Linkage disequilibrium between human leukocyte antigen (HLA) class II and HLA-G--possible implications for human reproduction and autoimmune disease

HLA and Nasal Polyposis Susceptibility: A Meta-analysis of Worldwide Studies

OBJECTIVES

Nasal polyposis (NP) is a common and recurrent condition of the sinonasal cavity which has significant impact on patients' quality of life. NP pathophysiology involves a complex interplay of genetic, environmental, and immunological factors. Several studies have explored the association between human leukocyte antigen (HLA) class II alleles and NP, but the results have been conflicting. The aim of this meta-analysis is to investigate the association between HLA class II alleles, specifically HLA-DQA1, HLA-DQB1, and HLA-DRB1and NP risk.

METHODS

A systematic review was conducted using electronic databases, including PubMed, Google Scholar, and Cochrane Library, to identify studies investigating the association between HLA class II alleles and NP. Eligible studies were identified by specific inclusion and exclusion criteria. The odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association between HLA class II alleles and NP risk. A random-effects model was used to calculate the pooled OR and corresponding 95% CI, and a study required a heterogeneity assessment value I2 < 25% to be considered for analysis.

STUDY DESIGN

Meta-analysis.

RESULTS

A total of four studies were included in this meta-analysis, involving a total of 258 NP alleles and 802 control alleles. The analysis indicated that DQA1*0201 (OR = 3.08, 95% CI [1.70, 5.59]) and DRB1*7 (OR = 2.04, 95% CI [1.14, 3.66]) were significantly associated with increased risk of NP. The analysis of the NP risk alleles DQA1*0201 and DRB1*7 had an I2 < 0% representing low heterogeneity. Sensitivity analysis with LFK indices showed minor asymmetry in either allele.

CONCLUSIONS

This meta-analysis provides evidence that the HLA-DQA1*0201 and HLA-DRB1*7 alleles are risk factors for the development of NP. These findings could contribute to a better understanding of the genetic predisposition of NP and may have implications for the development of novel approaches for the prevention and treatment of this condition.

Evaluation of HLA-G 14bp Ins/Del and +3142 C/G Polymorphisms in Type 1 Diabetes among South Indian Population

Background

Type 1 diabetes (T1D) is a multifactorial autoimmune disease, involving strong genetic components with familial predisposition. Human leukocyte antigen-G (HLA-G) is a non-classical HLA-class I molecule having several immunomodulatory functions. Polymorphisms in HLA-G are associated with several autoimmune diseases including T1D. This study aims to evaluate the association of HLA-G 14bp Ins/Del and +3142 C/G polymorphisms with T1D among the South Indian population.

Methods

The study was performed in a cohort of 123 T1D patients along with their 51 siblings and 126 parents. The association and linkage of HLA-G 14bp Ins/Del and +3142 C/G polymorphisms with T1D were analysed, and transmission disequilibrium test (TDT) was performed.

Results

Significantly increased frequencies of HLA-G 14bp Del/Del genotype (OR = 2.16, pc = 0.0302) and Del allele (OR = 1.71, pc = 0.0398) were observed in female patients compared to parents. Higher frequencies of DelDel/GG combined genotype (OR = 4.45, pc = 0.0049) and Del/G haplotype (OR = 2.91, pc = 0.0277) were observed in female patients compared to parents. TDT also revealed over-transmission of Del/G haplotype (25T vs 7UT; P = 0.0015) and a strong linkage disequilibrium between the studied polymorphisms.

Conclusion

This familial study shows the association of HLA-G 3'UTR 14bp Ins/Del polymorphism with the risk of T1D among the South Indian population, especially in females.

Investigating Serum sHLA-G Cooperation With MRI Activity and Disease-Modifying Treatment Outcome in Relapsing-Remitting Multiple Sclerosis

Relapsing-remitting multiple sclerosis (RRMS) is a demyelinating disease in which pathogenesis T cells have a major role. Despite the unknown etiology, several risk factors have been described, including a strong association with human leukocyte antigen (HLA) genes. Recent findings showed that HLA class I-G (HLA-G) may be tolerogenic in MS, but further insights are required. To deepen the HLA-G role in MS inflammation, we measured soluble HLA-G (sHLA-G) and cytokines serum level in 27 patients with RRMS at baseline and after 12 and 24 months of natalizumab (NTZ) treatment. Patients were divided into high (sHLA-G&gt;20 ng/ml), medium (sHLA-G between 10 and 20 ng/ml), and low (sHLA-G &lt;10 ng/ml) producers. Results showed a heterogeneous distribution of genotypes among producers, with no significant differences between groups. A significant decrease of sHLA-G was found after 24 months of NTZ in low producers carrying the +3142 C/G genotype. Finally, 83.3% of high and 100% of medium producers were MRI-activity free after 24 months of treatment, compared to 63.5% of low producers. Of note, we did not find any correlation of sHLA-G with peripheral cell counts or cytokines level. These findings suggest that serum sHLA-G level may partly depend on genotype rather than peripheral inflammation, and that may have impacted on MRI activity of patients over treatment.

New markers for predictions of acute and chronic rejection and graft outcomes in kidney transplant recipients; HLA-G gene 3'UTR 14 bp polymorphism and sHLA-G

The aim of this study was to evaluate the relation of Human Leukocyte Antigen-G (HLA-G) 14 bp ins/del (insertion/deletion) polymorphism and soluble HLA-G (sHLA-G) level with rejection in kidney transplant recipients. The study was planned as a case-control study involving two hundred fifty kidney transplant recipients. The case group consisted of 125 (female/male: 56/69) kidney transplant recipients diagnosed with acute (n = 52) and chronic rejection (n = 73). The control group consisted of one hundred twenty-five kidney transplant patients with no acute or chronic rejection matched by gender and age in the case group. The sHLA-G level in the recipient's plasma (at the time of rejection for the case, the same time as the case after the transplant for control) was analyzed by Enzyme-Linked Immunosorbent Assay (ELISA). HLA-G 3' untranslated region (3'UTR) polymorphism of recipient and donor was determined using agarose gel electrophoresis and DNA sequencing method. In our study, it was shown that acute rejection rate increased 1.06 times and chronic rejection rate increased 1.14 times in kidney transplant recipients with low serum sHLA-G levels. The rejection patients with the HLA-G 14 bp del/del genotype had higher sHLA-G levels post-transplantation. The frequency of acute rejection was lower in patients with HLA-G 14 bp del/del polymorphism than those with ins/ins and ins/del polymorphisms. This study proposes that HLA-G 3'UTR polymorphism and sHLA-G level might be useful in prediction of rejection in kidney transplant recipients.

Association of HLA-G 3'UTR 14-bp Ins/Del polymorphism with breast cancer among South Indian women

AIM

Human leucocyte antigen-G (HLA-G) and tumour necrosis factor-alpha (TNF-α) are potent immune mediators implicated in the pathogenesis of breast cancer. The polymorphisms in the 3' untranslated region (3'UTR) of HLA-G and promoter region of TNF-α are well known to influence their expression levels and may consequently contribute to varied disease predisposition. Therefore, in the present study, we explored the effect of HLA-G 3'UTR (14-bp Ins/Del and +3142 C/G) and TNF-α promoter (-238 G/A and -308 G/A) polymorphisms on breast cancer risk among South Indian women.

METHODS

A total of 342 women (100 patients with breast cancer, 142 patients with benign breast disorder and 100 healthy women volunteers) were enrolled for this study. Genotyping of HLA-G and TNF-α polymorphisms were performed by direct PCR DNA amplification and amplification refractory mutation system PCR methods, respectively.

RESULTS

Significantly higher frequencies of HLA-G 14-bp Ins allele and Ins/+3142G haplotype were observed in patients with breast cancer than healthy controls (OR=1.56, P_c=0.036) and patients with benign breast disorder (OR=1.47, P_c=0.046). Similarly, subgroup analysis based on age at diagnosis (age≤50 years and >50 years) of breast cancer revealed higher frequencies of 14-bp Ins allele and Ins/+3142G haplotype in the patients of age >50 years than healthy controls (OR=1.77, P_c=0.03). Additionally, the extended haplotypes and multifactor dimensionality reduction analysis of the studied polymorphisms revealed significant contribution of HLA-G 14-bp Ins/Del polymorphism towards breast cancer risk.

CONCLUSION

The findings of the present study suggest that the HLA-G 14-bp Ins/Del polymorphism could influence breast cancer pathogenesis among South Indian women.

The Role of Major Histocompatibility Complex in Organ Transplantation- Donor Specific Anti-Major Histocompatibility Complex Antibodies Analysis Goes to the Next Stage

Organ transplantation has progressed with the comprehension of the major histocompatibility complex (MHC). It is true that the outcome of organ transplantation largely relies on how well rejection is managed. It is no exaggeration to say that to be well acquainted with MHC is a shortcut to control rejection. In human beings, MHC is generally recognized as human leukocyte antigens (HLA). Under the current circumstances, the number of alleles is still increasing, but the function is not completely understood. Their roles in organ transplantation are of vital importance, because mismatches of HLA alleles possibly evoke both cellular and antibody-mediated rejection. Even though the control of cellular rejection has improved by recent advances of immunosuppressants, there is no doubt that antibody-mediated rejection (AMR), which is strongly correlated with donor-specific anti-HLA antibodies (DSA), brings a poor outcome. Thus, to diagnose and treat AMR correctly is a clear proposition. In this review, we would like to focus on the detection of intra-graft DSA as a recent trend. Overall, here we will review the current knowledge regarding MHC, especially with intra-graft DSA, and future perspectives: HLA epitope matching; eplet risk stratification; predicted indirectly recognizable HLA epitopes etc. in the context of organ transplantation.

HLAIb worldwide genetic diversity: New HLA-H alleles and haplotype structure description

The classical HLA class I genes (HLA Ia) were extensively studied because of their implication in clinical fields and anthropology. Less is known about worldwide genetic diversity and linkage disequilibrium for non-classical HLA class I genes (HLA Ib) and HLA pseudogenes. Notably, HLA-H, which is deleted in a fraction of the population, remains scarcely explored. The aims of this study were 1/ to get further insight into HLA-H genetic diversity and into how this variability potentially affects its expression and 2/ to define HLA Ib worldwide allelic diversity and linkage. Exome sequence data from the 1000 Genomes Project were used to define second field HLA-A, -E, -F, -G and -H typing using PolyPheMe software. Allelic and two-loci haplotype frequencies were estimated using Gene[Rate] software both at worldwide and continental levels. Eleven novel HLA-H alleles identified in exome data were validated by NGS performed on 25 genomic DNA samples from the same cohort. Phylogenetic analysis and frequency distribution of HLA-H alleles revealed three clades, each predominantly represented in Admixed American, European and East Asian populations, African populations and South Asian populations. Among these eleven novel alleles, two potentially encode complete transmembrane HLA proteins. We confirm the high LD between HLA-H and -A, and between HLA-H and -G, and show the three genes have distinct worldwide allelic distribution. Conversely, HLA-E and HLA-F both showed little LD, displayed restricted allelic diversity and practically no difference in their distribution across the planet. Our work thus reveals an unexpectedly high HLA-H genetic diversity, with alleles highly represented in Asia possibly encoding a functional HLA protein. Functional implication of these results remains to be explored, both in physiological and pathological contexts.

Immunologic Abnormalities, Treatments, and Recurrent Pregnancy Loss: What Is Real and What Is Not?

Recurrent pregnancy loss, depending on the definition, affects 1% to 3% of women aiming to have a child. Little is known about the direct causes of recurrent pregnancy loss, and the condition is considered to have a multifactorial and complex pathogenesis. The aim of this review was to summarize the evaluation and the management of the condition with specific emphasis on immunologic biomarkers identified as risk factors as well as current immunologic treatment options. The review also highlights and discusses areas in need of further research.

The Influence of Cytomegalovirus on Expression of HLA-G and its Ligand KIR2DL4 by Human Peripheral Blood Leucocyte Subsets

HLA-G is a non-classical class I HLA antigen, normally expressed in high levels only on extravillous cytotrophoblast. It has immunosuppressive properties in pregnancy and has also been found to be upregulated on leucocytes in viral infection. In this study, proportions of all leucocyte subsets expressing HLA-G were found to be low in healthy subjects positive or negative for cytomegalovirus (CMV). Significantly greater proportions of CD4+ CD69+ and CD56+ T cells expressed HLA-G compared to other T cells. However, following stimulation with CMV antigens or intact CMV, proportions of CD4+, CD8+, CD69+ and CD56+ T cells, and also B cells expressing HLA-G, were significantly increased in CMV+ subjects. Despite some subjects having alleles of HLA-G associated with high levels of expression, no relationship was found between HLA-G genotype and expression levels. Purified B cells from CMV+ subjects stimulated in mixed culture with CMV antigens showed significantly increased HLA-G mRNA expression by real-time polymerase chain reaction. Serum levels of soluble HLA-G were similar in CMV- and CMV+ subjects but levels in culture supernatants were significantly higher in cells from CMV+ than from CMV- subjects stimulated with CMV antigens. The HLA-G ligand KIR2DL4 was mainly expressed on NK cells and CD56+ T cells with no differences between CMV+ and CMV- subjects. Following stimulation with IL-2, an increase in the proportion of CD56+ T cells positive for KIR2DL4 was found, together with a significant decrease in CD56dimCD16+ NK cells. The results show that CMV influences HLA-G expression in healthy subjects and may contribute to viral immune evasion.

Cardiac Autoimmunity: Myocarditis

Myocarditis is the inflammation of the muscle tissues of the heart (myocardium). After a pathologic cardiac-specific inflammatory process, it may progress to chronic damage and dilated cardiomyopathy. The latter is characterized by systolic dysfunction, whose clinical correlate is heart failure. Nevertheless, other acute complications may arise as consequence of tissue damage and electrophysiologic disturbances. Different etiologies are involved in triggering myocarditis. In some cases, such as giant cell myocarditis or eosinophilic necrotizing myocarditis, it is an autoimmune process. Several factors predispose the development of autoimmune myocarditis such as systemic/local primary autoimmunity, viral infection, HLA and gender bias, exposure of cryptic antigens, mimicry, and deficient thymic training/Treg induction. Once the anti-myocardium autoimmune process is triggered, several components of the immune response orchestrate a sustained attack toward myocardial tissues with particular timing and immunopathogenic features. Innate response mediated by monocytes/macrophages, neutrophils, and eosinophils parallels the adaptive response, playing a final effector role and not only a priming function. Stromal cells like fibroblast are also involved in the process through specific cytokines. Furthermore, adaptive T cell responses have anti-paradigmatic features, as Th17 response is dispensable for acute myocarditis but is the main driver of the process leading to dilated cardiomyopathy. Humoral response, thought to be a bystander, is important in the appearance of late-stage hemodynamic complications. The complexity of that process, as well as the unspecific and variable clinical presentation, had generated difficulties for diagnosis and treatment, which remain suboptimal. In this chapter, we will discuss the most relevant immunopathogenic findings from a basic science and clinical perspective.

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.

Ex vivo immunosuppressive effects of mesenchymal stem cells on Crohn's disease mucosal T cells are largely dependent on indoleamine 2,3-dioxygenase activity and cell-cell contact

Introduction

Crohn’s disease (CD) is a disabling chronic enteropathy sustained by a harmful T-cell response toward antigens of the gut microbiota in genetically susceptible subjects. Growing evidence highlights the safety and possible efficacy of mesenchymal stem cells (MSCs) as a new therapeutic tool for this condition. Therefore, we aimed to investigate the effects of bone marrow-derived MSCs on pathogenic T cells with a view to clinical application.

Methods

T-cell lines from both inflamed and non-inflamed colonic mucosal specimens of CD patients and from healthy mucosa of control subjects were grown with the antigen muramyl-dipeptide in the absence or presence of donors’ MSCs. The MSC effects were evaluated in terms of T-cell viability, apoptotic rate, proliferative response, immunophenotype, and cytokine profile. The role of the indoleamine 2,3-dioxygenase (IDO) was established by adding a specific inhibitor, the 1-methyl-DL-tryptophan, and by using MSCs transfected with the small interfering RNA (siRNA) targeting IDO. The relevance of cell-cell contact was evaluated by applying transwell membranes.

Results

A significant reduction in both cell viability and proliferative response to muramyl-dipeptide, with simultaneous increase in the apoptotic rate, was found in T cells from both inflamed and non-inflamed CD mucosa when co-cultured with MSCs and was reverted by inhibiting IDO activity and expression. A reduction of the activated CD4⁺CD25⁺ subset and increase of the CD3⁺CD69⁺ population were also observed when T-cell lines from CD mucosa were co-cultured with MSCs. In parallel, an inhibitory effect was evident on the expression of the pro-inflammatory cytokines tumor necrosis factor-α, interferon-γ, interleukin-17A and -21, whereas that of the transforming growth factor-β and interleukin-6 were increased, and production of the tolerogenic molecule soluble HLA-G was high. These latter effects were almost completely eliminated by blocking the IDO, whose activity was upregulated in MSCs co-cultured with CD T cells. The use of a semipermeable membrane partially inhibited the MSC immunosuppressive effects. Finally, hardly any effects of MSCs were observed when T cells obtained from control subjects were used.

Conclusion

MSCs exert potent immunomodulant effects on antigen-specific T cells in CD through a complex paracrine and cell-cell contact-mediated action, which may be exploited for widespread therapeutic use.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0122-1) contains supplementary material, which is available to authorized users.

A population response analysis approach to assign class II HLA-epitope restrictions

Identification of the specific HLA locus and allele presenting an epitope for recognition by specific TCRs (HLA restriction) is necessary to fully characterize the immune response to Ags. Experimental determination of HLA restriction is complex and technically challenging. As an alternative, the restricting HLA locus and allele can be inferred by genetic association, using response data in an HLA-typed population. However, simple odds ratio (OR) calculations can be problematic when dealing with large numbers of subjects and Ags, and because the same epitope can be presented by multiple alleles (epitope promiscuity). In this study, we develop a tool, denominated Restrictor Analysis Tool for Epitopes, to extract inferred restriction from HLA class II-typed epitope responses. This automated method infers HLA class II restriction from large datasets of T cell responses in HLA class II-typed subjects by calculating ORs and relative frequencies from simple data tables. The program is validated by: 1) analyzing data of previously determined HLA restrictions; 2) experimentally determining in selected individuals new HLA restrictions using HLA-transfected cell lines; and 3) predicting HLA restriction of particular peptides and showing that corresponding HLA class II tetramers efficiently bind to epitope-specific T cells. We further design a specific iterative algorithm to account for promiscuous recognition by calculation of OR values for combinations of different HLA molecules while incorporating predicted HLA binding affinity. The Restrictor Analysis Tool for Epitopes program streamlines the prediction of HLA class II restriction across multiple T cell epitopes and HLA types.

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.

Relationship between HLA-G polymorphism and susceptibility to recurrent miscarriage: a meta-analysis of non-family-based studies

PURPOSE

The HLA-G 14-bp insertion/deletion polymorphism had been inconsistently associated with recurrent miscarriage (RM) risk. We examined the association by performing a meta-analysis.

METHODS

Eligible articles were searched in PubMed, EMBASE and CNKI without language limitation. We included all the articles about two or more miscarriages associated with HLA-G 14-bp polymorphism. The odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations. Statistical analyses were performed by the STATA10.0 software.

RESULTS

17 studies were included, representing 1786 cases and 1574 controls. The current meta-analysis showed that 14-bp polymorphism was not associated with RM risk in all genetic models and allele contrast(+14 bp vs. -14 bp: OR = 1.13; 95% CI, 0.96,1.32; +14 bp/+14 bp vs. -14 bp/-14 bp: OR = 1.16, 95% CI, 0.85, 1.59; +14 bp/-14 bp vs. -14 bp/-14 bp: OR = 1.21, 95% CI, 0.92,1.58; dominant model: OR = 1.33; 95% CI, 0.99,1.78; recessive model: OR = 1.06; 95% CI, 0.79,1.43). Moreover, a significant heterogeneity was evident across studies. On the other hand, the subgroup analysis demonstrated that there was a significant association between HLA-G 14-bp polymorphism and patients with three or more miscarriages(+14 bp vs. -14 bp: OR = 1.27; 95% CI, 1.04, 1.55; dominant model: OR = 1.52; 95% CI, 1.16, 1.99; and model +14 bp/-14 bp versus -14 bp/-14 bp: OR = 1.51; 95% CI, 1.15, 1.97;).

CONCLUSIONS

Our comprehensive meta-analysis indicated that there was insufficient evidence to demonstrate a conclusive association between the HLA-G 14-bp insertion/deletion polymorphism and the risk of RM. But HLA-G 14-bp insertion/deletion polymorphic variation was associated with RM risk in patients with three or more miscarriages. Larger and well-designed studies may eventually provide a better, comprehensive understanding of the association between the HLA-G 14-bp insertion/deletion polymorphism and RM in the future.

Role of HLA-G 14bp deletion/insertion and +3142C>G polymorphisms in the production of sHLA-G molecules in relapsing-remitting multiple sclerosis

HLA-G is believed to act as an anti-inflammatory molecule in Multiple Sclerosis (MS). The 3' untranslated region of the HLA-G gene is characterized by two polymorphisms, DEL/INS14bp and +3142C>G, which control soluble HLA-G (sHLA-G) production. The influence of these two HLA-G variants on sHLA-G serum and cerebrospinal fluid (CSF) levels was investigated in 69 Relapsing-Remitting MS patients grouped in magnetic resonance imaging (MRI) inactive and active disease. Serum and CSF sHLA-G levels were more elevated in high than in low DEL/INS 14bp and +3142C>G sHLA-G producers and were different among the various combined HLA-G genotypes in both MRI inactive and active diseases. The highest and the lowest sHLA-G values were identified in MS patients with C/C,DEL/DEL and G/G,INS/INS genotypes, respectively. Our preliminary findings suggest that serum and CSF sHLA-G levels in MS could be influenced by HLA-G polymorphisms irrespective of the inflammatory microenvironment.

Genetic variations in loci relevant to natural killer cell function are affected by ethnicity but are generally not correlated with susceptibility to HIV-1

Polymorphisms in cell surface receptors of natural killer cells and their ligands on target cells can affect susceptibility to viral infections including human immunodeficiency virus (HIV)-1. We found that the carriage of the human leukocyte antigen (HLA)-G minus 14-bp polymorphism, LILRB1 single nucleotide polymorphism rs1061680, and activating and inhibitory killer immunoglobulin-like receptors (KIRs) were different when data were compared between Caucasian, African Americans and Asian populations. However, carriage was similar when HIV-1 patients were compared with control donors, with the exception of the African American cohort.

Fetus specific T cell modulation during fertilization, implantation and pregnancy

Recently there is an increasing interest in aspects of a more specific immunoregulation during pregnancy. Understanding these mechanism might have a broader application not only for reproductive immunology but also in general for biology and medicine. Especially the induction, already before conception, of feto-specific T cells with a possibly regulatory function gives a biological explanation of local immunotolerance at the maternal fetal interface, supporting the epidemiological evidence of a feto/paternal-specific immuneregulation. Understanding the expression of specific HLA-classes on trophoblast and the crosstalk of these antigens with various cell types, specifically modulated in the decidua, resulting in the secretion of cytokines and (angiogenic) chemokines has given us a more and more detailed understanding of this regulation. This regulation could be induced by fetal cells circulating in the mother (microchimerism) and from the interaction with fetal subcellular fractions as exosomes, but also from paternal antigens present in seminal fluid. Molecular interaction between paternal and fetal antigens and receptors in endometrium and the decidua are discussed. This review highlights besides uNK cells, especially the function of CD4+ and CD8+ T cells with a regulatory function in the context of recurrent miscarriage and pre-eclampsia. Besides HLA, also male-specific minor histocompatibility antigens and the genetic background for these pregnancy complications are discussed.

Secondary recurrent miscarriage and H-Y immunity

BACKGROUND

Approximately half recurrent miscarriage (RM) cases remain unexplained after standard investigations. Secondary RM (SRM) is, in contrast to primary RM, preceded by a birth, which increases the transfer of fetal cells into the maternal circulation. Mothers of boys are often immunized against male-specific minor histocompatibility (H-Y) antigens, and H-Y immunity can cause graft-versus-host disease after stem-cell transplantation. We proposed the H-Y hypothesis that aberrant H-Y immunity is a causal factor for SRM.

METHODS

This is a critical review of the H-Y hypothesis based on own publications and papers identified by systematic PubMed and EMBASE searches.

RESULTS

SRM is more common after the birth of a boy and the subsequent live birth rate is reduced for SRM patients with a firstborn boy. The male:female ratio of children born prior and subsequent to SRM is 1.49 and 0.76 respectively. Maternal carriage of HLA-class II alleles presenting H-Y antigens to immune cells is associated with a reduced live birth rate and increased risk of obstetric complications in surviving pregnancies in SRM patients with a firstborn boy. In early pregnancy, both antibodies against HLA and H-Y antigens are increased in SRM patients compared with controls. Presence of these antibodies in early pregnancy is associated with a lower live birth rate and a low male:female ratio in subsequent live births, respectively. Births of boys are also associated with subsequent obstetric complications in the background population.

CONCLUSIONS

Epidemiological, immunogenetic and immunological studies support the hypothesis that aberrant maternal H-Y immune responses have a pathogenic role in SRM.

Novel alleles of HLA-DQ and -DR loci show association with recurrent miscarriages among South Indian women

BACKGROUND In this study, recurrent miscarriages (RMs) are defined as loss of two or more clinically detectable pregnancies before 20 weeks of gestation. HLA has been thought to play a role in RM. However, the results of earlier studies on the role of different human leucocyte antigen (HLA) genes were conflicting and inconclusive. In the present study, we investigate HLA genes (HLA-DRA, HLA-DRB1, HLA-DQA1 and HLA-DQB1) in RM couples with unknown etiology and normal couples. METHODS Blood samples from 143 RM couples and 150 control couples were analyzed, firstly to validate previously reported association studies and secondly to explore whether any novel alleles or haplotypes specific to Indian populations can be observed to be associated with RM. HLA typing was carried out by DNA sequencing. RESULTS Results suggest an association of the DQB1*03:03:02 allele with RM (odd ratio = 2.66; p(c) = 0.02; confidence interval = 1.47-4.84). Haplotypes of the DQA1 and DQB1 risk alleles also showed a significant association with RM, albeit not after Bonferroni correction for multiple comparisons. CONCLUSIONS HLA-DQB1 appears to have a strong involvement in the manifestation of RM in this population from South India. The current genetic analysis of RM and control couples not only highlights the genes exhibiting a strong etiological role but also reflects the protective nature of some HLA genes against RM. Nevertheless, most of these alleles/haplotypes were not those that are implicated in RM in other ethnic backgrounds, and hence require further validation in other populations of India, from different ethnic and/or geographic backgrounds.

HLA-G 14 bp deletion/insertion polymorphism in celiac disease

OBJECTIVES

Nonclassical major histocompatibility class I HLA-G antigen is a tolerogenic molecule that inhibits lytic activity of natural killer (NK) cells and cytotoxic T lymphocytes. Because of its immunomodulatory and tolerogenic properties, HLA-G molecules may have a role in celiac disease (CD). We analyzed the HLA-G 14 bp deletion/insertion polymorphism, known to have a functional effect on mRNA stability, in a group of 522 CD patients, stratified for the presence of HLA-DQ2 genotype, and 400 healthy individuals to evaluate the possible effect of the polymorphism on the risk to develop the disease.

METHODS

HLA-G 14 bp deletion/insertion polymorphism (rs1704) was detected by polymerase chain reaction and double-checked by direct sequencing.

RESULTS

The 14 bp inserted (I) allele and the homozygous I/I genotype were significantly more frequent in CD patients than in healthy controls. The presence of I allele was associated with an increased risk of CD (OR 1.35) and the effect of I allele was consistent with a recessive genetic model (P<0.001).

CONCLUSIONS

Our results also indicate that the effect of the HLA-G D/I polymorphism is restricted for HLA-DQ2, and not simply due to the presence of linkage disequilibrium with the major known risk factor; moreover we found that the presence of the I allele confers an increased risk of CD in addition to the risk conferred by HLA-DQ2 alone and that subjects that carry both DQ2 and HLA-G I alleles have an increased risk of CD than subjects that carry DQ2 but not the I allele.

HLA sharing among couples appears unrelated to idiopathic recurrent fetal loss in Saudi Arabia

BACKGROUND

Recurrent fetal loss (RFL) is a prevalent problem affecting approximately 1% of all women of childbearing age. Many factors can lead to RFL; however, recent studies have indicated the important role of the maternal immune system in this process. The human leukocyte antigens (HLA), HLA-linked genes and regulatory factors play an important role in fetal loss and in fetal development. The current retrospective study was preformed to examine the HLA alleles shared between couples with RFL in Saudi Arabia, using a large cohort of women (having three or more RFL). Specific HLA alleles that could influence this condition, or the number of miscarriages experienced, were expected to be highlighted in this way.

METHODS

A total of 253 consecutive patients who visited the RFL clinic at the King AbdulAziz Medical City, National Guard Hospital in Riyadh were included in this study. They included 54 consanguineous couples, 132 non-consanguineous couples and another 67 couples shared only their tribal origin. Clinical examinations as well as laboratory investigations were carried out on each patient. Class I HLA, HLA-A, HLA-B and HLA-C, and Class II HLA, HLA-DR and HLA-DQ, were typed for each patient and their partner.

RESULTS

No relationship was seen between sharing of HLA alleles and the number of RFL experienced by the couples, among neither consanguineous nor non-consanguineous couples.

CONCLUSIONS

Although the results of this study suggest that HLA sharing is not an indicative factor in RFL, definitive conclusions on this topic must be based on large case-control studies.

Study of the structure and impact of human leukocyte antigen (HLA)-G-A, HLA-G-B, and HLA-G-DRB1 haplotypes in families with recurrent miscarriage

A 14-base pair (bp) long insertion (ins)/deletion (del) polymorphism in exon 8 in the 3'-untranslated region of the human leukocyte antigen (HLA)-G gene is suggested to affect transcription of the gene. Carriage of the G14bp ins is associated with low levels of soluble HLA-G and increases the risk of recurrent miscarriage (RM). Due to existence of strong linkage disequilibrium (LD) in the HLA region, the primary susceptibility genes for RM in the HLA-G region have not yet been identified. HLA-A, -B, -DRB1, and -G14bp polymorphisms were investigated in 29 Caucasian families with two or more siblings suffering unexplained RM. Strong positive LD was detected between the G14bp ins and HLA-A*01, -A*11, -A*31, -B*08, and DRB1*03, whereas strong negative LD was found between G14bp ins and HLA-A*02, -A*03, and -A*24. The frequency of haplotypes with HLA-G14bp ins inherited from the mother was significantly increased in probands with RM (p = 0.05). The increased compatibility between probands and their mothers for maternal G14 ins positive haplotypes suggests that maternal-fetal compatibility for chromosomal segments adjacent to HLA-G locus is a risk factor for female offspring to experience RM in their later reproductive life.

Immunologic abnormality of intrahepatic cholestasis of pregnancy

PROBLEM

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy risk because of the possibility of pre-term delivery and sudden intrauterine fetal death. Its pathogenesis is still under discussion.

METHOD OF STUDY

The analysis of the recent findings on the complex immunologic events that occur in ICP were performed.

RESULTS

In ICP, an increase of type 1 cytokine (TNF-alpha, IFN-gamma) associated with a decrease of type 2 cytokine (IL-4). The decreased production of the suppressor cytokine TGF-beta2 may increase the type 1 cytokine. Fas appeared to be increased and FasL appeared to be decreased in syncytiotrophoblasts of ICP. The human leukocyte antigen gene (HLA-G, E) in extravillous trophoblasts of ICP were significantly decreased.

CONCLUSION

Th1/Th2 cytokine balance and HLA play important roles in the tolerance and maintenance of pregnancy. ICP may be resulting from breach of the maternal fetal immune tolerance during pregnancy.

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.

Human leukocyte antigen-G polymorphism in relation to expression, function, and disease

Human leukocyte antigen-G (HLA-G) is a nonclassical class Ib molecule belonging to the major histocompatibility complex. HLA-G appears to play a role in the suppression of immune responses and contribute to long-term immune escape or tolerance. The focus of this review is polymorphism in the HLA-G gene and protein and its possible importance in expression, function, and disease associations.

14-Base pair polymorphism of human leukocyte antigen-G as genetic determinant in heart transplantation and cyclosporine therapy monitoring

The 14-base pair (bp) polymorphism within the HLA-G gene has been investigated in heart transplant patients for the first time. The 14-bp polymorphism is associated with HLA-G mRNA stability and the patterns of alternative isoforms splicing, and therefore may influence the functionality of the HLA-G molecule. In heart transplantation, the highest production of soluble HLA-G was related to the -14/-14-bp genotype in the pre- and post-transplantation periods. Our study findings showed that the 14-bp polymorphism of the HLA-G gene influenced the expression of soluble HLA-G in heart transplantation and accordingly resulted in low rejection rates, being a possible marker of genetic variability associated with heart transplantation. In addition, the 14-bp polymorphism of the HLA-G gene is related to the absorber status of cyclosporine of each individual patient, and is useful for determining the oral dose of cyclosporine to manage patients (to adjust immunosuppressive protocols) so as to minimize the risk of a low or high immunosuppression and the side effects in the early stages of heart transplantation.

Association of the HLA-G 14 bp polymorphism with systemic lupus erythematosus

Human leukocyte antigen-G (HLA-G) is a nonclassical class I major histocompatibility complex molecule which is induced at the course of inflammatory pathologies, and its expression has been suggested as a possible mechanism of tissue protection against autoimmune inflammatory responses, therefore acting as a mechanism of immune surveillance. We investigated the influence of the 14 bp polymorphism of the HLA-G gene on systemic lupus erythematosus (SLE) by analyzing 293 patients with SLE and 460 healthy controls. The patient's group was not in Hardy-Weinberg equilibrium, presenting an excess of heterozygotes (P = 0.014). The heterozygote group exhibited lower systemic lupus erythematosus disease activity indexes than the homozygous deletion group and the homozygous insertion group (mean value = 2.29 against 2.97 and 3.4, respectively, P = 0.035). Photosensitive patients showed a higher frequency of heterozygotes and an equivalent lower frequency of homozygotes for deletion; on the other hand, patients without arthritis presented a higher frequency of heterozygotes than the arthritis group and also a lower frequency of the del/del genotype. Overall, our results support the idea of a role of the HLA-G insertion/deletion polymorphism and therefore a role for the HLA-G molecule, on the pathology of SLE.

Allergic women have reduced sHLA-G plasma levels at delivery

PROBLEM

HLA-G antigen maintains a tolerogenic condition at the foeto-maternal interface, counteracts inflammation in autoimmune diseases and soluble HLA-G (sHLA-G) levels decrease in allergic-asthmatics. Taking into consideration these findings, we analyzed if sHLA-G and interleukin-10 (IL-10) could be influenced by pregnancy and labour in allergic and non-allergic women.

METHOD OF STUDY

sHLA-G isoforms and IL-10 levels were determined in the plasma samples of 43 women (15 non-allergic, 28 allergic) during third trimester, at delivery and 2 years after pregnancy by immunoenzymatic assays.

RESULTS

A significant increase in sHLA-G and IL-10 levels was documented at delivery in both allergic and non-allergic women. Allergic women showed lower sHLA-G concentrations. sHLA-G1 was evidenced as the predominant plasma isoform.

CONCLUSION

The data showed increased sHLA-G and IL-10 concentrations at delivery, regardless of the allergic status. The sHLA-G1 isoform is mainly responsible for the increased sHLA-G levels at delivery.

A study of HLA-G polymorphism and linkage disequilibrium in renal transplant patients and their donors

The role of the Major Histocompatibility Complex (MHC) in transplantation immunology is widely known. Incompatibilities associated with Human Leukocyte Antigens (HLA) between donors and recipients are related to poorer prognosis in allograft acceptance and survival, often resulting in rejection episodes. HLA-A, HLA-B, HLA-DR and HLA-DQ compatibility are widely studied in clinical transplants but few studies investigated the influence of non-classical HLA loci, such as HLA-G, a non-classical class I HLA gene located at 6p21.31 in the MHC region, i.e. 300 kb telomeric to HLA-A. MHC region genes are characterized by extreme polymorphism as well as strong positive linkage disequilibrium (LD) between HLA loci (alleles). LD studies related to MHC region provide investigators with a tool to assess candidate genes with an at-risk HLA haplotype, with implications for allograft transplants, human reproduction and disease susceptibility. Many studies reported striking LD between HLA-G and HLAA alleles and also between HLA-G and HLA Class II alleles, but the biologicalimplications for these findings are not clear yet. DNA sequencing methodology was used to determine HLA-G (exons 2 and 3) polymorphisms from 52 patients who underwent kidney transplantation and their donors. It is the purpose of this study to investigate the influence of HLA-G polymorphism in a set of kidney transplants and the occurrence of rejection episodes. It was observed that pairs with 2 HLA-G matches presented a lower risk of rejection occurrence than those pairs with 0 or 1 match. It was also observed that subjects whose genotype presented one synonymous substitution (S) in one HLA-G allele in the HLA-G0101 group of alleles and another allele with a non-synonymous substitution (N/S) on HLA-G0103, HLA-G010401, HLA-G010403 or HLA-G0105N alleles, apparently had a greater chance of rejection episodes. Additionally, HLA-G, as well as HLA-A, -B e -DR, compatibility may also be important for allograft acceptance (rejection probability lower than 0.09%). Besides, heterozygous S/NS patients had a five times greater chance of rejection than S/S and NS/NS patients. Some haplotypes found in the present study were already described in literature: A01-G01B (010102 or 0106), A03-G0101A, A23-G010401, A26-G01B, A31-G0103, A02-G0101A, A24-G0101A, A33-G0103, A68-G01B. We have also described LD between HLA-G alleles and HLA class II DRB1 allelic groups and found significant LD between DRB104-G01B, DRB113-G010401, DRB114-G010108, DRB115-G0103, DRB103-G0101A and DRB103-G01B.

Human leukocyte antigen class II allele association to disease progression in Iranian patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most frequent type of leukemia in Western countries, but its incidence is low in Asian populations. In the present study we determined the frequency of DRB1 and DQB1 alleles in 87 Iranian CLL patients and 100 healthy controls using a polymerase chain reaction (PCR) technique. An increased frequency of DRB1*07 (p = 0.04), DQB1*06 (p = 0.01) alleles, and DRB1*13/DQB1*03 haplotype (p = 0.01) and decreased frequency of the DQB1*03 (p = 0.01) allele were observed in our patients compared with healthy controls. Comparison between patients with indolent (n = 42) and progressive (n = 38) disease revealed a significant increase in DRB1*04 and DRB5 alleles in progressive patients. Similarly, a higher frequency of DRB5 (p = 0.01) allele was observed in CD38(+) compared with CD38(-) patients. Classification of the patients into immunoglobulin variable region heavy-chain genes mutated and unmutated subtypes did not reveal significant differences for the expression of any of the HLA alleles or haplotypes between these two subtypes. Our findings observed in an Iranian population indicate that CLL could be associated with distinct HLA class II alleles and haplotypes of which the DQB1*06 allele and DRB1*13/DQB1*03 haplotype have not already been reported in CLL patients from other ethnic backgrounds. Some HLA class II alleles may contribute to disease progression in CLL.

The 14 bp deletion polymorphisms in HLA-G gene play an important role in the expression of soluble HLA-G in plasma

Soluble human leukocyte antigen-G (sHLA-G) functions as a multiple immunoregulator. A 14 bp insertion (+14 bp)/deletion (-14 bp) polymorphism in exon 8 of the HLA-G gene has been proposed to be associated with HLA-G mRNA stability and the expression of HLA-G. In the current study, a total of 150 normal Chinese Han population had been genotyped for the +14 bp/-14 bp polymorphism, and the expression of plasma sHLA-G was determined with enzyme-linked immunosorbent assay in these case-matched plasma. Data showed that genotype of 14 bp polymorphism was significantly associated with sHLA-G expression. Plasma sHLA-G level with the +14 bp/+14 bp genotype was dramatically lower than that with +14 bp/-14 bp (P = 0.004) and -14 bp/-14 bp genotypes (P = 0.003), while no dramatic difference was observed between the +14 bp/-14 bp and -14 bp/-14 bp genotypes (P > 0.05). In both males and females, plasma sHLA-G with the +14 bp/+14 bp genotype was also significantly lower when compared with other two respective 14 bp genotypes. Data also showed that sHLA-G expression was unrelated to gender. This study suggests that the 14 bp deletion polymorphism in the HLA-G gene plays an important role in sHLA-G expression and that interpretation of the potential biological functions of sHLA-G should be made with caution, taking the polymorphism into consideration.