Genetics of autoimmune thyroid disease: lack of evidence for linkage to HLA within families.

Clinical and epidemiologic observations, including the association of Graves' disease (GD) and Hashimoto's thyroiditis (HT) with the HLA gene complex, support a role for specific disease-related genes in the development of autoimmune thyroid disease (AITD). The combination of HLA and immunoglobulin heavy chain allotypes (Gm) has previously been reported to be predictive of AITD in multiply affected Japanese families. We have investigated the immunogenetics of AITD in families in the United States. Twenty-seven pedigrees including 15 with GD, 8 with HT, and 4 with both HT and GD were immunogenetically typed and analyzed for population and within family disease associations. The majority of families (63%) were multiplex for AITD. HLA-DR3 was increased in affected family members with GD and HLA-DR5 was increased in affected family members with HT. Formal linkage analysis was applied to test for coinheritance of disease with the HLA locus within families. The LIPED computer program was used to calculate the probability of linkage in terms of the lod score. Evidence from linkage analysis was consistently against linkage of either GD or HT to the HLA region under various penetrances and different modes of inheritance. The combination of HLA and Gm was not found to be predictive of disease in 7 selected multiplex families with multigenerational instances of AITD. T cell function was also examined in 3 pairs of siblings genetically identical for HLA and Gm but discordant for disease expression. We found no evidence of a global T cell defect in the small number of patients examined. We conclude that whereas there is an association of AITD with the HLA region, our linkage analysis demonstrates that alleles of the HLA region are not cosegregating with either GD or HT within these families. Thus, whereas HLA may increase susceptibility to AITD, as shown by the existence of an HLA association, the major genetic influence on the inheritance of AITD must be at another locus.     

Association of cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene polymorphism and non-genetic factors with Graves' ophthalmopathy in European and Japanese populations

OBJECTIVE: The development and severity of Graves' ophthalmopathy (GO) may result from a complex interplay of genetic and environmental factors. The aim of this study was to investigate the association of cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene polymorphism and non-genetic factors (age, sex, cigarette smoking) with GO in two different populations, Polish-Caucasians and Japanese. DESIGN: We investigated the distribution of CTLA-4 A49G polymorphism in 264 Caucasian patients with Graves' disease (GD), of which 95 had clinically evident GO (NOSPECS class >or=3) and 319 Japanese patients with GD, of which 99 had ophthalmopathy. The control groups consisted of healthy Polish adults (n=194), Polish centenarians (n=51) and Japanese adults (n=112). RESULTS: Allele G and G/G genotype were significantly increased in Caucasian patients with GD (48% and 25% respectively) and in Japanese patients with GD (69% and 47% respectively) compared with control groups. There were no significant differences in the G allele and G/G genotype frequencies in GO patients compared with GD patients without ophthalmopathy. Multiple logistic regression analysis demonstrated that cigarette smoking (P=0.03, odds ratio (OR)=1.7) and age of onset of GD over 42 Years (P=0.08; OR=1.6) were contributing factors associated with susceptibility to GO in Polish patients. In Japanese patients, a younger age of onset of GD had an effect on the development of GO (P=0.02, OR=1.8). CONCLUSIONS: (i) Allele G and G/G genotype confer genetic susceptibility to GD; (ii) CTLA-4 A49G polymorphism is not associated with the development of GO; (iii) different non-genetic factors may contribute to GO in different populations.     

Interleukin-12B gene polymorphism does not confer susceptibility to Graves' ophthalmopathy in Japanese population

Graves' disease (GD) is an autoimmune disorder with genetic predisposition and frequently associated with Graves' ophthalmopathy (GO). Interleukin 12 (IL-12) is an important mediator of inflammatory immune responses and is expressed in the thyroid and orbit. IL-12B gene, which encodes the p40 subunit of IL-12, is located at chromosome 5q31-33. The aim of the present study was to investigate whether IL-12B gene polymorphism is associated with the development of GD or GO. IL-12B gene polymorphism was studied in Japanese GD patients (n = 329) and healthy control subjects without anti-thyroid autoantibodies or a family history of autoimmune disorders (n = 226). The A/C polymorphism at position 1188 of the 3' untranslated region (3'UTR) of the IL-12B gene was analyzed using the polymerase chain reaction--restriction fragment length polymorphism method. There was no difference in allele or genotype frequency of the IL-12B gene polymorphism (1188A/C) between GD patients and control subjects. There was no association of the IL-12B gene polymorphism with ophthalmopathy, severity of hyperthyroidism or serum IgE levels. There was no association of the IL-12B gene polymorphism with serum IL-12 levels, which were significantly elevated in hyperthyroid phase of GD. In conclusion, IL-12B gene 1188A/C polymorphism is not associated with GD or GO susceptibility in Japanese.     

Lack of association of interleukin-18 gene polymorphisms with susceptibility of Japanese populations to Graves' disease or Graves' ophthalmopathy.

OBJECTIVE: To investigate whether polymorphisms of interleukin (IL)-18 gene confer susceptibility to Graves' disease (GD) and Graves' ophthalmopathy (GO). DESIGN: We performed a case control study on polymorphisms of IL-18 gene in Japanese patients with GD (n = 435), and healthy control subjects without antithyroid autoantibodies or family history of autoimmune disorders (n = 255). The C-4675G, C-607A, and G-137C polymorphisms in the promoter region and A105C (exon 5) polymorphism were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using restriction enzymes, sequence-specific PCR, and PCR-direct sequencing methods. RESULTS: None of the polymorphisms in the IL-18 gene were associated with development of Graves' disease. The CC genotype and C allele frequencies of IL-18 gene G-137C polymorphism tended to be greater in patients with ophthalmopathy than in patients without evident ophthalmopathy. However, the differences were not statistically significant. Although there were three major haplotypes, none of the haplotypes were statistically associated with susceptibility to GD or ophthalmopathy. CONCLUSIONS: These results suggest that IL-18 gene polymorphisms are not major genetic factors for susceptibility to GD in a Japanese population. Further studies with adequate sized data set in the subset analyses for GO are needed.     

More on smoking habits and Graves' ophthalmopathy

Since a relationship between cigarette smoking and the occurrence of Graves' ophthalmopathy has been recently postulated, we reviewed the smoking habits of 1730 women, including subjects without thyroid disease, with nontoxic goiter (NTG), toxic nodular goiter or toxic adenoma (TNG), Hashimoto's thyroiditis (HT), Graves' disease without ophthalmopathy (GD) or with ophthalmopathy (GO). The prevalence of smokers in NTG, TNG and HT was about 30%, not different from that of controls. Smokers were 47.9% in GD and 64.2% in GO groups. The latter figures were highly different from those of the other groups and also from each other. The percentage of heavy smokers was higher in patients with more severe ophthalmopathy. No clear explanation for this phenomenon can be offered. The absence of a high prevalence of smokers among patients with non-toxic goiter, nonautoimmune hyperthyroidism and Hashimoto's thyroiditis, limits the impact that smoking might have had in the pathogenesis of goiter, hyperthyroidism and autoimmune phenomena of GD and GO.     

The influence of human leucocyte antigen (HLA) genes on autoimmune thyroid disease (AITD): results of studies in HLA-DR3 positive AITD families

OBJECTIVE: Population-based, case-control studies have consistently shown association of Graves' disease (GD) with human leucocyte antigen (HLA)-DR3 in Caucasian populations. HLA association studies in Hashimoto's thyroiditis (HT) have also suggested an association with DR3, as well as with other HLA alleles. In contrast, HLA linkage studies in autoimmune thyroid disease (AITD) have been largely negative. The aim of the present study was to investigate the role of HLA in AITD and to explain the observed associations, but lack of linkage, by examining only AITD families with the associated allele, DR3. PATIENTS: We studied 99 probands (60 with GD and 39 with HT) from 99 multiplex, multigenerational Caucasian AITD families, and 135 age- and sex-matched Caucasian controls in association studies. In addition, a dataset of 34 Caucasian AITD families (out of the 99 families) with HLA-DR3 positive probands were analysed in linkage studies. DESIGN: HLA typing was performed using the technique of group-specific polymerase chain reaction-amplification with restriction enzyme digestion. Whole genome screening was performed using the ABI microsatellite panels. For fine mapping of the HLA region, we used the following markers: D6S276, D6S464, D6S439, D6S273, tumour necrosis factor alpha and D6S1610. LOD scores were calculated using the LIPED and GeneHunter programs. RESULTS: Case-control association analyses using the probands from our 99 Caucasian families showed an association of GD with DRB1*03 [P = 0.00032, relative risk (RR) = 3.4]. Linkage analysis for the HLA region in the 34 DR3 positive AITD families showed negative LOD scores throughout the region. The two-point LOD score at marker D6S273 (the closest to HLA-DRB1) was -3.0, and the multipoint LOD score was -7.6, demonstrating strong evidence against linkage to the HLA region in the subset of DR3 positive families. Whole genome screening in the subset of 34 DR3 positive families revealed one locus showing evidence for linkage to AITD: D3S1580 on chromosome 3q27 with a maximum two-point LOD score of 2.1. CONCLUSIONS: The HLA locus did not cosegregate with disease in DR3 positive families, suggesting that HLA genes are not major genes for AITD expression even within DR3 positive families; Hence, although HLA-DR3 was associated with GD in the probands, it was most likely a modulating gene and not causative; and, as the DR3 positive families showed evidence for linkage with D3S1580, it may imply that the DR3 gene modulated the effect of a susceptibility gene within the D3S1580 locus.     

Analysis of immune regulatory genes in familial and sporadic Graves' disease

Graves' disease (GD) is seen in apparently sporadic and familial forms. At least two immune regulatory genes are associated with GD, human leukocyte antigen (HLA) and cytotoxic T lymphocyte antigen-4 (CTLA-4). The aim of our study was to examine the contributions of HLA and CTLA-4 to the familial clustering of GD by analyzing them for association with familial and sporadic GD. We analyzed 160 Caucasian GD patients (69 familial and 91 sporadic), and 150 matched controls. Analysis of all GD patients demonstrated significant associations between GD and HLA-DR3 [P = 9.0 x 10(-7); relative risk (RR) = 3.8] and two CTLA-4 single nucleotide polymorphisms (SNPs), A/G(49) SNP (P = 0.03; RR = 1.5), and CT60 SNP (P = 0.03; RR = 1.4). Moreover, there was evidence for joint susceptibility to risk between HLA-DR3 and CTLA-4, giving a combined RR of 5.9. Subset analysis demonstrated no significant difference between the frequencies of HLA-DR3 and the susceptibility alleles of CTLA-4 A/G(49) and CT60 SNPs in the familial and sporadic GD subsets (P > 0.05). These results suggested that HLA-DR3 and CTLA-4 conferred a general increased risk for GD in both the sporadic and familial forms, and that the risk conferred by them was additive. However, HLA-DR3 and CTLA-4 did not have a stronger effect in the familial GD patients, suggesting that additional genes must contribute to the aggregation of GD within families.     

甲状腺刺激抗体与Graves眼病临床特点的关系

比较分析32例初诊的Graves眼病（GO）患者和27例无眼病Graves病（GD）患者甲状腺刺激抗体（TSAb）与临床特点的关系；并且分析影响糖皮质激素冲击治疗GO预后的因素，发现GO组TSAb水平明显高于GD组，且对预后有显著影响，提示TSAb可能是TSH受体抗体中与眼病损伤更为密切的抗体成分，可作为GO的预测指标。     

Usefulness of soluble ICAM-1 measurements for the evaluation of the disease activity and efficiency of therapy in patients with infiltrative Graves' ophthalmopathy

The authors studied serum levels of soluble intercellular adhesion molecule-1 (ICAM-1) in patients with progressive Graves' ophthalmopathy (GO), stable GO, hyperthyroid Graves' disease (GD) without GO and in healthy controls. The highest serum concentrations of sICAM-1 were observed in patients with progressive GO. In patients with stable GO and GD mean serum levels of sICAM-1 were elevated to a lesser degree. Mean serum concentrations of sICAM-1 decreased significantly during treatment of patients with the progressive GO parallel to the improvement of the eye changes. In patients with hyperthyroid GD serum levels of sICAM-1 decreased significantly after they had become euthyroid. Mean sICAM-1 level in the euthyroid GD was markedly decreased in comparison to the group of patients with progressive GO and slightly elevated when compared to stable GO. In conclusion, serum levels of sICAM-1 seems to be a good parameter of disease activity in progressive infiltrative GO. The decrease in sICAM-1 concentrations in patients with the progressive GO closely corresponds to the improvement of the clinical picture of the progressive GO.     

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.     

The combination of absent thyroid peroxidase antibodies and high thyroid-stimulating immunoglobulin levels in Graves' disease identifies a group at markedly increased risk of ophthalmopathy.

Among Graves' Disease (GD) patients, we have observed an unexpectedly high prevalence of antithyroperoxidase antibody (TPOAb) and antithyroglobulin antibody (TgAb) negativity in those with severe ophthalmopathy. To study the possible role of thyroid autoantibodies in the pathogenesis of Graves' ophthalmopathy (GO), TPOAb, TgAb, thyroid-stimulating immunoglobulin (TSI), and thyrotropin-binding inhibitory immunoglobulin (TBII) levels were measured, and the presence or absence of GO was assessed by a single observer in 100 consecutive patients with newly diagnosed, untreated GD who were nonsmokers. Ophthalmopathy was present in 43 patients. TSI levels (p = 0.001), and the prevalence of TPOAb-negativity (p = 0.002) were significantly higher in patients with ophthalmopathy compared to those without. Logistic regression analysis showed that TSI levels (p = 0.005) and the absence of TPOAb (p = 0.0025) were independent predictors of GO. No correlation between TBII or TgAb and eye disease was found. The prevalence of GO increased with each quartile of TSI levels. The prevalence was 20%, 36%, 52%, and 64% in the first, second, third and fourth quartiles of TSI, respectively. The odds ratio of GO (with 95% confidence intervals) when TSI levels were above the median level (1640%) was 3.6 (1.5-8.0), when TPOAb was negative it was 5.0 (1.7-14.4), and with both risk factors it was 36.6 (4.3-313.5). The prevalence of ophthalmopathy in this last group was 92.9%. The combination of negative TPOAb and high TSI levels appears to be associated with a markedly increased risk of clinically evident ophthalmopathy.     

Correlation of HLA types and clinical findings in Japanese patients with hyperthyroid Graves'' disease: evidence indicating the existence of four subpopulations

OBJECTIVES: To re-evaluate the associations of HLA types with Japanese patients having hyperthyroid Graves' disease, HLA types and clinical findings were correlated. DESIGN: Four independent clinical findings (ophthalmopathy, family history, age at onset and size of goitre) and two autoantibody titres, thyrotrophin binding inhibitor immunoglobulin (TBII) and anti-thyroid microsmall antibody (anti-M), were analysed. PATIENTS: Eighty-eight Japanese patients with hyperthyroid Graves' disease and 186 control subjects were assessed. MEASUREMENT: Serological HLA typing was performed on 73 antigens in HLA-A, -B, -C, -DR and -DQ loci. HLA-D and -DP (29 antigens) were determined by the restricted fragment length polymorphism (RFLP) methods. TBII and anti-M were measured by commercially available kits. RESULTS: Patients with potent antibody titres had HLA antigens commonly seen among all the patients with Graves' disease. Interestingly, however, HLA-B35 and -Cw11 were found to relate with negative and/or weak TBII, and HLA-B7 and absence of HLA-Aw19 with negative anti-M. Significant associations were observed between HLA-DRw8 and large goitre and absence of ophthalmopathy, and between HLA-DQw4 and a negative family history of diffuse goitre (corrected P less than 0.05). Several other antigens were also found to be significant. Among these antigens, four pairs of MHC classes I and II were found to relate to the clinical findings independently. HLA-DQw4 and negative -A31 pair was closely related to ophthalmopathy, negative family history and late onset of disease. The HLA-B5 and -Dw12 pair was associated with ophthalmopathy, positive family history and early onset of disease. The HLA-A11 and negative -DPw2 pair was associated with ophthalmopathy, negative family history and early onset of disease. The HLA-Bw46 and -DRw8 pair did not increase in frequency above that seen with HLA-DRw8 alone. These four antigen groups (HLA-DRw8, HLA-DQw4 and negative-A31, HLA-B5 and -Dw12, and HLA-A11 and negative -DPw2) were observed in the majority (68%) of patients with Graves' disease and at a significantly higher incidence than in the control group (P less than 0.05). CONCLUSION: There are four subpopulations of Japanese patients with hyperthyroid Graves' disease. This is one of the reasons why the association of HLA types in Japanese patients is rather weak when they are studied as one group.     

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.     

Development of Graves' disease in a patient under immunosuppressive therapy after liver transplantation

Susceptibility to Graves' disease (GD) is determined by multiple environmental and genetic factors, which are not fully understood. Because of the autoimmune etiology of the disease, recent reports describing the development of GD during long-term immunosuppressive treatment seem quite surprising. We report a second case of GD in a 17-yr old patient, treated with cyclosporin A and prednisone, after liver transplantation. The development of GD despite adequate immunosuppressive therapy may suggest that this patient had a genetic predisposition to autoimmunity and severe immunoregulatory defects. We analyzed the HLA-DRB1 alleles and cytotoxic T lymphocyte associated antigen-4 (CTLA-4) gene polymorphism (A/G) at position 49 in exon 1. The patient had the HLA-DRB1*03 allele which is known to confer susceptibility to GD. Further studies are necessary to identify genes that may predispose patients specifically to GD during immunosuppressive therapies.     

DIFFERENTIATION OF AUTOIMMUNE OPHTHALMOPATHY FROM GRAVES''HYPERTHYROIDISM BY ANALYSIS OF GENETIC MARKERS

Graves' hyperthyroidism and dysthyroid eye disease are closely related autoimmune conditions. Whether the eye disease is an integral part of Graves' disease or a separate entity is controversial. To investigate this we have examined the genetic associations of ophthalmopathy and hyperthyroidism, and compared their phenotype and gene frequencies with a control normal population. HLA-A, B, and DR antigens were typed in 67 patients with dysthyroid eye disease (GO), 60 hyperthyroid patients without significant eye disease (HT) and 500 normal subjects. Patients were also typed for a variety of other genetic markers: blood group systems (10), serum proteins (6) and red cell enzyme systems (10). Increased frequency of B8 and DR3 in Graves' disease was confirmed; B17 occurred less frequently and appears to be protective. HLA antigen frequencies for GO did not differ from HT. The MNS blood group showed a significant association with Graves' disease, the HT patients having a deficit of the s gene compared with controls. The most interesting finding was an increased frequency of blood group P in GO patients compared with either HT or controls. Significant differences were not seen with any of the other HLA antigens, blood groups, protein or enzyme markers considered individually. Multivariate analysis applied first to the HLA and then to the non-HLA systems indicated clear separation of the two patient groups. Although Graves' eye disease shares the same HLA associations as hyperthyroidism, it differs in the increased frequency of P blood group, suggesting that additional genetic factors may determine which patients with Graves' disease develop ophthalmopathy.     

Susceptibility genes in Graves’ ophthalmopathy: searching for a needle in a haystack?

The variety of clinical presentations of eye changes in patients with Graves' disease suggests that complex interactions between genetic, environmental, endogenous and local factors influence the development/severity of Graves' ophthalmopathy (GO). At present, the role of genetic factors in the development of GO remains unknown. Based on small case-control association studies with candidate genes, several susceptibility loci in GO have been proposed. These are human leucocyte antigen (HLA, 6p21.3), cytotoxic T-lymphocyte antigen-4 (CTLA-4, 2q33), tumour necrosis factor (TNF, 6p21.3), interferon-gamma (IFN-gamma, 12q14), intercellular adhesion molecule-1 (ICAM-1, 19p13), and thyroid stimulating hormone receptor gene (TSH-R, 14q31). Unfortunately, these results were either not confirmed or require replication in larger studies. There are many reasons for the lack of reproducibility of association studies in GO, including poor characterization of the studied groups and small sample sizes, which may result in both false positive and negative results. Thus, the genetic background of GO remains to be elucidated in future research. However, the possibility that GO may be a genetically heterogeneous disorder, or that the development of GO may be predominantly influenced by environmental factors such as cigarette smoking, can not be disregarded.     

Patients with severe Graves' ophthalmopathy have a higher risk of relapsing hyperthyroidism and are unlikely to remain in remission

OBJECTIVE: To evaluate the relationship between severity of Graves' ophthalmopathy (GO) and relapse/remission rate of associated thyroid disease. PATIENTS AND METHODS: One hundred and fifty-eight patients with Graves' disease (GD) were seen within the first 6-12 months after the onset of GO and were followed for at least 18 months. During treatment, GO was classified as mild (n = 65) or severe course (n = 93) by severity and activity scores. All patients received standard anti-thyroid drug (ATD) treatment for 1 year, and in cases of relapse another cycle of ATD, thyroidectomy or radioiodine therapy. RESULTS: Following ATD treatment, 27 patients (42%) with a mild course of GO went into thyroid disease remission, while only seven (8%) patients with a severe course of GO achieved remission (P < 0.0001). Eventually, 32 patients (49%) with a mild course needed definitive thyroid therapy and the remaining 9% preferred another cycle of ATD. However, among patients with a severe GO course, 84% needed definitive therapy (P < 0.0001) and 8% opted for another course of ATD treatment. The probability of relapse could also be predicted by TBII levels 12 months after initiation of ATD therapy, as 96.8% of patients with TBII levels above 7.5 IU/l relapsed (odds ratio 24.3). CONCLUSION: Patients with severe GO and high TBII are unlikely to go into remission. This allows early decision-making regarding definitive treatment of the thyroid in GD patients with severe GO or very high TBII levels.     

Genetic developments in autoimmune thyroid disease: an evolutionary process

The identification of genes placing individuals at an increased risk for the development of autoimmune thyroid disease (AITD) has been a slow process. However, over the last 20 years or so real progress has been made with the mapping of novel loci, via a number of different approaches. First, through the use of traditional immunological methods, Human Leucocyte Antigen (HLA)/Major Histocompatibility Complex (MHC) was the first gene region to be associated with AITD and consistent replications have been reported. Second, the CTLA-4 gene region on 2q33 was the first non-MHC replicated locus to be primarily identified using the candidate gene method. Third, family-based linkage studies led to the mapping of a new type 1 diabetes locus, the PTPN22 gene, which has subsequently been independently replicated as a susceptibility gene for Graves' disease (GD). Fourth, despite many unsuccessful attempts at implicating the TSHR gene as a susceptibility locus for GD, a recent approach of 'tagging' all the common variation within the gene has led to its identification as the first GD specific locus. Moreover, the use of tag single nucleotide polymorphisms (SNPs) has also been used to implicate the recently identified type 1 diabetes locus, CD25 as a susceptibility gene for GD. Finally, large scale, ongoing genome-wide association studies in multiple autoimmune diseases (AID) states, including AITD seem likely to lead to the identification of additional MHC and non-MHC susceptibility loci.     

CTLA-4 and not CD28 is a susceptibility gene for thyroid autoantibody production

One of the hallmarks of the human autoimmune thyroid diseases (AITDs) is the production of high titers of autoantibodies against thyroglobulin and thyroid peroxidase that often precedes the development of clinical disease. A high percentage of family members of patients with AITDs have significant titers of thyroid antibodies (TAbs), suggesting a genetic predisposition for their development, and segregation analyses have favored a dominant mode of inheritance. The aim of the present study was to identify the susceptibility genes for TAb production. We completed a genome-wide scan in 56 multiplex families (323 individuals) in which all family members with AITDs and/or detectable TAbs were considered affected. The highest 2-point logarithm of odds (LOD) score of 3.6 was obtained for marker D2S325 on chromosome 2q33 at 210.9 centimorgans. This locus showed no evidence for linkage to Graves' disease or Hashimoto's thyroiditis (2-point LOD scores, 0.42 for Graves' disease and -0.60 for Hashimoto's thyroiditis), demonstrating that the gene in this region conferred susceptibility to TAbs, but that clinical disease development required additional genetic and/or environmental factors. We then fine-mapped the region linked with TAbs using 11 densely spaced microsatellite markers. Multipoint linkage analysis using these markers showed a maximum LOD score of 4.2 obtained for marker D2S155 at 209.8 centimorgans (with heterogeneity, alpha = 0.41). As the linked region contained the CTLA-4 and CD28 genes, we then tested whether they were the susceptibility genes for TAbs on chromosome 2q33. The CD28 gene was sequenced in 15 individuals, and a new C/T single nucleotide polymorphism (SNP) was identified in intron 3. Analysis of this SNP revealed no association with TAbs in the probands of the linked families (families that were linked with D2S155) compared with controls. The CTLA-4 gene was analyzed using the known A/G(49) SNP, and the results showed a significantly increased frequency of the G allele in the probands of the linked families compared with the probands of the unlinked families or with controls (P = 0.02). We concluded that 1) a major gene for thyroid autoantibody production was located on chromosome 2q33; 2) the TAb gene on chromosome 2q33 was most likely the CTLA-4 gene and not the CD28 gene; and 3) CTLA-4 contributed to the genetic susceptibility to TAb production, but there was no evidence that it contributed specifically to Graves' or Hashimoto's diseases.     

CTLA-4 AT-repeat polymorphism reduces the inhibitory function of CTLA-4 in Graves' disease.

Graves' disease (GD) is thought to be an autoimmune disease with a strong genetic component. Candidate genes include human leukocyte antigen (HLA) class II genes and CTLA-4. The CTLA-4 gene has a variable length AT-repeat polymorphism in the 3'-untranslated region. We previously found that the AT-repeat of 104 bp or longer was associated with GD. In this study, we categorized patients with GD and normal controls (NC) by genotyping the CTLA-4 AT-repeat and investigated the function of CTLA-4. Peripheral blood mononuclear cells (PBMC) and DNA were prepared from adult Caucasians (NC = 34, GD = 37). Genotypes of the AT-repeat polymorphism were divided into three groups according to their alleles. We related the CTLA-4 polymorphism in each genotype to augmentation of T-cell proliferation induced by a soluble anti-CTLA-4 antibody during incubation with irradiated Epstein-Barr virus (EBV)-transformed B cells. Proliferation of T cells from subjects with the 86/86 bp (shorter) allele was less than T cells from patients with longer alleles. The length of the AT-repeat allele correlated inversely with augmentation of proliferation after CTLA-4 blockade in subjects with GD. The CTLA-4 AT-repeat polymorphism affects the inhibitory function of CTLA-4. The long AT-repeat allele is associated with reduced control of T-cell proliferation and thus contributes to the pathogenesis of GD.