts. In this context, we investigated the putative role of this molecule in the allogeneic hematopoietic cell transplantation setting.

DESIGN AND METHODS

The percentage of HLA-G(+) cells in peripheral blood of healthy donors and allo-transplanted patients was evaluated by flow cytometry. Their immunoregulatory and tolerogeneic properties were investigated in in vitro immunostimulatory and immunosuppression assays. Immunohistochemical analysis for HLA-G expression was performed in skin biopsies from allo-transplanted patients and correlated with the occurrence of graft-versus-host disease.

RESULTS

We identified a CD14(+)HLA-G(pos) population with an HLA-DR(low) phenotype and decreased in vitro immunostimulatory capacity circulating in peripheral blood of healthy individuals. Naturally occurring CD14(+)HLA-G(pos) cells suppressed T-cell responses and exerted an immunotolerogenic action on T cells by rendering them hyporesponsive and immunosuppressive in vitro. After allogeneic hematopoietic cell transplantation, HLA-G(pos) cells increase in blood. Interestingly, besides an increase in CD14(+)HLA-G(pos) cells, there was also a pronounced expansion of CD3(+)HLA-G(pos) cells. Of note, CD3(+)HLA-G(pos) and CD14(+)HLA-G(pos) cells from transplanted patients were suppressive in in vitro lymphoproliferation assays. Furthermore, we found an upregulation of HLA-G expression in skin specimens from transplanted patients that correlated with graft-versus-host disease. Inflammatory cells infiltrating the dermis of transplanted patients were also HLA-G(pos).

CONCLUSIONS

We report the presence of naturally occurring HLA-G(pos) monocytic cells with in vitro suppressive properties. HLA-G expressing regulatory blood cells were found in increased numbers after allogeneic transplantation. Epithelial cells in skin affected by graft-versus-host disease revealed elevated HLA-G expression.

Expression of nonclassical molecule human leukocyte antigen-G in oral lesions

INTRODUCTION

Human leukocyte antigen (HLA)-G is a nonclassic class I molecule that acts as a modulator of immune responses, and the expression of these molecules in virus-infected cells has been associated with subversion of the immune response.

OBJECTIVE

In this study, we performed a cross-sectional study, systematically comparing the expression of the HLA-G in benign, premalignant, and malignant oral lesions and correlating it with the presence of high-risk and low-risk human papillomavirus (HPV) types. SPECIMENS AND METHODS: Oral biopsies were collected from 51 patients and analyzed by immunohistochemistry using anti-HLA-G antibody. Human papillomavirus detection and typing from oral biopsies were obtained by polymerase chain reaction using GP5+/GP6+ and specific primers.

RESULTS

The 51 biopsies were stratified into 3 groups according to lesion grade: oral benign lesions (oral hyperplasia and papilloma, n = 16), oral premalignant lesions (oral leukoplakia with dysplasia and lichen planus, n = 17), and malignant lesions (oral squamous cell carcinoma, n = 18). Human leukocyte antigen-G overexpression was mainly observed in benign and premalignant oral lesions but was not related to HPV infection (P > .05). On the other hand, HPV DNA was detected in 24 (47%) oral lesions, mainly in benign and premalignant lesions, with the most frequent type detected being high-risk HPV type.

CONCLUSION

The HLA-G molecule was expressed in a significant number of benign oral lesions and was not correlated with HPV infection or oral cancer.

A genome-wide association study of plasma total IgE concentrations in the Framingham Heart Study

BACKGROUND

Atopy and plasma IgE concentration are genetically complex traits, and the specific genetic risk factors that lead to IgE dysregulation and clinical atopy are an area of active investigation.

OBJECTIVE

We sought to ascertain the genetic risk factors that lead to IgE dysregulation.

METHODS

A genome-wide association study (GWAS) was performed in 6819 participants from the Framingham Heart Study (FHS). Seventy of the top single nucleotide polymorphisms (SNPs) were selected based on P values and linkage disequilibrium among neighboring SNPs and evaluated in a meta-analysis with 5 independent populations from the Cooperative Health Research in the Region of Augsburg cohort, the British 1958 Birth Cohort, and the Childhood Asthma Management Program cohort.

RESULTS

Thirteen SNPs located in the region of 3 genes, FCER1A, signal transducer and activator of transcription 6 (STAT6), and IL13, were found to have genome-wide significance in the FHS cohort GWAS. The most significant SNPs from the 3 regions were rs2251746 (FCER1A, P = 2.11 × 10(-12)), rs1059513 (STAT6, P = 2.87 × 10(-8)), and rs1295686 (IL13, P = 3.55 × 10(-8)). Four additional gene regions, HLA-G, HLA-DQA2, HLA-A, and Duffy blood group, chemokine receptor (DARC), reached genome-wide statistical significance in a meta-analysis combining the FHS and replication cohorts, although the DARC association did not appear independent of SNPs in the nearby FCER1A gene.

CONCLUSION

This GWAS of the FHS cohort has identified genetic loci in HLA genes that might have a role in the pathogenesis of IgE dysregulation and atopy. It also confirmed the association of the known susceptibility loci FCER1A, STAT6, and IL13 for the dysregulation of total IgE.

Plasma soluble HLA-G is a potential biomarker for diagnosis of colorectal, gastric, esophageal and lung cancer

Human leukocyte antigen-G (HLA-G) is a novel tumor marker and its soluble isoforms produce secretory proteins. Increased soluble HLA-G (sHLA-G) levels have been reported in patients with melanoma, neuroblastoma, lymphoproliferative disorders, breast, ovarian and colorectal carcinoma when compared to healthy controls or subjects with benign neoplasms. The aim of this study is to investigate whether or not plasma sHLA-G can be used as a potential biomarker for cancer diagnosis. We measured plasma sHLA-G levels in 166 patients with early stages of colorectal cancer (CRC, n = 37), gastric cancer (GC, n = 28), esophageal squamous cell carcinoma (ESCC, n = 58) and non-small cell lung cancer (NSCLC, n = 43), and compared them to healthy controls (n = 260) by using a specific HLA-G enzyme-linked immunosorbent assay (ELISA). We found that plasma sHLA-G levels were significantly higher in cancer patients than in healthy controls (all P < 0.0001). The areas under the receiver-operating characteristic (ROC) curves for sHLA-G were 0.97, 0.91, 0.98 and 0.80 for healthy controls vs CRC, GC, ESCC and NSCLC, respectively. At 100% specificity, the highest sensitivity achieved to detect CRC, GC, ESCC and NSCLC was 94% [95% confidence interval (CI), 89-99], 85% (95% CI, 76-94), 91% (95% CI, 88-94) and 51% (95% CI, 43-59) at a cutoff value of 49 U/ml, respectively. These findings suggest that plasma sHLA-G may be a useful molecule in the differential diagnosis of these malignancies against healthy controls.

DA neurons derived from hES cells that express HLA-G1 are capable of immunosuppression

Human embryonic stem (hES) cells have the capacity for self-renewal and exhibit multipotentiality. hES cells have promise for serving as an unlimited source of ideal seed cells for cell transplantation. However, the rejection that occurs between the transplant recipient and the transplanted cell poses a major challenge for therapeutic transplantation. This study was designed to devise methods to enhance immune tolerance in cell therapy. We established an hES cell line that could stably express human leukocyte antigen-G1 (HLA-G1). The established HLA-G1-H1 hES cells still retained all the characteristics of normal human embryonic stem cells. By using the SDIA method, we induced dopaminergic (DA) neurons by coculturing HLA-G1-H1 hES cells with the mouse stromal cell line PA6. Tyrosine hydroxylase (TH)+neurons were detected on the 10th day of differentiation, and 70% of the HLA-G1-H1 hES cells were TH+mature DA neurons because the differentiation time was only 3 weeks. Cells that had been differentiating for different periods of time still expressed HLA-G1, and these differentiated DA neurons released dopamine and other catecholamines in response to K+ depolarization as measured by HPLC. After careful study, we found that HLA-G1-H1 hES cells are capable of inhibiting the proliferation of mixed T-lymphocytes. DA neurons derived from HLA-G1-H1 hES attenuated the release of proinflammatory cytokines IL-1β and IFN-γ from lipopolysaccharide (LPS)-stimulated BV2 microglia. The efficiency of inhibition was significant and dose-dependent. This method might be used to treat Parkinson's patients via cell transplantation.

Soluble human leukocyte antigen-G expression in hepatitis B virus infection and hepatocellular carcinoma

We investigated soluble human leukocyte antigen-G (sHLA-G) expression according to the phases of hepatitis B virus (HBV) infections and hepatocellular carcinoma (HCC). A total of 267 sera from anti-HBs positive healthy individuals (n = 50), chronic HBV carriers (n = 45), as well as patients with active hepatitis B (n = 46), liver cirrhosis (LC, n = 46) and early stage HCC (n = 80) were collected and assayed for sHLA-G. Relationships between sHLA-G levels and clinicopathologic parameters including HCC stages, differentiation grades, and levels of aminotransferases, HBV DNA and alpha-fetoprotein (AFP) were assessed. Concentrations of sHLA-G were higher in the active hepatitis B and HCC groups (median sHLA-G 53.7 and 178.8 U/ml, respectively) in comparison to other groups (P < 0.05), and there were no significant differences among sHLA-G levels of the anti-HBs positive, chronic HBV carrier and LC groups. Serum sHLA-G concentrations were not shown to be associated with clinicopathologic indices including the levels of aminotransferases, AFP, anti-HBs titer, HBV DNA, as well as HCC stages, numbers of tumor nodules, pathologic grades and presence of vessel invasion. The receiver-operating characteristic area under the curve (AUC) value of sHLA-G for differentiating HCC from LC was 0.98, which was greater than that of AFP (0.78) (P < 0.0001), and sensitivity and specificity of sHLA-G were, respectively, 90.0% and 95.7% for HCC when applying a cutoff level of 97.3 U/ml. Serum sHLA-G levels could be used as a diagnostic marker for HCC. Although sHLA-G levels did not reflect the severity of HBV infections and HCC, they were related with phases of the disease.

Allele frequencies of human leukocyte antigen-G in a Korean population

The human leukocyte antigen (HLA)-G is a nonclassical major histocompatibility complex class I molecule with relatively limited polymorphism. The differences in allele frequency according to ethnicity and country have not been studied enough, so far. Therefore, fundamental data including allele frequencies and polymorphism are needed for studies on immunological function of HLA-G in each population. We investigated allele frequencies and 14-bp polymorphism of the HLA-G in Koreans. HLA-G alleles and 14-bp polymorphisms were determined by sequence-based typing analysis of exons 2-4 and polymerase chain reaction of exon 8 in 200 unrelated individuals. Genotyping analysis identified eight different HLA-G alleles, which indicates that the Korean population presents limited HLA-G allelic polymorphism. HLA-G*01:01:01:01 and G*01:04:01 were frequent alleles (42.5% and 34.0%), and allelic frequencies were similar to those of other Asian populations. The 14-bp deletion alleles are higher (78%) in Koreans, although the frequencies of the 14-bp insertion/deletion polymorphism have been known to be nearly equal in many Caucasian populations. HLA-G*01:01:08 was reported strong linkage disequilibrium with the 14-bp deletion in a previous report; the same allele was accompanied with 14-bp insertion in our study. There are a few studies investigating allele frequencies, and most of them were studied before high-resolution method era. This is the first study regarding HLA-G genotypes in Korean, which were identified by high-resolution method. From this study, we identified HLA-G frequencies of a Korean population and expect this study could help further investigations for immunological and clinical implications of HLA-G.

Human leucocyte antigen-G: expression and function in airway allergic disease

Human leucocyte antigen-G (HLA-G) is a non-classical HLA class I molecule demonstrated originally in placental trophoblast cells. Recognition of the importance of HLA-G to the maternal immune accommodation of the semi-allogeneic fetus has led to investigations of its role in the suppression of immune responses and induction of tolerance. More recently, HLA-G has been shown to have increased expression in several immunological diseases including asthma and allergic rhinitis. The focus of this review is the potential role of HLA-G in immunological airway diseases.

Inhibition of human gamma delta [corrected] T-cell antitumoral activity through HLA-G: implications for immunotherapy of cancer

Vγ9Vδ2 T cells play a crucial role in the antitumoral immune response through cytokine production and cytotoxicity. Although the expression of the immunomodulatory molecule HLA-G has been found in diverse tumors, its impact on Vγ9Vδ2 T-cell functions remains unknown. Here we showed that soluble HLA-G inhibits Vγ9Vδ2 T-cell proliferation without inducing apoptosis. Moreover, soluble HLA-G inhibited the Vγ9Vδ2 T-cell production of IFN-γ induced by phosphoantigen stimulation. The reduction in Vγ9Vδ2 T-cell IFN-γ production was also induced by membrane-bound or soluble HLA-G expressed by tumor cell lines. Finally, primary tumor cells inhibited Vγ9Vδ2 T-cell proliferation and IFN-γ production through HLA-G. In this context, HLA-G impaired Vγ9Vδ2 T-cell cytotoxicity by interacting with ILT2 inhibitory receptor. These data demonstrate that HLA-G inhibits the anti-tumoral functions of Vγ9Vδ2 T cells and imply that treatments targeting HLA-G could optimize Vγ9Vδ2 T-cell-mediated immunotherapy of cancer.

HLA-G expression is associated with metastasis and poor survival in the Balb/c nu/nu murine tumor model with ovarian cancer

Aberrant HLA-G expression is associated with tumor invasiveness and poor clinical prognosis; however, there is a lack of preclinical animal model to address whether HLA-G plays a causal role in the unfavorable prognosis of malignancies. In the current study, ovarian carcinoma cell lines (HO-8910 and Ovcar-3) were transfected with HLA-G gene. HLA-G expression was analyzed with western blot and flow cytometry. Transwell experiment was performed to analyze the cell migration and invasion capability and/or multicellular spheroid formation was investigated with the 3D culture assay in vitro. The effects of HLA-G expression for tumor cell organ metastasis and for mouse survival was analyzed with the Balb/c nu/nu mouse model. Our data showed that HO-8910-G and Ovcar-3-G cells are of higher invasion potential compared with the parental HO-8910 and Ovcar-3 cells. Multicellular spheroid formation exists only in HO-8910-G cells in a 3D culture assay. In Balb/c nu/nu mouse model, widespread metastasis was observed in mice xenografted with HO-8910-G cells, but not in the group with parental cells. Mouse survival was dramatically decreased in HO-8910-G and Ovcar-3-G xenografted mice than that with HO-8910 and Ovcar-3 cells, respectively. In summary, our study provided the first evidence that HLA-G expression is associated with tumor metastasis and with poor survival in an animal model with ovarian cancer.