HLA-G 14-bp polymorphism regulates the methotrexate response in rheumatoid arthritis

Evidence for Epistatic Interaction between HLA-G and LILRB1 in the Pathogenesis of Nonsegmental Vitiligo

Vitiligo is the most frequent cause of depigmentation worldwide. Genetic association studies have discovered about 50 loci associated with disease, many with immunological functions. Among them is HLA-G, which modulates immunity by interacting with specific inhibitory receptors, mainly LILRB1 and LILRB2. Here we investigated the LILRB1 and LILRB2 association with vitiligo risk and evaluated the possible role of interactions between HLA-G and its receptors in this pathogenesis. We tested the association of the polymorphisms of HLA-G, LILRB1, and LILRB2 with vitiligo using logistic regression along with adjustment by ancestry. Further, methods based on the multifactor dimensionality reduction (MDR) approach (MDR v.3.0.2, GMDR v.0.9, and MB-MDR) were used to detect potential epistatic interactions between polymorphisms from the three genes. An interaction involving rs9380142 and rs2114511 polymorphisms was identified by all methods used. The polymorphism rs9380142 is an HLA-G 3'UTR variant (+3187) with a well-established role in mRNA stability. The polymorphism rs2114511 is located in the exonic region of LILRB1. Although no association involving this SNP has been reported, ChIP-Seq experiments have identified this position as an EBF1 binding site. These results highlight the role of an epistatic interaction between HLA-G and LILRB1 in vitiligo pathogenesis.

HLA-G-ILT2 interaction contributes to suppression of bone marrow B cell proliferation in acquired aplastic anemia

Acquired aplastic anemia (AA) is an autoimmune disease characterized by hematopoietic stem and progenitor cell destruction in bone marrow. The non-classic human leukocyte class I antigen (HLA-) G interacts with multiple cell subsets, such as T cells and B cells. HLA-G exerts powerful immune suppression by binding with its receptors, immunoglobulin-like transcripts (ILTs). Here, we compared 46 AA patients and 28 healthy controls. Soluble HLA-G levels in bone marrow supernatants from AA patients were higher than controls. The proportion of bone marrow B cells was decreased and the ILT2-expressing cells among CD19⁺ cells were increased in AA patients. In addition, the percentage of mature B cells among marrow B cells was increased in AA patient, while the percentage of pro-B plus pre-B cells was decreased. More immature B cells and pro-B plus pre-B cells expressed ILT2 in AA patients than in controls, while mature B cells expressing ILT2 did not differ significantly. Functional studies demonstrated that high-level soluble HLA-G inhibited bone marrow B cell proliferation by interacting with ILT2 in AA, and was blocked by anti-HLA-G and anti-ILT2 monoclonal antibodies. Together, these results suggest that the abnormal decrease of pro-B plus pre-B cells in AA patients was related to the enhanced suppression by the excess HLA-G and ILT2 proteins. Therapeutic blockade of the HLA-G-ILT2 interaction may help to normalize bone marrow B cell proliferation.

The HLA-G Immune Checkpoint Plays a Pivotal Role in the Regulation of Immune Response in Autoimmune Diseases

The human G-leukocyte antigen (HLA-G) molecule is a non-classical major histocompatibility complex (MHC) class I molecule. The pertinence of HLA-G has been investigated in numerous studies which have sought to elucidate the relevance of HLA-G in pathologic conditions, such as autoimmune diseases, cancers, and hematologic malignancies. One of the main goals of the current research on HLA-G is to use this molecule in clinical practice, either in diagnostics or as a therapeutic target. Since HLA-G antigens are currently considered as immunomodulatory molecules that are involved in reducing inflammatory and immune responses, in this review, we decided to focus on this group of antigens as potential determinants of progression in autoimmune diseases. This article highlights what we consider as recent pivotal findings on the immunomodulatory function of HLA-G, not only to establish the role of HLA-G in the human body, but also to explain how these proteins mediate the immune response.

HLA-G 14bp Ins/Del Polymorphism in the 3'UTR Region and Acute Rejection in Kidney Transplant Recipients: An Updated Meta-Analysis

Background and Objectives: Acute kidney injury (AKI) affects the survival rate of kidney transplant organs and patients. Acute rejection (AR) due to AKI may lead to kidney transplantation failure. It is known that there is a relationship between human leukocyte antigen-G (HLA-G), which is involved in immune regulation, and AR in transplant patients. Moreover, 14-bp insertion/deletion polymorphism in the 3' untranslated region (UTR) region of the HLA-G gene is known to affect HLA-G expression. However, its relationship to AR is still controversial. The aim of this study was to investigate whether HLA-G 14-bp insertion/deletion polymorphism contributed to the development of AR in kidney transplant patients using a meta-analysis. Materials and Methods: To perform our meta-analysis, eligible studies about HLA-G 14-bp insertion/deletion polymorphism and AR were searched in electronic databases until 1 June 2021. Finally, a total of 336 patients with AR and 952 patients without AR in relation to kidney transplantation were analyzed from a total of nine studies. Results: In our results, the Del allele and Ins/Del+Del/Del and Del/Del genotypes significantly increased susceptibility of AR in Asian populations [odds ratio (OR) = 2.359, 95% confidence interval (CI) = 1.568-3.550, p = 3.8 × 10^-5; OR = 3.357, 95% CI = 1.769-6.370, p = 0.002; OR = 2.750, 95% CI = 1.354-5.587, p = 0.0052 in each model, respectively]. Conclusions: Evidence of the present results indicate that HLA-G 14-bp insertion/deletion polymorphism is associated with susceptibility to AR in the Asian population.

Analysis of key markers: IL-10/sHLA-G in psoriasis patients and the identification of 14-bp INDEL in the HLA-G gene

BACKGROUND

Psoriasis is a chronic inflammation resulting from interactions between immunological and genetic factors. An important tolerogenic role in this autoimmunological disease is played by HLA-G, which is modulated by IL-10. Therefore, this study (N.=80) aimed to evaluate changes in the serum sHLA-G and IL-10 levels in active psoriasis vulgaris and in the early stages of treatment with Methotrexate (MTX) compared to healthy controls. The 14-bp INDEL of the HLA-G gene was evaluated to find possible associations with clinical and laboratory variables.

METHODS

The level of sHLA-G and IL-10 in serum was evaluated (ELISA tests) in patients before the first dose of MTX and at week 12 of treatment, compared to healthy control donors. The 14-bp INDEL in 3'UTR of the HLA-G gene was identified using gDNA templates isolated from full blood. HLA-G amplicons were obtained by PCR, separated by electrophoresis and sequenced.

RESULTS

The mean serum IL-10 level was 4.653±3.33 pg/mL in psoriatic patients, 13.3±9.64 pg/mL after short MTX treatment, compared to 6.23 pg/mL in healthy controls. In addition, the serum level of sHLA-G was 0.275±0.03 ng/mL and 0.332±0.06 ng/mL in patients before and after MTX treatment, respectively, and 0.302±0.08 ng/mL in the control group. A correlation was found (r=-0.43; P<0.005) between the IL-10 and BSA serum levels in psoriasis patients after MTX treatment, indicating health improvement. The three genotypes identified in the 3'UTR of the HLA-G revealed no association with sHLA-G level in serum.

CONCLUSIONS

The mean levels of sHLA-G and the key anti-inflammatory cytokine IL-10 in the blood of pretreatment psoriasis patients are low and indicate that the immunotolerance mechanisms have failed. Treatment of psoriasis patients with low systemic levels of sHLA-G and IL-10 brings them to the same or higher protein levels, respectively, as in healthy donors. Higher sHLA-G levels in healthy donors and after MTX treatment, compared to the sHLA-G levels in the acute phase of psoriasis, indicates its immune system surveillance function.

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 and clinical markers for predicting treatment responsiveness in rheumatoid arthritis

Although many drugs and therapeutic strategies have been developed for rheumatoid arthritis (RA) treatment, numerous patients with RA fail to respond to currently available agents. In this review, we provide an overview of the complexity of this autoimmune disease by showing the rapidly increasing number of genes associated with RA.We then systematically review various factors that have a predictive value (predictors) for the response to different drugs in RA treatment, especially recent advances. These predictors include but are certainly not limited to genetic variations, clinical factors, and demographic factors. However, no clinical application is currently available. This review also describes the challenges in treating patients with RA and the need for personalized medicine. At the end of this review, we discuss possible strategies to enhance the prediction of drug responsiveness in patients with RA.

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.

"HLA-G 3'UTR gene polymorphisms and rheumatic heart disease: a familial study among South Indian population"

BACKGROUND

Rheumatic heart disease (RHD) is an autoimmune disease where cross reactive CD4⁺ T cells are involved in the pathogenesis of valvular damage. Human Leukocyte Antigen-G (HLA-G), an immunosuppressive molecule playing a crucial role in the inhibition of T cell response is associated with the pathogenesis of various autoimmune and inflammatory diseases. Genetic polymorphisms within the 3'untranslated region (UTR) of HLA-G influences its expression and thus disease pathogenesis. Hence, the present study aims to unravel the association of 14 bp Ins/Del (rs66554220) and +3142 C/G (rs1063320) polymorphisms in 3' UTR of HLA-G with RHD.

METHODS

This familial study consists of 99 RHD families (99 RHD patients, 140 parents and 126 healthy siblings). The 14 bp Ins/Del and +3142 C/G polymorphisms were evaluated by PCR using sequence specific primers and its transmission disequilibrium (TD) was tested by TD test in 70 trio families.

RESULTS

The frequency of +3142 C/C genotype was high in patients with combined valvular lesions (CVL) (OR = 5.88; p_c = 0.012) and pooled RHD patients (P: OR = 2.76; p = 0.043; p_c = 0.076) when compared to healthy siblings. Under the additive (OR = 5.50; p_c = 0.026) and recessive genetic model (OR = 5.88; p_c = 0.012), the +3142 C/C genotype was significantly associated with CVL in patients.

CONCLUSION

The results suggest that the +3142 C/C genotype may be associated with minor risk for the development of RHD and is more likely to influence the severity of the disease.

Are gene polymorphisms related to treatment outcomes of methotrexate in patients with rheumatoid arthritis? A systematic review and meta-analysis

Aim: Identifying the predictors of responsiveness and adverse events in methotrexate (MTX) treated patients with rheumatoid arthritis (RA) has been the focus of most concern, but still without consistent consensus. Methods: PubMed and OVID EMBASE were searched to collect relevant studies that addressed correlations between gene polymorphisms and efficacy and/or toxicity in MTX-treated RA patients. Allelic, recessive, dominant and over-dominant model were applied. Results: A total of 68 studies were included. For associations with efficacy, AMPD1 34C>T polymorphism was related to responsiveness in dominant model (odds ratio [OR]: 1.77; 95% CI: 1.19–2.63) and over-dominant model (OR: 1.59; 95% CI: 1.04–2.45). ATIC T675C polymorphism had association with responsiveness in recessive model (OR: 2.54; 95% CI: 1.23–5.26). For associations with toxicity, polymorphisms in TYMS 1494 del6 and FPGS rs10106 were correlated to absenting overall adverse events in recessive model (OR: 0.68; 95% CI: 0.49–0.95) and dominant model (OR: 0.54; 95% CI: 0.35–0.83) respectively while MTHFR C677T was associated with presenting overall adverse events in allelic model (OR: 1.29; 95% CI: 1.02–1.63), recessive model (OR: 1.38; 95% CI: 1.00–1.89) and dominant model (OR: 1.41; 95% CI: 1.02–1.94). Conclusion: Polymorphisms in AMPD1 34C>T and ATIC T675C predict responsiveness. The absence of TYMS 1494 del6 and FPGS rs10106 and presence of MTHFR C677T predict adverse events in RA patients treated with MTX. Moreover, variations of the associations were found between Caucasians and non-Caucasians.

Elevation of plasma-soluble HLA-G in childhood nephrotic syndrome is associated with IgE

Background Nephrotic syndrome is related to immune system dysfunction. Soluble human leukocyte antigen-G has been suggested to have an immunomodulatory role. Additionally, human leukocyte antigen-G expression may be influenced by the 14-base pair insertion/deletion polymorphism. However, this molecule has not been investigated in nephrotic syndrome. Methods Fifty-five children with nephrotic syndrome were enrolled: 24 primary nephrotic syndrome patients and 31 recurrent nephrotic syndrome patients. A group of 120 healthy subjects were included as reference controls. Additionally, 22 patients in nephrotic syndrome remission after treatments were also included. Both nephrotic syndrome patients and healthy subjects were genotyped for the 14-base pair insertion/deletion polymorphism. Plasma soluble human leukocyte antigen-G concentrations and serum immunoglobulin concentrations were determined. Results Nephrotic syndrome patients showed significantly higher levels of both soluble human leukocyte antigen-G and immunoglobulin E compared to normal controls. Nephrotic syndrome patients presented a higher frequency of the -14-base pair allele than did normal controls. Soluble human leukocyte antigen-G concentrations in remission patients were dramatically lower compared to in nephrotic syndrome patients. Moreover, soluble human leukocyte antigen-G and immunoglobulin E were moderately correlated in nephrotic syndrome patients. Conclusions The present study demonstrated that plasma soluble human leukocyte antigen-G concentrations were significantly elevated and that a relationship between serum total immunoglobulin E in nephrotic syndrome patients and the human leukocyte antigen-G -14-base pair allele may be a risk factor for nephrotic syndrome. These findings suggest that soluble human leukocyte antigen-G may be used as a monitoring marker for nephrotic syndrome patients' condition.

Clinical correlates of human leucocyte antigen (HLA)-G in systemic sclerosis

Human leucocyte antigen (HLA)-G has a tolerogenic function and could play a role in the pathogenesis of immune-mediated diseases, including systemic sclerosis (SSc). The aim of this study was to evaluate HLA-G serum expression (sHLA-G) and the HLA-G gene 14 base pairs (bp) insertion/deletion (del(-)/del(+)) polymorphism in patients with Ssc, to search for possible associations with clinical and laboratory variables. sHLA-G was measured by enzyme-linked immunosorbent assay (ELISA) in sera from 77 patients with SSc and 32 healthy donors (HD); the 14 bp del(-)/del(+) polymorphism was evaluated by polymerase chain reaction (PCR) amplification of peripheral blood mononuclear cells (PBMC) genomic DNA. Receiver operating characteristics (ROC) analysis identified the HLA-G cut-off that best discriminated dichotomized clinical and serological variables, that was subsequently employed to subdivide SSc patients into HLA-G high (HLA-G(+)) and low (HLA-G(-)) profile groups. sHLA-G were not statistically different between SSc patients and HD, nor between distinct SSc autoantibody subsets. Subdividing SSc patients by HLA-G positivity or negativity yielded significant differences for the modified Rodnan skin score (mRss) (P = 0.032), 'general' (P = 0.031) and 'kidney' (P = 0.028) Medsger severity scores (MSS) and disease activity index, and especially Δ heart/lung (P = 0.005). A worse 'general' MSS (P = 0.002) and Δ heart/lung (P = 0.011) were more frequent in the low sHLA-G group. These two variables and mRss were associated with sHLA-G levels at logistic regression analysis. Treatment had no influence on sHLA-G. Moreover, a higher frequency of scleredema was detected in the del(+)/del(+) than the del(-)/del(+) group (P = 0.04). These data suggest modulatory effects of sHLA-G on SSc. Prospective studies are needed to investigate a role in predicting the disease course.

The paradox of high availability and low recognition of soluble HLA-G by LILRB1 receptor in rheumatoid arthritis patients

HLA-G is a regulatory molecule involved in immunologic tolerance. Growing evidence indicates that HLA-G plays a role in the regulation of inflammatory processes and autoimmune diseases. This study aimed at a systematic evaluation of soluble HLA-G (sHLA-G) in plasma of rheumatoid arthritis (RA) patients with long-lasting chronic inflammation. RA patients (n=68) and healthy controls (n=26) had their plasmatic sHLA-G measured by ELISA whereas the binding capability of sHLA-G to its cognate LILRB1 receptor was measured by a Luminex-based assay. All subjects were PCR-genotyped for HLA-G 14bp polymorphism (rs66554220). Significantly higher sHLA-G levels were observed in patients (p<0.001), however no significant differences were observed in LILRB1 binding capacity between RA patients and controls. Remarkably, the proportion of patients presenting specific binding of sHLA-G to LILRB1 was significantly decreased as compared to controls (56% vs. 81%, p=0.027). Patients without rheumatoid factor (RF-) were significantly overrepresented in the group of patients positive for LILRB1 binding as compared to patients without LILRB1 binding (31% vs 10%, p=0.033). Furthermore, methotrexate treated patients (n=58) revealed significantly lower LILRB1 binding to sHLA-G molecules than non-treated patients (medians: 12.2 vs. 67.7 units/ml, p=0.031). Unlike in controls, no significant differences in sHLA-G levels were observed among patients grouped by 14pb genotype. Thus, in a substantial number of late RA patients, the circulating sHLA-G molecules are impaired regarding LILRB1 recognition, meaning that although increased levels are observed; these molecules are not qualified to exert their protective functions against inflammation. Our findings offer new insights into the immunopathology of RA patients with long-lasting anti-RA-treatment and highlight the importance to also measure the binding capability of sHLA-G to LILRB1.

Human leukocyte antigen-G polymorphism influences the age of onset and autoantibody status in rheumatoid arthritis

The study was conducted to investigate the frequency of three gene polymorphisms in the 3'-untranslated region (3'-UTR) of human leucocyte antigen-G (HLA-G) gene in south Indian patients with rheumatoid arthritis (RA) and analyze their influence on disease susceptibility, phenotype and treatment response. HLA-G 14 bp insertion (Ins)/deletion (del) (rs66554220), HLA-G +3142G>C (rs1063320) and +3187A>G (rs9380142) polymorphism was analyzed in 221 RA patients and 200 healthy controls. Frequency of HLA-G genotypes or alleles did not differ between patients and controls. Analysis based on rheumatoid factor (RF) status revealed that the frequency of allele 'A' (rs9380142) was significantly higher in RF-positive than in RF-negative patients [84% vs 74%, Yates-corrected P value (Pc) = 0.04, odds ratio (OR) = 1.8, 95% confidence interval (CI) = 1.0-3.2]. A similar difference was maintained in RF-positive female patients than their RF-negative counterparts (83% vs 71%, Pc = 0.02, OR = 1.9, 95% CI = 1.0 to 3.4) and between RF-positive and RF-negative young onset RA (YORA) patients (84% vs 73%, Pc = 0.03, OR = 1.9, 95% CI = 1.0-3.2), suggesting that rs9380142 polymorphism influenced RF status. The 14 bp Ins allele of rs66554220 was significantly more prevalent in RF-positive YORA than in RF-positive late onset RA (LORA) patients (51% vs 25%, P = 0.03, OR = 3.1, 95% CI = 1.1-9.8). Frequency of the four major haplotypes [InsGA (48%), DelGA (22%), DelCG (18%), DelCA (9.7%)] observed did not differ between cases and controls. HLA-G does not appear to be a risk factor for development of RA in south Indian Tamils but may act as a genetic modifier of clinical phenotype in terms of autoantibody production, gender preference and age at disease onset.

HLA-G Molecules in Autoimmune Diseases and Infections

Human leukocyte antigen (HLA)-G molecule, a non-classical HLA-Ib molecule, is less polymorphic when compared to classical HLA class I molecules. Human leukocyte antigen-G (HLA-G) was first detected on cytotrophoblast cells at the feto-maternal interface but its expression is prevalent during viral infections and several autoimmune diseases. HLA-G gene is characterized by polymorphisms at the 3' un-translated region and 5' upstream regulatory region that regulate its expression and are associated with autoimmune diseases and viral infection susceptibility, creating an unbalanced and pathologic environment. This review focuses on the role of HLA-G genetic polymorphisms, mRNA, and protein expression in autoimmune conditions and viral infections.

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.

HLA-G 3' untranslated region polymorphisms influence the susceptibility for human papillomavirus infection

Human leukocyte antigen (HLA)-G molecule acts as a potential factor for the regulation of immune responses and its expression in virus-infected cells may enable them to escape immunosurveillance. Besides its polymorphic promoter region, the 3' untranslated region (UTR) seems to play an important role in regulating HLA-G expression. In this study, we investigated the influence of HLA-G 14 bp (rs66554220) and +3142 (rs1063320) polymorphisms in 179 women with active human papillomavirus (HPV) infection and 143 age-matched, unrelated, HPV-negative, normal Chinese Han population. Our findings showed that frequency of the allele +3142 C [31.3% vs 44.4%, odds ratio (OR) = 0.57, Pc < 0.01] and the genotype +3142 CC (10.6% vs 21.7%, OR = 0.43, Pc = 0.012) was significantly decreased in HPV infected patients compared with normal controls. Furthermore, the haplotype -14 bp/C was associated with a reduced risk for HPV infection (OR = 0.57, Pc = 0.001). Our findings also showed that HLA-G homozygous +14 bp/+14 bp genotype was significantly associated with an increased risk for HPV18 infection (OR = 12.95, P < 0.01), whereas HLA-G heterozygous +14 bp/-14 bp genotype increased risk for HPV58 (OR = 5.55, P < 0.05). Furthermore, frequency of the haplotype +14 bp/G was significantly increased in HPV18 infected patients (60.0% vs 27.3%, OR = 4.00, Pc < 0.05). Taken together, our results supported a role of the HLA-G 3' UTR polymorphisms as a susceptible factor for the active HPV infection, and suggested a possible interference of the HLA-G molecule in the response to virus infection.

Some basic aspects of HLA-G biology

Human leukocyte antigen-G (HLA-G) is a low polymorphic nonclassical HLA-I molecule restrictively expressed and with suppressive functions. HLA-G gene products are quite complex, with seven HLA-G isoforms, four membrane bound, and other three soluble isoforms that can suffer different posttranslational modifications or even complex formations. In addition, HLA-G has been described included in exosomes. In this review we will focus on HLA-G biochemistry with special emphasis to the mechanisms that regulate its expression and how the protein modifications affect the quantification in biological fluids.

Impact of HLA-G analysis in prevention, diagnosis and treatment of pathological conditions

Human leukocyte antigen-G (HLA-G) is a non-classical HLA class I molecule that differs from classical HLA class I molecules by low polymorphism and tissue distribution. HLA-G is a tolerogenic molecule with an immune-modulatory and anti-inflammatory function on both innate and adaptative immunity. This peculiar characteristic of HLA-G has led to investigations of its role in pathological conditions in order to define possible uses in diagnosis, prevention and treatment. In recent years, HLA-G has been shown to have an important implication in different inflammatory and autoimmune diseases, pregnancy complications, tumor development and aggressiveness, and susceptibility to viral infections. In fact, HLA-G molecules have been reported to alternate at both genetic and protein level in different disease situations, supporting its crucial role in pathological conditions. Specific pathologies show altered levels of soluble (s)HLA-G and different HLA-G gene polymorphisms seem to correlate with disease. This review aims to update scientific knowledge on the contribution of HLA-G in managing pathological conditions.

Transcriptional and posttranscriptional regulations of the HLA-G gene

HLA-G has a relevant role in immune response regulation. The overall structure of the HLA-G coding region has been maintained during the evolution process, in which most of its variable sites are synonymous mutations or coincide with introns, preserving major functional HLA-G properties. The HLA-G promoter region is different from the classical class I promoters, mainly because (i) it lacks regulatory responsive elements for IFN-γ and NF-κB, (ii) the proximal promoter region (within 200 bases from the first translated ATG) does not mediate transactivation by the principal HLA class I transactivation mechanisms, and (iii) the presence of identified alternative regulatory elements (heat shock, progesterone and hypoxia-responsive elements) and unidentified responsive elements for IL-10, glucocorticoids, and other transcription factors is evident. At least three variable sites in the 3' untranslated region have been studied that may influence HLA-G expression by modifying mRNA stability or microRNA binding sites, including the 14-base pair insertion/deletion, +3142C/G and +3187A/G polymorphisms. Other polymorphic sites have been described, but there are no functional studies on them. The HLA-G coding region polymorphisms might influence isoform production and at least two null alleles with premature stop codons have been described. We reviewed the structure of the HLA-G promoter region and its implication in transcriptional gene control, the structure of the HLA-G 3'UTR and the major actors of the posttranscriptional gene control, and, finally, the presence of regulatory elements in the coding region.

HLA-G +3142 polymorphism as a susceptibility marker in two rheumatoid arthritis populations in Brazil

In this study, we sought to investigate the genetic influence of two HLA-G 3'-untranslated region (3'-UTR) polymorphisms - 14 bp (rs66554220) and +3142C>G (rs1063320) and their compounding haplotypes in susceptibility to rheumatoid arthritis (RA) in a two-region Brazilian study comprising of 539 patients and 489 controls. All subjects were polymerase chain reaction (PCR) genotyped for the referred polymorphisms and logistic regression models controlling for sex, city and age were performed. Homozygozity for the +3142G allele was associated with an increased risk of RA [odds ratio (OR) = 1.45, 95% confidence interval (CI) = 1.075-1.959, P(Bonf)  = 0.030], whereas no association was observed for the 14 bp polymorphism. Haplotype comparisons between patients and controls showed a decreased frequency of the delC haplotype in patients (OR = 0.70, 95% CI = 0.521-0.946, P(Bonf)  = 0.040), which remained significant in the rheumatoid factor (RF)-positive group (OR = 0.66, 95% CI = 0.482-0.900, P(Bonf)  = 0.018), but not in the RF-negative group. These results corroborate the hypothesis of an involvement of HLA-G in the susceptibility of RA. The +3142G allele is associated with haplotype lineages that share high identity and are regarded as low producers. The presence of the G allele in homozygosis could be responsible for a low HLA-G expression profile that could favor the triggering of RA.

HLA-G is a component of the chronic lymphocytic leukemia escape repertoire to generate immune suppression: impact of the HLA-G 14 base pair (rs66554220) polymorphism

This work investigates the possibility that HLA-G, a molecule modulating innate and adaptive immunity, is part of an immune escape strategy of chronic lymphocytic leukemia cells. A 14 base pair insertion/deletion polymorphism (rs66554220) in the 3'-untranslated region of HLA-G influences mRNA stability and protein expression. The analysis of a cohort of patients with chronic lymphocytic leukemia confirmed that del/del individuals are characterized by higher levels of surface and soluble HLA-G than subjects with the other two genotypes. In line with its role in immunomodulation, the percentage of regulatory T lymphocytes is higher in del/del patients than in patients with the other genotypes and correlates with the amounts of surface or soluble HLA-G. Furthermore, addition of sHLA-G-rich plasma from patients with chronic lymphocytic leukemia induces natural killer cell apoptosis and impairs natural killer cell lysis, with effects proportional to the amount of soluble HLA-G added. Lastly, the presence of an HLA-G 14 base pair polymorphism is of prognostic value, with del/del patients showing reduced overall survival, as compared to those with other genotypes. These results suggest that: (i) the HLA-G 14 base pair polymorphism influences the levels of surface and soluble HLA-G expression, and (ii) the over-expression of HLA-G molecules contributes to creating tolerogenic conditions.

Matrix metalloproteinase-2 (MMP-2) generates soluble HLA-G1 by cell surface proteolytic shedding

Human leukocyte antigen-G (HLA-G) molecules are non-classical HLA class I antigens with an important role in pregnancy immune regulation and inflammation control. Soluble HLA-G proteins can be generated through two mechanisms: alternative splicing and proteolytic release, which is known to be metalloprotease mediated. Among this class of enzymes, matrix metalloproteinases (MMPs) might be involved in the HLA-G1 membrane cleavage. Of particular interest are MMP-2 and MMP-9, which regulate the inflammatory process by cytokine and chemokine modulation. We evaluated the effect of MMP-9 and MMP-2 on HLA-G1 membrane shedding. In particular, we analyzed the in vitro effect of these two gelatinases on the secretion of HLA-G1 via proteolytic cleavage in 221-G1-transfected cell line, in JEG3 cell line, and in peripheral blood mononuclear cells. The results obtained by both cell lines showed the role of MMP-2 in HLA-G1 shedding. On the contrary, MMP-9 was not involved in this process. In addition, we identified three possible highly specific cleavage sites for MMP-2, whereas none were detected for MMP-9. This study suggests an effective link between MMP-2 and HLA-G1 shedding, increasing our knowledge on the regulatory machinery beyond HLA-G regulation in physiological and pathological conditions.

Pharmacogenetics of disease-modifying antirheumatic drugs in rheumatoid arthritis: towards personalized medicine

Rheumatoid arthritis is a disease showing considerable heterogeneity in all its aspects, including response to therapy. The efficacy of disease-modifying antirheumatic drugs (DMARDs), with or without biological activity, has been unambiguously established. DMARDs improve the symptoms associated with the disease, and, even more importantly, are capable of stagnating the joint damage associated with the disease. Nonetheless, a considerable proportion of patients fail to achieve an adequate response and/or experience toxicity. This variability in treatment response between individuals has given rise to an extensive search for prognostic markers in order to personalize and optimize therapy in rheumatoid arthritis patients. Pharmacogenetics, the study of genetic variation underlying differential responses to drugs, is a rapidly progressing field in rheumatology that might enable personalized therapy in rheumatic diseases. This review will summarize the pharmacogenetics of commonly used synthetic and biological DMARDs.

New evidence for balancing selection at the HLA-G locus in South Amerindians

HLA-G is a non-classical HLA (Human Leukocyte Antigen) molecule characterized by limited tissue distribution under normal physiological conditions and low variability at both DNA and protein levels. Several studies suggest that HLA-G could play a role, as an immunoregulatory molecule, in situations as diverse as transplantation, cancer, viral infections and inflammatory diseases. A total of 237 individuals from 21 South American tribes speaking nine different linguistic families were studied in relation to the 14 bp insertion/deletion polymorphism at the HLA-G gene. A consistent (seven in nine) excess of heterozygosity in samples classified by language was obtained. Our data supply evidences for balancing selection acting at the HLA-G 14 bp INDEL region. Enhanced fetal survival in a pathogen-rich environment may account for these findings.

HLA-G and mother-child perinatal HIV transmission

Transplacental passage is a well-known phenomenon in HIV infection and immune responses at the maternal-fetal interface play a critical role in perinatal mother-to-child HIV transmission (MCHT). The high expression of HLA-G at the maternal-fetal interface and its role in mediating immune tolerance suggest that it could play an important role in MCHT. We investigated the role of HLA-G polymorphism in perinatal HIV transmission in 348 ART naïve mother-child pairs enrolled in a mother-child HIV transmission cohort, established in Nairobi, Kenya in 1986. Among the 348 children born to 266 HIV+ mothers, 258 were uninfected and 90 became infected perinatally. HLA-G exons 2 and 3 of 266 mothers and 251 children were sequenced and genotyped. Among 14 HLA-G alleles identified, only 4 alleles have a phenotype frequency above 10%. Correlation analysis showed that HLA-G(∗)01:03+ mothers were less likely to perinatally transmit HIV-1 to their children (p=0.038, Odds ratio:0.472, 95%CI:0.229-0.973). Mother-child HLA-G concordance was not associated with the increased perinatal HIV transmission. There was no significant difference in the general health between the transmitting mothers and the mothers who did not transmit HIV to their children.

HLA-G may predict the disease course in patients with early rheumatoid arthritis

The current management of early rheumatoid arthritis (ERA) is to start an intensive treatment as soon as possible. To avoid under/overtreatment, it is important to identify reliable ERA evolution biomarkers. HLA-G molecules has been associated with rheumatoid arthritis, suggesting a role in disease regulation. HLA-G antigens are expressed as membrane bound and soluble isoforms (mHLA-G, sHLA-G) that act as ligand for immune-inhibitory receptors (ILT2, ILT4, KIR2DL4). Expression of HLA-G is influenced by a 14 bp insertion/deletion polymorphism in exon 8 of the gene, where the deletion is associated with mRNA stability. We analyzed 23 ERA patients during a 12 months follow-up disease treatment for sHLA-G, IL-1beta, IL-6, IL-10 and TNF-alpha levels in plasma samples by ELISA, mHLA-G and ILT2 expression on peripheral blood CD14 positive cells by flow cytometry and typed HLA-G 14 bp deletion/insertion polymorphism by Real-Time PCR. Disease status (DAS28), ultrasonography with power Doppler and laboratory data were checked. Cytokine levels confirmed the anti-inflammatory effect of the treatment. sHLA-G, mHLA-G and ILT2 expression inversely correlated with DAS28 disease scores. The frequency of 14 bp deletion allele increased in patients with disease remission. Based on these results, HLA-G may be a candidate biomarker to evaluate early prognosis and disease activity in ERA patients.

Polymorphic variants in exon 8 at the 3' UTR of the HLA-G gene are associated with septic shock in critically ill patients

Introduction

Critically ill patients are characterized as individuals hospitalized in the Intensive Care Unit (ICU) and can evolve to sepsis, septic shock or even death. Among others, genetic factors can influence the outcome of critically ill patients. HLA-G is a non-classical class Ib molecule that has limited protein variability, presenting seven isoforms generated by alternative splicing, and presents immunomodulatory properties. Polymorphisms at the 3'UTR are thought to influence HLA-G gene expression. It was previously observed that increased sHLA-G5 levels were predictive of survival among septic shock patients. We assessed the frequencies of 7 polymorphisms in exon 8 at the 3' UTR of HLA-G and associated these variants with different clinical outcomes in critically ill patients.

Methods

Exon 8 at the 3' UTR of the HLA-G gene from 638 critically ill subjects was amplified by PCR and sequenced. Genotypes were identified using FinchTV software v.1.4.0 and the most probable haplotype constitution of each sample was determined by PHASE software v.2.1. Haplotype frequencies, linkage disequilibrium, heterozygosity test and Hardy-Weinberg Equilibrium were estimated using ARLEQUIN software v.3.5.

Results

Among all critically ill patients, an association between carriers of the +2960IN_+3142 G_+3187A haplotype and septic shock (P = 0.047) was observed. Septic patients who carried the +2960IN_+3142G_+3187A haplotype presented an increased risk for septic shock (P = 0.031).

Conclusions

The present study showed, for the first time, an association between polymorphisms in exon 8 at the 3 'UTR of HLA-G gene and outcomes of critically ill patients. These results may be important for understanding the mechanisms involved in evolution to septic shock in critically ill patients.

HLA-G polymorphisms, genetic susceptibility, and clinical outcome in childhood neuroblastoma

Neuroblastoma is the most common solid tumor in children less than 5 years of age. The early onset of neuroblastoma suggests that genes involved in fetal development and pregnancy may have a putative role in the etiology of neuroblastoma. The human leukocyte antigen subtype G (HLA-G) molecule plays an important role in immune response regulation and appears to regulate immune tolerance during early pregnancy as well as tumor immunosurveillance. Elevated levels of soluble HLA-G (sHLA-G) have been detected in a number of malignancies including serum samples from neuroblastoma and have been reported to be predictive of tumor relapse in neuroblastoma. In light of previous investigations suggesting that single nucleotide polymorphisms in the HLA-G gene may impact on protein expression levels and isoform production, we examined the influence of HLA-G polymorphisms on the susceptibility and clinical outcome of neuroblastoma in 163 neuroblastoma patients and 404 healthy controls. The distribution of HLA-G polymorphisms, alleles, or allelic groups did not differ between children diagnosed with neuroblastoma and healthy controls. Our analyses did not detect an association between common HLA-G polymorphisms and clinical outcome in patients treated for neuroblastoma.

The role of HLA--G 14-bp polymorphism in allo-HSCT after short-term course MTX for GvHD prophylaxis

HLA-G molecules are HLA class Ib antigens characterized by tolerogenic and immunoinhibitory functions. The HLA-G 14-bp insertion/deletion (ins/del) polymorphism controls protein expression and seems to be implicated in both MTX treatment response and SCT outcome. The aim of our study is to evaluate the role of HLA-G 14 bp polymorphism in subjects affected by hematological malignancies undergoing allo-SCT and receiving MTX therapy for GvHD prophylaxis. We performed a retrospective analysis of HLA-G 14 bp polymorphism using a specific PCR in 47 recipients and in their respective donors, and evaluated the correlation with the incidence of aGvHD, OS and disease-free survival (DFS) after allo-SCT. We did not observe any correlation between this polymorphism and the risk of aGvHD occurrence. On the contrary, we found that the recipients with a 14 bp ins/14 bp ins genotype were characterized by a lower OS and DFS in univariate and multivariate analysis (OS=OR: 3.235; DFS=OR: 3.302). These data indicate a role for recipient HLA-G 14 bp polymorphism in allo-SCT immunotolerance status and follow-up.

Association of the HLA-G gene +3142C>G polymorphism with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease that affects several organs and systems. Its etiology remains unknown, although it is probably multifactorial. The human leukocyte antigen G (HLA-G) is a nonclassic major histocompatibility complex I molecule characterized by restricted expression and low DNA polymorphism. HLA-G plays a role in immunosuppression through different mechanisms. In inflammatory diseases, it has been postulated that HLA-G expression may be a possible mechanism of tissue protection against exacerbated inflammatory response. On the 3' untranslated region (3' UTR) of the HLA-G gene, there is an insertion/deletion polymorphism of 14 bp (rs1704) that was shown to influence the mRNA stability. The influence of this polymorphism in disease susceptibility is controversial. Also in the 3' UTR there is a single nucleotide polymorphism C/G (rs1063320) on the position +3142, at a possible binding site for microRNAs (miRNAs) and having an influence on miRNA affinity. In this study, we analyzed the +3142C>G and the 14 bp polymorphisms in 195 SLE European-derived female patients. Our findings show a significant increase of the +3142G allele frequency among patients as compared with controls (0.58 vs 0.47, P = 0.011). Also, patients presented a higher frequency of the GG genotype (OR = 1.90, 95% CI: 1.08-3.42). Double heterozygotes for the two polymorphisms presented a milder mean systemic lupus erythematosus disease activity index (SLEDAI) than heterozygotes for only one of the variants or non-heterozygous individuals (1.56 vs 3.15 and 3.26, respectively, corrected P = 0.044). These results suggest the involvement of the HLA-G molecule on SLE susceptibility and outcome.

Linkage disequilibrium between HLA-G*0104 and HLA-E*0103 alleles in Tswa Pygmies

Nonclassical human leukocyte antigen (HLA)-G and -E loci are separated by approximately 660 kb on the short arm of chromosome 6. Interestingly, some functional and expression characteristics are relatively identical or associated for both molecules. For example, expression of HLA-E on the cell surface has been linked to preferential binding of nonameric leader peptides derived from the signal sequence of HLA-G. It has been suggested that these two molecules act synergistically in modulating susceptibility to infectious or chronic inflammatory diseases. A possible explanation for these observations is that HLA-E and HLA-G are evolving under analogous selective pressures and have functions that place them under selective regimes differing from classical HLA genes. The purpose of this study was to investigate the consistency of this hypothesis based on the characterization of the molecular polymorphism of these two genes and their linkage disequilibrium (LD) in three populations, i.e. Southeastern French (n = 57), Teke Congolese (n = 84) and Tswa Pygmies (n = 74). Allelic frequencies observed for HLA-G and HLA-E and for 14-bp ins/del polymorphism in the three populations were similar to those observed in the literature for populations from corresponding geographic areas. Only one of the recently described HLA-G polymorphisms (HLA-G*01:07-01:16) was found, i.e. HLA-G*01:15 in one individual from Congo. We showed that two haplotypes in Tswa Pygmies, i.e. HLA-G*01:04-E*01:03:01 and G*01:04-E*01:01, exhibited highly significant positive and negative D' values respectively. Although these LD could have functional implications, it is more likely because of the genetic drift as the two other populations did not display any significant LD.

Emerging topics and new perspectives on HLA-G

Following the Fifth International Conference on non-classical HLA-G antigens (HLA-G), held in Paris in July 2009, we selected some topics which focus on emerging aspects in the setting of HLA-G functions. In particular, HLA-G molecules could play a role in: (1) various inflammatory disorders, such as multiple sclerosis, intracerebral hemorrhage, gastrointestinal, skin and rheumatic diseases, and asthma, where they may act as immunoregulatory factors; (2) the mechanisms to escape immune surveillance utilized by several viruses, such as human cytomegalovirus, herpes simplex virus type 1, rabies virus, hepatitis C virus, influenza virus type A and human immunodeficiency virus 1 (HIV-1); and (3) cytokine/chemokine network and stem cell transplantation, since they seem to modulate cell migration by the downregulation of chemokine receptor expression and mesenchymal stem cell activity blocking of effector cell functions and the generation of regulatory T cells. However, the immunomodulatory circuits mediated by HLA-G proteins still remain to be clarified.

Implications of the polymorphism of HLA-G on its function, regulation, evolution and disease association

The HLA-G gene displays several peculiarities that are distinct from those of classical HLA class I genes. The unique structure of the HLA-G molecule permits a restricted peptide presentation and allows the modulation of the cells of the immune system. Although polymorphic sites may potentially influence all biological functions of HLA-G, those present at the promoter and 3′ untranslated regions have been particularly studied in experimental and pathological conditions. The relatively low polymorphism observed in the MHC-G coding region both in humans and apes may represent a strong selective pressure for invariance, whereas, in regulatory regions several lines of evidence support the role of balancing selection. Since HLA-G has immunomodulatory properties, the understanding of gene regulation and the role of polymorphic sites on gene function may permit an individualized approach for the future use of HLA-G for therapeutic purposes.

Functional polymorphisms and methotrexate treatment outcome in recent-onset rheumatoid arthritis

AIMS

Clinical response to methotrexate (MTX) treatment differs among rheumatoid arthritis patients. Genetic variation can partly account for this phenomenon. In this study, functional polymorphisms in genes related to the mechanism of action of MTX or immunopathogenesis of rheumatoid arthritis were studied for association with treatment outcome in a Dutch cohort of patients with early rheumatoid arthritis. Furthermore, tests for replication of previous research on these genetic variants were performed according to reported end points.

MATERIALS & METHODS

Seven polymorphisms in seven genes were analyzed in 205 genotyped patients with active rheumatoid arthritis. All patients received standardized MTX treatment (< or =25 mg per week orally) combined with folic acid. MTX treatment outcome was evaluated by disease activity score criteria and adverse drug events. The following genetic variants were analyzed and correlated: ABCB1 3435C>T, ITPA IVS2 +21A>C, HLA-G (-14 bp >+14 bp), TGFB1 +869T>C and TLR4 +896A>G. In case of significant differences, regression analyses were applied. Since carriers of the minor alleles of the SNPs DHFR 829C>T and IMPDH2 +787C>T were not observed, no statistical analyses could be performed.

RESULTS

No significant associations or replications of these genetic variants with MTX efficacy were demonstrated. Regarding toxicity, patients carrying the ABCB1 3435T-allele and TLR4 +896G-allele were 2.5-times more likely to develop adverse drug events at 6 months (odds ratio: 2.6; 95% CI: 1.1-6.2, and odds ratio: 2.5; 95% CI: 1.1-6.1, respectively). Additionally, this chance increased almost fourfold in patients with the two unfavorable genotypes (odds ratio: 3.9; 95% CI: 1.5-10.3). However, none of these associations remained significant after correction for multiple testing (p < 0.004).

CONCLUSION

Our data indicate that MTX toxicity was potentially associated with ABCB1 3435C>T and TLR4 +896A>G. However, after correction, none of these associations remained significant. Furthermore, no significant associations or replications of these functional variants with efficacy were found.

Pharmacogenomics in the treatment of inflammatory bowel disease

In recent years, the benefits of early aggressive treatment paradigms for inflammatory bowel disease have emerged. Symptomatic improvement is no longer considered adequate; instead, the aim of treatment has become mucosal healing and altered natural history. Nonetheless, we still fail to achieve these end points in a large number of our patients. There are many reasons why patients fail to respond or develop toxicity when exposed to drugs used for inflammatory bowel disease, but genetic variation is likely to account for a significant proportion of this. Some examples, notably thiopurine methyltransferase polymorphism in thiopurine treatment, are already established in clinical practice. We present a review of the expanding literature in this field, highlighting many interesting developments in pharmacogenomics applied to inflammatory bowel disease and, where possible, providing guidance on the translation of these developments into clinical practice.

HLA-G*0105N and HLA-G 14 bp dimorphisms in exon 8 in four distinct populations in mainland China

In this study, we investigated human leukocyte antigen (HLA)-G*0105N and the 14 bp deletion/insertion polymorphism in exon 8 of the HLA-G gene in 600 individuals from two southern Chinese Han populations (Hunan Han and Guangdong Han) and two northern Chinese populations (Inner Mongolia Han and Inner Mongolia Mongol), we also studied the linkage disequilibrium (LD) between HLA-G and HLA-A locus in these four populations. Our data showed that (1) the allele and haplotype frequencies of HLA-G and HLA-A loci did not differ significantly between the two southern Chinese Han populations, and showed remarkable homogeneity in the two northern Chinese populations; (2) HLA-G*0105N had significantly higher frequencies in the two northern Chinese populations with a frequency of 10.1% in the Inner Mongolia Han population, HLA-G 14 bp deletion/insertion frequency did not differ significantly between the southern and northern Chinese populations; (3) Ewens-Watterson homozygosity statistics at HLA-G*0105N, HLA-G 14 bp deletion/insertion polymorphism and HLA-A were consistent with neutral expectations for all populations; (4) HLA-G*0105N allele harbored the HLA-G 14 bp insertion in exon 8 and was linked to HLA-A*30, five HLA-G*0105N homozygotes were detected in the four populations; (5) haplotypes HLA-A*30-HLA-G*0105N and HLA-A*02-HLA-G 14 bp deletion were in significant LD across four populations, other LD patterns were more population-specific. Our data suggest that HLA-A*30-HLA-G*0105N-HLA-G 14 bp insertion is a conserved haplotype, the ethnic and/or geographic difference in HLA-G*0105N and HLA-G 14 bp distribution could largely be attributable to demographic factors other than selection. The LD patterns uncovered will facilitate the understanding of HLA-G role in associations previously described between HLA-A subregion and diseases.

Lack of association between HLA-G 14-bp polymorphism and systemic lupus erythematosus in a Han Chinese population

HLA-G is a non-classical HLA-class Ib molecule with multiple immunoregulatory properties. A 14-bp insertion/deletion polymorphism in the HLA-G gene has been suggested to influence the expression of HLA-G and to associate with certain pathological conditions, including autoimmune diseases. We investigated the influence of the 14-bp insertion/deletion polymorphism in the HLA-G gene on disease susceptibility in systemic lupus erythematosus by genotyping this polymorphism in 231 patients with systemic lupus erythematosus and 367 healthy controls and analyzing the levels of soluble HLA-G in a subset of patients with systemic lupus erythematosus and healthy subjects from a Han Chinese population. No statistically significant differences were observed in the frequencies of the 14-bp insertion/deletion HLA-G alleles or genotypes between controls and patients with systemic lupus erythematosus. However, a significant increased expression of soluble HLA-G was noted in patients with systemic lupus erythematosus (mean value = 230.2 U/ml vs 118.3 U/ml in controls, p = 0.0001). Moreover, patients with high levels of soluble HLA-G presented with higher disease activity and had more neurological involvement. Our results do not support the HLA-G 14-bp insertion/deletion polymorphism as a genetic factor influencing systemic lupus erythematosus susceptibility. It is possible that the expression of soluble HLA-G in systemic lupus erythematosus is enhanced as part of a mechanism to try to restore the tolerance process towards auto-antigens and to counteract inflammation. However, the participation of this molecule in the pathological process of the disease also could not be excluded. Lupus (2009) 18, 1259—1266.