DQA2 U allele: a genetic marker for relapse of Graves' disease

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

Introduction

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

Methods

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

Results

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

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.

HLA DQA1*0501 and DRB1*0301 antigens do not independently convey susceptibility to Graves' disease

Genes of, or closely associated to, the HLA complex are assumed to contribute to the genetic predisposition of Graves' disease. The aim of this study was to investigate the presence of the HLA DQA1*0501 and DRB1*0301 antigens in Greek patients with Graves' disease. In addition, we tried to establish if there is any association between these antigens and any of the clinical manifestations of the disease. We examined 117 patients with Graves' disease and 104 healthy controls. DNA was extracted from peripheral lymphocytes and the HLA DQA1*0501 and DRB1*0301 genomic regions were amplified by PCR and characterized by hybridization with sequence specific oligonucleotides (SSO). Two of the patients had a positive family history for Graves' disease and 46 had clinical thyroid eye disease (TED). The frequencies of both DQA1*0501 and DRB1*0301 antigens were significantly increased in patients compared to controls (relative risk [RR] 4.2 and 4.5 for each antigen respectively). Neither of these two antigens was an independent risk factor for Graves' disease. However, the combination of both these HLA antigens resulted in a striking increase in the RR for development of Graves' disease especially in females (RR/F=27, RR/M=8.4). No association was found between these antigens and positive family history or the presence of TED. These data suggest that HLA DQA1*0501 and DRB1*0301 antigens are not independent risk factors for the development of Graves' disease. On the contrary, the presence of both these alleles results in a significant increase in the RR for the development of Graves' disease in the Greek population, particularly in females.

Predictors of early remission of hyperthyroidism in children

Children with hyperthyroidism often require prolonged courses of antithyroid medication to achieve remission, and long-term compliance is problematic. To determine which clinical and laboratory features predict early remission, we reviewed the records of 191 patients less than 19 yr old with Graves' disease. We compared patients achieving remission within 2 yr (group 1, n = 27) with those who completed more than 2 yr of medical therapy but did not achieve a remission (group 2, n = 79). Patients who were in neither of the above categories (n = 85) were excluded from the statistical analysis. Variables that were measurable at the time of diagnosis, recorded in more than 50% of the study population and associated with early remission in the univariate analysis (P < or = 0.05), were entered into a stepwise multiple logistic regression analysis. Variables retaining a significant association with early remission (P < 0.05) were considered independent predictors of early remission. Patients achieving early remission were older (mean, 12.5 vs. 10.9 yr, P = 0.039) and had higher body mass indexes (BMI, 19.0 vs. 16.6, P = 0.002), higher BMI SD scores (-0.03 vs. -0.60, P = 0.004), lower heart rates (110 vs. 121, P = 0.023), smaller goiters (group 1: 60% with moderate/large goiter; group 2: 83%, P = 0.050), lower platelet counts (272 vs. 339 K/microL, P = 0.006), lower serum T4 and T3 concentrations at presentation (T4: 18.3 vs. 22.5 microg/dL, P = 0.015; T3: 439 vs. 613 ng/dL, P = 0.008), and were less likely to have a positive test for thyroid stimulating Igs (group 1: 50% vs. group 2: 93%, P = 0.008). Regression analysis identified BMI SD score and goiter size as independent predictors of early remission (P < 0.05). Eighty-six percent of patients with BMI SD score above -0.5 SD and minimal/small goiters achieved early remission, compared with 13% of those with BMI SD score below -0.5 SD and moderate/large goiters. We conclude that, of multiple clinical and laboratory variables associated with early remission, BMI SD score and goiter size are independent predictors. Algorithms employing these two variables can be used to facilitate counseling of patients and expedite therapeutic decisions.

Human lymphocyte antigens in Graves' disease: correlation with persistent course of disease

Graves' disease is a thyroid autoimmune disorder associated with specific human lymphocyte antigen (HLA) alleles, characterized by an unpredictable long-term course. To investigate possible relations between HLA phenotype and outcome of the disease, the authors typed for HLA antigens in 105 patients with Graves' disease with different course of disease. All patients were treated with antithyroid drugs for at least 12 months; 29 patients had stable remission 24 or more months after withdrawal of treatment; 76 patients had persistent disease--66 unremitting/relapsing hyperthyroidism, 10 stable hypothyroidism--36 or more months after onset of disease. The following findings emerged from this study: 1) HLA B8 and DR3 were increased significantly in Graves' patients versus 6,682 control subjects from the same geographic area (23.80% vs 12.01%, odds ratio [OR] 1.98, and 31.43% vs 18.00%, OR 1.75, respectively); the antigen combinations B8-DR3, B8-Cw7-DR3, and A1-B8-Cw7-DR3 were significantly more frequent in Graves' patients vs control subjects; in addition, these combinations were present exclusively in patients with persistent disease (B8-DR3 28.95%, OR 7.14, B8-Cw7-DR3 27.63%, OR 11.24, and A1-B8-Cw7-DR3 18.42%, OR 11.29). These data provide evidence that not only susceptibility to Graves' disease, but also persistent activity of the autoimmune process, producing either hyperthyroidism or stable hypothyroidism, is associated with specific HLA antigen phenotypes.

Molecular genetics of MHC class II alleles in Chinese patients with IgA nephropathy

We have studied the restriction fragment length polymorphism (RFLP) of the major histocompatibility complex (MHC) class II DQ and DR regions of 79 Chinese patients with IgA nephropathy (IgAN) and compared it with 104 normal Chinese controls. The DR and DQ alleles were confirmed by polymerase chain reaction using sequence specific primers. There was a significantly higher frequency of homozygous DQ beta 3b (DQ7) in patients with IgAN (16.4%) compared with controls (5.7%). Seventy-one IgAN patients had their renal biopsies graded according to histopathological severity: grades I, II or III. There was no statistical difference in the DR and DQ alleles among the three grades. Seventy-three patients were classified into group A with normal and stable renal function (serum creatinine < or = 150 mumol/liter) and group B with chronic renal failure (serum creatinine > 150 mumol/liter). There was a significant increase in frequency of DQA2 U (DX alpha U) allele in group B (66.9%) compared with group A (26.9%). Also, there was an increased frequency of DQ alpha 2 allele in the group A (40.4%) compared with group B (14.3%). Out of the 24 patients carrying the DQ alpha 2 allele, 17 were DQA2 U allele-negative and they all had normal renal function, suggesting that DQA2 U allele is associated with a poor prognostic factor in IgAN. The study shows that DQ alleles are probably the important genetic loci or are close markers for the disease susceptibility and prognostic index for IgAN in Chinese people.

HLA-DPB1 polymorphisms on the MHC-extended haplotypes of families of patients with Graves' disease: two distinct HLA-DR17 haplotypes

HLA-DPB1 polymorphisms were investigated in 217 members of 21 multiplex families of patients with Graves' disease, who had previously been haplotyped, using in vitro enzymatic DNA amplification and hybridization with sequence-specific oligonucleotide probes. Using the strategy of group-specific amplification, we were able to assign 19 DPB1 alleles with the use of 13 sequence specific oligonucleotide probes. No recombination was found between HLA-DPB1 and the HLA-DR/DQ complex in 243 informative meioses. HLA-DPB1*0401 was found to be the most common allele followed by DPB1*0101, *0201 and 0402 with allele frequencies of 0.4214, 0.1132, 0.1069 and 0.1006, respectively. Besides the strong linkage disequilibrium between HLA-DPB1*0101 allele and the HLA-B8, DR17/DQ2 haplotype; HLA-DPB1*0202 and *1101 alleles were also found to be significantly associated with HLA-B18 and DR7 with Pc < 0.001 and Pc < 0.009, respectively. HLA-DR17/DQ2 was found to be more commonly associated with HLA-DPB1*0101 on the Affected haplotypes (from family members affected with Graves' disease) while associated with DPB1*0401 on the Ab + ve haplotypes (deduced from thyroid autoantibody positive unaffected members). The differences in the frequency of this preferential association on the Affected and Ab + ve haplotypes was statistically significant (ch 2 = 10.18, df = 2, P < 0.007). Though it is rater unlikely that the HLA-DPBI polymorphism by itself could contribute a direct role towards the genetic susceptibility for the development of autoimmune thyroid disease, it could serve as a marker in identifying family members with the HLA-DR17/DQ2 haplotype who are more likely to develop Grave's disease or thyroid autoantibodies.

HLA-DPB1 polymorphisms in patients with hyperthyroid Graves' disease and early onset myasthenia gravis

Using the technique of in vitro enzymatic DNA amplification and dot blot hybridization with sequence-specific oligonucleotide (SSO) probes, a study of genetic polymorphism of HLA-DPB1 was performed in 83 unrelated patients with Graves' disease (GD), 48 patients with early onset myasthenia gravis (EOMG) and 100 normal British caucasoid subjects who were also tissue typed for HLA-A, B and DR antigens. HLA-DPB1*0401 was the commonest allele in both patient and control groups with gene frequencies of 0.380, 0.333 and 0.445 for GD, EOMG and controls, respectively. No significant independent association was found with any HLA-DPB1 allele. As expected, HLA-DR17 is significantly associated with Graves' disease (pc < 8 x 10(-3), RR = 2.9), while both HLA-B8 and DR17 are significantly associated with EOMG (pc < 2 x 10(-7), RR = 10.3 and pc < 0.02, RR = 3.4, respectively)] HLA-DR2 is also significantly increased in EOMG patients who were negative for HLA-DR17 (pc < 0.02, RR = 6.4). In addition, the co-occurrence of HLA-B8 with DPB1*0402 was significantly commoner in patients with GD (p < 0.021, RR = 6.2) and EOMG (p < 0.0007, RR = 10.8) than in controls, although the HLA-DPB1*0402 by itself showed no significant increase.

MHC-extended haplotypes in families of patients with Graves' disease

MHC-extended haplotypes were investigated in multiplex families of patients with hyperthyroid GD. Using a combination of both phenotypic (serology and protein electrophoresis) and genotypic (DNA-RFLP) markers, 159 MHC-extended haplotypes extending from HLA-A across the MHC class III (C2, Bf, C4A, and C4B) toward the HLA-DR/DQ complex were deduced from 217 (51 and 166 affected and unaffected) members of 21 families of patients with GD. Thyroid autoantibodies were measured and found positive in 27.1% of 166 clinically euthyroid unaffected members. Extended haplotypes were classified into four categories--affected (n = 40), Aff/Ab + ve (shared haplotype between affected and Ab + ve members, n = 31), Ab + ve (n = 29), and Ab - ve (n = 59)--based on the presence and absence of these haplotypes in 51 affected members with GD and 45 and 121 unaffected members who were respectively positive and negative for thyroid autoantibodies. Five recombinations were detected: three were found between HLA-A and B and two between HLA-B and the MHC class III. No recombination was found between or within the MHC class III and class II complex. Though the HLA-DR17 (DR beta 17(1) and DR beta 17(2)) allele was found to be significantly increased in both the affected and the Aff/Ab + ve when compared with the Ab - ve haplotypes (p < 0.042 and p < 0.018), the frequency of the HLA-B8, 2.7-kb SstI-4.5-kb TaqI/C2 Bf*S, 6.4-kb TaqI/C4A*Q0C4B*1, HLA-DR beta 17(1)/DQ alpha 2-DQ beta 2a extended haplotype was found to be significantly increased only in the affected haplotype (p < 0.05). These results suggest that while HLA-DR17 is a susceptibility allele shared between GD and individuals with positive thyroid autoantibodies, the HLA-B8, 2.7-kb SstI-4.5-kb TaqI/5'-3'C2 Bf*S, 6.4-kb TaqI/C4A*Q0B*1, DR beta 17(1)/DQ alpha 2-DQ beta 2a is a disease susceptibility-extended haplotype for Graves' disease.