The HLA gene complex in thyroid autoimmunity: from epidemiology to etiology

Pili annulati coincident with alopecia areata, autoimmune thyroid disease, and primary IgA deficiency: case report and considerations on the literature

Pili annulati is a rare autosomal dominant hair disorder clinically characterized by a pattern of alternating bright and dark bands of the hair, the bright bands appearing dark if observed by transmitted light. This pattern is due to the periodic occurrence of air-filled cavities along the hair cortex which scatter and reflect the light while precluding its transmission. A susceptibility region, including a possibly responsible Frizzled gene, has been mapped to the telomeric region of chromosome 12q, although a specific mutation has not been identified. The condition has sometimes been observed in concurrence with alopecia areata, and in this paper we report a case in whom the concomitant severe alopecia areata was associated with autoimmune thyroid disease and primary IgA deficiency - a quadruple complex which, to our knowledge, has never been previously described. The occurrence of multiple immune disorders in the same patient affected by pili annulati could represent a key to understanding the high prevalence of alopecia areata in this condition. Specifically, in individuals predisposed to autoimmune disease, the molecular alterations that cause the anatomical changes of pili annulati could prompt the immune response against the hair root that underlies alopecia areata.

Thyroid dermopathy and acropachy

Graves' disease is an autoimmune condition commonly associated with thyroid dysfunction and with anti-thyroid antibodies, usually TSH receptor stimulating antibodies. Thyroid autoimmunity also may be associated with extra thyroidal manifestations. Most common extra thyroidal manifestation is ophthalmopathy. Less common is thyroid dermopathy, usually occurring in pretibial area. Dermopathy is almost always associated with ophthalmopathy and in severe cases with acropachy. A common antigen with thyroid in tissues of the skin and the eyes, most likely TSH receptor, is involved in pathogenesis of extra thyroidal manifestations. Presence of dermopathy and acropachy are predictors of severity of autoimmune process. Local corticosteroid application is the standard therapy for dermopathy. Response to therapy is good in mild cases and poor in severe cases. Immune modulators and biotherapies are undergoing randomized trials for ophthalmopathy component of Graves' disease. Any therapy proven to be effective for ophthalmopathy can be utilized in future for management of dermopathy.

Genetic profiling in Graves' disease: further evidence for lack of a distinct genetic contribution to Graves' ophthalmopathy

BACKGROUND

Graves' disease (GD), including Graves' ophthalmopathy or orbitopathy (GO), is an autoimmune disease with an environmental and genetic component to its etiology. The genetic contribution to the GO clinical phenotype remains unclear. Previous data from our laboratory and others have suggested that GO has no specific genetic component distinct from GD itself, while other reports have occasionally appeared suggesting that polymorphisms in genes such as CTLA4 and IL23R specifically increase the risk for GO. One of the criticisms of all these reports has been the clinical definition of the GO phenotype as distinct from hyperthyroid GD devoid of clinically significant eye involvement. The objective of this study was to take advantage of a phenotypically pure group of GD patients with GO and examine a series of genes associated with GD to determine if any were more definitively associated with GO rather than Graves' thyroid disease itself.

METHODS

To further examine whether specific susceptibility genes are associated with GO, we have performed further genetic association studies using highly characterized GO patients, many of whom had undergone orbital decompression surgery for their exophthalmos. We genotyped HLA, CTLA4, IL23R, and TSHR genes in a group of 256 Caucasian patients with severe GO (n=199) and less severe GO (n=57), and 90 patients with GD but no clinically apparent GO.

RESULTS

We found that the allele and genotype frequencies were not statistically different between GO and non-GO patients for any of the genes and gene combinations assessed.

CONCLUSIONS

These results provide further evidence that patients with GO do not have a distinct genetic susceptibility to their eye disease and again suggest that environmental and/or epigenetic influences are at play.

Mechanisms of environmental influence on human autoimmunity: a National Institute of Environmental Health Sciences expert panel workshop

The mechanisms leading to autoimmune diseases remain largely unknown despite numerous lines of experimental inquiry and epidemiological evidence. The growing number of genome-wide association studies and the largely incomplete concordance for autoimmune diseases in monozygotic twins support the role of the environment (including infectious agents and chemicals) in the breakdown of tolerance leading to autoimmunity via numerous mechanisms. The present article reviews the major theories on the mechanisms of the environmental influence on autoimmunity by addressing the different degrees of confidence that characterize our knowledge. The theories discussed herein include (i) the role of innate immunity mediated by toll-like receptors in triggering the autoimmune adaptive response characterizing the observed pathology; (ii) changes in spleen marginal zone B cells in autoantibody production with particular focus on the B10 subpopulation; (iii) Th17 cell differentiation and T regulatory cells in the aryl hydrocarbon receptor model; (iv) self antigen changes induced by chemical and infectious agents which could break tolerance by post-translational modifications and molecular mimicry; and finally (v) epigenetic changes, particularly DNA methylation, that are induced by environmental stimuli and may contribute to autoimmunity initiation. We are convinced that these working hypotheses, in most cases supported by solid evidence, should be viewed in parallel with animal models and epidemiological observations to provide a comprehensive picture of the environmental causes of autoimmune diseases.

Association of polymorphisms in non-classic MHC genes with susceptibility to autoimmune hepatitis

BACKGROUND

Autoimmune hepatitis is a chronic, generally progressive inflammatory disorder of the liver, of which the cause is unclear. It was demonstrated that genetic factors are involved in its pathogenesis. Previous studies showed that human leukocyte antigen in the major histocompatibility complex (MHC) is associated with susceptibility to autoimmune hepatitis. Current genome scanning studies suggest that genes outside the MHC also play a critical role in autoimmune disorders. This article focuses on our current understanding of the polymorphisms of these genes and their roles in the pathogenesis of autoimmune hepatitis.

DATA SOURCES

Studies were identified by searching MEDLINE and PubMed for articles using the keywords autoimmune hepatitis, polymorphism, CTLA-4, Fas, TNF-alpha, TGF-beta1, TBX21 and VDR up to May 2011. Additional papers were identified by a manual search of the references from key articles.

RESULTS

According to the case-control studies on genetic polymorphisms, at least six genes (CTLA-4, Fas, TNF-alpha, TGF-beta1, TBX21 and VDR) are involved in autoimmune hepatitis besides HLA. So far, there has been no agreement about gene susceptibility and the actual clinical significance of these genes is still controversial.

CONCLUSION

Studies on gene polymorphisms outside the MHC and knowledge of genetic predispositions for autoimmune hepatitis may not only elucidate pathogenic mechanisms, but also provide new targets for therapy in the future.

Genetics of autoimmune thyroid disease in the Lebanese population

This study aims to investigate the association of human leukocyte antigen (HLA) class II genes and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) with autoimmune thyroid diseases in the Lebanese population. A total of 128 patients with autoimmune thyroid disease (55 with Graves' disease (GD) and 73 with Hashimoto's thyroiditis (HT)) were typed for HLA DQA1 (0301 and 0501) and DQB1 (0201, 0302, and 0303) and for 49A/G CTLA-4 using PCR-based sequence-specific priming methods. A total of 186 matched controls were typed for the same alleles and compared to the diseased population. Results showed no significant differences in HLA DQB1*0201 or DQB1*0301 allelic frequencies or CTLA-4 polymorphisms between patients and controls. For GD, there was a weak association with HLA DQB1*0302 [34.6% (19 of 55) vs. 21.5% (40 of 186), P = 0.048, odds ratio (OR) = 1.926, confidence interval (CI) = 0.999-3.715] and HLA DQB1*0302-DQA1*0501 haplotype [56.36% (31 of 55) vs. 40.8% (76 of 186), P = 0.042, OR = 1.870, CI = 1.018-3.433]. For HT, the frequencies of DQB1*0302-DQA1*0501 haplotype [28.8% (21of 73) vs. 14.5% (27 of 186), P = 0.008, OR = 2.378, CI = 1.241-4.558] and DQB1*0302-DQA1*0301 haplotype [60.2% (44 of 73) vs. 38.7% (72 of 186), P = 0.002, OR = 2.402, CI = 1.381-4.180] were significantly higher in patients. On the other hand, weak association was found between HT and DQA1*0301 allele [32.9% (24 of 73) vs. 20.9% (39 of 186), P = 0.044, OR = 1.846, CI = 1.011-3.373]. Findings show that DQB1*0302-DQA1*0501 and DQB1*0302-DQA1*0301 haplotypes may play a role in the pathogenesis of HT in the Lebanese population. For the 49A/G CTLA-4 polymorphism, no significant difference was found between patients and controls.

HLA molecules and nasal carriage of Staphylococcus aureus isolated from dialysis and kidney transplant patients at a hospital in Southern Brazil

Background

Healthy individuals can host Staphylococcus aureus in the nasopharynx, body surface and vagina. Most invasive infections by this bacterium are endogenous, caused by strains spread from the nasopharynx of carriers. S. aureus is a pathogen involved in the etiology of hospital- and community-acquired infections. Transplant and dialysis patients are at risk of colonization or infection by multi-resistant S. aureus. Infection is directly linked to individual immunity, and the major histocompatibility complex (MHC) plays a crucial role in determining susceptibility to diseases. Different MHC specificities have been shown to be more frequent in individuals suffering from certain diseases. This study aimed to investigate the association between HLA class I (HLA-A and -B) and class II (HLA-DRB1) molecules and nasal carriage of S. aureus in dialysis and kidney transplant patients at a hospital in Southern Brazil.

Results

The sample consisted of 70 dialysis and 46 kidney transplant patients, totaling 116 patients. All subjects were typed for HLA molecules using LABType^® SSO (One Lambda). Nasal swab samples of S. aureus were isolated from the nasal cavity (both nostrils) of patients undergoing dialysis or kidney transplantation.

In renal dialysis patients, HLA-A*02 was the most frequent allele in both carriers (25.5%) and non-carriers (21.2%) of S. aureus. Allele A*68 was not observed in the carrier group, but the allele was observed six times in the non-carrier group (p = 0.0097). Regarding HLA-B and HLA-DRB1, no allele was shown to be involved in protection against or susceptibility to carriage of S. aureus. In kidney transplant patients, allele A*03 was more frequent in the non-carrier (20.83%) than in the carrier (5.88%) group (p = 0.0486). HLA-B*15 was present in carriers (5.88%) and non-carriers (25%) (p = 0.0179). Regarding class II alleles, DRB1*03 appeared to be related to susceptibility to carriage of S. aureus (p = 0.0319).

Conclusions

Our findings suggest that HLA-DRB1*03 may be involved in susceptibility to nasal carriage of S. aureus in transplant patients. In addition, HLA-A*68 (dialysis patients) and HLA-A*03 and HLA-B*15 (transplant patients) appear to be associated with increased resistance to S. aureus nasal carriage.

Cutting edge: the etiology of autoimmune thyroid diseases

Significant progress has been made in our understanding of the mechanisms leading to autoimmune thyroid diseases (AITD). For the first time, we are beginning to unravel these mechanisms at the molecular level. AITD, including Graves' disease (GD) and Hashimoto's thyroiditis (HT), are common autoimmune diseases affecting the thyroid. They have a complex etiology that involves genetic and environmental influences. Seven genes have been shown to contribute to the etiology of AITD. The first AITD gene discovered, HLA-DR3, is associated with both GD and HT. More recently, this association was dissected at the molecular level when it was shown that substitution of the neutral amino acids Ala or Gln with arginine at position beta 74 in the HLA-DR peptide binding pocket is the specific sequence change causing AITD. Non-MHC genes that confer susceptibility to AITD can be classified into two groups: (1) immune-regulatory genes (e.g., CD40, CTLA-4, and PTPN22); (2) thyroid-specific genes-thyroglobulin and TSH receptor genes. These genes interact with environmental factors, such as infection, likely through epigenetic mechanisms to trigger disease. In this review, we summarize the latest findings on disease susceptibility and modulation by environmental factors.

Genetic factors of autoimmune thyroid diseases in Japanese

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT), are caused by immune response to self-thyroid antigens and affect approximately 2–5% of the general population. Genetic susceptibility in combination with external factors, such as smoking, viral/bacterial infection, and chemicals, is believed to initiate the autoimmune response against thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITDs. Various techniques have been employed to identify genes contributing to the etiology of AITDs, including candidate gene analysis and whole genome screening. These studies have enabled the identification of several loci (genetic regions) that are linked to AITDs, and, in some of these loci, putative AITD susceptibility genes have been identified. Some of these genes/loci are unique to GD and HT and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. Known AITD-susceptibility genes are classified into three groups: HLA genes, non-HLA immune-regulatory genes (e.g., CTLA-4, PTPN22, and CD40), and thyroid-specific genes (e.g., TSHR and Tg). In this paper, we will summarize the latest findings on AITD susceptibility genes in Japanese.

No association between IL12B gene polymorphisms and Graves' disease in the Chinese population

BACKGROUND

Graves' disease (GD) is one of the most common autoimmune thyroid disorders and has a striking characteristic of female preponderance.

OBJECTIVE

The main objective of this study was to investigate whether IL12B gene polymorphisms were associated with either GD itself or with gender bias in GD.

METHODS

GD patients (151 males, 97 females) and 211 healthy control subjects without antithyroid autoantibodies or a family history of autoimmune disorders were recruited for this study. The G/C polymorphism (rs6887695) of the IL12B gene was analyzed using the polymerase chain reaction-restriction fragment length polymorphism, and the deletion and insertion polymorphism (rs41292470) in the IL12B promoter was detected after polyacrylamide gel electrophoresis-silver staining method.

RESULTS

There was no significant difference between GD patients and normal subjects, and no differences in frequencies of genotypes or alleles of either polymorphism between male and female GD subjects.

CONCLUSION

We conclude that these IL12B gene polymorphisms were not associated with sex bias in GD and do not confer susceptibility to Graves' disease (GD) in the Chinese population.

The X chromosome and immune associated genes

The X chromosome is known to contain the largest number of immune-related genes of the whole human genome. For this reason, X chromosome has recently become subject of great interest and attention and numerous studies have been aimed at understanding the role of genes on the X chromosome in triggering and maintaining the autoimmune aggression. Autoimmune diseases are indeed a growing heath burden affecting cumulatively up to 10% of the general population. It is intriguing that most X-linked primary immune deficiencies carry significant autoimmune manifestations, thus illustrating the critical role played by products of single gene located on the X chromosome in the onset, function and homeostasis of the immune system. Again, the plethora of autoimmune stigmata observed in patients with Turner syndrome, a disease due to the lack of one X chromosome or the presence of major X chromosome deletions, indicate that X-linked genes play a unique and major role in autoimmunity. There have been several reports on a role of X chromosome gene dosage through inactivation or duplication in women with autoimmune diseases, for example through a higher rate of circulating cells with a single X chromosome (i.e. with X monosomy). Finally, a challenge for researchers in the coming years will be to dissect the role for the large number of X-linked microRNAs from the perspective of autoimmune disease development. Taken together, X chromosome might well constitute the common trait of the susceptibility to autoimmune diseases, other than to explain the female preponderance of these conditions. This review will focus on the available evidence on X chromosome changes and discuss their potential implications and limitations.

Hashimoto's Thyroiditis: From Genes to the Disease

Hashimoto's thyroiditis (HT) is the most prevalent autoimmune thyroid disorder. Intrathyroidal lymphocytic infiltration is followed by a gradual destruction of the thyroid gland which may lead to subclinical or overt hypothyroidism. Biochemical markers of the disease are thyroid peroxidase and/or thyroglobulin autoantibodies in the serum which are present with a higher prevalence in females than in males and increase with age. Although exact mechanisms of aetiology and pathogenesis of the disorder are not completely understood, a strong genetic susceptibility to the disease has been confirmed predominantly by family and twin studies. Several genes were shown to be associated with the disease occurrence, progression, and severity. Genes for human leukocyte antigen, cytotoxic T lymphocyte antigen-4, protein tyrosine phosphatase nonreceptor-type 22, thyroglobulin, vitamin D receptor, and cytokines are considered to be of utmost importance. Amongst endogenous factors for the disease development, the attention is focused predominantly on female sex, pregnancy with postpartum period and fetal microchimerism. Environmental factors influencing HT development are iodine intake, drugs, infections and different chemicals. Disturbed self-tolerance accompanied by the increased antigen presentation is a prerequisite for the HT occurrence, whereas proper interaction of thyroid cells, antigen presenting cells, and T cells are necessary for the initiation of thyroid autoimmunity. Secreted cytokines lead predominantly to T-helper type 1 (Th1) response as well as to Th 17 response which has only recently been implicated. Final outcome of HT is thyroid destruction which is mostly a consequence of the apoptotic processes combined with T-cell mediated cytotoxicity.

Promoter polymorphisms of the HLA-G gene, but not the HLA-E and HLA-F genes, is associated with non-segmental vitiligo patients in the Korean population

The aim of this study was to determine whether or not promoter polymorphisms of the class I major histocompatibility complex (HLA-E, HLA-F, and HLA-G) are associated with susceptibility to vitiligo. To identify a possible association with vitiligo, 241 patients with non-segmental vitiligo (NSV) and 395 healthy controls were recruited in this study. Three promoter single nucleotide polymorphisms (SNPs; rs1264459 of HLA-E, rs9258170 of HLA-F, and rs1736936 of HLA-G) were analyzed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and direct sequencing. Multiple logistic regression models (co-dominant 1, co-dominant 2, dominant, recessive, and log-additive models) were applied for odds ratios (ORs), 95% confidence intervals (CIs), and P values. To obtain the defined results, P values were recalculated by a Bonferroni correction. After the Bonferroni correction, the genotype of the SNP (rs1736936) of HLA-G was shown to have significant association with NSV (P = 0.045 in the recessive model). The genotype frequencies of the HLA-G SNP (rs1736936) had a significant correlation with the age of onset of NSV (P = 0.016 in the co-dominant 1 model and P = 0.027 in the dominant model). Our results suggest that HLA-G, but not HLA-E and HLA-F, may be associated with susceptibility to NSV in the Korean population.

Efficacy of HLA-DRB1∗03:01 and H2E transgenic mouse strains to correlate pathogenic thyroglobulin epitopes for autoimmune thyroiditis

Thyroglobulin (Tg), a homodimer of 660 kD comprising 2748 amino acids, is the largest autoantigen known. The prevalence of autoimmune thyroid disease, including Hashimoto's thyroiditis and Graves' disease, has provided the impetus for identifying pathogenic T cell epitopes from human Tg over two decades. With no known dominant epitopes, the search has long been a challenge for investigators. After identifying HLA-DRB1∗03:01 (HLA-DR3) and H2E(b) as susceptibility alleles for Tg-induced experimental autoimmune thyroiditis in transgenic mouse strains, we searched for naturally processed T cell epitopes with MHC class II-binding motif anchors and tested the selected peptides for pathogenicity in these mice. The thyroiditogenicity of one peptide, hTg2079, was confirmed in DR3 transgenic mice and corroborated in clinical studies. In H2E(b)-expressing transgenic mice, we identified three T cell epitopes from mouse Tg, mTg179, mTg409 and mTg2342, based on homology to epitopes hTg179, hTg410 and hTg2344, respectively, which we and others have found stimulatory or pathogenic in both DR3- and H2E-expressing mice. The high homology among these peptides with shared presentation by DR3, H2E(b) and H2E(k) molecules led us to examine the binding pocket residues of these class II molecules. Their similar binding characteristics help explain the pathogenic capacity of these T cell epitopes. Our approach of using appropriate human and murine MHC class II transgenic mice, combined with the synthesis and testing of potential pathogenic Tg peptides predicted from computational models of MHC-binding motifs, should continue to provide insights into human autoimmune thyroid disease.

Uveitis-associated epitopes of retinal antigens are pathogenic in the humanized mouse model of uveitis and identify autoaggressive T cells

Noninfectious uveitis is a leading cause of blindness and thought to involve autoimmune T cell responses to retinal proteins (e.g., retinal arrestin [soluble-Ag (S-Ag)]). There are no known biomarkers for the disease. Susceptibility is associated with HLA, but little is known about susceptible class II alleles or the potentially pathogenic epitopes that they present. Using a humanized HLA-transgenic mouse model of S-Ag-induced autoimmune uveitis, we identified several susceptible and resistant alleles of HLA-DR and -DQ genes and defined pathogenic epitopes of S-Ag presented by the susceptible alleles. The sequences of these epitopes overlap with some previously identified peptides of S-Ag ("M" and "N"), known to elicit memory responses in lymphocytes of uveitis patients. HLA-DR-restricted, S-Ag-specific CD4(+) T cells could be detected in blood and draining lymph nodes of uveitic mice with HLA class II tetramers and transferred the disease to healthy mice. Importantly, tetramer-positive cells were detected in peripheral blood of a uveitis patient. To our knowledge, these findings provide the first tangible evidence that an autoimmune response to retina is causally involved in pathogenesis of human uveitis, demonstrating the feasibility of identifying and isolating retinal Ag-specific T cells from uveitis patients and may facilitate their development as biomarkers for the disease.

Selective IgA deficiency in autoimmune diseases

Selective immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in Caucasians. It has previously been suggested to be associated with a variety of concomitant autoimmune diseases. In this review, we present data on the prevalence of IgAD in patients with Graves disease (GD), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), celiac disease (CD), myasthenia gravis (MG) and rheumatoid arthritis (RA) on the basis of both our own recent large-scale screening results and literature data. Genetic factors are important for the development of both IgAD and various autoimmune disorders, including GD, SLE, T1D, CD, MG and RA, and a strong association with the major histocompatibility complex (MHC) region has been reported. In addition, non-MHC genes, such as interferon-induced helicase 1 (IFIH1) and c-type lectin domain family 16, member A (CLEC16A), are also associated with the development of IgAD and some of the above diseases. This indicates a possible common genetic background. In this review, we present suggestive evidence for a shared genetic predisposition between these disorders.

Human leukocyte antigen in primary biliary cirrhosis: an old story now reviving

Primary biliary cirrhosis (PBC) is an autoimmune biliary disease characterized by injury of small and medium size bile ducts, eventually leading to liver cirrhosis and death. Although the causes remain enigmatic, recent evidence has strengthened the importance of genetic factors in determining the susceptibility to the disease. Besides the strong heritability suggested by familial occurrence and monozygotic twins concordance, for decades there has not been a clear association with specific genes, with the only exception of a low risk conferred by a class II human leukocyte antigen (HLA) variant, the DRB1*08 allele, at least in some populations. The picture has become more complete when strong protective associations between PBC and the HLA DRB1*11 and DRB1*13 alleles were found in Italian and UK series. However, HLA genes have begun again to attract interest thanks to recent genome-wide association studies (GWAS), which clearly demonstrated that the major components of the genetic architecture of PBC are within the HLA region. As expected in a genetically complex disease, GWAS also identified several novel non-HLA variants, but it is worth noting that all of them are in immuno-related genes. In this review, the paradigmatic tale of what, and how, we learned about HLA genes in PBC will be retraced with particular focus on how GWAS are enabling a rewriting the story of PBC pathogenesis. These recent discoveries will not only drive functional studies but will also hold the promise of developing novel disease-specific treatments.

Relative vitamin D insufficiency in Hashimoto's thyroiditis

BACKGROUND

Vitamin D insufficiency, defined as serum levels of 25-hydroxyvitamin D [25(OH)D3] lower than 30 ng/mL, has been reported to be prevalent in several autoimmune diseases such as multiple sclerosis and type 1 diabetes mellitus. The goal of the present study was to assess whether vitamin D insufficiency is also a feature of Hashimoto's thyroiditis (HT).

METHODS

We performed a prevalence case-control study that included 161 cases with HT and 162 healthy controls. Serum levels of 25(OH)D3, calcium, phosphorus, and parathyroid hormone were measured in all 323 subjects.

RESULTS

The prevalence of vitamin D insufficiency in HT cases (148 of 161, 92%) was significantly higher than that observed in healthy controls (102 of 162, 63%, p < 0.0001). Among HT cases, the prevalence rate of vitamin D insufficiency showed a trend to be higher in patients with overt hypothyroidism (47 of 50, 94%) or subclinical hypothyroidism (44 of 45, 98%) than in those with euthyroidism (57 of 66, 86%), but the differences were not significant (p = 0.083).

CONCLUSION

Vitamin D insufficiency is associated with HT. Further studies are needed to determine whether vitamin D insufficiency is a casual factor in the pathogenesis of HT or rather a consequence of the disease.

Association of an SNP with intrathymic transcription of TSHR and Graves' disease: a role for defective thymic tolerance

Graves' disease (GD) is the paradigm of an anti-receptor autoimmune disease, with agonistic auto-antibodies against the thyrotropin receptor (TSHR-thyroid-stimulating hormone receptor) being the underlying pathogenic effector mechanism. The TSHR belongs to the category of tissue-restricted antigens, which are promiscuously expressed in the thymus and thereby induce central T cell tolerance. In order to understand the association between TSHR gene polymorphisms and GD, we tested the hypothesis that TSHR gene variants affect susceptibility to GD by influencing levels of TSHR transcription in the thymus. We show that thymic glands from non-autoimmune donors homozygous for the rs179247 SNP predisposing allele of TSHR had significantly fewer TSHR mRNA transcripts than carriers of the protective allele. In addition, in heterozygous individuals, the TSHR predisposing allele was expressed at a lower level than the protective one as demonstrated by allele-specific transcript quantification. This unbalanced allelic expression was detectable in both thymic epithelial cells and thymocytes. Since the level of self-antigen expression is known to influence the threshold of central tolerance, these results are compatible with the notion that defective central tolerance contributes to the pathogenesis of GD, a scenario already implicated in type 1 diabetes mellitus, myasthenia gravis and autoimmune myocarditis.

Risk of canine cranial cruciate ligament rupture is not associated with the major histocompatibility complex

OBJECTIVES

To investigate the association of the major histocompatability (MHC) class II allele haplotype frequencies with the diagnosis of cranial cruciate ligament (CCL) rupture in two breeds of dog.

METHODS

DNA samples from populations of Labrador Retrievers and Golden Retrievers with CCL rupture and general populations of the same breeds were characterised for three DLA class II loci (DRB1*, DQA1* and DQB1*) alleles using sequence-based typing or reference strand-mediated conformation analysis.

RESULTS

Although distinct differences in haplotype types, frequencies and homozygozity were observed between the two breeds, no disease specific association could be identified for the development of the CCL rupture within either population.

CLINICAL SIGNIFICANCE

The risk for developing CCL rupture was not associated with DLA haplotype group(s) in Labrador Retrievers or Golden Retrievers, thus the hypothesis that there is an autoimmune basis to CCL rupture was not supported.

Radiotherapy-induced hyperthyroidism in a cystinotic kidney transplant patient with Hodgkin lymphoma

Hypothyroidism is a well-known complication of cystinosis. PTLD incidence in pediatric renal transplant population ranges between 1 and 4.5%. We describe the case of a young cystinotic patient who developed hyperthyroidism after radiotherapy for Hodgkin lymphoma. He is a 23-yr-old male who was diagnosed with cystinosis at the age of two. He developed renal failure and other extrarenal complications but never presented hypothyroidism. At the age of 12, he received a successful kidney transplant from a cadaveric donor. Two yr later, EBV-positive Hodgkin lymphoma was diagnosed and chemotherapy and radiotherapy were administered. He achieved remission. Eight yr later, autoimmune hyperthyroidism secondary to previous radiation was detected, and he slowly became symptomatic. Clinical symptoms and laboratory data spontaneously normalized. This is the first case of a cystinotic patient developing hyperthyroidism. Thyroid disorders, especially hypothyroidism, have been reported in association with neck irradiation. Hypothyroidism would have been considered to be a late complication of cystinosis and not a consequence of radiotherapy. Thyroid hormones, clinical examination, and history evaluation for thyroid dysfunction should be periodically monitored after neck radiotherapy. The thyroid should always be excluded from the irradiation fields. Multidisciplinary interaction in difficult cases should be encouraged.

Relationship between HLA-DRB1 polymorphism and susceptibility or resistance to multiple sclerosis in Caucasians: a meta-analysis of non-family-based studies

OBJECTIVE

To identify the contribution of HLA-DRB1 alleles to susceptibility or resistance to multiple sclerosis (MS) in Caucasians through a meta-analysis of non-family-based studies.

METHODS

A systematic review of case-control studies in Caucasians was performed. Studies examining allele or phenotype frequencies were analyzed separately. Odds ratio (OR) and 95% confidence intervals (CIs) were used. We also used the relatively predispositional effect (RPE) method to analyze several allele frequency studies to avoid skewed results due to some strongly associated alleles.

RESULTS

A total of 5464 cases and 7809 controls from 14 allele frequency studies and a total of 5401 cases and 7538 controls from 23 phenotype frequency studies were analyzed. DRB1*15 was definitely the strongest risk factor for MS (allele group, Pc<0.00013, OR 2.59, 95%CI 2.34-2.87; phenotype group, Pc<0.00013, OR 3.35, 95%CI 2.95-3.80). DRB1*03 frequencies were significantly increased among MS cases in the phenotype group (Pc= 0.0013, OR 1.21, 95%CI 1.09-1.33) but not in the allele group. DRB1*14 and DRB1*07 showed protective effects against MS in both groups (DRB1*14, allele group, Pc<0.00013, OR 0.53, 95%CI 0.42-0.66; phenotype group, Pc<0.00013, OR 0.57, 95%CI 0.45-0.71; DRB1*07, allele group, Pc<0.0026, OR 0.75, 95%CI 0.64-0.87; phenotype group, Pc<0.00013, OR 0.67, 95%CI 0.61-0.73). By RPE method, DRB1*14, and DRB1*07 showed protective effects after excluding DRB1*15 from the analysis. DRB1*03 was significantly higher in MS cases than controls after removing both DRB1*15 and DRB1*14.

CONCLUSIONS

In Caucasians, we highlighted the definite protective role of HLA-DRB1*14 and DRB1*07 for MS. DRB1*03 is probably the only risk factor for MS besides DRB1*15 and a common genetic foundation for autoimmune disease. Targeting to these alleles may have potential values in prevention or therapy for MS in the specific population.

Diseases associated with thyroid autoimmunity: explanations for the expanding spectrum

Anyone who has been in an endocrine clinic will appreciate that associations exist between autoimmune thyroid disease (AITD) and other autoimmune disorders. However, the full extent of these associations is still not fully appreciated, and new associations are being uncovered which may shed new light on the pathogenic basis for these connections, and the underlying reasons for them are only now becoming understood. This review is based on the British Thyroid Association Pitt-Rivers Lecture 2010. The first section provides an update on studies which have detailed the strength of various autoimmune disease associations, the second section discusses the environmental and genetic factors which underlie these associations and the final section describes some recently identified, unexpected AITD associations. Unravelling these associations further will illuminate the pathogenesis of autoimmune diseases and offers the prospect of new therapeutic approaches.

Pearls in autoimmunity

This manuscript does a review of the more frequent issues published at Autoimmunity Reviews, Journal of Autoimmunity and Autoimmunity in the period of January–December 2009. The following topics were commented: (1) multiple sclerosis (MS) and its relationships with Epstein Barr infection, with vitamin D polymorphism and the new modalities of MS treatment. (2) Type 1 diabetes and genetic discovers, studies with GAD 65 and IA-2 autoantigen and the association T1D and autoimmune organ-specific diseases. (3) Autoimmune thyroid disorders and its association with susceptibility genes and polymorphisms. (4) Multiplex autoantibody profiling approaches in MS and rheumatoid arthritis. (5) Th17 cytokine in primary biliary cirrhosis, experimental autoimmune encephalomyelitis and celiac disease. (6) Vitamin D and experimental autoimmune prostatitis and pulmonary alveolar proteinosis.

Injections of Clostridium botulinum neurotoxin A may cause thyroid complications in predisposed persons based on molecular mimicry with thyroid autoantigens

A woman with Hashimoto's thyroiditis, under replacement L-T4, repeatedly experienced, over a 10-year period, elevations of serum TSH after eyelid injections of Clostridium botulinum neurotoxin A (Btx). We hypothesized a link between Btx injections and TSH elevations via molecular mimicry, and aimed to verify our hypothesis. Using an in silico approach, we searched first for amino acid sequence homology between Btx and thyroid autoantigens, and next for HLA binding motifs within homologous segments. We found that (i) Btx and thyroid autoantigens share amino acid sequence homology; (ii) some homologous regions contain epitopes of both Btx and thyroid autoantigens; (iii) some of such regions contain HLA-DR3 and/or HLA-DR7 binding motifs, which predominate over other HLA-DRs. This is relevant because the patient's HLA-DR haplotype was DR3/DR7. In conclusion, clinical and bioinformatics data suggest a possible pathogenetic link between Btx and autoimmune thyroid diseases. Considering the wide and increasing medical and dermocosmetic use of Btx, and the frequently subclinical course of autoimmune thyroid diseases, we think that thyroid "complications" may pass frequently undetected in Btx-treated persons.

Comprehensive genotyping in two homogeneous Graves' disease samples reveals major and novel HLA association alleles

BACKGROUND

Graves' disease (GD) is the leading cause of hyperthyroidism and thyroid eye disease inherited as a complex trait. Although geoepidemiology studies showed relatively higher prevalence of GD in Asians than in Caucasians, previous genetic studies were contradictory concerning whether and/or which human leukocyte antigen (HLA) alleles are associated with GD in Asians.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a case-control association study (499 unrelated GD cases and 504 controls) and a replication in an independent family sample (419 GD individuals and their 282 relatives in 165 families). To minimize genetic and phenotypic heterogeneity, we included only ethnic Chinese Han population in Taiwan and excluded subjects with hypothyroidism. We performed direct and comprehensive genotyping of six classical HLA loci (HLA-A, -B, -C, -DPB1, -DQB1 and -DRB1) to 4-digit resolution. Combining the data of two sample populations, we found that B*46:01 (odds ratio under dominant model [OR]  = 1.33, Bonferroni corrected combined P [P(Bc)]  = 1.17 x 10⁻²), DPB1*05:01 (OR  = 2.34, P(Bc) = 2.58 x 10⁻¹⁰), DQB1*03:02 (OR  = 0.62, P(Bc)  = 1.97 x 10⁻²), DRB1*15:01 (OR  = 1.68, P(Bc) = 1.22 x 10⁻²) and DRB1*16:02 (OR  = 2.63, P(Bc)  = 1.46 x 10⁻⁵) were associated with GD. HLA-DPB1*05:01 is the major gene of GD in our population and singly accounts for 48.4% of population-attributable risk.

CONCLUSIONS/SIGNIFICANCE

These GD-associated alleles we identified in ethnic Chinese Hans, and those identified in other Asian studies, are totally distinct from the known associated alleles in Caucasians. Identification of population-specific association alleles is the critical first step for individualized medicine. Furthermore, comparison between different susceptibility/protective alleles across populations could facilitate generation of novel hypothesis about GD pathophysiology and indicate a new direction for future investigation.

Environmental triggers of thyroiditis: hepatitis C and interferon-α

Autoimmune thyroid diseases (AITD) are postulated to develop as a result of a complex interplay between several genetic and environmental influences. The pathogenesis of AITD is still not clearly defined. However, among the implicated triggers (e.g. iodine, infections, medications), more recent data confirmed strong associations of AITD with the hepatitis C virus (HCV) infection and interferon-α (IFNα) therapy. Moreover, it is likely that HCV and IFN act in synergism to trigger AITD in patients. Indeed, approximately 40% of HCV patients develop either clinical or subclinical disease while receiving IFNα. Interferon induced thyroiditis (IIT) can manifest as non-autoimmune thyroiditis (presenting as destructive thyroiditis, or non-autoimmune hypothyroidism), or autoimmune thyroiditis [presenting with clinical features of Graves' disease (GD) or Hashimoto's thyroiditis (HT)]. Although not yet clearly understood, it is thought that IFNα can induce thyroiditis via both immune stimulatory and direct toxic effects on the thyroid. In view of the high frequency of IIT, routine screening and surveillance of HCV patients receiving IFNα is recommended to avoid the complications, such as cardiac arrhythmias, associated with thyrotoxicosis. In summary, IIT is a common clinical problem that can be readily diagnosed with routine thyroid function screening of HCV patients receiving IFN. The treatment of IIT consists of the standard therapy for differing clinical manifestations of IIT such as GD, HT, or destructive thyroiditis. However, anti-thyroid medications are not recommended in this setting since they can potentially be hepatotoxic.

Analysis of immune regulatory genes' copy number variants in Graves' disease

BACKGROUND

Copy number variants (CNVs) have recently been reported to be associated with several autoimmune conditions. Moreover, loci involved in immunity are enriched in CNVs. Therefore, we hypothesized that CNVs in immune genes associated with Graves' disease (GD) may contribute to the etiology of disease.

METHODS

One hundred ninety-one North American Caucasian GD patients and 192 Caucasian controls were analyzed for CNVs in three major immune regulatory genes: CD40, PTPN22, and CTLA-4. Copy number was determined using quantitative-PCR (Q-PCR) assays specifically designed for determining copy numbers in genomic DNA. Additionally, a well-characterized CNV in the amylase gene was typed in a separate dataset of DNA samples that were derived from cell lines or blood.

RESULTS

No CNVs could be confirmed in the CD40 and CTLA-4 genes, even though a CD40 CNV is cataloged in the Database of Genomic Variants. Only the PTPN22 CNV was confirmed in our cohort, but it was rare and appeared in only two individuals. A key finding was that the source of DNA has a significant effect on CNV typing. There was a statistically significant increase in amylase locus deletions in cell line-derived DNA compared to blood-derived DNA samples.

CONCLUSIONS

We conclude that CNV analysis should be performed only using blood-derived DNA Samples. Additionally, the CTLA-4, CD40, and PTPN22 loci do not harbor CNVs that play a role in the etiology of GD.

HLA-DRB1*03 and DRB1*04 are associated with atrophic gastritis in an Italian population

BACKGROUND

Atrophic gastritis (AG) is often considered an autoimmune disorder and is associated with other autoimmune diseases. HLA-DRB1 alleles are often associated with autoimmune diseases, however HLA-DRB1 genotyping data in AG patients are lacking. The objective of the study was to evaluate the prevalence of HLA-DRB1 in AG patients.

METHODS

The occurrence of HLA-DRB1 alleles was assessed in 89 Italian AG patients (69.1% female) and 313 controls (47.3% females). Genomic DNA was extracted from peripheral venous blood, PCR-coamplified for HLA-DRB1 and typed using a reverse line-blot assay.

RESULTS

Compared to controls, prevalence of HLA-DRB1*03 (28.1% vs. 15.9%, p=0.01) and HLA-DRB1*04 (25.8% vs. 14.4%, p=0.01) was greater in AG patients, conferring an OR of 2.05 and 2.07, respectively. HLA-DRB1*01 occurred more frequently in controls than in AG patients (11.5% vs. 3.4%, p=0.01) conferring an OR of 0.27. AG patients carrying the HLA-DRB1*03 or *04 alleles were characterised by having more frequently autoimmune thyroid disease (70.4% vs. 42.2%, p=0.01) and intestinal metaplasia (86.4% vs. 62.2%, p=0.01).

CONCLUSIONS

In our population, over 50% of AG patients carry the HLA-DRB1*03 or *04 alleles associated with autoimmune diseases, suggesting that this subset of AG patients has a genetic predisposition to autoimmunity.

Type 1 diabetes associated with Hashimoto's thyroiditis and juvenile rheumatoid arthritis: a case report with clinical and genetic investigations

Autoimmune diseases are initiated by interaction between genetic and environmental factors and caused by the loss of immunologic tolerance to self-antigens. They cluster within families and individuals, but the aggregation in a triad is quite rare. We report a case of a young girl affected by three organ-specific autoimmune disorders, from which type 1 diabetes developed first, then Hashimoto's thyroiditis and juvenile rheumatoid arthritis were diagnosed. Hitherto unreported detailed genetic studies included genotyping of HLA class II, CTLA4, and PTPN22 gene regions. These genes have been associated with autoimmunity in general and some of their variants confer increased risk to all three diseases. Our results - with the limitation of reporting only on a single patient - contribute to the complex genetic background of these clustering organ-specific autoimmune diseases and the analysis of further similar cases might help to reveal how the major and minor genetic factors determine the individual clinical phenotype.

The autoimmunity of primary biliary cirrhosis and the clonal selection theory

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease in which an immune-mediated injury targets the small intrahepatic bile ducts. PBC is further characterized by highly specific serum antimitochondrial autoantibodies (AMA) and autoreactive T cells, a striking female predominance, a strong genetic susceptibility, and a plethora of candidate environmental factors to trigger the disease onset. For these reasons PBC appears ideal to represent the developments of the clonal selection theory over the past decades. First, a sufficiently potent autoimmunogenic stimulus in PBC would require the coexistence of numerous pre-existing conditions (mostly genetic, as recently illustrated by genome-wide association studies and animal models) to perpetuate the destruction of the biliary epithelium by the immune system via the persistence of forbidden clones. Second, the proposed modifications of mitochondrial autoantigens caused by infectious agents and/or xenobiotics well illustrate the possibility that peculiar changes in the antigen structure and flexibility may contribute to tolerance breakdown. Third, the unique apoptotic features demonstrated for cholangiocytes are the ideal setting for the development of mitochondrial autoantigen presentation to the immune system through macrophages and AMA thus turning the non traditional mitochondrial antigen into a traditional one. This article will review the current knowledge on PBC etiology and pathogenesis in light of the clonal selection theory developments.

Association of immunoglobulin A deficiency and elevated thyrotropin-receptor autoantibodies in two Nordic countries

Immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency, with suggested association with various types of autoimmunity, including Graves' disease. This study investigated the association of IgAD with elevated thyrotropin-receptor autoantibodies (TRAb). IgA was measured in TRAb-seropositive individuals from both Iceland (N = 299] and Sweden (N = 841]. In addition, TRAb levels were evaluated in 43 Icelandic and 50 Swedish IgAD individuals using Medizym TRA immunoassay, and positive samples were re-evaluated using BRAHMS TRAK human RIA. The IgAD individuals were HLA-genotyped to determine the HLA-B, DR, and DQ alleles. None of the 299 Icelandic TRAb-seropositive individuals had IgAD, whereas, a high prevalence of IgAD (14/841 (1:60)) was observed in the Swedish cohort (p = 0.027). The prevalence of TRAb-seropositivity in IgAD individuals was, however, increased in both cohorts. The HLA-DQ6 allele was associated with TRAb-seronegativity within the Icelandic IgAD cohort (p = 0.037). The prevalence of IgAD in TRAb-seropositive individuals in Sweden is 10 times higher than expected in the general population. Furthermore, TRAb seropositivity is common among IgAD individuals, both in Iceland and Sweden, suggesting a predisposition toward Graves' disease. These findings underline the significant association of IgAD with autoimmunity and its possible association with certain HLA-DQ alleles.

Immune-mediated bile duct injury: The case of primary biliary cirrhosis

Autoimmune cholangitis would be the appropriate name to define the immune-mediated bile duct injury following the breakdown of tolerance to mitochondrial proteins and the appearance of serum autoantibodies and autoreactive T cells. Nevertheless, the condition is universally named primary biliary cirrhosis (PBC). The disease etiology and pathogenesis remain largely unknown despite the proposed lines of evidence. One twin study and numerous epidemiology reports suggest that both a susceptible genetic background and environmental factors determine disease onset while a recent genome-wide association study proposed highly significant associations with several common genetic polymorphisms in subgroups of patients. Specific infectious agents and chemicals may contribute to the disease onset and perpetuation in a genetically susceptible host, possibly through molecular mimicry. Importantly, several murine models have been proposed and include strains in which PBC is genetically determined or induced by immunization with chemicals and bacteria. From a pathogenetic standpoint, new exciting data have demonstrated the unique apoptotic features of bile duct cells that allow the mitochondrial autoantigens to be taken up in their intact form within apoptotic blebs. We are convinced that the application of the most recent molecular techniques will soon provide developments in PBC etiology and pathogenesis with likely implications in diagnostics and therapeutics.

Different HLA class II (DRB1 and DQB1) alleles determine either susceptibility or resistance to NMO and multiple sclerosis among the French Afro-Caribbean population

BACKGROUND

Despite similarities, neuromyelitis optica (NMO) can be distinguished from multiple sclerosis (MS) by clinical, radiological and serological findings.

OBJECTIVE

This case-control study aimed to determine whether patients with NMO or with MS in an Afro-Caribbean population originating from French West Indies shared the same or different HLA class I and II pattern distribution.

METHODS

The association with HLA class II (DRB1 and DQB1) alleles was tested in 42 NMO patients, 163 MS patients and 150 healthy controls. HLA-DRB1 and DQB1 typing was undertaken on genomic DNA extracted from peripheral blood leucocytes.

RESULTS

By comparison with healthy controls, significantly increased frequency of HLA-DRB1 03 (26.2% vs. 13%, odds ratio 2.4, 95% confidence interval 1.31-4.28, p after correction, cp 0.045) was observed in patients with NMO. By contrast, in MS patients, HLA-DRB1 15 (24.8% vs. 13%, odds ratio 2.21, 95% CI 1.45-3.36, cp < 0.0015), but not DRB1 03 allele, was positively associated with the disease. Moreover, a modest protective effect of HLA-DRB1 11 in the MS group, independently of DRB1 15 association, was found (13.7% vs. 7% in controls, odds ratio 0.48, p 0.006), but did not survive Bonferroni correction.

CONCLUSION

In conclusion, comparison of the HLA-DRB1 and DQB1 distribution in NMO and MS in this Afro-Caribbean population shows important differences in the HLA associations among NMO and MS.

Hepatitis C and interferon induced thyroiditis

Autoimmune thyroid diseases (AITDs) are complex diseases that develop as a result of interactions between genetic, epigenetic, and environmental factors. Significant progress has been made in our understanding of the genetic and environmental triggers contributing to AITD. The major environmental triggers of AITD include iodine, smoking, medications, pregnancy, and possibly stress. In this review we will focus on two well-documented environmental triggers of AITD, hepatitis C virus (HCV) infection and interferon alpha (IFNa) therapy. Chronic HCV infection has been shown to be associated with increased incidence of clinical and subclinical autoimmune thyroiditis (i.e. the presence of thyroid antibodies in euthyroid subjects). Moreover, IFNa therapy of chronic HCV infection is associated with subclinical or clinical thyroiditis in up to 40% of cases which can be autoimmune, or non-autoimmune thyroiditis. In some cases interferon induced thyroiditis (IIT) in chronic HCV patients may result in severe symptomatology necessitating discontinuation of therapy. While the epidemiology and clinical presentation of HCV and interferon induced thyroiditis have been well characterized, the mechanisms causing these conditions are still poorly understood.

Screening for thyroid disease: defining high-risk populations

The pros and cons of population screening for thyroid disease have been hotly debated over the past several decades. This article addresses the issue from the point of view of the potential benefit of screening, that is, disease detection. Earlier diagnoses of hypothyroidism, hyperthyroidism, thyroid nodules, thyroid cancer and so on, with implementation of the indicated diagnostic and therapeutic interventions, avoid the adverse consequences of unrecognized and untreated progressive disease. Arguments against screening and case-finding often focus on cost considerations. To achieve the greatest yield at the lowest cost, our emphasis is on vulnerable populations with associated risk factors, and special situations such as pregnancy.

Phenotypical and functional alterations of CD8 regulatory T cells in primary biliary cirrhosis

The mechanisms that lead to loss of tolerance in autoimmune disease have remained both elusive and diverse, including both genetic predisposition and generic dysregulation of critical mononuclear cell subsets. In primary biliary cirrhosis (PBC), patients exhibit a multilineage response to the E2 component of pyruvate dehydrogenase involving antibody as well as autoreactive CD4 and CD8 responses. Recent data from murine models of PBC have suggested that a critical mechanism of biliary destruction is mediated by liver-infiltrating CD8 cells. Further, the number of autoreactive liver-infiltrating CD4 and CD8 cells is significantly higher in liver than blood in patients with PBC. Based on this data, we have studied the frequencies and phenotypic characterization of both CD4 and CD8 regulatory T cell components in both patients with PBC and age-sex matched controls. Our data is striking and indicate that CD8 Treg populations from PBC patients, but not controls, have significant phenotypic alterations, including increased expression of CD127 and reduced CD39. Furthermore, in vitro induction of CD8 Tregs by incubation with IL10 is significantly reduced in PBC patients. Importantly, the frequencies of circulating CD4+CD25+ and CD8+ and CD28- T cell subpopulations are not significantly different between patients and controls. In conclusion, these data identify the CD8 Treg subset as a regulatory T cell subpopulation altered in patients with PBC.

Genetic susceptibility to autoimmune thyroid disease: past, present, and future

BACKGROUND

Autoimmune thyroid diseases (AITD), including Graves' disease and Hashimoto's thyroiditis, arise due to complex interactions between environmental and genetic factors. There are sound data coming from epidemiological, family, and twin studies demonstrating a strong genetic influence on the development of AITD. In this review we summarize the new findings on the genetic susceptibility to AITD focusing on emerging mechanisms of susceptibility.

SUMMARY

Candidate gene analysis, whole-genome linkage screening, genome-wide association studies, and whole-genome sequencing are the major technologies that have advanced this field, leading to the identification of at least seven genes whose variants have been associated with AITD. One of the major ones is the HLA-DR gene locus. Recently, it was shown that substitution of the neutral amino acids Ala or Gln with arginine at position beta 74 in the HLA-DR peptide-binding pocket is key to the etiology of both Graves' disease and Hashimoto's thyroiditis. Several other genes have also been shown to confer susceptibility to AITD. These can be classified into two groups: (i) immune regulatory genes (cytotoxic T lymphocyte-associated protein 4, CD40, protein tyrosine phosphatase-22, and CD25) and (ii) thyroid-specific genes (thyroglobulin and thyrotropin receptor genes). The influence of individual genes on the development of AITD when assessed in a population appears to be weaker than would be expected from the data showing strong genetic susceptibility to AITD. Two possible mechanisms explaining this discrepancy are gene-gene interactions and subset effects.

CONCLUSIONS

Significant progress has been made in our understanding of the immunogenetic mechanisms leading to thyroid autoimmunity. For the first time we are beginning to unravel these mechanisms at the molecular level. It is hoped that these new data will be translated into novel therapies and prevention strategies in AITD, such as costimulatory blockade.

Shared genetic relationships underlying generalized vitiligo and autoimmune thyroid disease

BACKGROUND

Generalized vitiligo is an autoimmune disease of skin pigmentation that is associated with increased prevalence of other autoimmune diseases, particularly autoimmune thyroid disease (AITD; principally Hashimoto's disease and Graves' disease), both in vitiligo patients and their close relatives, suggesting a heritable predisposition involving, in part, shared susceptibility genes.

SUMMARY

This review summarizes current knowledge of vitiligo epidemiology and genetics, highlighting recent findings from genome-wide approaches to disease gene identification, emphasizing susceptibility loci shared with other autoimmune diseases, particularly AITD, as well as some important differences.

CONCLUSIONS

Inherited susceptibility to generalized vitiligo involves a number of specific genes, many of which are shared with other autoimmune diseases that are epidemiologically associated with vitiligo, including AITD, confirming a longstanding hypothesis about the genetic basis of these disorders. These genes provide potential therapeutic targets for novel approaches to treatment as well as for approaches to presymptomatic diagnosis and disease prevention in individuals with inherited susceptibility to this group of autoimmune diseases.

Diagnostic challenges in celiac disease and the role of the tissue transglutaminase-neo-epitope

The diagnosis of celiac disease (CD) remains a clinical challenge based on the incomplete specificity and sensitivity rates of current non-invasive tests. Furthermore, histological assessments fail to identify all overt cases and, in particular, do not manifest pathognomonic alterations in silent cases. Accordingly, the majority of CD cases are diagnosed with great delay. Recent research into the pathogenesis of CD, allowed us to identify a neo-antigen that appears to be the most promising serological tool for the detection of anti-tissue transglutaminase as well as anti-gliadin antibodies.

The role of glutamic or aspartic acid in position four of the epitope binding motif and thyrotropin receptor-extracellular domain epitope selection in Graves' disease

CONTEXT

Development of Graves' disease (GD) is related to HLA-DRB1*0301 (DR3),and more specifically to arginine at position 74 of the DRB1 molecule. The extracellular domain (ECD) of human TSH receptor (hTSH-R) contains the target antigen.

OBJECTIVE AND DESIGN

We analyzed the relation between hTSH-R-ECD peptides and DR molecules to determine whether aspartic acid (D) or glutamic acid (E) at position four in the binding motif influenced selection of functional epitopes.

RESULTS

Peptide epitopes from TSH-R-ECD with D or E in position four (D/E+) had higher affinity for binding to DR3 than peptides without D/E (D/E-) (IC(50) 29.3 vs. 61.4, P = 0.0024). HLA-DR7, negatively correlated with GD, and DRB1*0302 (HLA-DR18), not associated with GD, had different profiles of epitope binding. Toxic GD patients who are DR3+ had higher responses to D/E+ peptides than D/E- peptides (stimulation index 1.42 vs. 1.22, P = 0.028). All DR3+ GD patients (toxic + euthyroid) had higher responses, with borderline significance (Sl; 1.32 vs. 1.18, P = 0.051). Splenocytes of DR3 transgenic mice immunized to TSH-R-ECD responded to D/E+ peptides more than D/E- peptides (stimulation index 1.95 vs. 1.69, P = 0.036). Seven of nine hTSH-R-ECD peptide epitopes reported to be reactive with GD patients' peripheral blood mononuclear cells contain binding motifs with D/E at position four.

CONCLUSIONS

TSH-R-ECD epitopes with D/E in position four of the binding motif bind more strongly to DRB1*0301 than epitopes that are D/E- and are more stimulatory to GD patients' peripheral blood mononuclear cells and to splenocytes from mice immunized to hTSH-R. These epitopes appear important in immunogenicity to TSH-R due to their favored binding to HLA-DR3, thus increasing presentation to T cells.

Association of the amino acid motifs of BoLA-DRB3 alleles with mastitis pathogens in Japanese Holstein cows

The association of the polymorphism of bovine leukocyte antigen (BoLA-DRB3) genes, identified by the polymerase chain reaction sequence-based typing (PCR-SBT) method, with resistance and susceptibility to mastitis caused by Streptococci, coagulase-negative Staphylococci, Escherichia coli and Staphylococcus aureus was investigated. Blood samples for DNA extraction were collected from 170 Holstein cows (129 mastitis and 41 healthy cows) from 5 districts in Chiba prefecture, Japan. Susceptibility or resistance to the mastitis-causing pathogens was thought to vary by the presence of amino acid substitutions at the 9, 11, 13, and 30 positions. DRB3*0101 and DRB3*1501 had amino acid motifs of Glu(9), Ser(11), Ser(13), and Tyr(30), and they were considered to have susceptibility to all 4 mastitis pathogens. In contrast, DRB3*1101 and DRB3*1401 had amino acid motifs of Gln(9), His(11), Gly(13), and His(30) in these positions, and they also had Val(86), so these alleles were considered to have resistance to Streptococcal and coagulase-negative Staphylococcal mastitis. However, in the case of Escherichia coli mastitis, amino acid substitutions at the 9, 11, 13, and 30 positions had little effect, but rather substitutions at the 47, 67 positions of pocket 7, and at the 71, 74 positions of pocket 4, Tyr(47), Ile(67), Ala(71), and Ala(74), were associated with resistance. This motif was present in DRB3*1201.

HLA and CTLA4 polymorphisms may confer a synergistic risk in the susceptibility to Graves' disease

Graves' disease (GD) is an autoimmune disease characterized by hyperthyroidism due to the presence of autoantibodies against thyroid-stimulating hormone receptor, which is measured as thyroid-stimulating hormone-binding inhibitory immunoglobulin (TBII). Most of the GD patients are TBII-positive, but TBII is undetectable in a proportion of GD patients. We previously reported the association of HLA-A 02 and -DPB1 0501 with TBII-positive GD, whereas TBII-negative GD showed association with HLA-A 02 and DPB1 0202. Recently, polymorphisms of cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) gene are reported to be associated with GD. In this study, we investigated 329 (240 TBII-positive and 89 TBII-negative) GD patients and 378 controls for the polymorphisms in HLA-A, -DPB1 and CTLA4 (CT60, rs3087243, A/G) to investigate the contribution of these factors in the susceptibility to GD. A significant association with CTLA4 was found for the TBII-positive GD (G carriers in patients vs controls, 97.1 vs 91.8%; odds ratio (OR)=2.97, 95% confidence interval=1.29-6.87, P=0.008), but the association was weak and not significant for the TBII-negative GD (94.4 vs 91.8%; OR=1.50, 95% confidence interval=0.57-3.98, P=0.41). Stratification analyses suggested a possible synergistic interaction of CTLA4 with HLA-A 02 and -DPB1 0501 in the susceptibility to TBII-positive GD.

Tg.2098 is a major human thyroglobulin T-cell epitope

An HLA-DR variant containing Arginine at position 74 of the DRbeta1 chain confers a strong genetic susceptibility to autoimmune thyroid diseases (AITD), Graves' disease (GD) and Hashimoto's thyroiditis (HT), while Glutamine at position DRbeta1-74 is protective. We hypothesized that the DRbeta1-Arg74 variant is able to present pathogenic thyroglobulin (Tg) peptides to T-cells more efficiently, thereby triggering thyroid autoimmunity. Indeed, we have previously identified 4 human Tg (hTg) peptides that bind specifically to DRbeta1-Arg74 with much weaker binding to the protective variant DRbeta1-Gln74. The aim of our study was to examine in vivo whether an hTg peptide that binds strongly and specifically to DRbeta1-Arg74 is capable of stimulating T-cells during the induction of thyroiditis in a "humanized" mouse expressing human DR3, and in patients positive for Tg antibodies. Sequencing of exon 2 of the DR transgene in the DR3 mice, null for endogenous MHC II molecules, confirmed that they expressed the disease-associated DRbeta1-Arg74 variant, thus making them an ideal in vivo model to test the presentation of hTg peptides by DRbeta1-Arg74 HLA-DR. Induction of EAT in the DR3 mice lead to T-cell stimulation and proliferation to Tg.2098, a strong and specific DRbeta1-Arg74 binder, while a non-binding control peptide, Tg.2766 did not induce this response. Moreover, Tg.2098 stimulated T-cells from 4 individuals who were positive for thyroglobulin antibodies, demonstrating that Tg.2098 is an immunogenic peptide capable of being presented in vivo and activating T-cells in EAT and AITD. Energetic analysis of the complex formed by Tg.2098 and DRbeta-Arg74 has shown that the origin of the affinity was determined by residues 1, 7 and 9 in the peptide, while the selectivity of the peptide for the MHC was determined by the Asp in position 4. The disease-protective substitution R74Q, leads to reduction in affinity due to changes in local interaction with D4 as well as non-local interaction with other residues. The electrostatic potential on the surface of the DRbeta-Arg74-Tg.2098 complex has a unique signature which may be recognized by T-cell receptors leading to autoimmune thyroiditis. Taken together these findings suggest that Tg.2098, a strong and specific binder to the disease-associated HLA-DRbeta-Arg74, is a major human T-cell epitope and participant in the pathoetiology of AITD.

Stress and autoimmunity

The etiology of autoimmune disease is multifactorial, including genetic, environmental, hormonal, and immunological factors. Nevertheless, the onset of autoimmune disorders remains enigmatic. Physical and psychological stresses have been suggested in the development of autoimmune disease, since numerous animal and human studies demonstrated the effect of stressors on immune function. Moreover, many retrospective studies had found that a high proportion (up to 80%) of patients reported uncommon emotional stress before disease onset. This, however, is not surprising as the disease itself causes significant stress in the patient. Recent reviews discuss the possible role of psychological stress, and of the major stress-related hormones, in the pathogenesis of autoimmune disease and presume that the stress-triggered neuroendocrine hormones lead to immune dysregulation, which ultimately results in autoimmune disease by altering or amplifying cytokine production. However, there is no evidence based research to support this concept. Nonetheless, stress reactions should be discussed with autoimmune patients. Applied implications are discussed, concentrating on the need for multidisciplinary care interventions that target patients' disease symptoms and help them cope with their illness.