Polymorphism in the transmembrane region of the major histocompatibility complex class I chain-related gene A: association of five GCT repetitions with Graves' disease in children

Genotype-phenotype correlations in Graves' disease

Graves' disease (GD) is a heterogeneous autoimmune disease affecting with varying degrees of severity the thyroid gland, orbital tissues and skin. The pathogenesis of GD involves a complex interplay between multiple genetic, environmental and endogenous factors. Although the genetic predisposition to GD is well established, the significance of genotype-phenotype correlations and the role of epigenetic modifications in the disease pathogenesis remains largely unknown. In this review, we provide an up-to-date overview of genotype-phenotype correlations and summarize possible clinical implications of genetic and epigenetic markers in GD patients. We will specifically discuss the association of genetic markers and epigenetic modifications with age of GD onset, severity of Graves' hyperthyroidism and the development of clinically evident Graves' orbitopathy.

Low MICA Gene Expression Confers an Increased Risk of Graves' Disease: A Mendelian Randomization Study

Background: Expression of natural killer group 2 member D (NKG2D) ligand (NKG2DL) plays a major role as a "danger signal" on stressed cells to promote removal of the latter by NKG2D-expressing cytotoxic lymphocytes. NKG2DL expression has been found in peripheral immune cells as well, such as in macrophages; however, the effect of this expression is yet to be determined. Methods: We determined instrumental variables (IVs; R² <0.01 in linkage disequilibrium), explaining the major variance in major histocompatibility complex class I chain-related protein A (MICA) and B (MICB) gene expression levels from the expression-quantitative trait locus (eQTL) of NKG2DLs based on the RNA-seq analysis of peripheral blood mononuclear cells (PBMCs) from 381 Japanese. Simultaneously, the target outcomes were filtered by PheWAS from 58 health risks, using a community-based cohort study composed of 44,739 Japanese residents. Finally, we estimated the causal effect of gene expression levels on the outcomes using the Mendelian randomization approach. Results: We determined nine and four IVs, explaining 87.6% and 33.0% of MICA and MICB gene expression levels, respectively. In the association test, we identified 10 or 13 significant outcomes associated with the MICA or MICB eQTLs, respectively, as well as the causal effect of MICA expression on Graves' disease (GD) (p = 4.2 × 10^-3; odds ratio per 1 S.D. difference in the expression: 0.983 [confidence interval: 0.971-0.995]), using the weighted median estimator, without significant pleiotropy (p > 0.05), and the results were consistent across the sensitivity analyses. Conclusions: Our study provide novel evidence associating NKG2DL expression with GD, an autoimmune thyroiditis; direction of the effect indicated the immunoregulatory role of MICA expression in PBMCs, suggesting the importance of further functional assays in inflammatory diseases.

Genotype and phenotype predictors of relapse of graves' disease after antithyroid drug withdrawal

BACKGROUND

For patients with Graves' disease (GD), the primary goal of antithyroid drug therapy is to temporarily restore the patient to the euthyroid state and wait for a subsequent remission of the disease. This study sought to identify the predictive markers for the relapse of disease.

METHODS

To do this, we studied 262 GD patients with long enough follow-up after drug withdrawal to determine treatment outcome. The patients were divided into three groups by time of relapse: early relapse group (n = 91) had an early relapse within 9 months, late relapse group (n = 65) had a relapse between 10 and 36 months, and long-term remission group (n = 106) were either still in remission after at least 3 years or relapsed after 3 years of drug withdrawal. We assessed the treatment outcome of 23 SNPs of costimulatory genes, phenotype and smoking habits. We used permutation to obtain p values for each SNP as an adjustment for multiple testing. Cox proportional hazards models was performed to assess the strength of association between the treatment outcome and clinical and laboratory variables.

RESULTS

FOUR SNPS WERE SIGNIFICANTLY ASSOCIATED WITH DISEASE RELAPSE: rs231775 (OR 1.96, 95% CI 1.18-3.26) at CTLA-4 and rs745307 (OR 7.97, 95% CI 1.01-62.7), rs11569309 (OR 8.09, 95% CI 1.03-63.7), and rs3765457 (OR 2.60, 95% CI 1.08-6.28) at CD40. Combining risk alleles at CTLA-4 and CD40 improved the predictability of relapse. Using 3 years as the cutoff point for multivariate analysis, we found several independent predictors of disease relapse: number of risk alleles (HR 1.30, 95% CI 1.09-1.56), a large goiter size at the end of the treatment (HR 1.30, 95% CI 1.05-1.61), persistent TSH-binding inhibitory Ig (HR 1.64, 95% CI 1.15-2.35), and smoking habit (HR 1.60, 95% CI 1.05-2.42).

CONCLUSION

Genetic polymorphism of costimulatory genes, smoking status, persistent goiter, and TSH-binding inhibitory Ig predict disease relapse.

Association of MICA Alleles with Autoimmune Thyroid Disease in Korean Children

Background. Major histocompatibility complex class I chain-related gene A (MICA) is a ligand for the activating NKG2D receptor expressed on natural killer (NK) cells. We aimed to assess the association of MICA polymorphism with autoimmune thyroid disease (AITD) in Korean children. Methods. Eighty-one patients with AITD were recruited. We analyzed MICA polymorphisms by PCR-SSP and compared the results with those of 70 healthy controls. Results. In AITD, the allele frequencies of MICA∗010 (OR = 2.21; 95% CI, 1.30-3.76, P < 0.003, P(c) < 0.042) were higher than those of controls. Patients who did not have thyroid-associated ophthalmopathy showed higher frequencies of MICA∗010 (OR = 2.99; 95% CI, 1.47-6.08, P < 0.003, P(c) < 0.042) and lower frequencies of MICA∗008 (OR = 0.08; 95% CI, 0.01-0.62, P < 0.001, P(c) < 0.014) compared to those of controls. HLA-B∗46, which shows the strongest association with AITD compared with other HLA alleles, showed the strongest linkage disequilibrium with MICA∗010. Analyses of the associations between MICA∗010 and HLA-B∗46 with AITD suggest an association of the MICA allele with AITD. Conclusions. Our results suggest that innate immunity might contribute to the pathogenesis of AITD.

Divergent frequencies of IGF-I receptor-expressing blood lymphocytes in monozygotic twin pairs discordant for Graves' disease: evidence for a phenotypic signature ascribable to nongenetic factors

CONTEXT

Graves' disease (GD) is an autoimmune process of the thyroid and orbital connective tissues. The fraction of T and B cells expressing IGF-I receptor (IGF-IR) is increased in GD. It is a potentially important autoantigen in GD. Susceptibility to GD arises from both genetic and acquired factors.

OBJECTIVE

The aim of the study was to determine whether the increased frequency of IGF-IR-expressing T and B cells in GD results from genetic or nongenetic factors.

DESIGN/SETTING/PARTICIPANTS

Display of IGF-IR was assessed on blood lymphocytes from 18 pairs of monozygotic twins in the Danish Twin Registry, including seven discordant pairs, four pairs concordant for GD, and seven healthy pairs.

MAIN OUTCOME MEASURES

Subjects underwent physical examination and laboratory analysis. Surface display of IGF-IR on T and B cells was analyzed by flow cytometry.

RESULTS

Twins with GD display increased IGF-IR-expressing CD3(+) T cells and T cell subsets including total CD4(+), CD4(+) naive, CD4(+) memory, and CD8(+) cells (P < 0.0001, P = 0.0001, P = 0.0003, P = 0.01, and P = 0.02, respectively) compared to healthy twins. The frequency of IGF-IR-expressing B cells from affected twins was increased relative to healthy controls (P = 0.009). In pairs discordant for GD, affected twins exhibited increased frequency of IGF-IR(+) CD3(+), CD4(+), and CD4(+) naive T cells (P < 0.05, P = 0.03, and P = 0.03, respectively) compared to their healthy twin.

CONCLUSION

Our findings suggest that more frequent IGF-IR(+) T cells in GD cannot be attributed to genetic determinants. Rather, this skew appears to be acquired. These results underscore the potential role of nongenetic, acquired factors in genetically susceptible individuals.

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.

Immunoregulatory and susceptibility genes in thyroid and polyglandular autoimmunity

The etiology of autoimmune thyroid diseases (AITD) is based on genetic and nongenetic factors. Genome-wide screening and linkage analyses have identified several chromosomal regions that are linked to AITD. These are HT-1 (on chromosome 13q33) and HT-2 (chromosome 12q22) for Hashimoto's thyroiditis (HT), and GD-1 (chromosome 14q31), GD-2 (chromosome 20q11.2), and GD-3 (chromosome Xq21) for Graves' disease (GD). Several genes have been proposed as susceptibility or immunoregulatory genes. Most promising genes are those of the major histocompatibility complex (MHC) complex (chromosome 6), the cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene (chromosome 2), the CD40 (chromosome 20), the thyroglobulin gene (chromosome 8), and the autoimmune regulator gene (chromosome 21). This review summarizes evidence for pathogenetic involvement of several of these genes in various forms of autoimmune thyropathies. Most genetic data refer to GD, whereas less data are available for HT and thyroid-associated ophthalmopathy. Scarce data refer to AITD within the autoimmune polyglandular syndromes I and II. The realization of family studies in large samples from different populations might provide further insight in the genetic contribution to AITD. Data are also needed on the interaction among susceptibility genes. Finally, additional functional studies are warranted to clarify the possible role of allelic variants in the underlying pathogenic mechanisms of AITD.