Primary role of the HLA class II DRB1*0301 allele in Graves disease

Association Between HLA-DRB1 Alleles and Graves' Disease in Asian Populations: A Meta-Analysis

Graves' disease (GD) is an autoimmune disease that primarily affects the thyroid gland. It is the most common cause of hyperthyroidism. Genetic studies have shown that human leukocyte antigen (HLA) plays an important role in the development of GD. In this article, we performed a meta-analysis determined to evaluate the relationship between HLA-DRB1 alleles and GD. This meta-analysis included 9 studies (3582 cases in the case group and 23070 cases in the control group) and 27 alleles was performed. The combined results showed that, compared with the control group, GD patients have a significant increase in the frequency of DRB1*1403 (OR=2.50, 95% CI=1.78-3.51, pc<0.0001) and have a significant decrease in frequencies of DRB1* 0101 (OR=0.45, 95% CI=0.34-0.59, pc<0.0001) and DRB1*0701 (OR=0.44, 95% CI=0.35-0.55, pc<0.0001). The meta-analysis indicated that, in Asian populations, DRB1*1403 is a risk allele for GD, and DRB1*0101 and DRB1*0701 are protective against the occurrence of GD. We surprisingly discovered that the susceptibility alleles for GD in Asian populations are completely different from Caucasians and the protective alleles for GD in Asians are quite similar to those of Caucasians. The results of our study may provide new opportunities for gene-targeted therapy for GD in Asian populations.

Neoself Antigens Presented on MHC Class II Molecules in Autoimmune Diseases

Major histocompatibility complex (MHC) class II molecules play a crucial role in immunity by presenting peptide antigens to helper T cells. Immune cells are generally tolerant to self-antigens. However, when self-tolerance is broken, immune cells attack normal tissues or cells, leading to the development of autoimmune diseases. Genome-wide association studies have shown that MHC class II is the gene most strongly associated with the risk of most autoimmune diseases. When misfolded self-antigens, called neoself antigens, are associated with MHC class II molecules in the endoplasmic reticulum, they are transported by the MHC class II molecules to the cell surface without being processed into peptides. Moreover, neoself antigens that are complexed with MHC class II molecules of autoimmune disease risk alleles exhibit distinct antigenicities compared to normal self-antigens, making them the primary targets of autoantibodies in various autoimmune diseases. Elucidation of the immunological functions of neoself antigens presented on MHC class II molecules is crucial for understanding the mechanism of autoimmune diseases.

Significance of HLA in Graves' disease and Graves' orbitopathy in Asian and Caucasian populations - a systematic review

Introduction

Graves' disease (GD) and Graves' orbitopathy (GO) development were suspected to be HLA-related in both Asian and Caucasian populations. However, most studies were performed with application of serological methods or low resolution genetic typing, which led to inconsistent results even among the same population. The present review is intended to summarize the state-of-art knowledge on the HLA significance in GD and GO in Asians and Caucasians, as well as to find the most significant alleles for each of the populations.

Methods

PubMed was searched for relevant articles using the following search terms: HLA plus thyroid-associated ophthalmopathy or Graves' disease or Graves' orbitopathy or thyroid eye disease or thyroid-associated orbitopathy.

Results

In Asian population GD was found to be associated mostly with B*46:01, DPB1*05:01, DRB1*08:02/03, DRB1*16:02, DRB1*14:03, DRB1*04:05, DQB1*05:02 and DQB1*03:03, while DRB1*07:01, DRB1*01:01, DRB1*13:02, DRB1*12:02 are potentially protective. HLA-B*38:02, DRB1*16:02, DQA1*01:02, DQB1*05:02 can be considered associated with increased risk of GO in Asians, while HLA-B*54:01 may play protective role. In Caucasians, C*07:01, DQA1*05:01, DRB1*03, DQB1*02:01 are associated with GD risk while DRB1*07:01, DQA1*02:01 may be protective. Significance of HLA in the course of GD and novel aspects of HLA amino acid variants and potential HLA-based treatment modalities were also discussed.

Significance of HLA in the development of Graves' orbitopathy

Graves' disease (GD), similarly to most autoimmune disease, is triggered by environmental factors in genetically predisposed individuals. Particular HLA alleles increase or decrease GD risk. No such correlation was demonstrated for Graves' orbitopathy (GO) in Caucasian population. HLA-A, -B, -C, -DQB1 and -DRB1 genotyping was performed using a high-resolution method in a total number of 2378 persons including 70 patients with GO, 91 patients with non-GO GD and 2217 healthy controls to compare allele frequencies between GO, non-GO and controls. Significant associations between GO and HLA profile were demonstrated, with HLA-A*01:01, -A*32:01, -B*37:01, -B*39:01, -B*42:01, -C*08:02, C*03:02, DRB1*03:01, DRB1*14:01 and DQB1*02:01 being genetic markers of increased risk of GO, and HLA-C*04:01, -C*03:04, -C*07:02 and -DRB1*15:02 being protective alleles. Moreover, correlations between HLA alleles and increased or decreased risk of non-GO GD, but with no impact on risk of GO development, were revealed. Identification of these groups of GO-related and GO-protective alleles, as well as the alleles strongly related to non-GO GD, constitutes an important step in a development of personalized medicine, with individual risk assessment and patient-tailored treatment.

Actual Associations between HLA Haplotype and Graves' Disease Development

The association between HLA and the risk of Graves’ disease (GD) has been analyzed for many years. However, the results were often inconsistent and mostly regarded Asian populations. The purpose of our study was to perform HLA genotyping using a next-generation sequencing (NGS) method in Caucasians, to find out which alleles are eventually correlated with GD morbidity as well as which of them can be considered protective. HLA-A, -B, -C, -DQB1, -DRB1 were genotyped using a next-generation sequencing method in 2376 persons, including 159 GD patients and 2217 healthy controls. We have demonstrated a significant association between the risk of GD and the following alleles: HLA-B*08:01, -B*39:06, -B*37:01, -C*07:01, -C*14:02, -C*03:02, -C*17:01, -DRB1*03:01, -DRB1*11:01, -DRB1*13:03, -DRB1*01:03, -DRB1*14:01, -DQB1*03:01, DQB1*02:01. The alleles HLA-B*39:06, -B*37:01, -C*14:02, -C*03:02, -C*17:01, -DRB1*14:01 are novel GD-associated, previously not-reported independent ones with no linkage disequilibrium with other high-risk alleles. On the other hand, the frequencies of HLA-B*07:02, -C*07:02, -C*03:04, DRB1*07:01, -DQB1*02:02, -DQB1*03:03 were significantly lower in GD compared to controls. This study demonstrated the actual relationships between HLA and GD based on the NGS method and provided a novel set of alleles as a reliable tool for an individual personalized risk assessment.

Abrogation of self-tolerance by misfolded self-antigens complexed with MHC class II molecules

Specific MHC class II alleles are strongly associated with susceptibility to various autoimmune diseases. Although the primary function of MHC class II molecules is to present peptides to helper T cells, MHC class II molecules also function like a chaperone to transport misfolded intracellular proteins to the cell surface. In this study, we found that autoantibodies in patients with Graves' disease preferentially recognize thyroid-stimulating hormone receptor (TSHR) complexed with MHC class II molecules of Graves' disease risk alleles, suggesting that the aberrant TSHR transported by MHC class II molecules is the target of autoantibodies produced in Graves' disease. Mice injected with cells expressing mouse TSHR complexed with MHC class II molecules, but not TSHR alone, produced anti-TSHR autoantibodies. These findings suggested that aberrant self-antigens transported by MHC class II molecules exhibit antigenic properties that differ from normal self-antigens and abrogate self-tolerance, providing a novel mechanism for autoimmunity.

HLA Class I Upregulation and Antiviral Immune Responses in Graves Disease

CONTEXT

The origin of Graves disease (GD) remains elusive. However, evidence of an association between GD and viral infections is emerging. Human leukocyte antigen (HLA) class I presents viral antigens to circulating immune cells and plays a crucial role in the defense against viral infections.

OBJECTIVE

This work aimed to investigate HLA class I expression, enterovirus presence, and the viral immune response proteins signal transducer and activation of transcription 1 (STAT1) and protein kinase R (PKR) in thyroid tissue from GD patients.

METHODS

We collected thyroid tissue from core needle biopsies or surgical specimens from 48 GD patients and 24 controls. Standard immunohistochemistry was used to detect HLA class I and enteroviral capsid protein 1 (VP1) on formalin-fixed and paraffin-embedded tissue. STAT1 and PKR were examined by combined immunofluorescence staining. HLA class I expression score was the main outcome measure.

RESULTS

The HLA class I expression score, which takes both proportion and intensity of immunostaining into account, was significantly higher in GD patients (3.1 ± 3.3) than in controls (0.5 ± 0.9) (P < .001). Significantly more VP1 positive thyroid cells were found GD samples (50.1 ± 30.5%) than in controls (14.9 ± 10.5%) (P < .001). STAT1 and HLA class I were found within the same thyroid cells and PKR and VP1 were also colocalized within thyroid cells.

CONCLUSION

HLA class I is upregulated in GD and enterovirus protein is prevalent in thyroid tissue. The colocalization of HLA class I with STAT1 and VP1 with PKR indicates an antiviral tissue response. These findings support the concept of a link between viral infections and GD.

Critical amino acid variants in HLA-DRB1 allotypes in the development of Graves' disease and Hashimoto's thyroiditis in the Japanese population

The effects of amino acid variants encoded by human leukocyte antigen (HLA) class II on the development of Graves' disease (GD) and Hashimoto's thyroiditis (HT) have not been fully elucidated. We investigated the HLA-DRB1 genes of 243 GD patients and 82 HT patients in the Japanese population and compared the frequencies of HLA-DRB1 alleles and HLA-DRB1 amino acid variants between these patients and the Japanese populations previously reported by another institution. The frequencies of HLA-DRB1*04:05 and -DRB1*14:03 alleles were significantly higher and those of HLA-DRB1*01:01 and -DRB1*15:02 alleles were lower in GD patients than in controls. The frequencies of HLA-DRB1*08:03 and -DRB1*09:01 alleles were significantly higher and that of the HLA-DRB1*13:02 allele was lower in HT patients than in controls. A blind association analysis with all amino acid positions identified DRß9 and DRß31 for GD and DRß9, DRß13, and DRß21 for HT. The frequency of Glu-9 was significantly higher and that of Cys-9 was lower in GD patients than in controls. The frequencies of Lys-9 and Phe-13 were significantly higher in HT patients than in controls. DRß9 and DRß13 could be critical amino acid positions in the development of GD and HT.

Dysregulation of non-coding RNAs in autoimmune thyroid disease

Autoimmune thyroid disease (AITD) is a complex disorder with both genetic and environmental risk factors. A number of genetic factors such as HLA and CTLA-4 loci have been associated with risk of this disorder. In addition to these factors, recent studies have shown contribution of non-coding RNAs in the pathogenesis of this condition. Several microRNAs (miRNAs) and a number of long noncoding RNAs (lncRNAs) such as IFNG-AS1, Heg, NR_038461, NR_038462, T204821 and NR_104125 have been dysregulated in peripheral blood of patients with AITD. These transcripts are mostly enriched in pathways that modulate humoral and cellular immune responses such as those associated with antigen presentation and differentiation of Th1, Th2 and Th17 cells. Functional studies verified the role of a number of lncRNAs and miRNAs in regulation of critical immune-related pathways in AITD. Thus, they participate in the pathophysiology of AITD. In the current review, we summarize the results of studies that assessed participation of non-coding RNAs in the pathophysiology of AITD.

HLA Polymorphisms and Food Allergy Predisposition

Food allergy (FA) is a growing health problem that affects ∼8% of the children worldwide. Although the prevalence of FA is increasing, the underlying genetic mechanisms responsible for the onset of this immune disorder are not yet clarified. Genetic factors seem to play a leading role in the development of FA, though interaction with environmental factors cannot be excluded. The broader network of genetic loci mediating the risk of this complex disorder remains to be identified. The human leucocyte antigen (HLA) has been associated with various immune disorders, including FA. This review aims to unravel the potential associations between HLA gene functions and the manifestation and outcome of FA disorders. Exploring new aspects of FA development with the perspective to improve our understanding of the multifaceted etiology and the complex biological mechanisms involved in FA is essential.

Association of HLA-C*03:02 with methimazole-induced liver injury in Graves' disease patients

Methimazole (MMI) has been used for the treatment of Graves' Disease (GD) for more than half a century. The MMI treatment has been reported to be associated with hepatotoxicity. Previous studies have demonstrated that human leukocyte antigen (HLA) genetic polymorphisms were associated with many drugs-induced liver injuries. To investigate HLA genetic susceptibility to MMI-induced liver injury (MMI-DILI), we characterized both HLA class I and class Ⅱ in a well-characterized phenotypic cohort with 40 MMI-DILI cases and 118 MMI-tolerant controls. Among the 40 MMI-DILI cases, 57.5% were women and 50% were cholestatic liver damage with occurring time from days to months after MMI dosing. The frequency of HLA-C*03:02 was 6.7% (5/75) in the MMI-DILI case patients and 6.4% (4/62) in MMI-induced cholestatic/mixed liver damage, which were significantly different from the percentage of 0.4% (1/231) in the MMI-tolerant patients (odds ratio (OR) = 15.4, 95% confidence interval (CI) = 1.77-133.9, adjusted P = 0.0292; OR=14.9, 95% CI=2.38-182.9, adjusted P = 0.0323; respectively). HLA-A*02:01 was also found to be associated with MMI-induced cholestatic/mixed liver injury (OR = 3.13, 95%CI=1.45-6.91, adjusted P = 0.0464). The present study demonstrated that individuals carrying HLA-C*03:02 allele are at increased risk of developing MMI-induced DILI. These results may assist doctors to prevent the occurrence of hepatotoxicity in GD patients receiving MMI.

Genetic Mechanisms Highlight Shared Pathways for the Pathogenesis of Polygenic Type 1 Diabetes and Monogenic Autoimmune Diabetes

PURPOSE OF REVIEW

To highlight pathways important for the development of autoimmune diabetes by investigating shared mechanisms of disease in polygenic and monogenic diabetes.

RECENT FINDINGS

Genome-wide association studies have identified 57 genetic risk loci for type 1 diabetes. Progress has been made in unravelling the mechanistic effects of some of these variants, providing key insights into the pathogenesis of type 1 diabetes. Seven monogenic disorders have also been described where diabetes features as part of an autoimmune syndrome. Studying these genes in relation to polygenic risk loci provides a unique opportunity to dissect pathways important for the development of immune-mediated diabetes. Monogenic autoimmune diabetes can result from the dysregulation of multiple pathways suggesting that small effects on many immune processes are required to drive the autoimmune attack on pancreatic beta cells in polygenic type 1 diabetes. A breakdown in central and peripheral immune tolerance is a common theme in the genetic mechanisms of both monogenic and polygenic disease which highlights the importance of these checkpoints in the development and treatment of islet autoimmunity.

Fine mapping MHC associations in Graves' disease and its clinical subtypes in Han Chinese

Background

The classical human leucocyte antigen (HLA) genes were the most important genetic determinant for Graves’ disease (GD). The aim of the study was to fine map causal variants of the HLA genes.

Methods

We applied imputation with a Pan-Asian HLA reference panel to thoroughly investigate themajor histocompatibility complex (MHC) associations with GD down to the amino acid level of classical HLA genes in 1468 patients with GD and 1490 controls of Han Chinese.

Results

The strongest finding across the HLA genes was the association with HLA-DPβ1 position 205 (P_omnibus=2.48×10⁻³³). HLA-DPA1*02:02 was the strongest association among the classical HLA alleles, which was in perfect linkage disequilibrium with HLA-DPα1 residue Met11 (OR=1.90, P_binary=1.76×10⁻³¹). Applying stepwise conditional analysis, we identified amino acid position 205 in HLA-DPβ1, position 66 and 99 in HLA-B and position 28 in HLA-DRβ1 explain majority of the MHC association to GD risk. We further evaluated risk of two clinical subtypes of GD, namely persistent thyroid stimulating hormone receptor antibody -positive (pTRAb+) group and ‘non-persistent TRAb positive’ (pTRAb−) group after antithyroid drug therapy. We found that HLA-B residues Lys66-Arg69-Val76 could drive pTRAb− GD risk alone, while HLA-DPβ1 position 205, HLA-B position 69 and 199 and HLA-DRβ1 position 28 drive pTRAb+ GD risk. The risk heterogeneity between pTRAb+ and pTRAb− GD might be driven by HLA-DPα1 Met11.

Conclusions

Four amino acid positions could account for the associations of MHC with GD in Han Chinese. These distinct HLA association patterns indicated the two subtypes have distinct molecular mechanisms of pathogenesis.

Frank Stinchfield Award: Identification of the At-risk Genotype for Development of Pseudotumors Around Metal-on-metal THAs

BACKGROUND

Once touted as the future of hip arthroplasty, metal-on-metal (MoM) bearing surfaces have fallen sharply from favor with the emergence of a strong body of evidence demonstrating unacceptably high premature implant failure rates. The previously unpredictable development of adverse local tissue reactions (ALTRs) has been a substantive contributor to this. Although the underlying pathophysiology of these so-called "pseudotumors" is now well understood, the fundamental predisposing patient risk factors have remained elusive.

QUESTIONS/PURPOSES

The aim of this research, as a clinical-genotype correlation analysis, was to identify specific alleles (genes) associated with the development of ALTRs in patients with in situ MoM THAs.

METHODS

A case-control study of patients who received a large-head, primary MoM THA between 2005 and 2008 was performed with a minimum followup of 5 years. Twenty-six patients who had undergone revision of a primary MoM THA secondary to symptomatic ALTRs were recruited. The mean timeframe from primary MoM THA to symptomatic revision was 5.5 years (range, 1-10 years). Twenty-eight control subjects were randomly selected asymptomatic patients with no evidence of ALTRs on protocol-specific screening. Baseline demographics and high-resolution genotype (human leukocyte antigen [HLA] Class II) were collected for all patients. Cohorts were similar with respect to age at the time of primary MoM THA (mean, 54.8 versus 54.9 years, p = 0.95) and serum cobalt (mean, 5.5 versus 8.5 μg/L, p = 0.09) and chromium concentrations (mean, 2.9 versus 4.2 μg/L, p = 0.27). The association between genotype and revision surgery secondary to ALTRs was determined with gender as a covariate.

RESULTS

The prevalence of the risk genotype was 30% (16 of 54) among the entire cohort. Adjusting for sex, the odds of revision were 6.1 times greater among patients with the risk genotype present than among patients without (95% confidence interval [CI], 1.5-25.4; p = 0.01). Among females, the specificity of the risk genotype was 1.0 (95% CIexact, 0.5-1.0; pexact = 0.03), and for males, it was 0.8 (95% CIexact, 0.6-0.9; pexact < 0.01).

CONCLUSIONS

The findings of this study suggest that, among patients with a primary MoM THA, allelic variation within the HLA Class II loci may be a strong, independent risk factor associated with the need for subsequent revision surgery secondary to pseudotumor formation.

CLINICAL RELEVANCE

Given the hypothesis-generating nature of this novel undertaking, confirmatory prospective clinical studies are required to further elucidate this correlation and to explore the clinical utility of targeted genetic screening in this specific population. This research may, however, represent a key missing piece in the puzzle that is metal ion-induced pseudotumor formation.

Predictive Value of Gene Polymorphisms on Recurrence after the Withdrawal of Antithyroid Drugs in Patients with Graves' Disease

Graves' disease (GD) is one of the most common endocrine diseases. Antithyroid drugs (ATDs) treatment is frequently used as the first-choice therapy for GD patients in most countries due to the superiority in safety and tolerance. However, GD patients treated with ATD have a relatively high recurrence rate after drug withdrawal, which is a main limitation for ATD treatment. It is of great importance to identify some predictors of the higher recurrence risk for GD patients, which may facilitate an appropriate therapeutic approach for a given patient at the time of GD diagnosis. The genetic factor was widely believed to be an important pathogenesis for GD. Increasing studies were conducted to investigate the relationship between gene polymorphisms and the recurrence risk in GD patients. In this article, we updated the current literatures to highlight the predictive value of gene polymorphisms on recurrence risk in GD patients after ATD withdrawal. Some gene polymorphisms, such as CTLA4 rs231775, human leukocyte antigen polymorphisms (DRB1*03, DQA1*05, and DQB1*02) might be associated with the high recurrence risk in GD patients. Further prospective studies on patients of different ethnicities, especially studies with large sample sizes, and long-term follow-up, should be conducted to confirm the predictive roles of gene polymorphism.

Dissecting the Genetic Susceptibility to Graves' Disease in a Cohort of Patients of Italian Origin

Graves' disease (GD) is an autoimmune oligogenic disorder with a strong hereditary component. Several GD susceptibility genes have been identified and confirmed during the last two decades. However, there are very few studies that evaluated susceptibility genes for GD in specific geographic subsets. Previously, we mapped a new locus on chromosome 3q that was unique to GD families of Italian origin. In the present study, we used association analysis of single-nucleotide polymorphism (SNPs) at the 3q locus in a cohort of GD patients of Italian origin in order to prioritize the best candidates among the known genes in this locus to choose the one(s) best supported by the association. DNA samples were genotyped using the Illumina GoldenGate genotyping assay analyzing 690 SNP in the linked 3q locus covering all 124 linkage disequilibrium blocks in this locus. Candidate non-HLA (human-leukocyte-antigen) genes previously reported to be associated with GD and/or other autoimmune disorders were analyzed separately. Three SNPs in the 3q locus showed a nominal association (p < 0.05): rs13097181, rs763313, and rs6792646. Albeit these could not be further validated by multiple comparison correction, we were prioritizing candidate genes at a locus already known to harbor a GD-related gene, not hypothesis testing. Moreover, we found significant associations with the thyroid-stimulating hormone receptor (TSHR) gene, the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene, and the thyroglobulin (TG) gene. In conclusion, we identified three SNPs on chromosome 3q that may map a new GD susceptibility gene in this region which is unique to the Italian population. Furthermore, we confirmed that the TSHR, the CTLA-4, and the TG genes are associated with GD in Italians. Our findings highlight the influence of ethnicity and geographic variations on the genetic susceptibility to GD.

The clinical value of human leukocyte antigen HLA-DRB1 subtypes associated to Graves' disease in Romanian population

The aim of this study was to identify the primary susceptibility HLA-DRB1 alleles associated with GD in Romanian population and to seek whether specific HLA-DRB1 haplotypes are associated with differences in the clinical presentation of GD at diagnosis. Molecular typing of HLA-DRB1 alleles was performed in 77 Romanian Caucasian GD patients and 445 racially matched controls. In GD patients, age, presence of eye disease, goiter grade, autoantibody status and titer, TSH, FT4, FT3, TT3 levels were recorded at diagnosis. The allelic frequencies of HLA-DRB1*03 (41.55% vs. 17.75%, p < 0.0001, χ(2) = 20.81) and DRB1*11 (42.85% vs. 30.56%, p = 0.045, χ(2) = 3.98)were higher, whereas those of HLA-DRB1*01(3.89% vs. 16.40%, p = 0.007, χ(2) = 7.281) and DRB1*15 (10.38% vs. 21.34%, p = 0.038, χ(2) = 4.309)were lower in GD patients than in controls. FT4/TT3 ratio (p = 0.015) and anti-thyroglobulin antibodies (p = 0.024) were higher in *03/11 patients compared to *X/X, *11/Z, *03/Y patients (where X is any other allele than *03 and *11, Y is any other allele than *11, Z is any other allele than *03). In conclusion, HLA-DRB1*03 and DRB1*11 may be the primary susceptibility HLA-DRB1 alleles associated with GD in Romanian population, whereas HLA-DRB1*01 and DRB1*15 seem to be protective. At diagnosis, HLA-DRB1*03/11 GD patients had higher FT4/TT3 ratio and anti-thyroglobulin antibody levels.

Current concepts in the molecular pathogenesis of thyroid-associated ophthalmopathy

Graves' disease (GD) is a common autoimmune condition. At its core, stimulatory autoantibodies are directed at the thyroid-stimulating hormone receptor (TSHR), resulting in dysregulated thyroid gland activity and growth. Closely associated with GD is the ocular condition known as thyroid-associated ophthalmopathy (TAO). The pathogenesis of TAO remains enigmatic as do the connections between the thyroid and orbit. This review highlights the putative molecular mechanisms involved in TAO and suggests how these insights provide future directions for identifying therapeutic targets. Genetic, epigenetic, and environmental factors have been suggested as contributory to the development of GD and TAO. Thyroid-stimulating hormone receptor and insulin-like growth factor receptor (IGF-1R) are expressed at higher levels in the orbital connective tissue from individuals with TAO than in healthy tissues. Together, they form a functional complex and appear to promote signaling relevant to GD and TAO. Orbital fibroblasts display an array of cell surface receptors and generate a host of inflammatory molecules that may participate in T and B cell infiltration. Recently, a population of orbital fibroblasts has been putatively traced to bone marrow-derived progenitor cells, known as fibrocytes, as they express CD45, CD34, CXCR4, collagen I, functional TSHR, and thyroglobulin (Tg). Fibrocytes become more numerous in GD and we believe traffic to the orbit in TAO. Numerous attempts at developing complete animal models of GD have been largely unsuccessful, because they lack fidelity with the ocular manifestations seen in TAO. Better understanding of the pathogenesis of TAO and development of improved animal models should greatly accelerate the identification of medical therapy for this vexing medical problem.

The unusual association of Graves' disease, chronic spontaneous urticaria, and premature ovarian failure: report of a case and HLA haplotype characterization

Chronic spontaneous urticaria (CSU), defined as the occurrence of spontaneous wheals for more than six weeks, has been associated with autoimmune diseases. Herein, we report the unusual association of CSU, Graves' disease, and premature ovarian failure. Human leukocyte antigen (HLA) studies were performed. A 36-year-old woman presented symptoms and signs of hyperthyroidism for three months. In the same period, the patient complained of widespread urticarial wheals, intensely itchy, and poorly responsive to therapy with antihistaminic agents. Hyperthyroidism was confirmed biochemically, and treatment with methimazole was started. As hyperthyroidism improved, a marked improvement in her urticaria was also observed. However, the patient continued to complain of amenorrhea. Endocrine evaluation, at the age 38, was consistent with premature ovarian failure. This is the first report of coexistence of GD, CSU, and POF. The genetic background of such unusual association is a specific combination of HLA.

Association between age at diagnosis of Graves' disease and variants in genes involved in immune response

Background

Graves' disease (GD) is a complex disease in which genetic predisposition is modified by environmental factors. The aim of the study was to examine the association between genetic variants in genes encoding proteins involved in immune response and the age at diagnosis of GD.

Methods

735 GD patients and 1216 healthy controls from Poland were included into the study. Eight genetic variants in the HLA-DRB1, TNF, CTLA4, CD40, NFKb, PTPN22, IL4 and IL10 genes were genotyped. Patients were stratified by the age at diagnosis of GD and the association with genotype was analysed.

Results

Polymorphism in the HLA-DRB1, TNF and CTLA4 genes were associated with GD. The carriers of the HLA DRB1*03 allele were more frequent in patients with age at GD diagnosis ≤30 years than in patients with older age at GD diagnosis.

Conclusions

HLADRB1*03 allele is associated with young age at diagnosis of Graves' disease in polish population.

Genetic and epigenetic mechanisms in thyroid autoimmunity

Autoimmune thyroid diseases (AITD), including Graves' disease and Hashimoto's thyroiditis, are among the commonest autoimmune disorders, affecting approximately 5 % of the population. Epidemiological data support strong genetic influences on the development of AITD. Since the identification of HLA-DR3 as a major AITD susceptibility gene, there have been significant advances made in our understanding of the genetic mechanisms leading to AITD. We have shown that an amino acid substitution of alanine or glutamine with arginine at position 74 in the HLA-DR peptide binding pocket is a critical factor in the development of AITD, and we are continuing to dissect these mechanisms at the molecular level. In addition to the MHC class II genes, there are now several other confirmed gene loci associated with AITD, including immune-regulatory (CD40, CTLA-4, PTPN22, FOXP3, and CD25) and thyroid-specific genes (thyroglobulin and TSHR). Mechanistically, it is postulated that susceptibility genes interact with certain environmental triggers to induce AITD through epigenetic effects. In this review, we summarize some of the recent advances made in our laboratory dissecting the genetic-epigenetic interactions underlying AITD. As shown in our recent studies, epigenetic modifications offer an attractive mechanistic possibility that can provide further insight into the etiology of AITD.

Association between HLA-B*46 allele and Graves disease in Asian populations: a meta-analysis

Graves' disease (GD) is a leading cause of hyperthyroidism, which affects 1.0-1.6% of the general population. Previous studies reported a higher GD prevalence in Asian populations compared to Caucasian populations. The etiology of GD involves complex interactions between predisposing genes and environmental triggers. Genetic studies have shown that the human leukocyte antigen (HLA) is an important candidate genetic region associated with GD in Asian populations. However, the results were inconsistent and inconclusive. Here, we performed a meta-analysis to evaluate the role of the HLA-B*46 allele in GD in Asian populations. A total of 14 case-controlled studies on the association of the HLA-B*46 allele in 1743 GD patients and 5689 controls were included. Our results showed a trend toward an increased risk of GD in HLA-B*46-positive subjects compared to those HLA-B*46-negative (OR = 2.48; 95% CI = 1.96-3.13, P < 0.01). However, there were some limitations to the current meta-analysis, such as heterogeneity (P(heterogeneity )< 0.01 and I(2 )= 68.0%) or the different typing methods (serological and genotyping methods). The meta-analysis indicated that the HLA-B*46 allele is a risk factor for GD in Asian populations. Future studies on the role of the HLA-B*46 allele in GD should consider complications such as periodic paralysis, ophthalmopathy and recurrence.

Genetic variations in interleukin-12 related genes in immune-mediated diseases

The interleukin-12 (IL-12) family comprises a group of heterodimeric cytokines and their respective receptors that play key roles in immune responses. A growing number of autoimmune diseases has been found to be associated with genetic variation in these genes. Based on their respective associations with the IL-12 genes, autoimmune diseases appear to cluster in two groups that either show strong associations with the Th1/Th17 pathway (as indicated by genetic association with IL12B and IL23R) or the Th1/IL-35 pathway as the consequence of their association with polymorphisms in the IL12A gene region. The genetic associations are described in relation to what is known of the functionality of these genes in the various diseases. Comparing association data for gene families in different diseases may lead to better insight in the function of the genes in the onset and course of the disease.

Genetics of autoimmune thyroid disease in the Lebanese population

This study aims to investigate the association of human leukocyte antigen (HLA) class II genes and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) with autoimmune thyroid diseases in the Lebanese population. A total of 128 patients with autoimmune thyroid disease (55 with Graves' disease (GD) and 73 with Hashimoto's thyroiditis (HT)) were typed for HLA DQA1 (0301 and 0501) and DQB1 (0201, 0302, and 0303) and for 49A/G CTLA-4 using PCR-based sequence-specific priming methods. A total of 186 matched controls were typed for the same alleles and compared to the diseased population. Results showed no significant differences in HLA DQB1*0201 or DQB1*0301 allelic frequencies or CTLA-4 polymorphisms between patients and controls. For GD, there was a weak association with HLA DQB1*0302 [34.6% (19 of 55) vs. 21.5% (40 of 186), P = 0.048, odds ratio (OR) = 1.926, confidence interval (CI) = 0.999-3.715] and HLA DQB1*0302-DQA1*0501 haplotype [56.36% (31 of 55) vs. 40.8% (76 of 186), P = 0.042, OR = 1.870, CI = 1.018-3.433]. For HT, the frequencies of DQB1*0302-DQA1*0501 haplotype [28.8% (21of 73) vs. 14.5% (27 of 186), P = 0.008, OR = 2.378, CI = 1.241-4.558] and DQB1*0302-DQA1*0301 haplotype [60.2% (44 of 73) vs. 38.7% (72 of 186), P = 0.002, OR = 2.402, CI = 1.381-4.180] were significantly higher in patients. On the other hand, weak association was found between HT and DQA1*0301 allele [32.9% (24 of 73) vs. 20.9% (39 of 186), P = 0.044, OR = 1.846, CI = 1.011-3.373]. Findings show that DQB1*0302-DQA1*0501 and DQB1*0302-DQA1*0301 haplotypes may play a role in the pathogenesis of HT in the Lebanese population. For the 49A/G CTLA-4 polymorphism, no significant difference was found between patients and controls.

Selective IgA deficiency in autoimmune diseases

Selective immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in Caucasians. It has previously been suggested to be associated with a variety of concomitant autoimmune diseases. In this review, we present data on the prevalence of IgAD in patients with Graves disease (GD), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), celiac disease (CD), myasthenia gravis (MG) and rheumatoid arthritis (RA) on the basis of both our own recent large-scale screening results and literature data. Genetic factors are important for the development of both IgAD and various autoimmune disorders, including GD, SLE, T1D, CD, MG and RA, and a strong association with the major histocompatibility complex (MHC) region has been reported. In addition, non-MHC genes, such as interferon-induced helicase 1 (IFIH1) and c-type lectin domain family 16, member A (CLEC16A), are also associated with the development of IgAD and some of the above diseases. This indicates a possible common genetic background. In this review, we present suggestive evidence for a shared genetic predisposition between these disorders.

Relationship between HLA-DRB1 polymorphism and susceptibility or resistance to multiple sclerosis in Caucasians: a meta-analysis of non-family-based studies

OBJECTIVE

To identify the contribution of HLA-DRB1 alleles to susceptibility or resistance to multiple sclerosis (MS) in Caucasians through a meta-analysis of non-family-based studies.

METHODS

A systematic review of case-control studies in Caucasians was performed. Studies examining allele or phenotype frequencies were analyzed separately. Odds ratio (OR) and 95% confidence intervals (CIs) were used. We also used the relatively predispositional effect (RPE) method to analyze several allele frequency studies to avoid skewed results due to some strongly associated alleles.

RESULTS

A total of 5464 cases and 7809 controls from 14 allele frequency studies and a total of 5401 cases and 7538 controls from 23 phenotype frequency studies were analyzed. DRB1*15 was definitely the strongest risk factor for MS (allele group, Pc<0.00013, OR 2.59, 95%CI 2.34-2.87; phenotype group, Pc<0.00013, OR 3.35, 95%CI 2.95-3.80). DRB1*03 frequencies were significantly increased among MS cases in the phenotype group (Pc= 0.0013, OR 1.21, 95%CI 1.09-1.33) but not in the allele group. DRB1*14 and DRB1*07 showed protective effects against MS in both groups (DRB1*14, allele group, Pc<0.00013, OR 0.53, 95%CI 0.42-0.66; phenotype group, Pc<0.00013, OR 0.57, 95%CI 0.45-0.71; DRB1*07, allele group, Pc<0.0026, OR 0.75, 95%CI 0.64-0.87; phenotype group, Pc<0.00013, OR 0.67, 95%CI 0.61-0.73). By RPE method, DRB1*14, and DRB1*07 showed protective effects after excluding DRB1*15 from the analysis. DRB1*03 was significantly higher in MS cases than controls after removing both DRB1*15 and DRB1*14.

CONCLUSIONS

In Caucasians, we highlighted the definite protective role of HLA-DRB1*14 and DRB1*07 for MS. DRB1*03 is probably the only risk factor for MS besides DRB1*15 and a common genetic foundation for autoimmune disease. Targeting to these alleles may have potential values in prevention or therapy for MS in the specific population.

Pearls in autoimmunity

This manuscript does a review of the more frequent issues published at Autoimmunity Reviews, Journal of Autoimmunity and Autoimmunity in the period of January–December 2009. The following topics were commented: (1) multiple sclerosis (MS) and its relationships with Epstein Barr infection, with vitamin D polymorphism and the new modalities of MS treatment. (2) Type 1 diabetes and genetic discovers, studies with GAD 65 and IA-2 autoantigen and the association T1D and autoimmune organ-specific diseases. (3) Autoimmune thyroid disorders and its association with susceptibility genes and polymorphisms. (4) Multiplex autoantibody profiling approaches in MS and rheumatoid arthritis. (5) Th17 cytokine in primary biliary cirrhosis, experimental autoimmune encephalomyelitis and celiac disease. (6) Vitamin D and experimental autoimmune prostatitis and pulmonary alveolar proteinosis.

Analysis of immune regulatory genes' copy number variants in Graves' disease

BACKGROUND

Copy number variants (CNVs) have recently been reported to be associated with several autoimmune conditions. Moreover, loci involved in immunity are enriched in CNVs. Therefore, we hypothesized that CNVs in immune genes associated with Graves' disease (GD) may contribute to the etiology of disease.

METHODS

One hundred ninety-one North American Caucasian GD patients and 192 Caucasian controls were analyzed for CNVs in three major immune regulatory genes: CD40, PTPN22, and CTLA-4. Copy number was determined using quantitative-PCR (Q-PCR) assays specifically designed for determining copy numbers in genomic DNA. Additionally, a well-characterized CNV in the amylase gene was typed in a separate dataset of DNA samples that were derived from cell lines or blood.

RESULTS

No CNVs could be confirmed in the CD40 and CTLA-4 genes, even though a CD40 CNV is cataloged in the Database of Genomic Variants. Only the PTPN22 CNV was confirmed in our cohort, but it was rare and appeared in only two individuals. A key finding was that the source of DNA has a significant effect on CNV typing. There was a statistically significant increase in amylase locus deletions in cell line-derived DNA compared to blood-derived DNA samples.

CONCLUSIONS

We conclude that CNV analysis should be performed only using blood-derived DNA Samples. Additionally, the CTLA-4, CD40, and PTPN22 loci do not harbor CNVs that play a role in the etiology of GD.

Genetic susceptibility to autoimmune thyroid disease: past, present, and future

BACKGROUND

Autoimmune thyroid diseases (AITD), including Graves' disease and Hashimoto's thyroiditis, arise due to complex interactions between environmental and genetic factors. There are sound data coming from epidemiological, family, and twin studies demonstrating a strong genetic influence on the development of AITD. In this review we summarize the new findings on the genetic susceptibility to AITD focusing on emerging mechanisms of susceptibility.

SUMMARY

Candidate gene analysis, whole-genome linkage screening, genome-wide association studies, and whole-genome sequencing are the major technologies that have advanced this field, leading to the identification of at least seven genes whose variants have been associated with AITD. One of the major ones is the HLA-DR gene locus. Recently, it was shown that substitution of the neutral amino acids Ala or Gln with arginine at position beta 74 in the HLA-DR peptide-binding pocket is key to the etiology of both Graves' disease and Hashimoto's thyroiditis. Several other genes have also been shown to confer susceptibility to AITD. These can be classified into two groups: (i) immune regulatory genes (cytotoxic T lymphocyte-associated protein 4, CD40, protein tyrosine phosphatase-22, and CD25) and (ii) thyroid-specific genes (thyroglobulin and thyrotropin receptor genes). The influence of individual genes on the development of AITD when assessed in a population appears to be weaker than would be expected from the data showing strong genetic susceptibility to AITD. Two possible mechanisms explaining this discrepancy are gene-gene interactions and subset effects.

CONCLUSIONS

Significant progress has been made in our understanding of the immunogenetic mechanisms leading to thyroid autoimmunity. For the first time we are beginning to unravel these mechanisms at the molecular level. It is hoped that these new data will be translated into novel therapies and prevention strategies in AITD, such as costimulatory blockade.

The etiology of autoimmune thyroid disease: a story of genes and environment

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT) are prevalent autoimmune diseases, affecting up to 5% of the general population. Autoimmune thyroid diseases arise due to complex interactions between environmental and genetic factors. Significant progress has been made in our understanding of the genetic and environmental triggers contributing to AITD. However, the interactions between genes and environment are yet to be defined. Among the major AITD susceptibility genes that have been identified and characterized is the HLA-DR gene locus, as well as non-MHC genes including the CTLA-4, CD40, PTPN22, thyroglobulin, and TSH receptor genes. The major environmental triggers of AITD include iodine, medications, infection, smoking, and possibly stress. Recent data on the genetic predisposition to AITD lead to novel putative mechanisms by which the genetic-environmental interactions may lead to the development of thyroid autoimmunity.

Joint genetic susceptibility to type 1 diabetes and autoimmune thyroiditis: from epidemiology to mechanisms

Type 1 diabetes (T1D) and autoimmune thyroid diseases (AITD) frequently occur together within families and in the same individual. The co-occurrence of T1D and AITD in the same patient is one of the variants of the autoimmune polyglandular syndrome type 3 [APS3 variant (APS3v)]. Epidemiological data point to a strong genetic influence on the shared susceptibility to T1D and AITD. Recently, significant progress has been made in our understanding of the genetic association between T1D and AITD. At least three genes have been confirmed as major joint susceptibility genes for T1D and AITD: human leukocyte antigen class II, cytotoxic T-lymphocyte antigen 4 (CTLA-4), and protein tyrosine phosphatase non-receptor type 22. Moreover, the first whole genome linkage study has been recently completed, and additional genes will soon be identified. Not unexpectedly, all the joint genes for T1D and AITD identified so far are involved in immune regulation, specifically in the presentation of antigenic peptides to T cells. One of the lessons learned from the analysis of the joint susceptibility genes for T1D and AITD is that subset analysis is a key to dissecting the etiology of complex diseases. One of the best demonstrations of the power of subset analysis is the CTLA-4 gene in T1D. Although CTLA-4 showed very weak association with T1D, when analyzed in the subset of patients with both T1D and AITD, the genetic effect of CTLA-4 was significantly stronger. Gene-gene and genetic-epigenetic interactions most likely play a role in the shared genetic susceptibility to T1D and AITD. Dissecting these mechanisms will lead to a better understanding of the etiology of T1D and AITD, as well as autoimmunity in general.

Serological evidence of thyroid autoimmunity among schoolchildren in two different socioeconomic environments

CONTEXT

The mechanisms leading to thyroid autoimmunity are largely unknown.

OBJECTIVE

Our objective was to assess the role of environment in the development of thyroid autoimmunity.

DESIGN

Prevalence of thyroid autoantibodies in two neighboring populations living in completely different socioeconomic circumstances (Russian Karelia and Finland) was studied.

SETTING

We studied two population-based cohorts partly sharing the same ancestry.

PATIENTS OR OTHER PARTICIPANTS

A total of 532 schoolchildren from Russian Karelia and 532 schoolchildren in Finland matched for age, gender, and season of the blood sampling were included.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

The prevalence of thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TGAb) and HLA-DQ alleles was measured.

RESULTS

The prevalence of TPOAb was significantly lower in Russian Karelian than in Finnish children (0.4 vs. 2.6%, P=0.006). A similar difference was observed for TGAb (0.6 vs. 3.4%, P=0.002). Finnish girls tested positive for both TPOAb (4.3 vs. 0.4%, P=0.01) and TGAb (5.3 vs. 0.9%, P=0.01) more frequently than Finnish boys. Seven of the 23 tested subjects with signs of thyroid autoimmunity (30%) had increased serum TSH concentrations as a sign of subclinical hypothyroidism. The frequency of HLA genotypes did not differ between the two countries or between autoantibody-positive and -negative subjects.

CONCLUSIONS

The prevalence of thyroid autoimmunity is lower in Russian Karelia than in Finland. This difference was not related to ethnic background or HLA-DQ alleles. The results support the idea that the Russian Karelian environment, which is characterized by inferior prosperity and standard of hygiene, may provide protection against thyroid autoimmunity.

The HLA gene complex in thyroid autoimmunity: from epidemiology to etiology

The autoimmune thyroid diseases (AITD) comprise a cadre of complex diseases whose underlying pathoetiology stems from a genetic-environmental interaction, between susceptibility genes (e.g. CTLA-4, HLA-DR, thyroglobulin) and environmental triggers (e.g. dietary iodine), that orchestrates the initiation of an autoimmune response to thyroid antigens, leading to the onset of disease. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITD. Several AITD susceptibility genes have been identified, with HLA genes, in particular, appearing to be of major importance. Early studies showed association of HLA-DR3 with Graves' disease (GD) in Caucasians. More recently, the importance of an amino acid substitution at position 74 of the DR beta 1 chain of HLA-DR3 (DRb1-Arg74), in susceptibility to Graves' disease, has been shown. Furthermore, there is increasing evidence for a genetic interaction between thyroglobulin variants and DRb1-Arg74 in conferring risk for GD. Mechanistically, the presence of an arginine at position 74 elicits a significant structural change in the peptide binding pocket of HLA-DR, potentially affecting the binding of pathogenic thyroidal peptides. Future therapeutic interventions may attempt to exploit this new bolus of knowledge by endeavoring to block or modulate pathogenic peptide presentation by HLA-DR.

Peptides presented in vivo by HLA-DR in thyroid autoimmunity

The association of the major histocompatibility complex (MHC) genes with autoimmune diseases together with the ectopic expression of class II molecules by epithelial cells of the target tissue gives to these molecules a central role in the pathogenesis of the disease, in its regulation and in the persistence of the immune response in situ. HLA-DR molecules expressed by thyroid follicular cells in thyroid autoimmune diseases are compact molecules stably associated with peptides. The nature of these peptides is of vital importance in the understanding of the disease, since these MHC-II-peptide complexes are going to be recognized by both effector and regulatory T cells in situ. In this chapter, we review the current state of the analysis of naturally processed peptides presented by MHC class II molecules in the context of autoimmunity and we discuss our data of natural HLA-DR ligands eluted from Graves' disease affected thyroid glands, from where autoantigen-derived peptides have been identified.

New HLA DRB1 and DQB1 haplotypes in a pedigree of familial Graves' disease in Japan

The present study demonstrated genetic analysis of human leukocyte antigen (HLA) in a familial Graves' disease linked to autoimmune mechanism. The proband was a 17 year-old female. At 15 years, Graves' disease was diagnosed with serum TSH was <0.015 IU/ml; free T(3), 13.6 pg/ml; free T(4), 4.51 ng/dl; and TSH receptor antibody (TRAb), 94.1%. She had two brothers (19 and 13 years-old), who manifested Graves' disease at 18 and 13 years, respectively. They also had elevated TRAb as high as 48.4 and 49.1%, respectively. There was a strong family history of Graves' disease in their maternal pedigree. Namely, their two aunts and a cousin had Graves' disease, and their onset ages of Graves' disease were also during their teen-age years. However, there was no patient with Graves' disease in the paternal pedigree. We checked HLA-DRB and -DQB haplotype in the members of maternal pedigree and proband's father. The members of maternal pedigree including both affected and unaffected Graves' disease had haplotypes of DRB1*150101 and DQB1*0602, except for the cousin who had DRB1*140301 and DQB1*030101. The haplotypes of DRB1*150101 and DQB1*0602 were different from susceptible HLA types in Japanese childhood onset Graves' disease. However, two cases of Graves' disease also had HLA types of DRB1*40501 and DQB1*0401, in addition to the haplotypes of DRB1*150101 and DQB1*0602. There was no other autoimmune disease including type 1 diabetes mellitus in their family. The present findings indicated that familial Graves' disease was found mainly in the maternal females and become overt during their teen-age years. They had new HLA haplotypes distinct from those susceptibly in Japanese Graves' patients. Further study will be necessary to analyze the mutant locus of DNA to elucidate pathogenesis of familial Graves' disease.

HLA-DQ haplotypes in Spanish and German families with Graves' disease: contribution to DQA1*0501-DQB1*0301 mediated genetic susceptibility from fathers

Genetic and environmental factors are involved in the pathogenesis of Graves' disease. The human leukocyte antigen (HLA) locus is considered to be one risk factor for Graves' disease but parent of origin effects have not been studied. Therefore, we investigated the transmission of HLA risk haplotypes DQA1*0501, DQA1*0501-DQB1*0201 (DQ2), and DQA1*0501-DQB1*0301 (DQ7) in two Graves' disease family-cohorts from Spain and Germany. Altogether 208 trio-families (109 from Spain and 99 from Germany; n = 624 individuals) with Graves' disease were genotyped for HLA-DQ alleles DQA1*0501 and the haplotypes DQA1*0501-DQB1*0201 (DQ2) and DQA1*0501-DQB1*0301 (DQ7). Since both family groups-German and Spanish-showed the same pattern of HLA transmission and nontransmission, they were analyzed together. HLA DQA1*0501 and DQA1*0501-DQB1*0201 (DQ2) were significantly overtransmitted from the parents to the affected offspring (204 vs. 131, p = 0.0057, pc = 0.0228 and 109 vs. 55, p = 0.0036, pc = 0.0144, respectively). These haplotypes were preferentially transmitted from fathers and DQA1*0501-DQB1*0301 (DQ7) was also more prevalent in fathers (24.0% vs. 17.1%, p = 0.0162, pc = 0.0648). We conclude, that HLA DQA1*0501 and DQA1*0501-DQB1*0201 (DQ2) are strongly associated with Graves' disease in both populations. A parent of origin effect of risk haplotypes can not be excluded at present, warranting further family studies.

The genetic basis of thyroid autoimmunity

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT), are prevalent autoimmune diseases, affecting up to 5% of the general population. AITDs arise due to interplay between environmental and genetic factors. In the past decade, significant progress has been made in our understanding of the genetic contribution to the etiology of AITDs. Excitingly, several AITD susceptibility genes have been identified and characterized. Some of these susceptibility genes are specific to either GD or HT, while others confer susceptibility to both conditions. The first AITD susceptibility gene locus identified was the Human-Leukocyte-Antigen DR (HLA-DR) gene locus. Subsequently, a quintet of non-HLA genes, including the cytotoxic T lymphocyte antigen (CTLA-4), CD40, protein tyrosine phosphatase-22 (PTPN22), thyroglobulin, and thyroid-stimulating hormone receptor (TSHR) gene, has been shown to contribute to the susceptibility to AITDs. Recently, the mechanisms by which these new AITD genes predispose to AITDs have been dissected. In this review, we overview and highlight the recent data on the genes predisposing to AITDs and the putative mechanisms by which they confer susceptibility to disease.

Interaction of HLA-DRB1 alleles with CTLA-4 in the predisposition to Graves' disease: the impact of DRB1*07

OBJECTIVE

To study interactions between the two most widely confirmed Graves' disease (GD) loci: HLA-DRB1 and CTLA-4. HLA-DRB1*03 (risk allele) and DRB1*07 (protective allele) were analyzed in this aspect, the linked TNF G(-308)A polymorphism was also considered.

DESIGN

A case-control study of 429 patients with GD compared to 308 healthy subjects. The impact of genes and their interactions were analyzed by stepwise logistic regression.

RESULTS

The independent effects of DRB1*03 and DRB1*07 were confirmed in our study both by stratification studies and logistic regression. CTLA-4 did not appear to be associated with GD when the interactions with other genes were considered. By logistic regression we observed a significant interaction between DRB1*07 and CTLA-4 and revealed that CTLA-4 49G attenuated the DRB1*07-related protection, the effect noticed also in three-way stratification studies. We confirmed that the TNF G(-308)A polymorphism is only a marker of the DRB1 status.

CONCLUSION

Our results stress the importance of complex gene interactions in the multigene predisposition to GD. The interactions between two predisposing loci, DRB1 and CTLA-4, are exerted rather by DRB1*07 than DRB1*03 allele: CTLA-4 acts via switching off the protective DRB1*07 influence, whereas the effect of DRB1*03 is independent.

Possible interaction between HLA-DRbeta1 and thyroglobulin variants in Graves' disease

Graves' disease (GD) is influenced by two major susceptibility loci, HLA-DR3 and thyroglobulin (Tg). Recently we have shown that specific HLA-DR and Tg gene sequences predispose to Graves' disease. Individuals carrying at least one arginine at position 74 of the DRbeta1 chain (denoted the R- genotype) have a significantly increased risk of GD, as do individuals homozygous for the single nucleotide protein (SNP) in exon 33 of the Tg gene (denoted the CC genotype). Therefore, for the current study we hypothesized that these two genes may interact to influence the etiology of GD. To test this hypothesis, we analyzed the genotypes of 185 Caucasian patients with GD and 143 Caucasian controls for both genes. We tested for an interaction effect, that is, is one gene's effect on GD greater when the other gene is also present than when the other gene is absent? A logistic regression analysis yielded an estimate of 4.31 for the interaction term (p = 0.053). Our results may suggest an interaction between the R- and CC variants in conferring susceptibility to GD. These results, if confirmed, may imply that these two variants interact biologically to increase the odds of GD.

Genetic analysis of families with autoimmune diabetes and thyroiditis: evidence for common and unique genes

CONTEXT

Epidemiological data suggest a common genetic susceptibility to type 1 diabetes (T1D) and autoimmune thyroid disease (AITD).

OBJECTIVE

Our objective was to identify the joint susceptibility genes for T1D and AITD.

DESIGN

We conducted a family-based linkage and association study.

SETTING

The study took place at an academic medical center.

PARTICIPANTS

Participants included 55 multiplex families (290 individuals) in which T1D and AITD clustered (T1D-AITD families).

MAIN OUTCOME MEASURES

We conducted tests for linkage and family-based associations (transmission disequilibrium test) with four candidate genes: human leukocyte antigen (HLA), cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), insulin variable number of tandem repeats (VNTR), and thyroglobulin.

RESULTS

Linkage evidence to HLA appeared when subjects with either T1D or AITD were considered affected [maximum LOD score (MLS), 2.2]. The major HLA haplotype contributing to the shared susceptibility was DR3-DQB1*0201, with DR3 conferring most of the shared risk. The CTLA-4 gene showed evidence for linkage only when individuals with both T1D and AITD were considered affected (MLS, 1.7), and the insulin VNTR showed evidence for linkage when individuals with either T1D or AITD were considered affected (MLS, 1.9); i.e. it may contribute to the familial aggregation of T1D and AITD.

CONCLUSIONS

The HLA class II locus contributes to the shared risk for T1D and AITD, and the major HLA haplotype contributing to this association is DR3-DQB1*0201. Additional non-HLA loci contribute to the joint susceptibility to T1D and AITD, and two potential candidates include the CTLA-4 and insulin VNTR loci.

Association of HLA-DR and -DQ Genes with Graves Disease in Koreans

Graves disease (GD) is an autoimmune thyroid disease and is associated with human leukocyte antigen (HLA)-DR3 and DQA1*0501 in Caucasians. However, the association of HLA with GD is less clear-cut in East Asian populations. We analyzed HLA-DRB1 and -DQB1 associations with GD in 198 Korean patients compared with 200 healthy controls. HLA-DRB1*0803 (27.8% vs. 14.5% in controls, OR = 2.27, corrected p [p(c)] = 0.03) and *1602 (5.1% vs. 0%, OR = 22.34, p(c) = 0.03) alleles and closely linked haplotypes, DRB1*0803-DQB1*0601 and DRB1*1602-DQB1*0502, conferred susceptibility to GD in Koreans. Weak association of DRB1*0301 with GD susceptibility was observed in male patients only (12.5% vs. 3.5%, OR = 3.57, p < 0.05). HLA-DRB1*0101, *0701, *1202, and *1302 alleles were weakly associated with resistance to the disease (OR < 0.5, p < 0.05). Some HLA alleles were weakly associated with clinical characteristics in GD patients. Patients with DRB1*1301-DQB1*0603 developed their diseases in younger ages and were more frequently associated with larger goiter (p < 0.05). Although HLA class II alleles associated with GD in Koreans were different from those in Caucasians, some associations are shared, such as association of DRB1*0301 in male patients and protective effect of DRB1*0701 to GD susceptibility.

CT60 single nucleotide polymorphisms of the cytotoxic T-lymphocyte-associated antigen-4 gene region is associated with Graves' disease in an Italian population

Graves' disease (GD) is an autoimmune and polygenic disorder. Several studies have shown that human leukocyte antigen (HLA) class II and the cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene are involved in the genetic susceptibility. We performed a case control study on 150 patients with GD and 301 controls, matched for age and gender, to verify the association of three polymorphisms located in CTLA-4 region (A49G, [AT](n)-3'UTR, and CT60) and of HLA-DRB1 and DQB1 loci with the disease in an Italian population. The prevalence of patients with GD carrying the G allele of CT60 was significantly higher compared to control subjects (p = 0.02, odds ratio [OR] = 1.82). The allelic frequency of the G allele of CT60 was also significantly higher in patients with GD (p = 0.02). The G allele frequency of A49G in patients was significantly higher compared to control subjects (p = 0.04). The 280 allele phenotype frequency of (AT)(n)-3'UTR was also significantly higher in patients (p = 0.04). The G allele of A49G, the G allele of CT60, and the 280 allele of (AT)(n)-3'UTR microsatellite were significantly increased in patients with GD with thyroid-associated ophthalmopathy (TAO) compared to controls (p = 0.04, p = 0.03, and p = 0.02, respectively), however, we did not find any significant difference between TAO and non-TAO patients. We also found the HLA-DRB1*03 allele to be associated with GD; interestingly, the association of the CTLA-4 markers was independent from the HLA DRB1*03 status. These results highlight the role of the CTLA-4 locus, in addition to HLA, in the susceptibility to GD. Inside the CTLA-4 region, CT60 appears to be the most associated polymorphism to GD, however, further studies are needed to identify the etiologic variant.

The contribution of immune regulatory and thyroid specific genes to the etiology of Graves' and Hashimoto's diseases

The autoimmune thyroid diseases (AITD) are complex diseases which are caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility in combination with external factors (e.g. dietary iodine) are believed to initiate the autoimmune response to thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITD. Various techniques have been employed to identify the genes contributing to the etiology of AITD, including candidate gene analysis and whole genome screening. These studies have enabled the identification of several loci (genetic regions) that are linked with AITD, and in some of these loci putative AITD susceptibility genes have been identified. Some of these genes/loci are unique to Graves' disease (GD) and Hashimoto's thyroiditis (HT) and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune modifying genes (e.g. HLA, CTLA-4) and thyroid specific genes (e.g. TSHR, Tg). Most likely these loci interact and their interactions may influence disease phenotype and severity.