Human Leukocyte antigen-G Molecules Research Articles

The correlation between soluble human leukocyte antigen (sHLA-G) levels and +3010 polymorphism.

Human leukocyte antigen-G (HLA-G) is classified as non-classical HLA, located in the short arm of chromosome 6 and composed of seven introns and eight exons. The HLA-G gene has a lower frequency polymorphism in the coding area and higher variability at the regulatory 5'- and 3'-untranslated regions linked to HLA-G microRNA regulation. HLA-G molecule is known to have an immunomodulatory and tolerogenic features role. In 199 Saudi individuals, we examined the association between plasma soluble HLA-G (sHLA-G) levels and eight polymorphic different sites, including 14bp ins/del/+3003T-C/+3010C-G/+3027C-A/+3035C-T/+3142C-G/+3187A-G/+3196C-G single nucleotide polymorphisms (SNPs) in exon 8 in the HLA-G gene. Our results revealed higher frequency for rs17179101C (97%), rs1707T (92%) and rs9380142A (73%) alleles. Greater frequencies for the tested genotypes were observed in 3027C/C (rs17179101) (93%), 14bp (rs1704) ins/del (92%), +3003T/T (rs1707) (85%) and +3035C/T (rs17179108) (79%) SNP genotypes. Moreover, we observed a significant association of sHLA-G with +3010G/C (rs1710) SNP. In conclusion, we showed a significant association between 3010G/C (rs1710) SNP and the sHLA-G level among our sample for Saudi populations. Our findings demonstrated that specific SNP within the HLA-G gene is linked to sHLA-G molecule secretion, suggesting sHLA-G levels may be regulated genetically.

Soluble HLA-G (sHLA-G) measurement might be useful as an early diagnostic biomarker and screening test for gastric cancer

Gastric cancer (GC) is the fifth most frequent malignancy worldwide and has a high mortality rate related to late diagnosis. Although the gold standard for the GC diagnosis is endoscopy with biopsy, nonetheless, it is not cost-effective and is invasive for the patient. The Human leukocyte antigen G (HLA-G) molecule is a checkpoint of the immune response. Its overexpression in cancer is associated with immune evasion, metastasis, poor prognosis, and lower overall survival. We evaluate the plasma levels of soluble HLA-G, (sHLA-G) in patients with GC and benign gastric pathologies using an ELISA test. A higher concentration of sHLA-G in patients with GC than in those with benign pathologies, higher levels of plasma sHLA-G in women with GC compared with men and significant differences in the sHLA-G levels between the benign gastric pathologies evaluated, was our main findings. As no significant differences were found between the GC assessed stages in our study population, we suggest that sHLA-G is not an adequate marker for staging GC, but it does have diagnostic potential. In addition to providing information on the potential of sHLA-G as a diagnostic marker for GC, our study demonstrate that HLA-G molecules can be found in the membrane of exosomes, which highlights the need to perform studies with a larger number of samples to explore the functional implications of HLA-G positive exosomes in the context of gastric cancer, and to determine the clinical significance and possible applications of these findings in the development of non-invasive diagnostic methods.

Peripheral HLA-G/ILT-2 immune checkpoint axis in acute and convalescent COVID-19 patients

The immunosuppressive non-classical human leukocyte antigen-G (HLA-G) can elicits pro-viral activities by down-modulating immune responses. We analysed soluble forms of HLA-G, IL-6 and IL-10 as well as on immune effector cell expression of HLA-G and its cognate ILT-2 receptor in peripheral blood obtained from hospitalised and convalescent COVID-19 patients. Compared with convalescents (N = 202), circulating soluble HLA-G levels (total and vesicular-bound molecules) were significantly increased in hospitalised patients (N = 93) irrespective of the disease severity. During COVID-19, IL-6 and IL-10 levels were also elevated. Regarding the immune checkpoint expression of HLA-G/ILT-2 on peripheral immune effector cells, the frequencies of membrane-bound HLA-G on CD3+ and CD14+ cells were almost identical in patients during and post COVID-19, while the frequency of ILT-2 receptor on CD3+ and CD14+ cells was increased during acute infection. A multi-parametric correlation analysis of soluble HLA-G forms with IL-6, IL-10, activation markers CD25 and CD154, HLA-G, and ILT-2 expression on immune cells revealed a strong positive correlation of soluble HLA-G forms with membrane-bound HLA-G molecules on CD3+/CD14+ cells only in convalescents. During COVID-19, only vesicular-bound HLA-G were positively correlated with the activation marker CD25 on T cells. Thus, our data suggest that the elevated levels of soluble HLA-G in COVID-19 are due to increased expression in organ tissues other than circulating immune effector cells. The concomitant increased expression of soluble HLA-G and ILT-2 receptor frequencies supports the concept that the immune checkpoint HLA-G/ILT-2 plays a role in the immune-pathogenesis of COVID-19.

The double-sided of human leukocyte antigen-G molecules in type 1 autoimmune hepatitis.

The immunomodulatory effects of HLA-G expression and its role in cancers, human liver infections and liver transplantation are well documented, but so far, there are only a few reports addressing autoimmune liver diseases, particularly autoimmune hepatitis (AIH).Method and materialsWe analyzed the genetic and phenotypic characteristics of HLA-G in 205 type 1 AIH patients (AIH-1) and a population of 210 healthy controls from Sardinia (Italy).ResultsAnalysis of the HLA-G locus showed no substantial differences in allele frequencies between patients and the healthy control population. The HLA-G UTR-1 haplotype was the most prevalent in both AIH-1 patients and controls (40.24% and 34.29%). Strong linkage was found between the HLA-G UTR-1 haplotype and HLA-DRB1*03:01 in AIH-1 patients but not controls (D’ = 0.92 vs D’ = 0.50 respectively; P = 1.3x10-8). Soluble HLA-G (sHLA-G) levels were significantly lower in AIH-1 patients compared to controls [13.9 (11.6 – 17.4) U/mL vs 21.3 (16.5 – 27.8) U/mL; P = 0.011]. Twenty-four patients with mild or moderate inflammatory involvement, as assessed from liver biopsy, showed much higher sHLA-G levels compared to the 28 patients with severe liver inflammation [33.5 (23.6 – 44.8) U/mL vs 8.8 (6.1 – 14.5) U/mL; P = 0.003]. Finally, immunohistochemistry analysis of 52 liver biopsies from AIH-1 patients did not show expression of HLA-G molecules in the liver parenchyma. However, a percentage of 69.2% (36/52) revealed widespread expression of HLA-G both in the cytoplasm and the membrane of plasma cells labeled with anti-HLA-G monoclonal antibodies.ConclusionThis study highlights the positive immunomodulatory effect of HLA-G molecules on the clinical course of AIH-1 and how this improvement closely correlates with plasma levels of sHLA-G. However, our results open the debate on the ambiguous role of HLA-G molecules expressed by plasma cells, which are pathognomonic features of AIH-1.

Systematic Evaluation of HLA-G 3'Untranslated Region Variants in Locally Advanced, Non-Metastatic Breast Cancer Patients: UTR-1, 2 or UTR-4 are Predictors for Therapy and Disease Outcome.

Despite major improvements in diagnostics and therapy in early as well as in locally advanced breast cancer (LABC), metastatic relapse occurs in about 20% of patients, often explained by early micro-metastatic spread into bone marrow by disseminated tumor cells (DTC). Although neoadjuvant chemotherapy (NACT) has been a successful tool to improve overall survival (OS), there is growing evidence that various environmental factors like the non-classical human leukocyte antigen-G (HLA-G) promotes cancer invasiveness and metastatic progression. HLA-G expression is associated with regulatory elements targeting certain single-nucleotide polymorphisms (SNP) in the HLA-G 3’ untranslated region (UTR), which arrange as haplotypes. Here, we systematically evaluated the impact of HLA-G 3’UTR polymorphisms on disease status, on the presence of DTC, on soluble HLA-G levels, and on therapy and disease outcome in non-metastatic LABC patients. Although haplotype frequencies were similar in patients (n = 142) and controls (n = 204), univariate analysis revealed that the UTR-7 haplotype was related to patients with low tumor burden, whereas UTR-4 was associated with tumor sizes >T1. Furthermore, UTR-4 was associated with the presence of DTC, but UTR-3 and UTR-7 were related to absence of DTC. Additionally, increased levels of soluble HLA-G molecules were found in patients carrying UTR-7. Regarding therapy and disease outcome, univariate and multivariate analysis highlighted UTR-1 or UTR-2 as a prognostic parameter indicative for a beneficial course of disease in terms of complete response towards NACT or progression-free survival (PFS). At variance, UTR-4 was an independent risk factor for a reduced OS besides already known parameters. Taken into account the most common HLA-G 3’UTR haplotypes (UTR-1–UTR-7, UTR-18), deduction of the UTR-1/2/4 haplotypes to specific SNPs revealed that the +3003C variant, unique for UTR-4, seemed to favor a detrimental disease outcome, while the +3187G and +3196G variants, unique for UTR-1 or UTR-2, were prognostic parameters for a beneficial course of disease. In conclusion, these data suggest that the HLA-G 3’UTR variants +3003C, +3187G, and +3196G are promising candidates for the prediction of therapy and disease outcome in LABC patients.

The role of maternal HLA-DR and HLA-G loci in determining the risk of sporadic congenital heart defects in the next generation

The paper considers the role of maternal HLA-DR (Human Leukocyte Antigens-DR) and HLA-G (Human Leukocyte Antigen-G) loci in determining the risk of the formation of sporadic congenital heart defects without chromosomal diseases in the next generation. The HLA-G molecule expressed on trophoblast performs a protective function by blocking killer receptors on natural killer cells (NK cells). At the same time, the maternal alleles of HLA-DRB1 restrict the immune response to allogeneic antigens of the paternal embryo, which may affect the severity of inflammation in the mother-embryo system and through this mechanism induce the formation of heart disease.Objective: to study the frequency distribution of the combinations of alleles and genotypes of HLA-G 3’UTR and HLA-DRB1 in women with children with sporadic congenital heart defects without chromosomal diseases. Children characteristics and research methods. There were formed 2 groups: Main Group (103 women with children with sporadic congenital heart defects without chromosomal diseases) and Control Group (103 women with conditionally healthy children). Genomic DNA was isolated by phenol-chloroform extraction. Typing of HLA-G 3’UTR 14-bp insertion/deletion was performed by amplification of polymorphic regions of genes by polymerase chain reaction with further electrophoretic detection in polyacrylamide gel 6.0. The frequency analysis of 14 alleles of the HLA-DRB1 gene was performed by real-time polymerase chain reaction. In the course of this work the authors identified predictor and protective combined genotypes.Conclusion. HLA-DRB1 and HLA-G 3’UTR 14-bp ins/del (rs 1704) make a significant contribution to determining the risk of the formation of sporadic congenital heart defects without chromosomal diseases in the next generation.

Comprehensive Transcriptomic Analysis Reveals the Role of the Immune Checkpoint HLA-G Molecule in Cancers.

Human leukocyte antigen G (HLA-G) is known as a novel immune checkpoint molecule in cancer; thus, HLA-G and its receptors might be targets for immune checkpoint blockade in cancer immunotherapy. The aim of this study was to systematically identify the roles of checkpoint HLA-G molecules across various types of cancer. ONCOMINE, GEPIA, CCLE, TRRUST, HAP, PrognoScan, Kaplan-Meier Plotter, cBioPortal, LinkedOmics, STRING, GeneMANIA, DAVID, TIMER, and CIBERSORT were utilized. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed. In this study, we comprehensively analysed the heterogeneous expression of HLA-G molecules in various types of cancer and focused on genetic alterations, coexpression patterns, gene interaction networks, HLA-G interactors, and the relationships between HLA-G and pathological stage, prognosis, and tumor-infiltrating immune cells. We first identified that the mRNA expression levels of HLA-G were significantly upregulated in both most tumor tissues and tumor cell lines on the basis of in-depth analysis of RNAseq data. The expression levels of HLA-G were positively associated with those of the other immune checkpoints PD-1 and CTLA-4. Abnormal expression of HLA-G was significantly correlated with the pathological stage of some but not all tumor types. There was a significant difference between the high and low HLA-G expression groups in terms of overall survival (OS) or disease-free survival (DFS). The results showed that HLA-G highly expressed have positive associations with tumor-infiltrating immune cells in the microenvironment in most types of tumors (P<0.05). Additionally, we identified the key transcription factor (TF) targets in the regulation of HLA-G expression, including HIVEP2, MYCN, CIITA, MYC, and IRF1. Multiple mutations (missense, truncating, etc.) and the methylation status of the HLA-G gene may explain the differential expression of HLA-G across different tumors. Functional enrichment analysis showed that HLA-G was primarily related to T cell activation, T cell regulation, and lymphocyte-mediated immunity. The data may provide novel insights for blockade of the HLA-G/ILT axis, which holds potential for the development of more effective antitumour treatments.

Expression of membrane-bound human leucocyte antigen-G in systemic sclerosis and systemic lupus erythematosus

Human leucocyte antigen-G (HLA-G) is a nonclassical class I major histocompatibility complex (MHC) molecule characterized by complex immunoregulatory and tolerogenic functions. Membrane-bound HLA-G is expressed on the surface of different cell populations in both physiological and pathological conditions. Systemic sclerosis (SSc) is a multisystem autoimmune disease characterized by widespread tissue fibrosis, vascular lesions and immunological alterations. Systemic lupus erythematosus is the prototypic systemic autoimmune disease affecting virtually any organ system, such as skin, joints, central nervous system, or kidneys. In SSc and SLE patients, the membrane expression of HLA-G on monocytes (0.88 ± 1.54 and 0.43 ± 0.75, respectively), CD4+ (0.42 ± 0.78 and 0.63 ± 0.48, respectively), CD8+ (2.65 ± 3.47 and 1.29 ± 1.34, respectively) and CD4+ CD8+ double-positive cells (13.87 ± 15.97 and 3.79 ± 3.11, respectively) was significantly higher than in healthy controls (0.12 ± 0.07; 0.01 ± 0.01; 0.14 ± 0.20 and 0.32 ± 0.38, respectively) (p < 0.0001). Our results show that in SSc and SLE the membrane expression of HLA-G by different subpopulations of peripheral blood mononuclear cells (PBMC) is increased, suggesting a potential role of HLA-G molecules in the complex immunological pathogenesis of these two autoimmune disorders.

Evaluation of membrane-bound and soluble forms of human leucocyte antigen-G in systemic sclerosis.

Systemic sclerosis (SSc) is a complex disease characterized by immune dysregulation, extensive vascular damage and widespread fibrosis. Human leucocyte antigen-G (HLA-G) is a non-classic class I major histocompatibility complex (MHC) molecule characterized by complex immunomodulating properties. HLA-G is expressed on the membrane of different cell lineages in both physiological and pathological conditions. HLA-G is also detectable in soluble form (sHLA-G) deriving from the shedding of surface isoforms (sHLA-G1) or the secretion of soluble isoforms (HLA-G5). Several immunosuppressive functions have been attributed to both membrane-bound and soluble HLA-G molecules. The plasma levels of sHLA-G were higher in SSc patients (444·27±304·84 U/ml) compared to controls (16·74±20·58U/ml) (P<0·0001). The plasma levels of transforming growth factor (TGF)-β were higher in SSc patients (18937±15217 pg/ml) compared to controls (11099±6081 pg/ml; P=0·003), and a significant correlation was found between TGF-β and the plasma levels of total sHLA-G (r=0·65; P<0·01), sHLA-G1 (r=0·60; P=0·003) and HLA-G5 (r=0·47; P=0·02). The percentage of HLA-G-positive monocytes (0·98±1·72), CD4+ (0·37±0·68), CD8+ (2·05±3·74) and CD4+ CD8+ double-positive cells (14·53±16·88) was higher in SSc patients than in controls (0·11±0·08, 0·01±0·01, 0·01±0·01 and 0·39±0·40, respectively) (P<0·0001). These data indicate that in SSc the secretion and/or shedding of soluble HLA-G molecules and the membrane expression of HLA-G by peripheral blood mononuclear cells (PBMC) is clearly elevated, suggesting an involvement of HLA-G molecules in the immune dysregulation of SSc.

Increased plasmatic soluble HLA-G levels in endometrial cancer

Human Leukocyte Antigen-G (HLA-G) is known as an immune suppressive molecule; it interacts with several immune cells and inhibits their functions. HLA-G molecule is highly represented in pathological conditions including malignant transformation. To the best of our knowledge this is the first study that focuses on the expression of soluble HLA-G (sHLA-G) in endometrial cancer (EC). We aimed at exploring sHLA-G plasma levels and its prognostic value in EC.We examined total sHLA-G expression as well as the sHLA-G1 and HLA-G5 isoforms expression in plasma samples from 40 patients with EC and 45 healthy controls by a specific sandwich ELISA. Immunoprecipitation and Coomassie blue staining were performed to explore the presence of plasmatic sHLA-G monomers and dimers.sHLA-G plasma level was significantly enhanced in patients with EC compared to healthy controls (p = 0.028). Additionally, HLA-G5 molecules were highly represented than sHLA-G1 molecules in EC, at the borderline of significance (p = 0.061). Interestingly, sHLA-G has been shown to be increased in early stages (Stages I and II) as well as in high grade EC (Grade 3) that is associated with rapid spread of the disease (p = 0.057). sHLA-G positive EC plasma were majorly in monomeric form (75%). Clinically, all the HLA-G dimers were detected in early stages and in high grade of EC.Our data strengthen the implication of HLA-G molecules in EC etiology and especially in progression.

HLA-G molecules and clinical outcome in Chronic Myeloid Leukemia

The human leukocyte antigen-G (HLA-G) gene encodes a tolerogenic protein known to promote tumor immune-escape. We investigated HLA-G polymorphisms and soluble molecules (sHLA-G) in 68 chronic myeloid leukemia (CML) patients. Patients with G*01:01:01 or G*01:01:02 allele had higher value of sHLA-G compared to G*01:01:03 (109.2 ± 39.5 vs 39.9 ± 8.8 units/ml; p = 0.03), and showed lower event free survival (EFS) (62.3% vs 90.0%; p = 0.02). The G*01:01:03 allele was associated with higher rates and earlier achievement of deep molecular response (MR)4.5 (100% vs 65%, median of 8 vs 58 months, p = 0.001). HLA-G alleles with higher secretion of sHLA-G seem associated with lower EFS, possibly because of an inhibitory effect on the immune system. Conversely, lower levels of sHLA-G promoted achievement of MR4.5, suggesting increased cooperation with immune system.

Increased levels of soluble HLA-G molecules in Tunisian patients with chronic hepatitis B infection.

Hepatitis B virus (HBV) infection is a global health problem. The mechanisms of immune tolerance in HBV infection are still unclear. The host immune response plays a critical role in determining the outcome of HBV infection. Human leucocyte antigen-G (HLA-G) is involved in immunotolerogenic process and infectious diseases. This study aimed to explore the implication of soluble HLA-G (sHLA-G) and its isoforms in HBV infection. Total sHLA-G (including shedding HLA-G1 and HLA-G5) was analysed by ELISA in 95 chronic HBV patients, 83 spontaneously resolvers and 100 healthy controls (HC). To explore the presence of sHLA-G dimers, we performed an immunoprecipitation and a Western blot analysis on positive samples for sHLA-G in ELISA. The serum levels of sHLA-G were significantly increased in patients with chronic HBV patients compared to spontaneously resolvers and HC (P<.0001). Interestingly, we found an increased level of sHLA-G1 in chronic HBV patients than in spontaneously resolvers and HC (P<.001). In addition, the expression of HLA-G5 seems to be higher in the sera of chronic HBV patients than spontaneously resolvers (P=.026). The analysis of HLA-G dimers showed the presence of homodimers in 93% of chronic HBV patients, 67% in spontaneously resolvers and 60% in HC. These results provide evidence that sHLA-G may have a crucial role in the outcome of HBV infection and could be proposed as a biomarker for infection outcome. Based on its tolerogenic function, HLA-G might be considered as a new promising immunotherapeutic approach to treat the chronic infection with HBV.

Simple in vitro generation of human leukocyte antigen-G–expressing T-regulatory cells through pharmacological hypomethylation for adoptive cellular immunotherapy against graft-versus-host disease

BackgroundMajor barriers in using classical FOXP3+ regulatory T cells (Tregs) in clinical practice are their low numbers in the circulation, the lack of specific cell surface markers for efficient purification and the loss of expression of Treg signature molecules and suppressive function after in vitro expansion or in a pro-inflammatory microenviroment. A surface molecule with potent immunosuppressive function is the human leukocyte antigen-G (HLA-G), which is normally expressed in placenta protecting the “semi-allogeneic” fetus from maternal immune attack. Because HLA-G expression is strongly regulated by methylation, we asked whether hypomethylating agents (HA) may be used in vitro to induce HLA-G expression on conventional T cells and convert them to Tregs. MethodsHuman peripheral blood T cells were exposed to azacytidine/decitabine and analyzed for HLA-G expression and their in vitro suppressor properties. ResultsHA treatment induces de novo expression of HLA-G on T cells through hypomethylation of the HLA-G proximal promoter. The HA-induced CD4+HLA-Gpos T cells are FOXP3 negative and have potent in vitro suppression function, which is dependent to a large extent, but not exclusively, on the HLA-G molecule. Converted HLA-Gpos suppressors retain their suppressor function in the presence of tumor necrosis factor (TNF) and preserve hypomethylated the HLA-G promoter for at least 2 days after azacytidine exposure. Decitabine-treated T cells suppressed ex vivo the proliferation of T cells isolated from patients suffering from graft-versus-host disease (GVHD). DiscussionWe propose, in vitro generation of HLA-G–expressing T cells through pharmacological hypomethylation as a simple, Good Manufacturing Practice (GMP)-compatible and efficient strategy to produce a stable Treg subset of a defined phenotype that can be easily purified for adoptive immunotherapy.

The impact of IL10 polymorphisms and sHLA-G levels on the risk of schizophrenia.

Early life immune aberrations have strongly been associated with the risk of schizophrenia. Amongst them, inflammation induced neurodevelopmental origin has emerged as one of the widely recognized underlying mechanisms. Interleukin-10 (IL-10) is an important anti-inflammatory and immunoregulatory cytokine. It modulates the expression of another immuno-inhibitory molecule, Human Leukocyte Antigen-G (HLA-G), predominantly expressed at the feto-maternal interface. Under physiological conditions, IL-10 and HLA-G molecules regulate the feto-maternal immune homeostasis by limiting the inflammatory states and influence the outcome of pregnancy. The aberrant expression of these molecules can cause pregnancy complications, which are known to confer strong risk to schizophrenia in the offspring. However, there is a considerable lack of information on the effect of the functional interactions between IL-10 and HLA-G on the risk of schizophrenia. We therefore examined the impact of possible correlation between IL-10 genetic variations and the plasma levels of soluble HLA-G (sHLA-G) on schizophrenia risk. Genotyping of IL10 (-592 C>A, -1082 A>G) single nucleotide polymorphisms (SNPs) was performed by PCR-RFLP method in 219 schizophrenia patients and 197 healthy subjects and levels of sHLA-G were estimated by ELISA in 46 patients and 44 healthy subjects. There was no significant difference in the genotype and allele frequencies between the groups for both the IL10 SNPs analyzed. However, we observed a correlation between IL10 genetic variation and plasma levels of sHLA-G in schizophrenia patients. Patients carrying CC genotype of IL10 -592C>A polymorphism had significantly lower sHLA-G levels compared to CA and AA genotypes. Our findings suggest the impact of possible correlation between IL-10 and HLA-G on schizophrenia risk.

The prognostic impact of soluble and vesicular HLA-G and its relationship to circulating tumor cells in neoadjuvant treated breast cancer patients

The non-classical human leukocyte antigen G (HLA-G) molecule and its soluble forms exert multiple immune suppressive regulatory functions in malignancy and in stem cells contributing to immune escape mechanisms. HLA-G can be secreted as free soluble HLA-G molecules or via extracellular vesicles (EVs). Here we evaluated these soluble HLA-G forms as prognostic marker for prediction of the clinical outcome of neoadjuvant chemotherapy (NACT) treated breast cancer (BC) patients. Plasma samples of BC patients procured before (n=142) and after (n=154) NACT were quantified for total soluble HLA-G (sHLA-Gtot) and HLA-G levels in ExoQuick™ derived EV fractions (sHLA-GEV) by ELISA. The corresponding increments were specified as free sHLA-G (sHLA-Gfree). Total and free sHLA-G were significantly increased in NACT treated BC patients compared to healthy controls (n=16). High sHLA-Gfree levels were exclusively associated to estrogen receptor expression before NACT. Importantly, high sHLA-GEV levels before NACT were related to disease progression and the detection of stem cell-like circulating tumor cells, but high sHLA-Gfree levels indicated an improved clinical outcome. Thus, this study demonstrates for the first time that the different sHLA-G subcomponents represent dissimilar qualitative prognostic impacts on the clinical outcome of NACT treated BC patients, whereas the total sHLA-G levels without separating into subcomponents are not related to clinical outcome.

Study of Soluble HLA-G in Congenital Human Cytomegalovirus Infection.

Human leukocyte antigen-G (HLA-G) is a nonclassical HLA class I antigen that is expressed during pregnancy contributing to maternal-fetal tolerance. HLA-G can be expressed as membrane-bound and soluble forms. HLA-G expression increases strongly during viral infections such as congenital human cytomegalovirus (HCMV) infections, with functional consequences in immunoregulation. In this work we investigated the expression of soluble (s)HLA-G and beta-2 microglobulin (component of HLA) molecules in correlation with the risk of transmission and severity of congenital HCMV infection. We analyzed 182 blood samples from 130 pregnant women and 52 nonpregnant women and 56 amniotic fluid samples from women experiencing primary HCMV infection. The median levels of sHLA-G in maternal serum of women with primary HCMV infection were higher in comparison with nonprimary and uninfected pregnant women (p < 0.001). AF from HCMV symptomatic fetuses presented higher sHLA-G levels in comparison with infected asymptomatic fetuses (p < 0.001), presence of HLA-G free-heavy chain, and a concentration gradient from amniotic fluid to maternal blood. No significant statistical difference of beta-2 microglobulin median levels was observed between all different groups. Our results suggest the determination of sHLA-G molecules in both maternal blood and amniotic fluid as a promising biomarker of diagnosis of maternal HCMV primary infection and fetal HCMV disease.

New Developments in HLA-G in Cardiac Transplantation

Human Leukocyte Antigen-G (HLA-G) is a non-classical class 1b protein, whose gene is located on chromosome 6 (6p21.31). HLA-G inhibits the immune cells’ cytotoxic activity by interacting with specific receptors on their membranes. Since it is a naturally occurring immune modulator, HLA-G has been investigated in transplantation. Indeed, a number of investigations reveal that HLA-G expression is influenced by genetic polymorphisms and in turn, those polymorphisms are associated with detrimental or beneficial outcomes in various pathological situations. The present review introduces the HLA-G molecule, the gene and its polymorphisms. It focuses on the expression of HLA-G and the role of polymorphisms primarily in heart transplant outcomes, secondarily in other transplant organs, as well as the role of the allograft and effect of medical therapy. We discuss the limitations in HLA-G transplant investigations and future directions. The immune inhibiting activity of HLA-G has a great deal of potential for its utilization in enhancing diagnostic, preventive and therapeutic strategies against rejection in the setting of transplantation.

Relation Between HLA-G Gene Null Allele (HLA-G*0105N) and Recurrent Miscarriage

: Human leukocyte antigen-G (HLA-G) is a nonclassical HLA-class I antigen located on chromosome 6. HLA-G is highly expressed on cytotrophoblast cells at the fetomaternal interface and involved in the development of pregnant uterus as an immune privileged site. Expression of HLA-G is thought to have a critical role in the protection of the semiallogenic fetus from maternal immune attack during pregnancy. HLA-G molecules bind inhibitory receptors on maternal T cells and NK cells and subsequently inhibit their cytolytic activities. Because of mRNA alternative splicing of HLA-G primary transcript, the HLA-G protein exists in both membrane-bound (HLA-G1 to G4) and soluble (HLA-G5 to G7) isoforms. HLA-G gene contains 15 alleles, including the HLA-G*0105N null allele. A single base-pair deletion of a cytosine (1597delC) results in open reading frame mutation, which leads to a premature stop codon. The HLA-G*0105N allele is unable to generate the HLA-G1, HLA-G5, and HLA-G4 isoforms. However, it is still able to produce other HLA-G proteins, in which exon 3 is removed by alternative splicing, including HLA-G2, G3, G6 and G7 isoforms. HLA-G*0105N null allele has been described in healthy adults with successful and normal pregnancies, which suggests that HLA-G function is not restricted to the HLA-G1 isoform. Description of healthy individual homozygous for HLA-G*0105N allele recommends that truncated HLA-G2 and G3 isoforms encoded by null allele are able to compensate for the lack of the HLA-G1, G4 and G5 isoforms. Results of the numerous studies on the null allele of HLA-G gene indicated that its selection may have increased the frequency of the HLA-G*0105N. Studies on the null allele of HLA-G gene could be useful in determining the frequency of genetic variants of HLA-G alleles in different ethnic groups.

Insights into HLA-G Genetics Provided by Worldwide Haplotype Diversity.

Human leukocyte antigen G (HLA-G) belongs to the family of non-classical HLA class I genes, located within the major histocompatibility complex (MHC). HLA-G has been the target of most recent research regarding the function of class I non-classical genes. The main features that distinguish HLA-G from classical class I genes are (a) limited protein variability, (b) alternative splicing generating several membrane bound and soluble isoforms, (c) short cytoplasmic tail, (d) modulation of immune response (immune tolerance), and (e) restricted expression to certain tissues. In the present work, we describe the HLA-G gene structure and address the HLA-G variability and haplotype diversity among several populations around the world, considering each of its major segments [promoter, coding, and 3′ untranslated region (UTR)]. For this purpose, we developed a pipeline to reevaluate the 1000Genomes data and recover miscalled or missing genotypes and haplotypes. It became clear that the overall structure of the HLA-G molecule has been maintained during the evolutionary process and that most of the variation sites found in the HLA-G coding region are either coding synonymous or intronic mutations. In addition, only a few frequent and divergent extended haplotypes are found when the promoter, coding, and 3′UTRs are evaluated together. The divergence is particularly evident for the regulatory regions. The population comparisons confirmed that most of the HLA-G variability has originated before human dispersion from Africa and that the allele and haplotype frequencies have probably been shaped by strong selective pressures.

Analysis of HLA-G gene polymorphism and protein expression in invasive breast ductal carcinoma

The human leukocyte antigen G (HLA-G) is a non-classical HLA class I molecule predominantly expressed in trophoblastic placental cells to protect the fetus during pregnancy. However, evidence has shown that this molecule may be implicated in the immune escape mechanism of tumor cells. Thus, the aim of this study was to evaluate the frequency of 14-bp insertion/deletion HLA-G polymorphism, as well as the expression of this molecule in patients with invasive breast ductal carcinoma (IDC). A significant association between the expression of HLA-G and the presence of metastasis in lymph nodes (p=0.01) was observed and the expression of HLA-G was significantly higher in patients with shorter survival time (p=0.03). The analysis suggests that the polymorphism observed in patients with IDC may be inducing a higher expression of the HLA-G molecule, which may possibly contribute to shorter survival time and a worse clinical prognosis for such patients.