Meta-analysis of the relationship between 14bp insertion/deletion polymorphism of HLA-G gene and susceptibility to systemic lupus erythematosus

Association Study of rs1632947, rs1233334, and rs371194629 Polymorphisms in Human Leukocyte Antigen G Gene Expression and soluble Human Leukocyte Antigen G with Lupus

Systemic lupus erythematosus is a chronic autoimmune disease that has been associated with human leukocyte antigen G (HLA-G) in previous studies on immunological diseases. This study aimed to investigate the association between three HLA-G gene polymorphisms (rs1632947, rs1233334, and rs371194629) and their impact on HLA-G mRNA expression and soluble HLA-G levels in serum. Genotyping was performed using TaqMan probe PCR. RNA extraction, reverse transcription PCR, and real-time PCR assays were conducted to assess the expression of the HLA-G gene in tissue samples. Soluble HLA-G was measured using enzyme-linked immunosorbent assay in serum. Results show a significant difference in the frequency of the G allele for two 5'-untranslated region (UTR) polymorphisms of the HLA-G gene (rs1632947 and rs1233334) located at positions -964 and -725, respectively, between lupus patients and controls, with p-values of 0.009 and 0.040, respectively. In addition, the study identified the 14 bp insertion allele of the rs371194629 polymorphism located in the 3' UTR of the gene as a risk factor for lupus, with a p-value of 0.001. Our results also indicate that lupus-related alleles may increase the risk of developing the disease by upregulating the expression of HLA-G and increasing soluble HLA-G levels in serum. The findings of the study suggest that the identified genetic variants may play a role in the development of lupus and could be useful in identifying individuals at risk for the disease. These results are important for advancing our understanding of the genetic basis of lupus and may have implications for the development of new treatments and diagnostic tools for the disease.

Association Study of 3-untranslated region Haplotype of Human leukocyte antigen-G Gene with Lupus

Background: Human leukocyte antigen-G (HLA-G) is a pivotal protein involved in immune regulation and tolerance, while systemic lupus erythematosus (SLE) is a multifaceted autoimmune condition influenced by genetic and environmental factors. Research indicates that variations and mutations in HLA-G may impact SLE development. Objective: This study aimed to explore the relationship between polymorphisms in the 3'-untranslated region (UTR) of the HLA-G gene and SLE. Methods: DNA from 100 SLE patients and 100 controls was analyzed using polymerase chain reaction to amplify the target sequence. Allele and genotype frequencies were determined, and haplotypes were assessed using Haploview v.4.2 software, with linkage disequilibrium calculated. Results: Findings revealed that the +2960 Ins allele was significantly linked to SLE as a risk factor, with the Del allele showing a protective effect. In addition, the +3010C allele and +3187A allele were significantly associated with SLE at both allele and genotype levels. The +3142 GG homozygote was notably linked to SLE at the genotype level. Haplotype analysis identified UTR-2 haplotypes as risk factors for SLE, whereas the UTR-1 haplotype was protective, shedding light on genetic factors influencing SLE risk. Conclusion: This study underscores the importance of HLA-G gene 3'-UTR polymorphisms in SLE susceptibility, suggesting their potential as diagnostic or therapeutic targets.

HLA-G in Allergy: Does It Play an Immunoregulatory Role?

Allergy is an inflammatory process determined by a cascade of immune events characterized by T-helper 2 lymphocytes polarization leading to interleukin-4 upregulation, IgE secretion, and mast cell and eosinophil activation. HLA-G molecules, both in membrane-bound and in soluble forms, are known to play a key immunoregulatory role and their involvement in allergic diseases is supported by increasing literature data. HLA-G expression and secretion is specifically induced in peripheral blood mononuclear cells of allergic patients after in vitro incubation with the causal allergen. Elevated levels of soluble HLA-G molecules are detected in serum of patients with allergic rhinitis correlating with allergen-specific IgE levels, clinical severity, drug consumption and response to allergen-specific immunotherapy. HLA-G genetic polymorphisms confer susceptibility to allergic asthma development and high levels of soluble HLA-G molecules are found in plasma and bronchoalveolar lavage fluid of patients with allergic asthma correlating with allergen-specific IgE levels. Interestingly, allergic pregnant women have lower plasma sHLA-G levels than non-allergic women during the 3rd trimester of pregnancy and at delivery. Finally, in allergic patients with atopic dermatitis HLA-G molecules are expressed by T cells, monocytes-macrophages and Langerhans cells infiltrating the dermis. Although at present is difficult to completely define the role of HLA-G molecules in allergic diseases, it may be suggested that they are specifically expressed and secreted by immune cells during the allergic reaction in an attempt to suppress allergic inflammation.

Immunogenetic Relationship of HLA-G 14 bp Insertion/Deletion Polymorphism and Toll-Like Receptor 9 with Systemic Lupus Erythematosus in Egyptian Patients: A Case-Control Study

Introduction

The level of expression of the immunoregulatory human leukocyte antigen-G (HLA-G) has been suggested to play a role in the immunopathogenesis of systemic lupus erythematosus (SLE). A 14 bp insertion/deletion (ins/del) polymorphism in the 3ˊuntranslated region of HLA-G gene may influence the level of expression. The role of Toll-like receptor 9 (TLR9) in the pathogenesis of SLE has been highlighted. Data among Egyptian patients are quite limited.

Purpose

To detect the association of HLA-G 14 bp ins/del gene polymorphism with the susceptibility to SLE and to correlate TLR9 serum level with disease activity among Egyptian patients.

Patients and Methods

A case-control study that included 102 SLE female patients and 102 healthy matched volunteers as controls was carried out. Disease activity in patients was determined using the modified Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). HLA-G 14 bp ins/del genotype was detected by polymerase chain reaction (PCR). TLR9 serum level was estimated using enzyme-linked immunosorbent assay (ELISA) technique.

Results

The ins/ins genotype was significantly increased among SLE patients compared to healthy subjects (58.8% vs 9.8%; odds ratio [OR] = 11.79, P < 0.001). The 14 bp ins allele was significantly more frequent in SLE patients than in healthy subjects (65.7% vs 27.9%, respectively) and significantly associated with an increased risk of SLE (OR 4.94, P < 0.001). The mean TLR9 serum level showed a significant increase in SLE patients compared to healthy subjects (397.04±137.86 vs 195.22±45.14 ng/L, p < 0.001) and was significantly associated with disease activity as well as to patients’ HLA-G genotypes (p < 0.001).

Conclusion

Among Egyptian population, HLA-G 14 bp ins/ins homozygous genotype and ins allele may constitute a potential risk for SLE susceptibility, while TLR9 serum level is significantly associated with disease activity.

Susceptibility role of soluble HLA-G and HLA-G 14-bp insertion/deletion polymorphism in inflammatory bowel disease

Background

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders of the gastrointestinal tract. It is fundamentally related to a dysregulated immune response in the intestinal mucosa against microbiota in genetically predisposed individuals. Among the genetic and immunological factors that are suggested to have role in etiology and pathogenesis of IBD are human leukocyte antigen (HLA)-G molecules. Therefore, soluble HLA-G (sHLA-G) serum level and genetic association with HLA-G 14-bp insertion (Ins)/deletion (Del) polymorphism was analyzed in 100 IBD patients; 50 ulcerative colitis (UC) and 50 Crohn’s disease (CD), and 100 controls.

Results

sHLA-G level was significantly elevated in IBD patients compared to controls (174.7 ± 27.1 vs. 126.8 ± 15.1; corrected probability [pc] < 0.001). The level was also elevated in UC patients compared to CD patients but the difference was not significant (180.5 ± 27.1 vs. 168.9 ± 26.3; p = 0.059). Receiver operating characteristic analysis confirmed the significance of sHLA-G in total IBD, UC, and CD patients (area under curve = 0.944, 0.961, and 0.927, respectively). The genetic association was analyzed under five genetic models (allele, recessive, dominant, overdominant, and codominant). At the allele level, Del allele frequency was significantly increased in total IBD patients (Odds ratio [OR] = 1.93; 95% confidence interval [CI] = 1.27–2.94; pc = 0.018) and CD patients (OR = 2.08; 95% CI = 1.23–3.54; pc = 0.042) compared to controls. Among UC patients, a similar increased frequency was observed, but the pc value was not significance (OR = 1.79; 95% CI = 1.07–3.00; p = 0.031). At the genotypic level, Del/Del genotype was associated with a significantly increased IBD-risk in total patients under codominant model (OR = 4.06; 95% CI = 1.56–10.56; pc = 0.024). sHLA-G level was not influenced by the Ins/Del polymorphism.

Conclusions

This study demonstrated a significant increase in serum level of sHLA-G in UC and CD patients. Further, HLA-G 14-bp Ins/Del polymorphism may be associated with susceptibility to IBD, particularly CD.

Analysis of HLA-G expression in renal tissue in lupus nephritis: a pilot study

BACKGROUND

The study aimed to investigate whether HLA-G antigen is expressed in the kidneys of patients affected by lupus nephritis (LN) and whether its detection in renal biopsies could be adopted as a marker of treatment response and prognosis.

METHODS

Thirty renal biopsies from patients with LN were selected and analyzed through immunohistochemistry. Laboratory and clinical data were retrospectively collected at baseline, 6 and 12 months and at the latest clinical appointment. A number of patients (63.3%) were treated with rituximab (RTX) +/- methylprednisolone in the induction phase. The expression of HLA-G in glomeruli, tubules and infiltrating cells was examined and compared between lupus patients who achieved either complete or partial renal response and those who did not respond to treatment.

RESULTS

HLA-G staining was observed in the glomeruli of 20 of 30 samples from patients with LN. The expression of the antigen was detected in podocytes, along glomerular capillary walls, on parietal glomerular epithelial cells and within the juxtaglomerular apparatus. Seventy per cent of patients whose glomeruli expressed HLA-G achieved partial or complete response at 6 months and 75% at the latest available follow up compared with 30% and 40%, respectively, of those who did not show any expression. The pattern of staining in tubules and infiltrating cells was highly variable precluding any clinical correlation.

CONCLUSION

This study demonstrates that HLA-G is expressed in renal tissue in LN. Our retrospective data suggest that its expression could correlate with response to treatment.

Genetic association between HLA-G 14-bp polymorphism and diseases: A systematic review and meta-analysis

BACKGROUND

HLA-G is an immune checkpoint molecule. Since a differential molecule expression has been reported even for healthy individuals, many studies have focused on polymorphisms at HLA-G regulatory regions, particularly the 3' untranslated region (3'UTR). The presence/absence of a 14-bp sequence was the first polymorphism described and it is the most studied in association between HLA-G and disorders.

METHODS

In this study, we performed a systematic review and meta-analysis of all association studies published regarding the HLA-G 14-bp.

RESULTS

We verified association between 14-bp alleles and diseases in the following situations: (1) presence of 14-bp (insertion) conferred susceptibility to preeclampsia (child alleles evaluated) and systemic lupus erythematosus (OR = 1.42; 95%CI = 1.04-1.93; p = 0.026 and OR = 1.13; 95%CI = 1.01-1.27, p = 0.028); (2) 14-bp absence (deletion) was associated with increased risk to breast cancer (OR = 1.23; 95%CI = 1.06-1.43; p = 0.006) and human Cytomegalovirus infection (OR = 2.06; 95%CI = 1.60-2.64; p < 0.0001); and (3) a risk association was observed between the group of reproductive disorders and the 14-bp insertion (OR = 1.12; 95%CI = 1.01-1.24; p = 0.034).

CONCLUSIONS

Considering that others 14-bp associations were inconclusive and that other variation sites observed at HLA-G 3'UTR exhibit a proven role on post-transcriptional regulation of HLA-G expression, the complete 3'UTR segment should be analyzed in terms of disease susceptibility, instead of a single polymorphism.

Human leucocyte antigen-G 14-bp InDel polymorphism and oral squamous cell carcinoma risk in Chinese Han population: A case-control study

Human leucocyte antigen-G (HLA-G) is a nonclassical HLA class I molecule involved in tumour immune escape. The purpose of this study was to investigate the association between the 14-bp insertion/deletion (InDel) polymorphism in the 3' untranslated region (3'-UTR) of HLA-G gene and oral squamous cell carcinoma (OSCC) risk in Chinese Han population (216 cases and 193 healthy controls), and furthermore, to evaluate serum soluble HLA-G (sHLA-G) levels in the OSCC patients. Our results demonstrated that the Ins allele was significantly less frequent in the OSCC patients than that in the healthy controls (odds ratio [OR] = 0.75; 95% confidence interval [CI]: 0.57-0.99; p = 0.040). Distribution of the 14-bp genotypes in the OSCC patients and the healthy controls revealed that the Ins/Ins genotype was associated with decreased OSCC risk in both the codominant model (Ins/Ins versus Del/Del; OR = 0.57; 95% CI = 0.33-0.99; p = 0.044) and the log-additive model (OR = 0.76; 95% CI: 0.58-0.99; p = 0.044). The serum sHLA-G level was significantly higher in the OSCC patients than those in the healthy controls (p < 0.001). Receiver operating characteristic (ROC) curve revealed the valuable diagnostic value of sHLA-G for OSCC detection, with an area under the ROC curve (AUC) of 0.891 (95% CI: 0.856-0.925, p < 0.001). The OSCC patients with Ins/Ins genotype had lower serum sHLA-G levels than those with Ins/Del and Del/Del genotypes (p = 0.015). Furthermore, serum sHLA-G levels were significantly increased with the increasing TNM stages of the OSCC patients (p = 0.017). Our findings revealed that the HLA-G 14-bp InDel polymorphism might be a genetic risk factor for OSCC susceptibility, and the serum sHLA-G may act as a promising biomarker for noninvasive diagnosis of OSCC.

Mesenchymal stem cells upregulate Treg cells via sHLA-G in SLE patients

BACKGROUND

Soluble human leukocyte antigen-G (sHLA-G) is a non-classical HLA class I molecule, exhibiting strong immunosuppressive properties by inducing the differentiation of T regulatory cells (Treg). Mesenchymal stem cells (MSCs) transplantation alleviates disease progression in systemic lupus erythematosus (SLE) patients. However, the underlying mechanisms are largely unknown.

OBJECTIVES

To explore whether sHLA-G is involved in upregulating effects of MSCs on Treg, which contributes to therapeutic effects of MSCs transplantation in SLE.

METHODS

The serum sHLA-G levels of SLE patients and healthy controls were detected by ELISA. The percentages of peripheral blood CD4+ILT2+, CD8+ILT2+, CD19+ILT2+ cells and Treg cells were examined by flow cytometry. Ten patients with active SLE, refractory to conventional therapies, were infused with umbilical cord derived MSCs (UC-MSCs) and serum sHLA-G was measured 24h and 1month after infusion. The mice were divided into three groups: C57BL/6 mice, B6.MRL-Fas^lpr mice infused with phosphate buffer saline (PBS), and B6.MRL-Fas^lpr mice infused with bone marrow MSCs (BM-MSCs). Then, the concentrations of serum Qa-2 were detected. Peripheral blood mononuclear cells (PBMCs) were isolated from SLE patients and co-cultured with UC-MSCs for 3days at different ratios (50:1, 10:1, and 2:1) with or without HLA-G antibody, and the frequencies of CD4+CD25+Foxp3+ T cells were then determined by flow cytometry.

RESULTS

The concentrations of serum sHLA-G were comparable between SLE patients and healthy controls. However, there was a negative correlation between sHLA-G levels and SLE disease activity index (SLEDAI) scores in active SLE patients (SLEDAI>4). We found that serum sHLA-G levels were negatively correlated with blood urea nitrogen, serum creatinine and 24-hour urine protein in SLE patients. The sHLA-G levels were significantly lower in SLE patients with renal involvement than those without renal involvement. The expression of ILT2 on CD4+ T cells from SLE patients decreased significantly compared to that of healthy controls. A positive correlation between the frequencies of Treg and CD4+ILT2+ T cells was found in SLE patients. The levels of sHLA-G increased 24h post UC-MSCs transplantation. The concentrations of Qa-2 in BM-MSCs transplanted mice were significantly higher than those of control group. In vitro studies showed that MSCs increased the frequency of Treg cells in SLE patients in a dose-dependent manner, which was partly abrogated by the anti-HLA-G antibody.

CONCLUSIONS

Our results suggested that MSCs may alleviate SLE through upregulating Treg cells, which was partly dependent on sHLA-G.

Recent Advances in Our Understanding of HLA-G Biology: Lessons from a Wide Spectrum of Human Diseases

HLA-G is a HLA-class Ib molecule with potent immunomodulatory activities, which is expressed in physiological conditions, where modulation of the immune response is required to avoid allograft recognition (i.e., maternal-fetal interface or transplanted patients). However, HLA-G can be expressed de novo at high levels in several pathological conditions, including solid and hematological tumors and during microbial or viral infections, leading to the impairment of the immune response against tumor cells or pathogens, respectively. On the other hand, the loss of HLA-G mediated control of the immune responses may lead to the onset of autoimmune/inflammatory diseases, caused by an uncontrolled activation of the immune effector cells. Here, we have reviewed novel findings on HLA-G functions in different physiological and pathological settings, which have been published in the last two years. These studies further confirmed the important role of this molecule in the modulation of the immune system.

Association of HLA-G 3' Untranslated Region Polymorphisms with Systemic Lupus Erythematosus in a Japanese Population: A Case-Control Association Study

HLA-G plays a role in fetal-maternal tolerance as well as immunoregulation, and has been suggested to be involved in autoimmune diseases and cancers. HLA-G encodes two potentially functional polymorphisms in the 3' untranslated region, 14bp insertion/deletion (14bp indel, rs371194629) and a single nucleotide polymorphism rs1063320, previously reported to affect HLA-G expression level or splicing isoform and to be associated with susceptibility to systemic lupus erythematosus (SLE). However, the results of SLE association studies are inconsistent, probably due to the small sample size of each study and lack of consideration of linkage disequilibrium (LD) with HLA-class II haplotypes in each population. In this study, we performed association studies of these polymorphisms on 843 patients with SLE and 778 healthy controls in a Japanese population, in many of whom HLA-DRB1 alleles have been genotyped at the four-digit level. LD was detected between DRB1*13:02, protective against multiple autoimmune diseases in the Japanese, and the rs1063320 G (D' = 0.86, r2 = 0.02) and with 14bp del (D' = 0.62, r2 = 0.01), but not between SLE-susceptible DRB1*15:01 and HLA-G. Although significant association with overall SLE was not detected, 14bp ins allele was significantly associated with SLE with the age of onset <20 years, when compared with healthy controls (P = 0.0067, PFDR = 0.039, OR 1.44, additive model) or with SLE patients with the age of onset ≥20 (P = 0.033, PFDR = 0.0495, OR 2.09, additive model). This association remained significant after conditioning on DRB1*13:02 or DRB1*15:01. On the other hand, significant association was detected between rs1063320 C and anti-RNP antibody and anti-Sm antibody positive SLE, which was dependent on negative LD with DRB1*13:02. eQTL analysis showed reduced HLA-G mRNA level in 14bp ins/ins individuals. In conclusion, our observations showed that HLA-G 14bp ins allele represents a genetic contribution on early-onset SLE independent of DRB1.

HLA-G coding region and 3'untranslated region (3'UTR) in two Chinese Han populations

In this study, exons 2-4 and 3'untranslated region (3'UTR) of human leukocyte antigen (HLA)-G gene were investigated for 201 and 104 healthy unrelated Han samples recruited from Hunan Province, southern China and central Inner Mongolia Autonomous Region, northern China, respectively, using sequence-based typing and cloning methods. Totally 12 HLA-G alleles in the coding region, 9 variable sites in 3'UTR, 8 3'UTR haplotypes and 15 HLA-G extended haplotypes (EHs) incorporating the coding region and 3'UTR were observed. Very strong linkage disequilibrium (LD) was observed between HLA-A and HLA-G, and between HLA-G coding region and 3'UTR in each population (all global P=0.0000). Seven HLA-A-G haplotypes showed significant LD in both populations. Three HLA-G alleles in the coding region, 4 polymorphic sites in the 3'UTR, 3 3'UTR haplotypes and 4 HLA-G EHs differed significantly in their distributions between the 2 Chinese Han populations (all P≤0.0001). There was evidence for balancing selection acting on HLA-G 3'UTR positions +3010, +3142 and +3187 in the two populations. The NJ dendrograms demonstrated the existence of two basic HLA-G lineages and indicated that, HLA-G*01:01:01, the most common HLA-G allele, formed a separate lineage from other alleles. Our results shed new lights into HLA-G genetics among Chinese Han populations. The findings reported here are of importance for future studies related to post-transcriptional regulation of HLA-G allelic expression and the potential role of HLA-G in disease association in populations of Chinese ancestry.

HLA-G 14-bp Ins/Ins Genotype in Patients Harbouring Helicobacter pylori Infection: A Potential Risk Factor?

H. pylori is a potent pathogen due to its capacity to successfully evade host defence mechanisms. Despite inducing immune responses in infected individuals, sometimes these responses fail to clear the infection and the bacterium establishes a persistent infection leading to chronic inflammation. In this context, we hypothesized that human leucocyte antigen G (HLA-G), a non-classical major histocompatibility complex molecule that has the ability to regulate immune responses both in physiological and in pathological conditions, may play an important role in promoting tolerance and helping H. pylori to subvert host defence and consequently establish a chronic infection. Therefore, we evaluated the expression of HLA-G 14-bp Ins/Del polymorphism in patients harbouring H. pylori infection, as well as their relationship with histological and demographic variables, to gain a better understanding of the actual role of HLA-G and its genetic polymorphisms in bacterial infection. Sixty-eight patients with clinical symptoms suggestive of H. pylori infection were enrolled to assess HLA-G 14-bp Ins/Del polymorphism allele and genotype frequencies. After adjustment for covariates (age and gender), the odds of having the genotype Ins/Ins, compared to Del/Del, were 3.77 times greater among HP+ cases than among controls. These findings suggest that the 14-bp Ins/Ins genotype, already associated with inflammatory and autoimmune diseases as well as some viral and parasitic infections, could confer a greater risk of developing H. pylori infection.

Association of CD40 polymorphisms and haplotype with risk of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease that is caused by genetic and environmental factors. Current evidence shows that the CD40-CD40L system plays a crucial role in the development, progression and outcome of SLE. CD40, which stimulates lymphocyte proliferation and differentiation, is an important immunomodulator and is expressed in the thyroid follicular cells as well as antigen-presenting cells. The aim of the present study was to investigate whether CD40 gene polymorphism confers susceptibility to SLE and its impact on CD40 expression in Chinese. We analyzed four single nucleotide polymorphisms of CD40 gene rs1883832C/T, rs13040307C/T, rs752118C/T, and rs3765459G/A in 205 patients with SLE and 220 age- and sex-matched controls, using Snapshot SNP genotyping assays and DNA sequencing method. Soluble CD40 (sCD40) levels were measured by ELISA. There were significant differences in the genotype and allele frequencies of CD40 gene rs1883832 C/T polymorphism between the group of patients with SLE and the control group (P < 0.05). sCD40 levels were increased in patients with SLE compared with controls (P < 0.01). Moreover, genotypes carrying the CD40 rs1883832 T variant allele were associated with increased CD40 levels compared with the homozygous wild-type genotype in patients with SLE. The rs1883832 C/T polymorphism of CD40 and its sCD40 levels were associated with SLE in the Chinese population. These data suggest that CD40 gene may play an essential role in the development of SLE.