Major histocompatibility class II genes polymorphism in insulin dependent diabetes mellitus with or without associated thyroid autoimmunity

Major histocompatibility complex class II (DRB1*, DQA1*, and DQB1*) and DRB1*04 subtypes' associations of Hashimoto's thyroiditis in a Greek population

Hashimoto's thyroiditis (HT) is an autoimmune disease resulting from complex interactions between genetic and environmental factors. The disease is associated with certain human leukocyte antigen (HLA) class II alleles in various populations. We aimed to determine in this study, for the first time in a Greek population, the association of HLA-DRB1*, -DQA1*, and -DQB1* alleles with HT. HLA-DRB1*, -DQA1*, and -DQB1* alleles' and -DRB1*04 subtypes' distribution was evaluated in 125 patients with HT and in 500 healthy control individuals by using a DNA-based sequence-specific primer method. Chi(_)squared tests and Bonferroni correction method were applied in the statistical analysis of the data. Significantly higher frequency of DRB1*04 (24.8% vs 7.7%, P < 0.0001) was observed in HT patients, while HLA-DRB1*07 was significantly decreased (2.8% vs 7.9%, P < 0.05). HLA-DRB1*04 subtyping showed a significant increase of DRB1*0405 (21% vs 7.8%, P < 0.0001) in HT patients. Also significant high frequencies of DQB1*0201 (14.8% vs 8.2%, P < 0.001), DQB1*0302 (18.8% vs 7.0%, P < 0.0001), and DQA1*0301 (25.6% vs 7.8%, P < 0.0001) were recorded in the patient group. Conducting the first research of this kind in a Greek population, our study tries to provide an evaluation of the prevalence of HT relating to HLA-DRB1*0405, and we report a relative risk of 2.7 for HT in a Greek population.

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

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

Immunogenetics of Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) is an organ-specific T-cell mediated disease. It is a complex disease, with a strong genetic component. To date, significant progress has been made towards the identification and functional characterization of HT susceptibility genes. In this review, we will summarize the recent advances in our understanding of the genetic input to the pathogenesis of HT.

Analysis of HLA genes in families with autoimmune diabetes and thyroiditis

Type 1 diabetes (T1D) and autoimmune thyroid disease (AITD) are the most common autoimmune endocrine disorders. The similar pathogenesis of T1D and AITD and their tendency to occur together suggest that their etiology may involve common genetic factors. We hypothesized that the human leukocyte antigen (HLA) locus may contribute in part to the joint susceptibility to T1D and AITD. We therefore analyzed a data set of 40 multiplex families in which T1D and AITD clustered ("T1D-AITD families") for linkage and association with the HLA class II locus. We found evidence for linkage of the HLA region to T1D (maximum logarithm of odds score [MLS] = 7.3), to Hashimoto thyroiditis (HT) (MLS = 1.5), and to both (MLS = 3.8). Transmission disequilibrium test analysis revealed significant association of both T1D and AITD with HLA-DR3; however, only T1D was associated with HLA-DR4. We concluded that the finding of evidence for linkage of HLA with HT is in contrast to the strong evidence against linkage found in previous studies of AITD-only families; therefore, it is possible that the AITD phenotype seen in T1D families has a different genetic etiology than the AITD phenotype in AITD-only families; that HLA-DR3 was the major HLA allele contributing to the joint genetic susceptibility to T1D and AITD, whereas other alleles (e.g., DR4) are phenotype specific; and that because the logarithm of odds score for T1D + HT was lower than for T1D alone, additional non-HLA loci must contribute to the shared genetic susceptibility to T1D and AITD.

The etiology of autoimmune diabetes and thyroiditis: evidence for common genetic susceptibility

Type 1 diabetes (T1D) and the autoimmune thyroid diseases (AITD) are the most common autoimmune endocrine diseases. Both are organ-specific T-cell mediated diseases. Abundant epidemiological data support a strong genetic basis for both T1D and AITD. Furthermore, both diseases commonly occur in the same individuals and in the same families. Indeed, studies suggest that the etiology of T1D and AITD may involve common genetic factors. Two immune regulatory genes, HLA and CTLA-4 contribute to the susceptibility to both diseases. Additionally, two tissue-specific genes, the insulin VNTR in T1D and Thyroglobulin in AITD play a major role in their pathogenesis. Therefore, it is likely that both immune regulatory and target tissue genes contribute to these and other autoimmune diseases.

HLA-DQ polymorphisms modify the risk of thyroid autoimmunity in children with type 1 diabetes mellitus

OBJECTIVE

Type 1 diabetes mellitus (DM1) is frequently accompanied by thyroid autoimmunity (TAI). The aims of the present study were to estimate the prevalence of TAI and to determine the contribution of HLA-DQA1 and -DQB1 polymorphisms to TAI susceptibility among children with DM1. PATIENTS AND METLHODS: Screening for TAI was performed in 285 children with DM1 by measuring autoantibodies against thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg). HLA-DQA1 and -DQB1 were genotyped using PCR-SSP.

RESULTS

Repeated positivity of anti-TPO and/or anti-Tg was found in 45/285 children with DM1 (15.8%). The prevalence was significantly higher in girls than in boys (26.7% vs 6.7%; p<10(-5)). The HLA-DQB1*0302 allele conferred susceptibility to TAI in children with DM1 (OR 2.7, 95% CI 1.1-6.4), while the DQB1*05 alleles acted protectively (OR 0.2, CI 95% 0.08-0.7).

CONCLUSIONS

HLA-DQ polymorphisms significantly modify the risk of TAI in children with DM1.

Polymorphisms of HLA class II predispose children and adolescents with type 1 diabetes mellitus to autoimmune thyroid disease

To determine the prevalence of autoimmune thyroid disease (AITD) in children and adolescents with type 1 diabetes mellitus (DM), and assess whether the development of AITD is correlated with specific DQ-A and DQ-B loci of the HLA class II antigens, we analyzed thyroid function using anti-thyroid antibodies and HLA-DQ-A and -DQ-B polymorphisms in 69 patients with type 1 DM, in 75 normal healthy controls, and in 21 patients with AITD but without type 1 DM. Eighteen patients (26%) in the diabetic patients had AITD. In the diabetic patients, DQA1*0301 and DQB1*0302 occurred more frequently than in controls [DQA1*0301: OR = 1.939, 95% CI = 1.210-3.109 (P = 0.008, P(c) (corrected P) < 0.05); DQB1*0302: OR = 2.558, 95% CI = 1.354-4.832 (P = 0.005, P(c), > 0.05)]. Compared with controls, non-diabetic subjects with AITD showed higher frequency of DQA1*0301 (P(c), < 0.05) and DQB1*0601 (P(c) > 0.05), but these alleles were not contributing factors in the development of AITD in diabetic patients. In diabetic patients, DQB1*0201, known as susceptible allele of type 1 DM was not a contributing factor in the development of AITD in diabetic patients. Unlike DQB1*0201, DQB1*0401 was more frequently found in diabetic patients with AITD than in controls [OR = 4.053, 95% CI = 1.607-10.221 (P = 0.0017, P(c) < 0.05)] or than in non-diabetic AITD patients [OR = 15.769, 95% CI = 1.905-130.530(P = 0.002, P(c) < 0.05)]. In non-diabetic subjects, DQB1*0401 did not provide susceptibility for AITD. Our results suggest that HLA DQB1*0401 is a predisposing genetic marker for the development of AITD in patients with type 1 DM in Korea.

Viral clearance in hepatitis C (1b) infection: relationship with human leukocyte antigen class II in a homogeneous population

The aim of this study was to investigate the possibility of a significant relationship between human leukocyte antigen (HLA) class II and the clearance of hepatitis C virus (HCV). The study group consisted of 156 Irish women who iatrogenically received HCV 1b-contaminated Anti-D immunoglobulin between May 1977 and November 1978. Thus, the study population was homogeneous in terms of gender, source of infection, and ethnicity. On Screening in 1994, all individuals were anti-HCV antibody positive by recombinant immunoblot assay, while 46% (n = 72) of the group were HCV-positive by reverse transcriptase-polymerase chain reaction (RT-PCR). HLA DRB1 and DQB1 status was molecularly defined by high resolution reverse line probe hybridization methodology. Clearance of HCV 1b was found to be associated with DRB1*01. However, this association was lost after Bonferroni correction for multiple comparisons. Extended haplotype analysis between specific DRB1 and DQB1 allelic combinations identified a significant reduction in the frequency of DQB1*0501 in the presence of DRB1*0701 in the persistently infected individuals in the study group (P <.05). No associations with either viral clearance or persistence were found at the DQB1 locus. Our results suggest that HLA DRB1*01 appears to contribute to the spontaneous resolution of a primary HCV infection in the Irish population. The presence of DRB1*0701 in the absence of DQB1*0501 possibly reflects an influence of this allele in persistence of HCV infection. Defined and homogeneous patient populations offer the best opportunity to illuminate previously disguised immunogenetic factors important in the clearance of HCV 1b.