Association of the HLA-DRB1*0301 and HLA-DQA1*0501 alleles with Graves' disease in a population representing the gene contribution from several ethnic backgrounds

HLA and Non-HLA gene polymorphisms in autoimmune hepatitis patients of North Indian adults

Autoimmune hepatitis (AIH) is a chronic and progressive disease of the liver. This is a multifactorial autoimmune disease with both environmental factors and genetic factors playing a role in its pathogenesis. Certain environmental agents like viruses, drugs, etc., can trigger the disease in a genetically susceptible individual. The present study was aimed to explore the distribution of human leukocyte antigen (HLA)-DRB1, Protein tyrosine phosphatase non-receptor type 22 (PTPN22) and Cytotoxic T-Lymphocyte-associated protein 4 (CTLA-4) polymorphisms in North Indian adult AIH patients and their associations with clinical and pathological characteristics associated with the disease. A total of 147 subjects with 47 cases and 100 healthy controls were enrolled. Diagnosis of AIH was made by Revised International Autoimmune Hepatitis Group scoring system. HLA-DRB1 Typing was done by Luminex-based reverse Sequence-Specific Oligonucleotide Probing (SSOP). Single nucleotide variant (SNV) genotyping for CTLA-4 and PTPN22 was done by simple probe-based SNP arrays. Results indicated SLA positive AIH patients are poor responders to therapy. A significant predispositional association of HLA-DRB1*03 was observed in AIH patients from the North Indian population (p= 0.0001, OR=4.83 (2.30-10.15). The frequency of the GG genotype of CTLA-4 CT 60 was significantly increased in AIH patients compared to controls. Multinomial analysis showed that CTLA-4 CT 60 is an independent predictor for cases.

HLA-G and the MHC Cusp Theory

Human leukocyte antigens (HLA) are significant genetic risk factors in a long list of diseases. However, the mechanisms underlying these associations remain elusive in many cases. The best-characterized function of classical major histocompatibility complex (MHC) antigens is to allow safe presentation of antigenic peptides via a self/non-self-discrimination process. Therefore, most hypotheses to date have posited that the observed associations between certain HLA molecules and human diseases involve antigen presentation (AP). However, these hypotheses often represent inconsistencies with current knowledge. To offer answers to the inconsistencies, a decade ago we have invoked the MHC Cusp theory, postulating that in addition to its main role in AP, the MHC codes for allele-specific molecules that act as ligands in a conformationally-conserved cusp-like fold, which upon interaction with cognate receptors can trigger MHC-associated diseases. In the ensuing years, we have provided empirical evidence that substantiates the theory in several HLA-Class II-associated autoimmune diseases. Notably, in a recent study we have demonstrated that HLA-DRB1 alleles known to protect against several autoimmune diseases encode a protective epitope at the cusp region, which activates anti-inflammatory signaling leading to transcriptional and functional modulatory effects. Relevant to the topic of this session, cusp ligands demonstrate several similarities to the functional effects of HLA-G. The overall goal of this opinion article is to delineate the parallels and distinctive features of the MHC Cusp theory with structural and functional aspects of HLA-G molecules.

Evaluation of HLA class I and HLA class II allele profile and its relationship with clinical features in patients with alopecia areata: a case-control study

BACKGROUND

Alopecia areata (AA) is an autoimmune disease where autoimmune dysregulations along with genetic susceptibility are hypothesized to play a role in pathogenesis.

OBJECTIVE

The aim of this study in to evaluate HLA-A, HLA-B, HLA-C, HLA-DQB1, and HLA-DRB1 profile and its relationship with clinical features in AA patients.

MATERIALS AND METHODS

Ninety-eight patients with AA and 100 healthy controls were included in the study. HLA-A, HLA-B, HLA-C, HLA-DQB1, and HLA-DRB1 frequencies were analyzed using polymerase chain reaction-sequence specific primers (PCR-SSP).

RESULTS

HLA-B*39 and HLA-HLA-DRB1*15 allele frequencies were increased (p = .022 and p = .023, respectively), HLA-A*11 and HLA-B*35 frequencies were decreased (p = .006 and p = .014, respectively) in AA patients. HLA-B*13 and HLA-DRB1*11 were associated with poor prognostic factors. A class I allele, HLA-B*13 was associated with recurrence (p = .023) and presence of nevus flammeus (p = .022), while the class II allele HLA-DRB1*11 was associated with widespread hair loss (diffuse or universal alopecia) (p = .026), presence of ophiasis (p = .049) and juvenile onset (p = .018).

CONCLUSION

Belonging to two different classes of HLA family, HLA-B*13 and HLA-DRB1*11 alleles identified separate set of risk factors. In addition to increasing the risk of AA, HLA alleles may affect the prognosis of the disease.

Haplotype Shuffling and Dimorphic Transposable Elements in the Human Extended Major Histocompatibility Complex Class II Region

The major histocompatibility complex (MHC) on chromosome 6p21 is one of the most single-nucleotide polymorphism (SNP)-dense regions of the human genome and a prime model for the study and understanding of conserved sequence polymorphisms and structural diversity of ancestral haplotypes/conserved extended haplotypes. This study aimed to follow up on a previous analysis of the MHC class I region by using the same set of 95 MHC haplotype sequences downloaded from a publicly available BioProject database at the National Center for Biotechnology Information to identify and characterize the polymorphic human leukocyte antigen (HLA)-class II genes, the MTCO3P1 pseudogene alleles, the indels of transposable elements as haplotypic lineage markers, and SNP-density crossover (XO) loci at haplotype junctions in DNA sequence alignments of different haplotypes across the extended class II region (∼1 Mb) from the telomeric PRRT1 gene in class III to the COL11A2 gene at the centromeric end of class II. We identified 42 haplotypic indels (20 Alu, 7 SVA, 13 LTR or MERs, and 2 indels composed of a mosaic of different transposable elements) linked to particular HLA-class II alleles. Comparative sequence analyses of 136 haplotype pairs revealed 98 unique XO sites between SNP-poor and SNP-rich genomic segments with considerable haplotype shuffling located in the proximity of putative recombination hotspots. The majority of XO sites occurred across various regions including in the vicinity of MTCO3P1 between HLA-DQB1 and HLA-DQB3, between HLA-DQB2 and HLA-DOB, between DOB and TAP2, and between HLA-DOA and HLA-DPA1, where most XOs were within a HERVK22 sequence. We also determined the genomic positions of the PRDM9-recombination suppression sequence motif ATCCATG/CATGGAT and the PRDM9 recombination activation partial binding motif CCTCCCCT/AGGGGAG in the class II region of the human reference genome (NC_ 000006) relative to published meiotic recombination positions. Both the recombination and anti-recombination PRDM9 binding motifs were widely distributed throughout the class II genomic regions with 50% or more found within repeat elements; the anti-recombination motifs were found mostly in L1 fragmented repeats. This study shows substantial haplotype shuffling between different polymorphic blocks and confirms the presence of numerous putative ancestral recombination sites across the class II region between various HLA class II genes.

Neuromyelitis optica is an HLA associated disease different from Multiple Sclerosis: a systematic review with meta-analysis

Neuromyelitis Optica and Multiple Sclerosis are idiopathic inflammatory demyelinating diseases of the central nervous system that currently are considered distinct autoimmune diseases, so differences in genetic susceptibility would be expected. This study aimed to investigate the HLA association with Neuromyelitis Optica by a systematic review with meta-analysis. The STROBE instrument guided research paper assessments. Thirteen papers published between 2009 and 2020 were eligible. 568 Neuromyelitis Optica patients, 41.4% Asians, 32.4% Latin Americans and 26.2% Europeans were analyzed. Only alleles of the DRB1 locus were genotyped in all studies. Neuromyelitis Optica patients have 2.46 more chances of having the DRB1*03 allelic group than controls. Ethnicity can influence genetic susceptibility. The main HLA association with Neuromyelitis Optica was the DRB1*03:01 allele in Western populations and with the DPB1*05:01 allele in Asia. Differences in the Multiple Sclerosis and Neuromyelitis Optica genetic susceptibility was confirmed in Afro descendants. The DRB1*03 allelic group associated with Neuromyelitis Optica has also been described in other systemic autoimmune diseases.

Distinct HLA and non-HLA associations in different subtypes of ANCA-associated vasculitides in North India

AIM

Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is an autoimmune disease characterized by necrotizing small vessel vasculitis that can affect various organs and present multiple symptoms. Susceptibility to AAV is multifactorial and most likely caused by an amalgamation of genetic and environmental factors. The aim of the present study was to explore the distribution of human leukocyte antigen (HLA)-DRB1/DQB1, protein tyrosine phosphatase non-receptor type 22 (PTPN22) and cytotoxic T-Lymphocyte-associated protein 4 (CTLA-4) polymorphisms in North Indian AAV patients and their associations with clinical and pathological characteristics associated with the disease.

METHODS

A total of 150 AAV patients and 150 healthy controls were recruited. The clinical classification showed 128 as granulomatosis with polyangiitis (GPA) and 21 as microscopic polyangiitis. Only 1 case of eosinophilic granulomatosis with polyangiitis was encountered, which was excluded from analysis. HLA-DRB1/DQB1 alleles were determined by polymerase chain reaction-sequence-specific primer (PCR-SSP) method and single nucleotide variant genotyping for CTLA-4 and PTPN22 was done by simple probe-based SNP arrays.

RESULTS

A significant predispositional association of DRB1*03 and DQB1*02 alleles, were confirmed in proteinase 3 (PR3)-AAV patients, whereas DRB1*10, DRB1*14 and DQB1*05 were protective alleles in AAV, PR3-AAV and GPA patients. GG genotype of CTLA-4 + 49A/G was increased in patients as compared to controls and showed an association with AAV, PR3-AAV and GPA patients.

CONCLUSION

The study indicated strong genetic associations were linked with PR3 antineutrophil cytoplasmic antibody specificity and it appears that PR3-AAV and MPO-AAV have distinct genetic backgrounds.

Comprehensive research on thyroid diseases associated with autoimmunity: autoimmune thyroid diseases, thyroid diseases during immune-checkpoint inhibitors therapy, and immunoglobulin-G4-associated thyroid diseases

Various thyroid diseases are associated with autoimmunity. Major autoimmune thyroid diseases are Graves' disease (GD) and Hashimoto's thyroiditis (HT). Thyrotropin receptor is an autoantigen in GD, and its immunogenicity has been examined. Immune-checkpoint inhibitor (ICI) is recently widely used for treatment of malignant tumors, but cases of thyroid diseases during ICI treatment have been increasing. Thyroid diseases during ICI therapy have been investigated in immunological and clinical aspects, and their Japanese official diagnostic guidelines were established. In addition, serum and tissue immunoglobulin-G4 levels have been examined in association with clinicopathological characteristics in GD, HT, and Riedel's thyroiditis. We review these diseases associated with thyroid autoimmunity and comprehensively discuss their potential application in future research and therapeutic options.

Exophthalmos and multinodular goitre, an unusual combination

Multinodular goitre is not associated with eye disease, unless in a rare case of Marine-Lenhart syndrome where it coexists with Grave's disease. Therefore, other causes of exophthalmos need to be ruled out when the eye disease is seen in a patient with multinodular goitre. Confusion can arise in patients with features suggestive of Graves' ophthalmopathy in the absence of thyroid-stimulating hormone receptor autoantibodies and no evidence of other causes of exophthalmos. We present a case of multinodular goitre in a patient with exophthalmos which flared up after iodine contrast-based study. A 61-year-old Australian presented with a pre-syncopal attack and was diagnosed with toxic multinodular goitre. At the same time of investigations, to diagnose the possible cause of the pre-syncopal attack, computerised tomographic (CT) coronary artery angiogram was requested by a cardiologist. A few days after the iodine contrast-based imaging test was performed, he developed severe eye symptoms, with signs suggestive of Graves' orbitopathy. MRI of the orbit revealed features of the disease. Although he had pre-existing eye symptoms, they were not classical of thyroid eye disease. He eventually had orbital decompressive surgery. This case poses a diagnostic dilemma of a possible Graves' orbitopathy in a patient with multinodular goitre. Learning points: Graves' orbitopathy can occur in a patient with normal autothyroid antibodies. The absence of the thyroid antibodies does not rule out the disease in all cases. Graves' orbitopathy can coexist with multinodular goitre. Iodine-based compounds, in any form, can trigger severe symptoms, on the background of Graves' eye disease.

Genetic fine mapping of systemic lupus erythematosus MHC associations in Europeans and African Americans

Genetic variation within the major histocompatibility complex (MHC) contributes substantial risk for systemic lupus erythematosus, but high gene density, extreme polymorphism and extensive linkage disequilibrium (LD) have made fine mapping challenging. To address the problem, we compared two association techniques in two ancestrally diverse populations, African Americans (AAs) and Europeans (EURs). We observed a greater number of Human Leucocyte Antigen (HLA) alleles in AA consistent with the elevated level of recombination in this population. In EUR we observed 50 different A-C-B-DRB1-DQA-DQB multilocus haplotype sequences per hundred individuals; in the AA sample, these multilocus haplotypes were twice as common compared to Europeans. We also observed a strong narrow class II signal in AA as opposed to the long-range LD observed in EUR that includes class I alleles. We performed a Bayesian model choice of the classical HLA alleles and a frequentist analysis that combined both single nucleotide polymorphisms (SNPs) and classical HLA alleles. Both analyses converged on a similar subset of risk HLA alleles: in EUR HLA- B*08:01 + B*18:01 + (DRB1*15:01 frequentist only) + DQA*01:02 + DQB*02:01 + DRB3*02 and in AA HLA-C*17:01 + B*08:01 + DRB1*15:03 + (DQA*01:02 frequentist only) + DQA*02:01 + DQA*05:01+ DQA*05:05 + DQB*03:19 + DQB*02:02. We observed two additional independent SNP associations in both populations: EUR rs146903072 and rs501480; AA rs389883 and rs114118665. The DR2 serotype was best explained by DRB1*15:03 + DQA*01:02 in AA and by DRB1*15:01 + DQA*01:02 in EUR. The DR3 serotype was best explained by DQA*05:01 in AA and by DQB*02:01 in EUR. Despite some differences in underlying HLA allele risk models in EUR and AA, SNP signals across the extended MHC showed remarkable similarity and significant concordance in direction of effect for risk-associated variants.

Exploring Genetic Attributions Underlying Radiotherapy-Induced Fatigue in Prostate Cancer Patients

CONTEXT

Despite numerous proposed mechanisms, no definitive pathophysiology underlying radiotherapy-induced fatigue (RIF) has been established. However, the dysregulation of a set of 35 genes was recently validated to predict development of fatigue in prostate cancer patients receiving radiotherapy.

OBJECTIVES

To hypothesize novel pathways, and provide genetic targets for currently proposed pathways implicated in RIF development through analysis of the previously validated gene set.

METHODS

The gene set was analyzed for all phenotypic attributions implicated in the phenotype of fatigue. Initially, a "directed" approach was used by querying specific fatigue-related sub-phenotypes against all known phenotypic attributions of the gene set. Then, an "undirected" approach, reviewing the entirety of the literature referencing the 35 genes, was used to increase analysis sensitivity.

RESULTS

The dysregulated genes attribute to neural, immunological, mitochondrial, muscular, and metabolic pathways. In addition, certain genes suggest phenotypes not previously emphasized in the context of RIF, such as ionizing radiation sensitivity, DNA damage, and altered DNA repair frequency. Several genes also associated with prostate cancer depression, possibly emphasizing variable radiosensitivity by RIF-prone patients, which may have palliative care implications. Despite the relevant findings, many of the 35 RIF-predictive genes are poorly characterized, warranting their investigation.

CONCLUSION

The implications of herein presented RIF pathways are purely theoretical until specific end-point driven experiments are conducted in more congruent contexts. Nevertheless, the presented attributions are informative, directing future investigation to definitively elucidate RIF's pathoetiology. This study demonstrates an arguably comprehensive method of approaching known differential expression underlying a complex phenotype, to correlate feasible pathophysiology.

Pooled genome wide association detects association upstream of FCRL3 with Graves' disease

Background

Graves’ disease is an autoimmune thyroid disease of complex inheritance. Multiple genetic susceptibility loci are thought to be involved in Graves’ disease and it is therefore likely that these can be identified by genome wide association studies. This study aimed to determine if a genome wide association study, using a pooling methodology, could detect genomic loci associated with Graves’ disease.

Results

Nineteen of the top ranking single nucleotide polymorphisms including HLA-DQA1 and C6orf10, were clustered within the Major Histo-compatibility Complex region on chromosome 6p21, with rs1613056 reaching genome wide significance (p = 5 × 10⁻⁸). Technical validation of top ranking non-Major Histo-compatablity complex single nucleotide polymorphisms with individual genotyping in the discovery cohort revealed four single nucleotide polymorphisms with p ≤ 10⁻⁴. Rs17676303 on chromosome 1q23.1, located upstream of FCRL3, showed evidence of association with Graves’ disease across the discovery, replication and combined cohorts. A second single nucleotide polymorphism rs9644119 downstream of DPYSL2 showed some evidence of association supported by finding in the replication cohort that warrants further study.

Conclusions

Pooled genome wide association study identified a genetic variant upstream of FCRL3 as a susceptibility locus for Graves’ disease in addition to those identified in the Major Histo-compatibility Complex. A second locus downstream of DPYSL2 is potentially a novel genetic variant in Graves’ disease that requires further confirmation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3276-z) contains supplementary material, which is available to authorized users.

Thyrotropin Receptor Epitope and Human Leukocyte Antigen in Graves' Disease

Graves' disease (GD) is an organ-specific autoimmune disease, and thyrotropin (TSH) receptor (TSHR) is a major autoantigen in this condition. Since the extracellular domain of human TSHR (TSHR-ECD) is shed into the circulation, TSHR-ECD is a preferentially immunogenic portion of TSHR. Both genetic factors and environmental factors contribute to development of GD. Inheritance of human leukocyte antigen (HLA) genes, especially HLA-DR3, is associated with GD. TSHR-ECD protein is endocytosed into antigen-presenting cells (APCs), and processed to TSHR-ECD peptides. These peptide epitopes bind to HLA-class II molecules, and subsequently the complex of HLA-class II and TSHR-ECD epitope is presented to CD4+ T cells. The activated CD4+ T cells secrete cytokines/chemokines that stimulate B-cells to produce TSAb, and in turn hyperthyroidism occurs. Numerous studies have been done to identify T- and B-cell epitopes in TSHR-ECD, including (1) in silico, (2) in vitro, (3) in vivo, and (4) clinical experiments. Murine models of GD and HLA-transgenic mice have played a pivotal role in elucidating the immunological mechanisms. To date, linear or conformational epitopes of TSHR-ECD, as well as the molecular structure of the epitope-binding groove in HLA-DR, were reported to be related to the pathogenesis in GD. Dysfunction of central tolerance in the thymus, or in peripheral tolerance, such as regulatory T cells, could allow development of GD. Novel treatments using TSHR antagonists or mutated TSHR peptides have been reported to be effective. We review and update the role of immunogenic TSHR epitopes and HLA in GD, and offer perspectives on TSHR epitope specific treatments.

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.

Autoimmune thyroid disease in the use of alemtuzumab for multiple sclerosis: a review

OBJECTIVE

The monoclonal antibody alemtuzumab has been demonstrated to reduce the risks of relapse and accumulation of sustained disability in multiple sclerosis (MS) patients when compared to β-interferon. The development of autoimmune diseases, including thyroid disease, has been reported in the literature with a frequency of 20 to 30%. In this article, we describe 4 cases of alemtuzumab-induced thyroid disease in patients with MS. We also performed a systematic review of the available literature.

METHODS

Four patients who had received alemtuzumab for MS and subsequently developed thyroid dysfunction are presented. We compared our patients' clinical courses and outcomes to established disease patterns. We also undertook a systematic review of the published literature.

RESULTS

All 4 patients presented with initial hyperthyroidism associated with elevated thyroid-stimulating hormone (TSH) receptor antibodies (TRAb). In 2 cases, hyperthyroidism did not remit after a total of 24 months of carbimazole therapy, and they subsequently underwent subtotal thyroidectomy. The third case subsequently developed biochemical hypothyroidism and required thyroxine replacement, despite having a markedly raised initial TRAb titer. Autoimmunity following alemtuzumab therapy in MS appears to occur as part of an immune reconstitution syndrome and is more likely in smokers who have a family history of autoimmune disease.

CONCLUSION

Management of alemtuzumab-induced thyroid disease is similar to the management of "wild-type" Graves' disease. The use of alemtuzumab in this setting will necessitate close monitoring of thyroid function and early intervention when abnormalities are developing.

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.

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.

Cutting edge: the etiology of autoimmune thyroid diseases

Significant progress has been made in our understanding of the mechanisms leading to autoimmune thyroid diseases (AITD). For the first time, we are beginning to unravel these mechanisms at the molecular level. AITD, including Graves' disease (GD) and Hashimoto's thyroiditis (HT), are common autoimmune diseases affecting the thyroid. They have a complex etiology that involves genetic and environmental influences. Seven genes have been shown to contribute to the etiology of AITD. The first AITD gene discovered, HLA-DR3, is associated with both GD and HT. More recently, this association was dissected at the molecular level when 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 the specific sequence change causing AITD. Non-MHC genes that confer susceptibility to AITD can be classified into two groups: (1) immune-regulatory genes (e.g., CD40, CTLA-4, and PTPN22); (2) thyroid-specific genes-thyroglobulin and TSH receptor genes. These genes interact with environmental factors, such as infection, likely through epigenetic mechanisms to trigger disease. In this review, we summarize the latest findings on disease susceptibility and modulation by environmental factors.

Human leukocyte antigen-DQA1 gene allelic distribution: experience of a major tertiary care center in Lebanon

AIMS

DQA1 is a human leukocyte antigen (HLA) class II molecule that is similar to the other class II molecules DR and DP. This study is the first of its kind to describe the distribution of HLA-DQA1 alleles in Lebanon.

METHODS

HLA-DQA1 typing was detected using the polymerase chain reaction/sequence-specific priming method in 111 Lebanese individuals referred for HLA typing and possible bone marrow donation.

RESULTS

Our data was compared to that of several populations. Some similarities were found between the Lebanese, Tunisian, Spanish, and Kuwaiti populations.

CONCLUSION

This very first report from Lebanon will be of great help for later research to study the association of DQA1 alleles with major diseases in the Lebanese population and will add to the published international literature related to this important histocompatibility locus.

Spontaneous lupus-like syndrome in HLA-DQ2 transgenic mice with a mixed genetic background

To investigate the role of HLA-DQ2 in the pathogenesis of associated immune disorders, we generated transgenic mice that expressed HLA-DQ2 in the absence of endogenous murine class II molecules (AE(0)DQ2). These AE(0)DQ2 mice with a mixed genetic background spontaneously developed skin lesions on their ears, whereas control AE(0)DQ6 genotype control mice (also with a mixed genetic background) did not. The skin lesions were characterized by deep subepidermal blistering with hydropic degeneration and lymphoid infiltration in the subepidermal area as determined by histopathology. Immunofluorescence analysis revealed thick band-like granular deposition of IgG, IgM, and a thin band of IgA deposition along the basement membrane. AE(0)DQ2 mice also developed significant and progressive hematuria and proteinuria as compared with the AE(0)DQ6 mice (p < 0.05). Histopathology showed immune complex deposits in the glomeruli of AE(0)DQ2 mice. Immunofluorescence analysis showed progressive mesangial and capillary wall deposition of IgA, IgM, IgG and C1q in the kidney. With electron microscopy, the deposits showed a 'fingerprint' substructure; and tubuloreticular structures were identified within endothelial cells. Conversely, these changes were not observed in AE(0)DQ6 mice. Serum anti-double stranded (ds)DNA IgM and IgG levels were also significantly elevated among AE(0)DQ2 mice compared with AE(0)DQ6 mice (p < 0.001). In conclusion, AE(0)DQ2 mice spontaneously develop an autoimmune lupus-like syndrome and are useful model for this disease. It remains to be determined whether genetic admixture played a role in the development of this systemic lupus erythematosus-like syndrome in HLA-DQ2 transgenic mice. Lupus (2010) 19, 815-829.

Tumor necrosis factor alpha (TNF-alpha) polymorphisms in Chinese patients with Graves' disease

OBJECTIVES

Tumor necrosis factor alpha (TNF-alpha) may play a central role in the development of Graves' disease (GD). The aim of this study was to investigate the association of TNF-alpha polymorphisms with GD in Chinese population.

DESIGN AND METHODS

Genomic DNA was extracted from peripheral blood lymphocyte of 436 GD patients and 316 control subjects. TNF-alpha polymorphisms at positions -308 (G-308A, rs1800629), -238 (G-238A, rs361525), and +419 (G+419A, rs3093661) were genotyped.

RESULTS

The distribution of TNF-alpha -238 and +419 allelic frequencies between GD and control individuals was significantly different. Both the G alleles of TNF-alpha -238 (OR 2.385, 95%CI 1.359-4.184) and +419 (OR 2.293, 95%CI 1.303-4.035) SNPs conferred higher risk of GD as compared with A alleles. No significant difference of -308 allelic frequency was observed. Further haplotype analysis revealed that the haplotype GGG was associated with an increased risk of GD (OR 1.554, 95%CI 1.125-2.146), whereas the haplotype GAA was found to be protective (OR 0.419, 95%CI 0.239-0.736).

CONCLUSIONS

This study demonstrated the association of TNF-alpha gene with GD in Chinese patients.

Heritability of levels of autoantibodies to thyroid antigens using the method of plotting regression of offspring on midparent (ROMP)

Only a few methods can be applied in a simple manner to estimate the genetic control of autoimmunity in humans. Here we examined the heritability of autoantibodies to two thyroid antigens; thyroglobulin (Tg) and thyroperoxidase (TPO, formerly known as thyroid microsomal antigen), using methods of regression of offspring on mid-parental values (ROMP). With the data sets available, affected and unaffected siblings were compared by this rapid screening method using results determined by hemagglutination (HA). The presence of both types of autoantibodies showed positive heritability in patients with Graves' thyrotoxicosis (TT), but it was not observed in chronic lymphocytic or Hashimoto's thyroiditis (CLT) patients. Since these assays have been extensively used over the years by most diagnostic and research laboratories, they should provide some insight as to which quantifiable parameters may be usefully accumulated to help select groups of patients and their families for further genetic study. ROMP may also be useful to determine the sequential appearance of different types of antibody in predicting disease onset in other family members, and in distinguishing maternal and paternal effects on imprinting. The method may be extended to study epitope spreading and other measures of disease progression.

Patogênese das doenças tiroidianas autoimunes

A doença tiroidiana autoimune (DAIT), que afeta de 2% a 5% da população ocidental, é o transtorno autoimune órgão-específico mais comum. Sua apresentação clínica varia do hipertiroidismo da doença de Graves (DG) ao hipotiroidismo associado à tiroidite de Hashimoto (TH). A exata etiologia da DAIT permanece desconhecida, mas a interação entre suscetibilidade genética e fatores ambientais desencadeadores parece ser de fundamental importância no seu desenvolvimento. Postula-se que fatores genéticos responderiam por 79% da suscetibilidade à DAIT e os ambientais por 21%. Genes imunomoduladores, como o complexo maior de histocompatibilidade (MHC), antígeno-4 associado ao linfócito T citotóxico (CTLA-4), a molécula CD40 e a proteína tirosina fosfatase-22 (PTPN22) e os genes específicos da glândula tiróide, como receptor do TSH (TSHR) e tiroglobulina (TG) têm sido identificados. A natureza exata do envolvimento do meio ambiente no desenvolvimento da DAIT não é bem conhecida, mas vários fatores ambientais têm sido envolvidos, como o conteúdo de iodo na dieta, estresse, drogas e infecções. Entretanto, não há evidência clara de causalidade e os mecanismos pelos quais fatores ambientais desencadeariam a autoimunidade tiroidiana, em indivíduos geneticamente predispostos, ainda permanecem não completamente entendidos. O conhecimento dos mecanismos precisos de interação entre fatores ambientais e genes na indução da autoimunidade tiroidiana poderia resultar desenvolvimento de novas estratégias de prevenção e tratamento.

The proinflammatory cytokine TNF-alpha -308 AA genotype is associated with polyglandular autoimmunity

Data regarding polymorphisms of immunoregulatory genes in polyglandular autoimmunity (PGA) are lacking. We have analyzed whether the polymorphism of the proinflammatory cytokine gene TNF-alpha; -308 and mutations of the autoimmune regulator (AIRE) gene were associated with PGA in adults. Sixty-seven patients with PGA and 209 healthy controls were genotyped by multiplex minisequencing with capillary electrophoresis on an ABI PRISM-310 genetic analyzer. HLA DRB1 typing was performed using polymerase-chain-reaction-amplified DNA hybridized with sequence-specific-oligonucleotide probes (PCR-SSO). The TNF-alpha; -308*A allele occurred more frequently in patients (0.269) than in controls (0.163, P = 0.008, P(c) = 0.016). Also, TNF-alpha; -308*A carriers were more frequent in patients than controls (47.8% vs. 31.1%, OR = 1.89, 95%CI = 1.19-3.00). The frequency of the AA genotype was increased in PGA (P = 0.014, P(c) = 0.042). PGA patients with autoimmune thyroid disease and the TNF-alpha; -308 AA genotype showed the highest prevalence of thyroid autoantibodies (TPO, P = 0.04; Tg, P = 0.003). HLA-DRB1*03 and TNF-alpha; -308*A alleles were strongly associated in patients with PGA (87.5%, P(c) < 0.00001). The AIRE R257X and 13bpdel mutations were not observed in patients with PGA. The association of TNF-alpha; -308*A with PGA might be directly or indirectly due to the association with HLA-DRB1*03.

Early onset of polyglandular failure is associated with HLA-DRB1*03

OBJECTIVES

Polyglandular failure or autoimmunity (PGA) involves at least two endocrine diseases. Several genes may play a role in its etiology. This study analyzed 1) whether HLA-DRB1, HLA-DQB1, and MHC class I chain-related gene A (MICA) polymorphisms are associated in PGA and 2) whether PGA patients display stronger associations with these immune genes than patients with monoglandular autoimmunity (MGA).

DESIGN

Association study.

METHODS

HLA-DRB1, HLA-DQB1, and MICA alleles were analyzed in 73 patients with PGA, 283 with MGA, and 206 healthy controls. The HLA-DRB1 and HLA-DQB1 polymorphisms were determined with PCR-amplified DNA being hybridized with PCR-sequence-specific oligonucleotide probes. MICA microsatellites were typed by PCR amplification and fragment size analysis on a DNA sequencer.

RESULTS

HLA-DRB1*03 was strongly increased in patients with PGA (50.7%) versus both controls (21.8%, P(c)<0.0001; RR=2.32, 95% CI=1.62-3.33) and MGA (11.4%, P(c)<0.0001). HLA-DRB1*03 was highly prevalent in PGA patients with early versus late disease onset (P<0.05, logistic regression analysis). HLA-DRB1*04 allele carriers were more present in PGA versus controls (53.4% vs 22.4%, P(c)<0.0001, RR=2.38, 95% CI=1.68-3.38). Further, HLA-DQB1*02 was increased in PGA versus controls (P(c)<0.01), whereas HLA-DQB1*06 was decreased (P(c)<0.001). Patients with PGA showed more MIC A5.1 and less MIC A6 allele carriers than controls (NS). Presence of the MIC A5.1 allele was not associated with the HLA-DRB1*03 or HLA-DQB1 alleles.

CONCLUSIONS

HLA-DRB1*03 is a stronger genetic marker in PGA than in MGA, foremost in those with early disease onset.

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.

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.

Low prevalence of hypothyroidism among black and Mulatto people in a population-based study of Brazilian women

Objective African-Americans have been shown to have low prevalence of hypothyroidism. Brazil has a high ethnic admixture allowing further exploration into whether environmental factors can explain the ethnic differences. Design A survey, representative of the population of Rio de Janeiro, a large metropolitan city in Brazil. Factors studied included race, parity, income, schooling, and smoking. Population The survey was carried out in Rio de Janeiro whereby households (1500) were selected using three-stage probability sampling. A total of 1298 (86.5%) women participated in the survey (non-response: 13.5%). Measurements TSH from blood drawn at the households. Anti-thyroperoxidase (anti-TPO) antibodies and free T4 were also measured. Results Overall prevalence of hypothyroidism (TSH > 4 mUI/ml or taking medication) was 12.3%. Prevalence was 6.9% in black people, 8.8% in Mulatto people, and 16.7% among white people. The mean serum TSH of the population was 2.65 (95% confidence interval 2.33-2.97). The TSH distribution of black and Mulatto people was shifted to the left compared to white people. After adjustment for age, income, smoking and presence of anti-TPO, Black and Mulatto people were still protected from hypothyroidism. The adjusted odds ratio for black compared to white people was 0.45 (95% CI 0.30-0.68) and for Mulatto people was 0.34 (95% CI 0.18-0.63). Serum TSH levels were significantly lower in smokers than in non-smokers, but there was no association between number of cigarettes smoked and serum TSH level. Conclusions This is the first time it has been demonstrated that Mulatto people have a prevalence of hypothyroidism which lies between that of white and black people, independent of the prevalence of anti-TPO and smoking.

Sequence-based typing of the complete coding sequence of DQA1 and phenotype frequencies in the Dutch Caucasian population

Typing of DQA1 by sequencing has been a challenge because of a 3-nucleotide deletion in exon 2 in half of the alleles. Furthermore, 19 of the 28 alleles cannot be identified on basis of exon 2 alone, but need additional exon information. With the sequencing strategy presented here the complete exons 1-4 are sequenced heterozygously, enabling identification of all DQA1 alleles by sequence-based typing (SBT). Exons 1-4 were amplified and sequenced separately, the combined sequences were used for automated allele assignment. The method was validated by typing 21 individuals with all possible different allele group combinations. In addition 26 quality control samples were correctly typed by this method. To determine the phenotype frequencies 155 unrelated Dutch Caucasian individuals were DQA1 typed. In total 15 known and two new DQA1 alleles were identified. DQA1*0103 and *0505 were the most frequent alleles with phenotype frequencies of 30% and 29%, respectively. The SBT method presented here is an improvement compared to already existing protocols in that the complete exon sequence is obtained for all coding exons, using identical polymerase chain reaction conditions. Furthermore, all exons are sequenced heterozygously, facilitating allele assignment and reducing the number of amplification reactions.

HLA-DPB1*0202 Is Associated with a Predictor of Good Prognosis of Graves’ Disease in the Japanese

Whereas most patients with Graves' disease (GD) have antibodies against the thyrotropin receptor, which are measured as thyrotropin-binding inhibitory immunoglobulin (TBII), the TBII of 10% or less of Japanese patients with GD is undetectable at the first visit and throughout the entire clinical course, and these patients tend to respond well to medications and follow the better clinical course. Therefore, the absence of TBII at the first visit may be a predictor of good prognosis. Ninety-seven patients with GD who had remained TBII negative for at least 2 years from the onset, as well as 142 typical TBII-positive GD patients, were examined to reveal the HLA-linked immunogenetic background for this predictor. Compared with a healthy control population, the frequencies of HLA-A*0206 (OR=2.17, p=9.73x10(-4)) and DPB1*0501 (OR=3.26, p=3.31x10(-7)) carriers were increased in the typical patients, whereas those of HLA-A*0201 (OR=2.16, p=1.92x10(-3)), A*0207 (OR=3.19, p=7.17x10(-4)), and DPB1*0202 (OR=3.13, p=3.97x10(-4)) were increased in the TBII-negative group. These two patient groups were associated with similar HLA-A alleles and different HLA-DPB1 alleles, suggesting the presence of two genetic factors for GD within the HLA region; one is HLA-A linked and may be related to thyroid organ specificity, the other is HLA-DP linked and may control the severity of autoimmunity.

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.

Neutrophils from Brazilian patients with Graves' disease: some biochemical and functional aspects

Graves' disease shows important systemic inflammatory complications and has been considered to be systemic autoimmune thyroid, skeletal muscle and connective tissue syndrome. Neutrophils participate in the pathophysiology of the two major immune and inflammatory manifestations of the disease, ophthalmopathy and myxedema, and may worsen the inflammatory picture. In this study we analysed some biochemical and functional aspects of neutrophils in Graves' disease patients to assess their participation in these processes. The results show that the complement and/or Fcgamma receptor-mediated oxygen radical production by neutrophils was increased when patient cells were compared with controls. However the percentage of cells expressing complement and IgG receptors and the per-cell fluorescence, were similar, indicating that the increased oxidative burst was not due to an abnormal expression of mediating receptors. The production of hydrogen peroxide was also increased in hyperthyroid patient neutrophils as compared to controls. Conversely, antioxidant defences (superoxide dismutase activity and reduced glutathione content) in neutrophils from patients were not significantly different from healthy controls. The liberation of potent oxidative compounds together with the absence of adequate quenching of them by antioxidant mechanisms could be responsible for greater tissue damage in inflammatory conditions, as is the case in ophthalmopathy and myxedema patients. Considering our results and those of other workers, we encourage and suggest an associated antioxidant therapy to complement the conventional anti-thyroid therapy, especially in obvious inflammatory cases and in individuals who smoke.

Unravelling the genetic complexity of autoimmune thyroid disease: HLA, CTLA-4 and beyond

The autoimmune thyroid diseases (AITDs) including Graves' disease (GD) and autoimmune hypothyroidism (AIH) are the commonest of the autoimmune conditions affecting 2-5% of the western population. Twin studies have clearly demonstrated that AITDs are caused by a combination of both environmental and genetic factors. Association of the HLA class II region with AITD has been documented for over 20 years now, but the primary aetiological variant in this region remains unknown. More recently the CTLA-4 gene region has been identified as the second locus conferring susceptibility to AITD. In contrast to HLA, a polymorphism of the CTLA-4 gene, which encodes an important negative regulator of the immune system, has been identified as a candidate for a primary determinant for AITD. A large number of candidate gene and genome wide linkage studies have been involved in the search for the elusive 'third' locus. The thyroglobulin (Tg) gene in humans maps to chromosome 8q, which has been linked in family studies to AITD. A number of association studies in humans and the mouse model for AITD are beginning to implicate the Tg gene although convincing evidence for a primary causative role is still needed. The establishment of large DNA disease resources along with more detailed genetic maps and the development of faster, more effective, high throughput genotyping and sequencing methods, provides some sense of optimism that novel loci will be identified in the near future and the complex aetiology of AITD will be further unraveled.

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.

Como entender a associação entre o sistema HLA e as doenças auto-imunes endócrinas

A introdução de nova nomenclatura para os componentes do complexo principal de histocompatibilidade (Major Histocompatibility Complex - MHC) e a descrição de novos métodos moleculares para a tipificação dos alelos do MHC contribuíram, grandemente, para o entendimento e identificação do extenso polimorfismo do sistema. No entanto, para o não especialista, essas novas aquisições têm dificultado o entendimento do papel do MHC em associação com as doenças. Assim, neste artigo, foram revisados os conceitos atuais acerca dos genes e moléculas do MHC, os métodos de tipificação desses marcadores de histocompatibilidade e a nomenclatura vigente para os componentes do sistema. Esses aspectos são extremamente importantes para o entendimento do polimorfismo do MHC, dando embasamento para a compreensão dos mecanismos propostos de associação desses marcadores com as doenças auto-imunes endócrinas como diabetes mellitus do tipo 1, doença de Graves e tireoidite de Hashimoto, doença de Addison, síndrome poliglandular auto-imune e insuficiência ovariana prematura.

Searching for the autoimmune thyroid disease susceptibility genes: from gene mapping to gene function

The autoimmune thyroid diseases (AITD) are complex diseases that are caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility, in combination with external factors (e.g., dietary iodine), is 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 used 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., human leukocyte antigen, cytotoxic T lymphocyte antigen-4) and thyroid-specific genes (e.g., TSH receptor, thyroglobulin). Most likely these loci interact, and their interactions may influence disease phenotype and severity. It is hoped that in the near future additional AITD susceptibility genes will be identified and the mechanisms by which they induce AITD will be unraveled.

Association of Graves' disease with intragenic polymorphism of the thyrotropin receptor gene in a cohort of Singapore patients of multi-ethnic origins

Thyrotropin (TSH) receptor (TSHr) mutations have been investigated in relation to Graves' disease (GD) genetic susceptibility under the hypothesis that a modified antigen may have novel immunogenic properties. The prevalence of three germline polymorphisms--D36H, P52T, and D727E--were studied in a cohort of multiracial GD patients together with their associations with disease state, Graves' ophthalmopathy, and thyroid autoantibodies titers. Polymerase chain reaction products of exon 1 and 10e of the TSHr were generated from 164 GD patients (109 Chinese, 34 Malays, and 21 Indians) and 240 individuals with no thyroid illnesses (74 Chinese, 84 Malays, and 82 Indians). Mutations were detected by single-strand conformational polymorphism and confirmed with direct sequencing. The D36H mutation was absent, while significant ethnic differences in the distribution of the P52T and D727E mutations were found. The levels of thyroid autoantibodies also differed significantly amongst the three ethnic groups, with the Indian cohort having the lowest titer. Both the P52T and D727E mutations were not associated with GD. An intron mutation, C/G+63IVS1, was detected and showed significant association with GD. Overall, it conferred a twofold increase risk of GD, while subgroup analysis showed increased odds ratios of 2.4 for Chinese (p = 0.008) and 2.8 for Indian (p = 0.049) but not for the Malay ethnic group. Together with recent identification of disease susceptibility markers in the region of the TSHr gene, these results are supportive of genetic factors existing in this region that may be in linkage disequilibrium with the inheritance of various TSHr polymorphisms.

Autoimmune diseases in vitiligo: do anti-nuclear antibodies decrease thyroid volume?

An increased prevalence of autoimmune thyroiditis (AT) in vitiligo patients is well known. The aim of this study was firstly, to evaluate the clinical course of patients with both vitiligo and AT and secondly, to identify additional autoimmune disorders affecting the thyroid gland in a large cohort of vitiligo patients. We analysed a study group of 106 vitiligo patients and 38 controls. A detailed thyroid examination including sonography was performed in all study participants. In addition, the study participants were HLA typed and screened for various autoimmune disorders. AT was significantly more frequent in vitiligo patients than in controls (21%versus 3%; P < 0.01). In 12 of the 22 patients with AT, vitiligo was the initial disease preceding AT by 4-35 years. In the other 10 patients with AT, both vitiligo and AT were diagnosed within one year. There were two individuals with diabetes mellitus type 1 and a single patient with Addison's disease. Anti-nuclear antibody (ANA), anti-smooth muscle cell antibody, and parietal cell antibody levels occurred with a similar frequency in patients and controls. In all vitiligo patients with both elevated ANA levels and AT (n = 6), the atrophic but not the goitrous variant was diagnosed. These vitiligo patients with both AT and elevated ANA levels had a significantly smaller thyroid volume compared to the vitiligo patients with AT whose ANA levels were normal (6.7 +/- 4.5 ml versus 13.4 +/- 9.1 ml, respectively; P < 0.05). The same was found in the entire study group: Thyroid volume of all vitiligo patients (with or without concomitant AT) was significantly smaller in the presence of ANA (6.9 +/- 5.3 versus 10.5 +/- 5.9 ml, respectively; P < 0.05). However, this phenomenon was not observed in the control group. There was a trend for a decreased frequency of HLA-DR3 (6.7%versus 23%) in our study group, but after correction for the number of comparisons, no HLA-allele was statistically significant associated neither with vitiligo nor with multiple autoimmune diseases in our patient sample. Our findings suggest that AT is the most frequent autoimmune disease associated with vitiligo. In our patients, AT presented simultaneously or after the onset of vitiligo but not before. Elevated ANA levels were associated with the atrophic variant of AT and may affect the volume of the thyroid gland, and there was no statistically significant association with the HLA system.