Association of CTLA-4 gene A-G polymorphism (IDDM12 locus) with acute-onset and insulin-depleted IDDM as well as autoimmune thyroid disease (Graves' disease and Hashimoto's thyroiditis) in the Japanese population

Immune-related adverse effects of checkpoint immunotherapy and implications for the treatment of patients with cancer and autoimmune diseases

During the past decade, there has been a revolution in cancer therapeutics by the emergence of antibody-based immunotherapies that modulate immune responses against tumors. These therapies have offered treatment options to patients who are no longer responding to classic anti-cancer therapies. By blocking inhibitory signals mediated by surface receptors that are naturally upregulated during activation of antigen-presenting cells (APC) and T cells, predominantly PD-1 and its ligand PD-L1, as well as CTLA-4, such blocking agents have revolutionized cancer treatment. However, breaking these inhibitory signals cannot be selectively targeted to the tumor microenvironment (TME). Since the physiologic role of these inhibitory receptors, known as immune checkpoints (IC) is to maintain peripheral tolerance by preventing the activation of autoreactive immune cells, IC inhibitors (ICI) induce multiple types of immune-related adverse effects (irAEs). These irAEs, together with the natural properties of ICs as gatekeepers of self-tolerance, have precluded the use of ICI in patients with pre-existing autoimmune diseases (ADs). However, currently accumulating data indicates that ICI might be safely administered to such patients. In this review, we discuss mechanisms of well established and newly recognized irAEs and evolving knowledge from the application of ICI therapies in patients with cancer and pre-existing ADs.

CTLA-4: From mechanism to autoimmune therapy

CD28 and CTLA-4 are both important stimulatory receptors for the regulation of T cell activation. Because receptors share common ligands, B7.1 and B7.2, the expression and biological function of CTLA-4 is important for the negative regulation of T cell responses. Therefore, elimination of CTLA-4 can result in the breakdown of immune tolerance and the development of several diseases such as autoimmunity. Inhibitory signals of CTLA-4 suppress T cell responses and protect against autoimmune diseases in many ways. In this review, we summarize the structure, expression and signaling pathway of CTLA-4. We also highlight how CTLA-4 defends against potentially self-reactive T cells. Finally, we discuss how the CTLA-4 regulates a number of autoimmune diseases that indicate manipulation of this inhibitory molecule is a promise as a strategy for the immunotherapy of autoimmune diseases.

Association and gene-gene interaction analyses for polymorphic variants in CTLA-4 and FOXP3 genes: role in susceptibility to autoimmune thyroid disease

PURPOSE

Polymorphic variants of cytotoxic T-lymphocyte antigen-4 (CTLA-4) and forkhead box protein P3 (FOXP3) genes are implicated in dysregulated immune homeostasis and autoimmune disorders. We analyzed the association between CTLA-4 rs231775 and FOXP3 rs3761548, rs3761549 polymorphisms and predisposition to autoimmune thyroid disease (AITD), inclusive of Hashimoto's thyroiditis (HT) and Graves' disease (GD) in South-Indian population.

METHODS

A total of 355 AITD subjects (comprising 275 HT and 80 GD) and 285 randomly selected age- and sex-matched control subjects were genotyped for the aforementioned polymorphisms by PCR-RFLP method.

RESULTS

The rs231775 "G" allele was preponderant in HT and GD subjects when compared with controls and exerted a dominant influence on the susceptibility to HT (p = 0.009) and GD (p = 0.02), respectively. There was no allelic association of rs3761548 and rs3761549 polymorphisms with AITD susceptibility, albeit a significant difference in genotype distribution with respect to rs3761549. Haplotype analysis revealed an increased frequency of rs3761548 "C"-rs3761549 "T" in HT and GD subjects, thereby associating it with disease predisposition (p = 0.03). Epistatic interaction analysis by multifactor dimensionality reduction approach revealed redundancy between CTLA-4 and FOXP3 genes in influencing the susceptibility to AITD.

CONCLUSIONS

The genetic variation in CTLA-4 gene with reference to rs231775 polymorphism contributes to an increased predisposition to HT and GD. Also, in conjunction with FOXP3 gene variants it seems to influence the susceptibility to HT and GD respectively. The significance of these findings in combination with antithyroid antibody screening could plausibly contribute towards meticulous case-finding for effective treatment of HT and GD.

Association study of IL2RA and CTLA4 Gene Variants with Type I Diabetes Mellitus in children in the northwest of Iran

Introduction: A variety of genetic predisposing factors and environmental factors are known to influence the pathogenesis of type-1 diabetes (T1D). This study intended to investigate the association of cytotoxic T-lymphocyte associated protein 4 (CTLA4) and interleukin 2 receptor subunit alpha (IL2RA) gene polymorphisms with type 1 diabetes in children of northwest of Iran. Methods: Genomic DNA was extracted by salting-out method. PCR amplification and direct sequencing methods were used for genotyping of CTLA4 (exon 1) and IL2RA (intron 1) genes in all patients and controls. SNPStats was used to calculate odds ratios (ORs), 95% confidence intervals (CIs), and p values. Results: In this study, the frequency of G allele and GG genotype of CTLA-4 (+49A/G) polymorphism in T1D patients were significantly different from those in the controls (26% vs. 11%, p = 0.006). Moreover, a significant difference was observed between patients and control group in the allele frequencies of the new SNP (chr2:203868145) that was identified in exon one of CTLA4 (14% vs. 3%, p = 0.006). The results showed that the GG homozygous genotype of +49 A>G was associated with increased glycemic level in T1D patients in the study population (95% CI = 10.47, p = 0.0067). However, no significant association was found between IL2RA (ss52580101C>A) polymorphism and T1D patients (2% vs. 4%, p = 0.41). Conclusion: The results further support the association of T1D with +49A>G SNP in the CTLA4 gene in the population of northwest of Iran. However, no significant relationship was observed between ss52580101C>A polymorphism of IL2RA gene and T1D in this study.

Immunogenetics of type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is an autoimmune disease arising through a complex interaction of both genetic and immunologic factors. Similar to the majority of autoimmune diseases, T1DM usually has a relapsing remitting disease course with autoantibody and T cellular responses to islet autoantigens, which precede the clinical onset of the disease process. The immunological diagnosis of autoimmune diseases relies primarily on the detection of autoantibodies in the serum of T1DM patients. Although their pathogenic significance remains uncertain, they have the practical advantage of serving as surrogate biomarkers for predicting the clinical onset of T1DM. Type 1 diabetes is a polygenic disease with a small number of genes having large effects (i.e. HLA), and a large number of genes having small effects. Risk of T1DM progression is conferred by specific HLA DR/DQ alleles [e.g., DRB1*03-DQB1*0201 (DR3) or DRB1*04-DQB1*0302 (DR4)]. In addition, HLA alleles such as DQB1*0602 are associated with dominant protection from T1DM in multiple populations. A discordance rate of greater than 50% between monozygotic twins indicates a potential involvement of environmental factors on disease development. Viral infections may play a role in the chain of events leading to disease, albeit conclusive evidence linking infections with T1DM remains to be firmly established. Two syndromes have been described in which an immune-mediated form of diabetes occurs as the result of a single gene defect. These syndromes are termed autoimmune polyglandular syndrome type I (APS-I) or autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), and X-linked poyendocrinopathy, immune dysfunction and diarrhea (XPID). These two syndromes are unique models to understand the mechanisms involved in the loss of tolerance to self-antigens in autoimmune diabetes and its associated organ-specific autoimmune disorders. A growing number of animal models of these diseases have greatly helped elucidate the immunologic mechanisms leading to autoimmune diabetes.

CTLA4 variants and haplotype contribute genetic susceptibility to myasthenia gravis in northern Chinese population

BACKGROUND

Cytotoxic T lymphocyte-associated antigen-4 (CTLA4), a critical negative regulator of the T-cell response, has been considered a candidate for many autoimmune diseases. Evidence from Caucasians supported a genetic predisposition of CTLA4 to myasthenia gravis (MG), but the contribution in East Asians has not been established.

OBJECTIVES

To investigate the role of CTLA4 variants in the susceptibility to MG and the contribution to subtypes of MG.

METHODS

Six autoimmune disease-related risk alleles of CTLA4 (rs1863800, rs733618, rs4553808, rs5742909, rs231775, and rs3087243) were investigated for MG in northern Chinese. 168 patients with MG (mean age 37.1±20.5 years, 64 men and 104 women) and 233 healthy controls (mean age 53.3±8.7 years, 96 men and 137 women) were screened, and the contribution of CTLA4 to the general risk of MG and each subgroup was explored.

RESULTS

rs1863800*C, rs733618*C, and rs231775*G were significantly associated with the whole cohort of patients with MG after permutation correction for multiple-testing adjustment (P = 0.027, 0.001, and 0.032, respectively). A risk haplotype (CCACG) [odds ratio (OR) = 1.535, range = 1.150-2.059, P = 0.004)] was also identified. The stratified subtype analysis indicated that the positive contribution was possibly derived from early onset MG (EOMG), seropositive MG (SPMG), female patients, and MG without thymoma. No association was observed in juvenile MG/LOMG, and MG coupled with thymoma.

CONCLUSION

A predisposing effect of rs1863800*C, rs733618*C, and rs231775*G of CTLA4 gene to general risk of MG in Chinese was demonstrated for the first time, which was likely derived from EOMG, SPMG, MG without thymoma and the female patients.

Cytotoxic T-lymphocyte associated antigen 4 polymorphism and Hashimoto's thyroiditis susceptibility: a meta-analysis

The association between cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) exon-1 +49 A/G polymorphism and Hashimoto's thyroiditis (HT) has been widely studied. The results, however, are mixed. This study provides a comprehensive evaluation of the relationship between the genetic risks of CTLA-4 +49 A/G polymorphism and HT. A meta-analysis was conducted in over 4,600 subjects included in 18 case-control studies that were published up to November 15th, 2012. Our meta-analysis indicated that the CTLA-4 genotype was associated with the risk of HT in the allele comparison, homozygote comparison, heterozygote comparison, the dominant genetic model and the recessive genetic model. In the dominant genetic model, variant G allele carriers (GG + GA) of CTLA-4 +49 A/G polymorphism increased the risk of HT comparing to the homozygote AA [odds ratio (OR) = 1.70, 95% confidence interval (CI) 1.37-2.12 for GG + AG vs. AA]. The analysis by ethnicity groups suggested that Asian population (OR = 2.13, 95% CI 1.48-3.07 for GG + AG vs. AA) and Caucasian population (OR = 1.47, 95% CI 1.13-1.91 for GG + AG vs. AA) had significant increased HT risks. The association remained significant after adjusting for publication bias using the trim and fill method. Sensitivity analysis showed that the results were less stable, suggesting that these results should be explained with caution. In summary, this meta-analysis suggested that CTLA-4 +49 A/G polymorphism may be a risk factor for HT.

Common variants on cytotoxic T lymphocyte antigen-4 polymorphisms contributes to type 1 diabetes susceptibility: evidence based on 58 studies

In the past decade, a number of case–control studies have been carried out to investigate the relationship between the CTLA4 gene polymorphisms and type 1 diabetes (T1D). However, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of all available studies dealing with the relationship between the CTLA4 polymorphism and T1D. In total, 58 association studies on two CTLA4 polymorphisms (G49A and C60T) and risk of T1D, including a total of 30,723 T1D cases and 45,254 controls were included. In a combined analysis, the summary per-allele odds ratio (OR) for T1D of the G49A and C60T polymorphism was 1.42 [95% confidence interval (CI): 1.31–1.53, P<10⁻⁵] and 1.23 (95% CI: 1.18–1.29, P<10⁻⁵), respectively. Significant results were also observed using dominant or recessive genetic model. In the subgroup analysis by ethnicity and sample size, significantly increased risks were also found for these polymorphisms. This meta-analysis demonstrated that the G49A and C60T polymorphism of CTLA4 is a risk factor associated with increased T1D susceptibility, but these associations vary in different ethnic populations.

Prevention of autoimmune diabetes by DNA vaccination

DNA vaccination with antigen expression plasmids has been introduced as a simple method of inducing immunity to the antigens of infectious agents or tumors. Although DNA vaccination is generally immunostimulatory, it is possible to design suppressive vaccines that protect against autoimmune diseases such as Type 1 diabetes. In mice prone to diabetes, investigators have delivered a plasmid encoding an islet-cell antigen such as insulin B chain, glutamic acid decarboxylase, or antigen/immunoglobulin G-Fc fusion constructs, with or without co-delivery of another gene encoding a cytokine or other immunoregulatory molecule. This approach has led to protection against disease, related to the generation of regulatory T-cells and increased production of regulatory cytokines. DNA vaccination is a promising approach to autoimmune disease prevention.

The CTLA4 +49A/G polymorphism is associated with an increased risk of Hashimoto's thyroiditis in Asian but not Caucasian populations: an updated meta-analysis

The polymorphism +49A/G in the cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) gene has been implicated in susceptibility to Hashimoto's thyroiditis (HT), but the findings are not clear-cut. This study aimed to investigate the association between CTLA-4 polymorphisms and HT risk using an updated meta-analysis. A meta-analysis was carried out of 14 previous studies that investigated the CTLA-4 +49A/G polymorphism and HT risk. +49A/G was associated with a significantly increased HT risk in both allele analysis and all genetic models (allele analysis: G vs. A: P < 0.001, OR = 1.379, 95 % CI = 1.244-1.529). Subgroup analysis by ethnicity showed a significantly increased HT risk with the G allele and all other genetic models in the Asian subgroup (P < 0.001). In the Caucasian subgroup, no significant association was detected between the CTLA-4 +49 G allele and HT, or in the genetic model analysis (P = 0.05). This gene-based analysis indicates that the cumulative effect of the +49A/G polymorphism in CTLA-4 is associated with HT in Asians, but appears to have no effect on HT in Caucasians.

Association of Hashimoto's thyroiditis with cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and inducible co-stimulator (ICOS) genes in a Kuwaiti population

Analysing two CTLA-4 markers [exon 1 A49G single nucleotide polymorphism (SNP) and exon 4 3'UTR (AT)n repeat] and the ICOS intron 4 (GT)n marker for their potential association with HT, and exploring the effect of the tested SNPs on the CTLA-4 isoform expression at the mRNA and protein levels. Total of 270 age-gender-ethnically matched subjects were genotyped by fluorescent-labelled restriction fragment length polymorphism, multiplex PCR, and fragment analysis. Sequencing was used to confirm the genotyping results. Expression of the full-length and soluble CTLA-4 mRNAs analysed using real-time PCR. Sera from subjects were screened for sCTLA-4 using ELISA. Tested subjects revealed ten alleles and sixteen genotypes of CTLA-4 3'UTR(AT)n. The 3'UTR(AT)n was significantly associated with HT: allele (AT)15 and genotype 15/15 were found to cause susceptibility to HT (P = 0.004, OR = 2.13, 95 % CI = 1.26-3.58 and P = 0.029, OR = 2.77, 95 % CI = 1.1-6.94, respectively), whereas allele (AT)6 and genotype 6/6 were found to be protective of HT (P = 0.00002, OR = 0.36, 95 % CI = 0.227-0.57 and P = 0.001, OR = 0.357, 95 % CI = 0.1980.64, respectively). SNP A49G and ICOS(GT)n revealed no significant association with HT (P > 0.05). The expression of sCTLA-4 was inversely proportional to the number of 3'UTR(AT)n repeats, with heterozygous and longer (AT)n repeats showing lower levels of sCTLA-4 mRNA than those with shorter alleles in HC and HT (P = 0.001 and P = 0.04, respectively). Significant increase in the serum level of sCTLA-4 was observed in HT patients compared with the HC (P = 0.0007). The novel finding in our study is that the CTLA-4 3'UTR(AT)n proven to be a key player in the pathogenesis of HT.

Updated analysis of studies on the cytotoxic T-lymphocyte-associated antigen-4 gene A49G polymorphism and Hashimoto's thyroiditis risk

Published data on the association between the cytotoxic T-lymphocyte-associated antigen-4 gene A49G polymorphism and the risk for Hashimoto's thyroiditis (HT) are inconclusive. A meta-analysis was performed to derive a more precise estimation. Published case-control studies in English or Chinese were identified. In total, 24 studies with 2295 cases and 4521 controls were investigated. A random-effect model was performed irrespective of between-study heterogeneity. Study quality was assessed in duplicate, and subgroup analyses were conducted by ethnicity or age. Overall, the 49G allele was associated with an increase in HT risk [odds ratio (OR) = 1.31; 95% confidence interval (95%CI) = 1.17-1.47; P < 0.00001]. In a subgroup analysis by ethnicity, comparison of allele 49G with 49A generated a 27% increased risk among East Asians (OR = 1.48; 95%CI = 1.24-1.76; P < 0.00001) and whites (OR = 1.27; 95%CI = 1.12-1.44; P = 0.0002). We also found an increased risk among adults (OR = 1.31; 95%CI = 1.17-1.47; P < 0.00001) but not among children (OR = 1.44; 95%CI = 0.75-2.79; P = 0.27), possibly owing to the small sample sizes in children. No publication biases were observed. This meta-analysis suggested that the cytotoxic T-lymphocyte-associated antigen-4 gene 49G allele was associated with an increased HT risk, especially in adults.

CTLA-4 (+49A/G) polymorphism and type-1 diabetes in Turkish children

OBJECTIVE

To evaluate the contribution of cytotoxic T-Iymphocyte antigen-4(CTLA-4)+49A/G polymorphism to the susceptibility to type-1 diabetes (T1D) in Turkish children.

METHODS

A case-control study was designed to include 91 Turkish children with T1D and 99 healthy controls. CTLA-4 (+99A/G) gene polymorphism typing was done by PCR amplification followed by restriction fragment length polymorphism method.

RESULTS

The genotype and allele frequencies of the CTLA-4 (+99A/G)polymorphism in patients with T1D were not different from those in the controls (p>0.05). The allele frequency of G was 36.2% in patients with T1D,and 31.8% in controls (p>0.05). Additionally, this polymorphism was not associated with the clinical and laboratory characteristics of the patients with T1D (p>0.05).

CONCLUSIONS

Our case-control study suggests that the CTLA-4 (+99A/G) gene polymorphism is not associated with T1D in the Turkish population.

Association between the CTLA-4 +49A/G polymorphism and type 1 diabetes: a meta-analysis

BACKGROUND

+49A/G polymorphism of the cytotoxic T-lymphocyte-associated antigen-4 gene (CTLA-4) has been associated with type 1 diabetes (T1D). However, results were inconsistent. The aim of this study was to quantitatively summarize the evidence for CTLA-4 +49A/G polymorphism and T1D.

METHODS

Electronic search of PubMed was conducted to select studies. Case-control studies containing available genotype frequencies of CTLA-4 +49 were chosen, and the odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of this association.

RESULTS

49 case-control studies, including 8976 cases and 11012 controls, were identified. 8 studies were eliminated from the total 49 studies because of p<0.05 (p value for Hardy-Weinberg equilibrium in the control group) in these studies, which induce significant publication bias. The overall results suggested that the variant genotypes were highly associated (p<0.01) with T1D risk in all genetic models (additive model: OR 1.345, 95% CI 1.249-1.448, p<0.001; recessive model: OR 1.530, 95% CI 1.370-1.708, p<0.001; dominant model: OR 1.409, 95% CI 1.263-1.572 p<0.001). Similarly, in subgroup analyses for ethnicity (Caucasian, Asian), the results were positive.

CONCLUSION

This meta-analysis suggests that the CTLA-4 +49A/G polymorphism is highly associated (p<0.01) with increased risk of T1D, especially in Caucasians and Asians. To validate this association, further studies with more participants worldwide are needed to examine associations between this polymorphism and T1D. Otherwise, we found that the studies of Africans are rare. More studies in Africans are needed especially.

Association of cytotoxic T-lymphocyte associated antigen 4 gene polymorphism with type 1 diabetes mellitus: a meta-analysis

To evaluate the association between costimulatory molecule cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene polymorphism and type 1 diabetes mellitus(T1DM), sixty-three published studies before December, 2011 were included. Meta-analysis was performed for each genotype in a random/fixed effect model. The combined odds ratio (OR) with 95% confidence interval (95%CI) was calculated to estimate the strength of the association. Overall, significant correlation was noted between CTLA-4 gene polymorphism (i.e. +49A/G, CT60A/G in a per-allele model) and the risk of T1DM (for +49A/G: OR=1.47, 95%CI=1.36-1.60, P<0.001; for CT60A/G: OR=1.31, 95%CI=1.18-1.45, P<0.001). However, no significant association was noted between C(-318)T polymorphism and T1DM. In the subgroup analysis, for +49A/G and CT60A/G, the statistically significant associations were also demonstrated in diverse racial descents (Caucasian and Asian) and age of onset (<20 years and >20 years). In conclusion, our results suggest that CTLA-4 polymorphism contributes to the susceptibility of T1DM.

Association between the CTLA-4 +49A/G polymorphism and Graves' disease: A meta-analysis

The +49A/G polymorphism of the cytotoxic T-lymphocyte-associated antigen-4 gene (CTLA-4) has been associated with Graves’ disease (GD). However, results have been inconsistent. The aim of this study was to quantitatively summarize the evidence for CTLA-4 +49A/G polymorphism and GD. Electronic search of PubMed was conducted to select studies. Case-control studies containing available genotype frequencies of CTLA-4 +49 were chosen, and Odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of this association. Forty-two case-control studies including 8,288 cases and 9,372 controls were identified. Three studies were eliminated from the total 42 studies due to a p-value <0.05 (p-value for Hardy-Weinberg equilibrium in control group) in these studies which induced significant publication bias. The overall results suggested that the variant genotypes were highly associated (p<0.01) with GD risk in all genetic models (additive model: OR, 1.443; 95% CI, 1.319–1.578; p<0.001; recessive model: OR, 1.589; 95% CI, 1.396–1.808; p<0.001; dominant model: OR, 1.621; 95% CI, 1.430–1.837; p<0.001). Similarly, in the subgroup analyses for ethnicity (Caucasian, Asian), the results were positive. This meta-analysis suggests that the CTLA-4 +49A/G polymorphism is highly associated (p<0.01) with increased risk of GD, especially in Caucasians and Asians. To validate this association, further studies with larger participants worldwide are needed to examine associations between this polymorphism and GD.

Association of CTLA-4 (+49A/G) gene polymorphism with type 1 diabetes mellitus in Egyptian children

OBJECTIVE

To investigate the distribution of cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) (+49 A/G) gene variants and the association of these variants with the clinical and laboratory findings in Egyptian children with Type-1 Diabetes (T1D).

METHODS

A case control study was done for 104 Egyptian children with T1D and 78 age and sex matched healthy control. CTLA-4 (+49 A/G) gene polymorphism typing was done by PCR amplification followed by restriction fragment length polymorphism (RFLP) method.

RESULTS

CTLA-4 G allele and GG homozygous genotype were significantly increased in T1D patients than in control group (P = 0.047, P = 0.048 respectively). There is no statistical difference between patient with optimal diabetic control (HbA1c < 8.5) and poor control (HbA1c ≥ 8.5) as regarding the CTLA-4 gene variant. The CTLA-4 GG genotype was statistically associated with younger age of patients (P = 0.027) and younger age of presentation (P = 0.036). Insignificant association was found between CTLA-4 alleles / genotypes and diabetic complications.

CONCLUSION

The CTLA-4 +49 GG homozygous genotype is associated with T1D in Egyptian children especially with younger age of onset and in younger patients, and not associated with grades of diabetic control or diabetic complication.

The soluble CTLA-4 receptor and its role in autoimmune diseases: an update

CTLA-4, initially described as a membranebound molecule, is a costimulatory receptor transducing a potent inhibitory signal. Increasing evidence shows the CTLA-4 gene to be an important susceptibility locus for autoimmune endocrinopathies and other autoimmune disorders. A soluble form of cytotoxic T-lymphocyte-associated antigen-4 (sCTLA-4) has been established and shown to possess CD80/CD86 binding activity and in vitro immunoregulatory functions. sCTLA-4 is generated by alternatively spliced mRNA. Whereas low levels of sCTLA-4 are detected in normal human serum, increased serum levels are observed in several autoimmune diseases (e.g. Graves’ disease, myasthenia gravis, systemic lupus erythematosus, type 1 diabetes, systemic sclerosis, coeliac disease, autoimmune pancreatitis and primary biliary cirrhosis). The biological significance of increased sCTLA-4 serum levels is not fully clarified yet. On the one hand, it can be envisaged that sCTLA-4 specifically inhibits early T-cell activation by blocking the interaction of CD80/CD86 with the costimulatory receptor CD28. On the other hand, higher levels of sCTLA-4 could compete for the binding of the membrane form of CTLA-4 with CD80/CD86 in the later phases of T-lymphocyte activation, causing a reduction in inhibitory signalling. This double-edged nature of sCTLA-4 to block the binding of CD28 to CD80/CD86 may result in different outcomes during the clinical course of an autoimmune disease.

+49G > A polymorphism in the cytotoxic T-lymphocyte antigen-4 gene increases susceptibility to hepatitis B-related hepatocellular carcinoma in a male Chinese population

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is an important regulator and functions negatively in immune response. Its nonsynonymous polymorphism +49G > A (dbSNP: rs231775) has been linked to an elevated risk of T-cell-mediated autoimmune diseases, infectious diseases, and even carcinomas. Here, we examined the genotypes at rs231775 of 1003 subjects in a Han Chinese population to detect the association between this single-nucleotide polymorphism (SNP) and hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) susceptibility, including 375 HBV-related HCC patients, 209 non-HCC patients with HBV infection, and 419 healthy controls. Our results indicated a weak trend for the relationship between rs231775 and HBV-related HCC susceptibility, although the statistical level was not significant. However, a significant difference was identified in males between HBV-related HCC patients and healthy controls. The data revealed that the frequency of the A/A genotype was higher in patients compared with healthy controls (odds ratio [OR] = 1.79, 95% confidence interval [95% CI] 1.05-3.08). The G allele appeared to have a protective effect in developing HBV-related HCC. Subjects with the A allele had higher HCC susceptibility than those with the G allele (OR = 1.31, 95% CI 1.03-1.66). These results suggested that the A/A genotype and A allele of rs231775 increased the risk of developing HBV-related HCC in a male Chinese population.

Association of polymorphism at position 49 in exon 1 of the cytotoxic T-lymphocyte-associated factor 4 gene with Graves' disease refractory to medical treatment, but not with amiodarone-associated thyroid dysfunction

BACKGROUND

Recently, the G allele of the cytotoxic T-lymphocyte-associated factor 4 (CTLA-4) exon 1 single-nucleotide polymorphism (CTLA-4 A/G(49)) has been identified as the most informative marker in patients with Graves' disease. Patients with the G/G genotype are refractory to medical treatment and frequently relapse after discontinuation of antithyroid drugs. Therefore, we analyzed CTLA-4 A/G(49) in patients who had been treated with (131)I. Further, a preliminary report has suggested that amiodarone-associated thyroid dysfunction (AATD) has a relationship with human leukocyte antigen (HLA) class I and class II.

METHOD

CTLA-4 genotypes in exon 1 (A/G(49)) and CT60 were analyzed in 415 Japanese patients with Graves' disease and 65 patients with AATD.

RESULTS

The frequencies of the G alleles and G/G genotype at the both polymorphisms were significantly higher in Graves' patients compared with normal subjects. Compared with CT60, the frequencies of the G alleles and G/G genotypes at the A/G(49) were more significantly higher in patients with persistently positive thyrotropin receptor antibody despite >5 years of antithyroid drug therapy, compared with those whose thyrotropin receptor antibody became negative in <5 years (p < 0.0001). Consequently, the frequencies of the G/G genotype and G allele at the A/G(49) were also significantly higher in patients with Graves' disease who received (131)I therapy (p < 0.05). However, there was no significant difference in the A/G polymorphisms in the 65 patients with AATD.

CONCLUSIONS

The G/G genotype in exon 1 (A/G(49)) is frequently expressed in Graves' disease patients who are refractory to antithyroid drug treatment. Therefore, the G/G genotype in A/G(49) would be a useful predictor of Graves' patients who are suitable for radioiodine therapy. Although the number of analyzed patients was small, our preliminary data suggest that the CTLA-4 gene polymorphisms might be unassociated with AATD.

The onset of diabetes in three out of four sisters: a Japanese family with type 1 diabetes. A case report

Type 1A diabetes is an autoimmune disease characterized by the destruction of insulin-producing beta-cells in the pancreas. The HLA-DR and -DQ genes are well established as being associated with increased risk for type 1 diabetes. Moreover, polymorphisms in CTLA4 have been reported to be associated with susceptibility to type 1 diabetes and autoimmune thyroid disease (AITD). In both Caucasian and Japanese populations, the lifetime risk in siblings of type 1 diabetic probands is much higher than that in general populations. However, in Japan, where the prevalence of type 1 diabetes is less than one-tenth that of most Caucasian populations, it is rare for type 1 diabetes to develop in three or more siblings within a family. Here, we report a Japanese family in which type 1 diabetes occurred in three siblings amongst four sisters. Three probands of type 1 diabetes had the same combination of HLA haplotypes, DRB1(*)0405-DQB1(*)0401/ DRB1(*)0802-DQB1(*)0302, which occurs significantly more often in type 1 diabetes patients than in control subjects in the Japanese population. With respect to the rs3087243 (+6230G>A) polymorphism of CTLA4, the first sister had type 1 diabetes and AITD and had the GG genotype, whereas the second and third sisters, who had type 1 diabetes without AITD, had the AG genotype. This is the first report of a family in which type 1A diabetes developed in three siblings. We performed genetic analysis of HLA-DR, -DQ, and CTLA4 in all family members. Even in a country where the prevalence of type 1 diabetes is low, diabetic proband siblings should be monitored for the onset of type 1 diabetes.

Functional genetic variations in cytotoxic T-lymphocyte antigen 4 and susceptibility to multiple types of cancer

Antitumor T lymphocytes play a pivotal role in immunosurveillance of malignancy. The CTL antigen 4 (CTLA-4) is a vital negative regulator of T-cell activation and proliferation. This study examined whether genetic polymorphisms in CTLA-4 are associated with cancer susceptibility. A two-stage investigation using haplotype-tagging single nucleotide polymorphism approach and multiple independent case-control analyses was performed to assess the association between CTLA-4 genotypes and cancer risk. Functional relevance of the polymorphisms was examined by biochemical assays. We found that the 49G>A polymorphism in the CTLA-4 leading sequence causing (17)Ala to (17)Thr amino acid substitution is associated with increased susceptibility to multiple cancers, including lung, breast, esophagus, and gastric cardia cancers. Genotyping in 5,832 individuals with cancer and 5,831 control subjects in northern and southern Chinese populations showed that the CTLA-4 49AA genotype had an odds ratio of 1.72 (95% confidence interval, 1.50-2.10; P = 3.4 x 10(-7)) for developing cancer compared with the 49GG genotype. Biochemical analyses showed that CTLA-4-(17)Thr had higher capability to bind B7.1 and stronger inhibitory effect on T-cell activation compared with CTLA-4-(17)Ala. T cells carrying the 49AA genotype had significantly lower activation and proliferation rates compared with T cells carrying the 49GG genotype upon stimulation. These results are consistent with our hypothesis and indicate that genetic polymorphisms influencing T-cell activation modify cancer susceptibility.

The role of genetics in Graves' disease and thyroid orbitopathy

Graves' disease is a complex autoimmune disorder characterized by multiple systemic manifestations of overproduction of thyroid hormone, and in some cases, orbitopathy. The etiology of this disorder is multifactorial, involving heritable abnormalities of immune regulation as well as environmental triggers. The goal of this paper is to provide a review of recent research investigating candidate genes involved in the pathophysiology of both Graves' disease per se and of thyroid orbitopathy.

Cytotoxic T-lymphocyte associated antigen 4 gene polymorphisms and autoimmune thyroid disease: a meta-analysis

CONTEXT

Cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) polymorphisms have been widely examined for their associations with autoimmune thyroid diseases [Graves' disease (GD) and Hashimoto thyroiditis (HT)], but their relative population effect remains unclear.

OBJECTIVE

The aim was to generate large-scale evidence on whether the CTLA-4 polymorphisms (A49G and CT60) and haplotypes thereof increase the susceptibility to GD and/or HT.

DESIGN, SETTING, AND PARTICIPANTS

Meta-analyses of group-level data were reviewed from 32 (11,019 subjects) and 12 (4,479) published and unpublished studies for the association of the A49G polymorphism with GD and HT, respectively (PubMed and HuGeNet search until July 2006). There were 15 (n = 7246) and six (n = 3086) studies available for the CT60 polymorphism, respectively. Meta-analyses of individual-level data from 10 (4906 subjects) and five (2386) collaborating teams for GD and HT, respectively, were also reviewed.

MAIN OUTCOME MEASURES

Association of gene variants and haplotypes with GD and HT was measured.

RESULTS

Group-level data suggested significant associations with GD and HT for both A49G [odds ratios 1.49 (P = 6 x 10(-14)) and 1.29 (P = 0.001) per G allele, respectively] and CT60 [1.45 (P = 2 x 10(-9)) and 1.64 (P = 0.003) per G allele, respectively]. Results were consistent between Asian and Caucasian descent subjects. Individual-level data showed that compared with the AA haplotype, the risk conferred by the GG haplotype was 1.49 (95% confidence interval 1.31,1.70) and 1.36 (95% confidence interval 1.16,1.59) for GD and HT, respectively. Data were consistent with a dose-response effect for the G allele of CT60.

CONCLUSION

The CT60 polymorphism of CTLA-4 maps an important genetic determinant for the risk of both GD and HT across diverse populations.

Cytotoxic T lymphocyte-associated molecule-4 gene polymorphism and hyperthyroid Graves' disease relapse after antithyroid drug withdrawal: a follow-up study

CONTEXT

We previously showed an association between the exon1 +49 A/G single nucleotide polymorphism (SNP) and the relapse of Graves' disease (GD). The G allele was associated with early relapse.

OBJECTIVE

In this follow-up study, we sought to replicate the result by genotyping nine additional polymorphisms and recruiting another 60 GD patients.

DESIGN AND PARTICIPANTS

The GD patients were divided into three groups: recurred within 9 months, between 10-36 months, and more than 36 months. There were 65 patients with early recurrence, 55 with medium recurrence, and 88 with late recurrence. Although several SNPs were associated with recurrence, the most significant marker was still exon1 +49 A/G. Separate analysis of the genotypes for the 60 newly enrolled patients indicated that our present study was not biased by the previous samples. Once exon1 +49 A/G was included in the model to predict recurrence, other markers would not add more predictive information. Haplotype analysis did not show an additional value once exon1 +49 A/G was compulsorily included.

RESULTS

Multivariate logistic regression analysis showed that GG genotype of exon1 +49 A/G SNP had an adjusted odds ratio of 2.2 (95% confidence interval, 1.1-4.4) compared with the combined group of GA plus AA. Other significant predictors were large goiter size at the end of the treatment and positive TSH-binding inhibitory Ig at the end of the treatment.

CONCLUSIONS

This follow-up study confirms the usefulness of the exon1 +49 A/G SNP of the cytotoxic T lymphocyte-associated molecule-4 gene in predicting recurrence after cessation of treatment. There is no additional power by including other polymorphisms to predict recurrence.

The predictive value of CTLA-4 and Tg polymorphisms in the recurrence of Graves' disease after antithyroid withdrawal

Graves' disease (GD) is a multifactorial disease that develops as a result of complex interactions between genetic and environmental factors. The aim of our study is to determine the frequency of cytotoxic T-lymphocyte- associated antigen-4 (CTLA-4) A/G and TG C/T exon 33 SNPs (Tg E33SNP) in GD and to evaluate the relation between recurrence and these polymorphisms. A total of 187 subjects, including 97 previously treated GD patients and 90 age and gender matched control subjects were studied. We examined the relationship between the A/G and C/T polymorphism and various clinical and laboratory variables among patients with GD. TT genotype frequency in the GD patients was significantly higher than the controls. Number of recurrent patients was significantly higher in AG and GG carriers in comparison to AA carriers (57% and 45% vs 14%, p = 0.0001). CTLA-4 AG genotype had an eightfold (OR: 8.050; 95% CI: 2.87-22.5; p = 0.0001) and GG genotype had a sevenfold (OR: 7.025; 95% CI: 1.67-29.4; p = 0.007) increase in the risk of recurrence in the patients with GD. In conclusion, early interpretation for definitive treatment procedures (i.e., radioactive iodine or surgery) may be considered in the patients with G allele and E33SNP of Tg gene is conformed the susceptibility to GD in a Turkish population and having TT genotype increases the susceptibility to GD.

The common −318C/T polymorphism in the promoter region of CTLA4 gene is associated with reduced risk of ophthalmopathy in Chinese Graves' patients

Studies in the past have clearly established that CTLA4 is a susceptible gene for Graves' disease (GD). However, association studies between CTLA4 and the risk of developing Graves' ophthalmopathy (GO) in GD patients have shown conflicting results. In this study, associations of five CTLA4 single nucleotide polymorphisms (-1722A/G, -1661A/G, -318C/T, +49G/A, CT60) with GD risk and GO susceptibility in GD patients were investigated in a Chinese population. Our results showed that either +49A/G or CT60 polymorphism was associated with GD susceptibility in the Chinese population. Significant differences in the distribution of the genotypes or alleles evaluated between GD patients with and without clinically evident GO were only found for -318C/T polymorphism (P = 0.03). Multiple logistic regressions revealed that the -318T allele was negatively associated with GO under both additive and dominant genetic models (adjusted OR = 0.56, 95%CI 0.35-0.89, P = 0.014; adjusted OR = 0.51, 95%CI 0.30-0.84, P = 0.009, respectively). Stratification analysis according to gender demonstrated different scenarios concerning the role of the -318T allele in GO risk: a significant protective role for GO was only confirmed in male but not in female GD patients. Haplotype analyses showed that only the haplotypes containing the -318T allele played a protective role in GO. In conclusion, results from this study suggested that the -318T allele might play a protective role in GO susceptibility for GD patients at least in the Chinese population. However, extended analyses with larger sample size should be carried out in patients from different ethnic origins to further verify this association.

CTLA4 polymorphisms and ophthalmopathy in Graves' disease patients: association study and meta-analysis

Studies in the past have clearly established that cytotoxic T-lymphocyte antigen-4 (CTLA4) is a susceptible gene for Graves' disease (GD). However, association studies between the CTLA4 exon-1 +49A/G polymorphism and the risk of developing Graves' ophthalmopathy (GO) in GD patients have revealed conflicting results. In this study, associations of two CTLA4 polymorphisms (+49A/G and CT60) with GD risk and GO susceptibility in GD patients were investigated in a Chinese population. In addition, a meta-analysis was performed to better assess the purported association between the +49A/G polymorphism and GO susceptibility in GD patients. Our results demonstrated that both the +49A/G and CT60 polymorphisms were associated with GD susceptibility in the Chinese population. No significant association with GO susceptibility in GD patients was confirmed regardless of which polymorphism was tested individually. Similarly, the meta-analysis results provided minimal evidence about the role of the +49A/G polymorphism and GO risk in GD patients. Interestingly, haplotypic analysis demonstrated different scenarios concerning the role of CTLA4 in GO susceptibility in the Chinese GD patients. We found that the +49A-CT60G haplotype was marginally statistically associated with the increased risk of GO in GD patients (OR = 1.63, 95%CI 1.00-2.64, p = 0.05). In conclusion, our results suggested that CTLA4 might be involved in the susceptibility to GD in the Chinese population. Although neither +49A/G nor CT60 polymorphism was associated with the risk of GO in GD patients, the haplotypic analysis provided some evidence about its role in GO susceptibility in the Chinese GD patients. We suggest that more association studies recruiting haplotypic analysis should be performed to investigate the role of CTLA4 gene in GO susceptibility in patients from different nations.

Lack of a genetic association between the CTLA-4 gene and Graves' disease in Koreans

Graves' disease (GD) is a complex autoimmune thyroid disease with a strong genetic component. The cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene, which encodes a negative regulator of the T-lymphocyte immune response, has been reported to be associated and/or linked to GD. Therefore, in order to determine the contribution of CTLA-4 in GD in Koreans, we genotyped the five single nucleotide Polymorphisms (SNPs) of the CTLA-4 gene, including +49, CT60, JO31, JO30, and JO27-1 in Korean spatients with GD and healthy controls. Two hundred seventy-eight Korean patients with GD from the Thyroid Clinic and 472 healthy controls from the Health Screening Center of Samsung Medical Center were enrolled in this study. The +49A/G polymorphism of the CTLA-4 gene exon 1 was sequenced directly and the genotyping of the remaining 4 SNPs was accomplished using a Snapshot. In addition, the association of haplotypes with a combination of the above markers was also examined in 278 Korean patients with GD and 472 controls. The results showed that there was no significant positive association between any individual SNP or haplotype comprising of the four 3 untranslated region (UTR) SNPs (CT60, JO31, JO30, and JO27-1) and GD. These data provide little support for CTLA-4 to play a role in the genetic predisposition to GD in Koreans. However, it will be necessary to validate or replicate this association in other independent large-size ethnic groups.

Polymorphisms at +49A/G and CT60 sites in the 3' UTR of the CTLA-4 gene and APECED-related AIRE gene mutations analysis in sporadic idiopathic hypoparathyroidism

Autoimmune diseases such as Graves' disease and type 1 diabetes have been linked with +49A/G and CT60 single nucleotide polymorphisms (SNPs) in the 3' UTR of the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene. Both these SNPs are functionally relevant and linked with T-lymphocyte activation. Hypoparathyroidism is seen in 70% of patients with autoimmune polyendocrinopathy candidiasis ectodermal dystrophy syndrome (APECED). Although calcium sensing receptor autoantibodies (CaSRAb) and generalized activation of T lymphocytes are reported among patients with sporadic idiopathic hypoparathyroidism (SIH), CTLA-4 gene SNPs and APECED-related autoimmune regulator (AIRE) gene mutations have not been assessed in them. We studied lead CTLA-4 gene SNPs and APECED-related AIRE gene mutations in 73 patients with SIH and 114 healthy subjects. The CTLA-4 gene SNPs +49A/G in exon 1, CT60A/G in 3' UTR and -318C/T in the promoter region were genotyped by polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) using BstEII, NcoI and MseI endonucleases, respectively. The APECED-related AIRE gene mutations, which is R257X (Finn-major) in exon 6, 4-bp insertion and 13-bp deletion in exon 8, and Iranian Jews population 'Y85C' mutation in exon 2, were studied by PCR-RFLP (Taq-I), PCR and nucleotide sequencing, respectively. CaSRAb were studied by immunoblotting. The frequencies of CTLA-4 A/A(49), A/G(49) and G/G(49) genotypes in the patients (47.9%, 38.4% and 13.7%) and controls (45.6%, 39.5% and 14.9%, respectively) and the frequencies of CT60 A/A, A/G, and G/G genotypes in the patient (42.4%, 37.0% and 20.6%) and the control (38.6%, 40.4% and 21.0%, respectively) groups were not significantly different. The frequencies of various haplotypes including genetic loci +49A/G and CT60 and frequencies of G alleles at these positions were comparable between patient and the control groups and its presence did not correlate with clinical and biochemical indices of the disease. None of the patients had APECED-related AIRE gene mutations. Lack of significant difference in the pattern of CTLA-4 A/G(49) and/or CT60A/G genotypes and absence of common APECED syndrome-related AIRE gene mutations among patients and controls suggest that these sites do not play a role in the development of the SIH.

CTLA4 gene polymorphism and autoimmunity

CD28 and cytotoxic T-lymphocyte antigen-4 (CTLA4) are two receptors that have critical but opposing functions in T-cell stimulation. CD28 promotes a number of T-cell activities, whereas in contrast CTLA4 is an essential inhibitor of T-cell responses. Because of its inhibitory role, CTLA4 is a strong candidate susceptibility gene in autoimmunity and several studies suggest disease-associated polymorphisms. In this review, we discuss recent progress in relating CTLA4 polymorphisms to disease susceptibility and consider the putative mechanisms by which CTLA4 may act to inhibit autoimmunity.

CTLA-4 gene polymorphisms and susceptibility to type 1 diabetes mellitus: a HuGE Review and meta-analysis

The authors performed a meta-analysis of 33 studies examining the association of type 1 diabetes mellitus with polymorphisms in the cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene, including the A49G (29 comparisons), C(-318)T (three comparisons), and (AT)n microsatellite (six comparisons) polymorphisms. The studies included 5,637 cases of type 1 diabetes and 6,759 controls (4,775 and 5,829, respectively, for analysis of the A49G polymorphism). The random-effects odds ratio for the *G (Ala) allele versus the *A (Thr) allele was 1.45 (95% confidence interval (CI): 1.28, 1.65), with significant between-study heterogeneity (p < 0.001). The effect size tended to be higher in type 1 diabetes cases with age of onset <20 years (odds ratio (OR) = 1.61), and there was a significant association between the presence of glutamic acid decarboxylase-65 autoantibodies and the *G allele among type 1 diabetes cases (OR = 1.49). Larger studies showed more conservative results (p = 0.011). After exclusion of studies with fewer than 150 subjects and studies with significant deviation from Hardy-Weinberg equilibrium in the controls, the summary odds ratio was 1.40 (95% CI: 1.28, 1.54). Available data showed no strong association for the 106-base-pair allele of the microsatellite polymorphism (OR = 0.99, 95% CI: 0.64, 1.55) or the *T allele of the C(-318)T polymorphism (OR = 0.92, 95% CI: 0.45, 1.89). This meta-analysis demonstrates that the CTLA-4*G genotype is associated with type 1 diabetes.

Lack of association between IL-12B gene polymorphism and autoimmune thyroid disease in Japanese patients

Interleukin (IL)-12 is a key factor in cell-mediated immunity that drives the development of Th1 cells and stimulates T lymphocytes and natural killer cells to produce interferon (INF)-gamma. The IL-12B gene, which encodes the p40 subunit of IL-12, is located at chromosome 5q31-33 and a linkage finding for autoimmune thyroid disease (AITD) on 5q31-33 in a Japanese population has been reported. It is also reported that the A/C polymorphism in the 3' untranslated region (UTR) of the IL-12B gene (1188A/C) is associated with IL12B mRNA expression levels. We attempted to determine whether genetic polymorphisms of the IL-12B gene are associated with AITD. One hundred three patients with Hashimoto's thyroiditis, 90 patients with Graves' disease, and 123 healthy control subjects were recruited. We detected the 1188A/C polymorphism using a PCR-RFLP method and the A/T polymorphism in intron 4 of the IL-12B gene using a cycle sequencing method. These IL-12B gene polymorphisms showed strong linkage disequilibrium, and their genotype and allele frequencies in the patients did not differ from those in the control subjects. Our results suggest that IL-12B gene polymorphisms were unlikely to have an effect on the development of Hashimoto's thyroiditis or Graves' disease in Japanese patients.

Promoter polymorphism of SLC11A1 (formerly NRAMP1) confers susceptibility to autoimmune type 1 diabetes mellitus in Japanese

Defective function of antigen-presenting cells has been postulated to be one of the non-HLA-linked susceptibility factors for type 1 diabetes mellitus, though the underlying genetic factors remain unclear. SLC11A1 (formerly NRAMP1), a divalent cation transporter, plays a crucial role in macrophage activation. We performed a case-control study in 224 healthy and 95 type 1 diabetic Japanese subjects, examining the length polymorphisms in the promoter region (-377 to -222) of SLC11A1, which may influence transcriptional activity. Alleles designated 2, 3, and 7 have been identified in Japanese subjects. The frequency of allele 7 was significantly higher in subjects with type 1 diabetes (9.47%) than in the healthy controls (4.46%). The difference is more marked in the subpopulation of Japanese subjects with type 1 diabetes; diabetic subjects with at least one protective HLA class II allele and those without any susceptibility HLA class II haplotypes, DR4-DQ4 or DR9-DQ9, had a much higher allele 7 frequency than controls. These findings suggest that the novel promoter polymorphism of SLC11A1 influences the susceptibility to type 1 diabetes in Japanese subjects.

The Diabetes Susceptibility Locus Idd5.1 on Mouse Chromosome 1 Regulates ICOS Expression and Modulates Murine Experimental Autoimmune Encephalomyelitis

Linkage analysis and congenic mapping in NOD mice have identified a susceptibility locus for type 1 diabetes, Idd5.1 on mouse chromosome 1, which includes the Ctla4 and Icos genes. Besides type 1 diabetes, numerous autoimmune diseases have been mapped to a syntenic region on human chromosome 2q33. In this study we determined how the costimulatory molecules encoded by these genes contribute to the immunopathogenesis of experimental autoimmune encephalomyelitis (EAE). When we compared levels of expression of costimulatory molecules on T cells, we found higher ICOS and lower full-length CTLA-4 expression on activated NOD T cells compared with C57BL/6 (B6) and C57BL/10 (B10) T cells. Using NOD.B10 Idd5 congenic strains, we determined that a 2.1-Mb region controls the observed expression differences of ICOS. Although Idd5.1 congenic mice are resistant to diabetes, we found them more susceptible to myelin oligodendrocyte glycoprotein 35-55-induced EAE compared with NOD mice. Our data demonstrate that higher ICOS expression correlates with more IL-10 production by NOD-derived T cells, and this may be responsible for the less severe EAE in NOD mice compared with Idd5.1 congenic mice. Paradoxically, alleles at the Idd5.1 locus have opposite effects on two autoimmune diseases, diabetes and EAE. This may reflect differential roles for costimulatory pathways in inducing autoimmune responses depending upon the origin (tissue) of the target Ag.

CTLA-4 gene polymorphism and its association with Graves' disease in the Lebanese population

Graves' disease is an organ-specific autoimmune disease that has a female predominance. It is probably the result of a complex interaction of genetic and environmental factors. This disease is characterized by immune system activation, evidenced by elevated serum thyroid-specific autoantibodies and lymphocytic infiltration of the target organ (the thyroid gland), associated with raised levels of circulating activated T lymphocytes. Several reports have demonstrated genetic linkage and association between the genetic markers of the CTLA-4 gene on chromosome 2q33 and Graves' disease. In order to confirm this association in the Lebanese population, a bi-allelic A/G polymorphism at position 49 of CTLA-4 exon 1 was studied in 34 patients with Graves' disease, and in 38 healthy individuals, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. The results showed a significant increase in allele and genotype frequencies in patients with Graves' disease compared to controls. This suggests that the CTLA-4 gene might play a role in the development of Graves' disease in the Lebanese population.

Mechanisms of genetic susceptibility to type I diabetes: beyond HLA

An individual's predisposition to Type I diabetes (T1D) is largely determined by complex interactions between several genetic loci and other, nonheritable factors. In T1D, the HLA locus has been known for decades to contribute 50% of the inherited risk. Outside the HLA are many proposed candidate loci with smaller effects, but only two confirmed candidate genes, the INS-VNTR and the CTLA-4 genes, which together do not contribute more than 15% of the risk. Because of the high frequency of the disease-associated DNA variants of these genes, understanding the biological mechanisms of such DNA variation in the context of T1D can have tremendous impact on the development of preventive therapeutics. However, establishing a causal relationship between common DNA variations and disease-predisposing functional effects is not trivial and remains difficult, as the effects are expected to be subtle. The variable-number tandem-repeat (VNTR) region upstream of the insulin gene is known to mediate expression in the thymus and pancreas, whereas various polymorphisms in the 5' and 3' regulatory regions of CTLA-4 are thought to alter gene expression and a coding A49G polymorphism exerts effects on post-translational processing. This review details the latest efforts in elucidating the functional mechanisms that explain the genetic association of the INS-VNTR and CTLA-4 genes with T1D.

Association between IL-18 gene promoter polymorphisms and CTLA-4 gene 49A/G polymorphism in Japanese patients with type 1 diabetes

Interleukin-18 (IL-18) is a potent proinflammatory cytokine which is strongly associated with the development of diabetes in NOD mice. To test the putative involvement of IL-18 gene polymorphism in predisposition to human type 1 diabetes, the SNPs at position -607 (C/A) and -137 (G/C) in the promoter region of IL-18 gene were analyzed by sequence-specific PCR in 116 patients with type 1 diabetes and 114 normal controls. A linkage disequilibrium found only three of the four possible haplotypes defined by these SNPs. The distribution of the IL-18 gene genotypes at position -607 was significantly different between patients with type 1 diabetes and normal controls (P=0.023). Furthermore, there was a significant increase in haplotype 1 (-607C/-137G) in the patients compared with controls (P=0.006). The association study of the susceptible CTLA-4 genotype (GG at nucleotide position 49 in exon 1) or HLA-DR4-DQB1*0401 and type 1 diabetes showed that the predisposing IL-18 gene haplotype modulates the risk on CTLA-4 GG genotype, but not on HLA-DR4-DQB1*0401 haplotype. Among subjects carrying the CTLA-4 GG genotype, the frequency of IL-18 haplotype 1 in patients with type 1 diabetes was significantly higher than that in controls (91% vs. 71%, P=0.012). However, IL-18 haplotype 1 was not frequent in patients who do not exhibit the CTLA-4 high-risk genotype. These results suggest that the IL-18 gene polymorphism is associated with a type 1 diabetes susceptibility, and there might be a gene-gene interaction between IL-18 gene with susceptible CTLA-4 gene.

Cytotoxic T lymphocyte-associated molecule-4 polymorphism and relapse of Graves' hyperthyroidism after antithyroid withdrawal

We studied the A/G single nucleotide polymorphism (SNP) at position 49 in exon 1 of the cytotoxic T lymphocyte-associated molecule-4 gene in 148 Chinese Graves' disease (GD) patients and 171 controls. Our primary aim was to test for the association of this SNP with the relapse of the hyperthyroidism after antithyroid withdrawal. Our secondary aim was to investigate the relationship between GD patients and controls according to the SNP genotypes. All GD patients were divided into the following three groups according to the time of relapse after drug discontinuation: group 1, early relapse within 9 months; group 2, relapse between 10 and 36 months; and group 3, relapse 3 or more years after discontinuation of treatment. There was a significant difference of genotype frequencies (P < 0.001) and allele frequencies (P < 0.001) among the three groups of patients. The frequency of the G/G genotype decreased from 79% to 64% and 39% in groups 1, 2, and 3, respectively. Compared with controls, a strong association (P < 0.001) of G allele was found for group 1, and moderate significance (P = 0.04) was found for group 2, but no association (P = 0.33) was found for group 3. At the end of treatment, the percentage of patients with persistent TSH-receptor antibody was statistically different (A/A, 9.0%; A/G, 20.8%; G/G, 45.5%; P = 0.004). Using 3 yr as the cutoff point for multivariate logistic regression analysis, we found that the G/G genotype (adjusted odds ratio, 3.1 compared with A/G plus A/A; 95% confidence interval, 1.3-7.1), larger goiter size at the end of treatment, and positive TSH-receptor antibody at the end of treatment were independent risk factors of recurrence. We conclude that the A/G polymorphism of the cytotoxic T lymphocyte-associated molecule-4 gene affects the progress of GD. The G/G genotype is associated with poor outcome.

Altering immune tolerance therapeutically: the power of negative thinking

The etiology of most human autoimmune diseases remains largely unknown. However, investigators have identified several negative regulatory mechanisms acting at the level of innate and/or adaptive immunity. Mutations resulting in a deficiency of some key regulatory molecules are associated with systemic or organ-specific inflammatory disorders, which often have a prominent autoimmune component. Genetic studies have implicated the negative regulator cytotoxic T-lymphocyte antigen 4 (CTLA-4) and other regulatory molecules in human autoimmune diseases. In addition to CTLA-4, key inhibitory molecules include programmed death 1 and B and T lymphocyte attenuator. Transforming growth factor beta1 and interleukin-10 also play major anti-inflammatory and regulatory roles. Tumor cells and infectious agents use negative regulatory pathways to escape immunity. The therapeutic blockage of negative signaling (particularly of CTLA-4) increases immunity against tumor antigens but also induces or aggravates autoimmune diseases. It appears that under normal conditions, the immune system is under strong "negative influences" that prevent autoimmunity and that release of this suppression results in disease. Regulation involves communication between the immune system and nonlymphoid tissues, and the latter can deliver inhibitory or stimulatory signals. Recent studies reveal that the generation of negative signals by selective engagement of inhibitory molecules is feasible and is likely to be of therapeutic benefit in autoimmune diseases and allograft rejection.

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.

Interactions of HLA-DRB4 and CTLA-4 genes influence thyroid function in Hashimoto's thyroiditis in Japanese population

Hashimoto's thyroiditis (HT) is an autoimmune disease of the thyroid gland, and like many other autoimmune diseases, it is associated with the HLA and CTLA-4 gene. We have examined the distribution of the HLA DRB4*0101 allele and a CTLA-4 exon 1 A/G polymorphism in Japanese HT patients and controls and investigated possible interactions of these genes with thyroid function. Seventy Japanese HT patients and 105 controls were included in this study. HT was diagnosed on the basis of positivity for thyroid peroxidase (TPO) autoantibodies and the presence of a palpable diffuse goiter. Genotyping was performed by polymerase chain reaction (PCR)-based methods. CTLA-4-GG or -AG was more prevalent in the patients, and the odds ratio for the G allele was 4.95. The frequency of DRB4*0101-positive individuals was significantly higher in HT (odds ratio=2.17). The TSH values of HT patients at the time of diagnosis were compared to CTLA-4 genotype and HLA-DRB4*0101 positivity. They were slightly higher in the CTLA-4-AG group than in the -GG group and significantly higher in the HLA-DRB4*0101-positive group than in the -negative group (p<0.01). When the TSH values were compared in 4 groups based on positivity or negativity for HLA-DRB4*0101 and CTLA-4 GG or AG, they were found to be significantly higher in the CTLA-4-AG and HLA-DRB4*0101-positive group than in the 3 other groups (F=5.75, 3 degrees of freedom, p<0.01). These findings suggest that the interaction between the HLA-DRB4 and CTLA-4 genes determines the thyroid function of TPO-positive goitrous Japanese HT patients.

No association of CTLA4 gene with celiac disease in the Basque population

BACKGROUND

Celiac disease (CD) is an autoimmune disorder caused by intolerance to ingested gluten that develops in genetically susceptible individuals. The contribution of human leukocyte antigen (HLA) genes to the genetic risk to CD has been known for a long time; however, non-HLA genetic factors are likely to be required for the development of the disease. Several studies have associated the CD28/CTLA4 region on chromosome 2q33 with the disease in different populations. The CTLA4 gene encodes a receptor involved in the control of T-cell proliferation and mediates T-cell apoptosis. AIM To determine the contribution of two polymorphisms of the CTLA4 to the disease: the A/G dimorphism at position +49 in exon 1 and the (AT)(n) microsatellite in the 3' untranslated region.

PATIENTS

Forty-one celiac families of Basque origin (43 patients with CD and 80 first-degree relatives).

METHODS

Restriction enzyme digestion of polymerase chain reaction amplified genomic DNA for the A/G dimorphism and polymerase chain reaction followed by high-resolution electrophoresis for the (AT)(n) microsatellite. For disease association studies, the Affected Family Based Controls approach was used.

RESULTS

The frequency of the A allele of 49 A/G polymorphism was 67.47% in the celiac allele group compared with 70.13% in the Affected Family Based Controls group. These differences were not significant. Analysis of the (AT)(n) polymorphism identified 17 different alleles, ranging from 262 to 312 bp in length, but no allele was significantly associated with the disease.

CONCLUSIONS

Our results did not show any evidence of association of any of the CTLA4 gene polymorphisms with the disease. This may result from population-specific differences in genetics and environmental susceptibility to CD.

Association of the CTLA-4 gene 49 A/G polymorphism with type 1 diabetes and autoimmune thyroid disease in Japanese children

OBJECTIVE

To clarify the role of the T-lymphocyte-associated-4 (CTLA-4) polymorphism in the susceptibility to child-onset type 1 diabetes with regard to its clinical characteristics and complications with autoimmune thyroid disease (AITD) in the Japanese population.

RESEARCH DESIGN AND METHODS

The CTLA-4 49 A/G polymorphism was detected by the PCR-restriction fragment-length polymorphism (RFLP) method in 97 type 1 diabetic subjects and 20 patients with Graves' disease, a cohort which included 4 patients who also had type 1 diabetes.

RESULTS

The genotypes and allele frequencies of this polymorphism did not differ between the type 1 diabetic subjects and the control subjects. The G allele frequency was 63.9% in the type 1 diabetic subjects. The G allele frequency in the subgroup of patients with a high titer of autoantibodies to the GAD antibody (Ab) was 72.9% (P = 0.0499 vs. control subjects); in the subgroup of patients without HLA DRB1*0405, it was 72.6% (P = 0.0271 vs. control subjects); and in the subgroup of patients with a residual beta-cell function, it was 78.6% (P = 0.0391 vs. control subjects). The G allele frequency in the patients with Graves' disease was also significantly higher at 78.1% (P = 0.0405 vs. control subjects). Furthermore, the frequency in our diabetic subjects complicated with Graves' disease was even higher (87.5%).

CONCLUSIONS

We have demonstrated that a distinct association exists between the G allele of CTLA-4 and high values of GAD Ab, residual beta-cell function, and the absence of HLA-DRB1*0405.