Relationship between HLA antigens and infectious agents in contributing towards the development of Graves' disease

Comorbid Autoimmune Diseases in Patients With Myasthenia Gravis: A Retrospective Cross-Sectional Study of a Chinese Cohort

Introduction: The phenomenon of coexisting autoimmune diseases (ADs) in patients with myasthenia gravis (MG) has attracted considerable attention. However, few studies have investigated the burden and potential clinical associations of ADs in Chinese MG cohorts.

Methods: In this retrospective cross-sectional study, we reviewed the records of 1,132 patients with MG who were admitted to Huashan Hospital Fudan University from August 2013 to August 2020. Patients were excluded if they had incomplete medical records (n = 336).

Results: Comorbid ADs were found in 92 of 796 Chinese patients with MG (11.6%), among which, hyperthyroidism (6.7%), hypothyrosis (2.6%), and vitiligo (0.8%) were predominant. Patients with MG with ADs were predominantly female, younger at the onset of MG symptoms, and had a lower frequency of thymoma. Compared to the general population, we found a significantly higher percentage of hyperthyroidism (8.5-fold increase, p < 0.001), hypothyrosis (2.6-fold increase, p < 0.001), vitiligo (1.3-fold increase, p < 0.001), rheumatoid arthritis (1.4-fold increase, p < 0.001), immune thrombocytopenic purpura (193.1-fold increase, p < 0.001), autoimmune hemolytic anemia (7.4-fold increase, p < 0.001), autoimmune hepatitis (5.1-fold increase, p < 0.001), and polymyositis (11.5-fold increase, p < 0.001) in patients with MG with ADs. Patients with MG with ADs presented a lower proportion of previous history of MC (0 vs. 5.6%, p < 0.05) than those without ADs. The proportion of MGFA Class I at onset in patients with MG with ADs was significantly higher than that in patients with MG without ADs (77.0 vs. 52.7%, p < 0.05). The proportion of MuSK-positive in patients with MG with ADs was significantly lower than that in patients with MG without ADs (0 vs. 4.8%, p < 0.05).

Conclusion: In conclusion, we observed a higher frequency of concurrent ADs in a Chinese MG cohort. Furthermore, MG combined with ADs tended to have mild clinical presentation.

Cross-Reactivity between Chemical Antibodies Formed to Serum Proteins and Thyroid Axis Target Sites

In some instances, when chemicals bind to proteins, they have the potential to induce a conformational change in the macromolecule that may misfold in such a way that makes it similar to the various target sites or act as a neoantigen without conformational change. Cross-reactivity then can occur if epitopes of the protein share surface topology to similar binding sites. Alteration of peptides that share topological equivalence with alternating side chains can lead to the formation of binding surfaces that may mimic the antigenic structure of a variant peptide or protein. We investigated how antibodies made against thyroid target sites may bind to various chemical–albumin compounds where binding of the chemical has induced human serum albumin (HSA) misfolding. We found that specific monoclonal or polyclonal antibodies developed against thyroid-stimulating hormone (TSH) receptor, 5′-deiodinase, thyroid peroxidase, thyroglobulin, thyroxine-binding globulin (TBG), thyroxine (T4), and triiodothyronine (T3) bound to various chemical HSA compounds. Our study identified a new mechanism through which chemicals bound to circulating serum proteins lead to structural protein misfolding that creates neoantigens, resulting in the development of antibodies that bind to key target proteins of the thyroid axis through protein misfolding. For demonstration of specificity of thyroid antibody binding to various haptenic chemicals bound to HSA, both serial dilution and inhibition studies were performed and proportioned to the dilution. A significant decline in these reactions was observed. This laboratory analysis of immune reactivity between thyroid target sites and chemicals bound to HSA antibodies identifies a new mechanism by which chemicals can disrupt thyroid function.

Prevalence and risk of thyroid diseases in myasthenia gravis

OBJECTIVES

To estimate the prevalence of thyroid diseases and the cumulative risk of thyroid diseases during a follow-up period after myasthenia gravis (MG) diagnosis compared with non-MG controls.

MATERIALS AND METHODS

We used the Taiwan National Health Insurance Database linked to Registry of Catastrophic Illness database to identify patients with MG. The controls were composed of those who did not have MG and were matched with the MG patients by sex, age, and the index date. We recorded thyroid disease histories before and after the index date.

RESULTS

Our study included 5813 MG patients and 29 065 controls. The prevalence of thyroid diseases in the MG patients at diagnosis was 18.4%, which was nearly 3.9-fold greater than that in the control group. (Odds ratio [OR] 3.895, 95% Confidence interval [CI] 3.574-4.246) After excluding pre-existing thyroid diseases, the incidence of comorbid thyroid diseases was 8.7% in the MG patients and 4% in the control group. The MG patients had a 2.36-fold increased risk of developing thyroid diseases compared to the control group. (crude hazard ratio [HR] 2.360, 95% CI 2.095-2.659) The cumulative probabilities of developing thyroid diseases at 1, 5, and 10 years after the index date were 21.6%, 24.9%, and 28.7%, respectively, in the MG patients, while the cumulative probabilities were 6.5%, 8.8%, and 11.8%, respectively, in control group (log-rank test <0.0001).

CONCLUSIONS

The current population-based study showed a higher prevalence of pre-existing thyroid diseases and a higher cumulative probability of thyroid diseases during follow-up after MG diagnosis than in the general population.

Immunological Reactivity Using Monoclonal and Polyclonal Antibodies of Autoimmune Thyroid Target Sites with Dietary Proteins

Many hypothyroid and autoimmune thyroid patients experience reactions with specific foods. Additionally, food interactions may play a role in a subset of individuals who have difficulty finding a suitable thyroid hormone dosage. Our study was designed to investigate the potential role of dietary protein immune reactivity with thyroid hormones and thyroid axis target sites. We identified immune reactivity between dietary proteins and target sites on the thyroid axis that includes thyroid hormones, thyroid receptors, enzymes, and transport proteins. We also measured immune reactivity of either target specific monoclonal or polyclonal antibodies for thyroid-stimulating hormone (TSH) receptor, 5′deiodinase, thyroid peroxidase, thyroglobulin, thyroxine-binding globulin, thyroxine, and triiodothyronine against 204 purified dietary proteins commonly consumed in cooked and raw forms. Dietary protein determinants included unmodified (raw) and modified (cooked and roasted) foods, herbs, spices, food gums, brewed beverages, and additives. There were no dietary protein immune reactions with TSH receptor, thyroid peroxidase, and thyroxine-binding globulin. However, specific antigen-antibody immune reactivity was identified with several purified food proteins with triiodothyronine, thyroxine, thyroglobulin, and 5′deiodinase. Laboratory analysis of immunological cross-reactivity between thyroid target sites and dietary proteins is the initial step necessary in determining whether dietary proteins may play a potential immunoreactive role in autoimmune thyroid disease.

Complicating autoimmune diseases in myasthenia gravis: a review

Myasthenia gravis (MG) is a rare autoimmune disease of skeletal muscle endplates. MG subgroup is relevant for comorbidity, but usually not accounted for. MG patients have an increased risk for complicating autoimmune diseases, most commonly autoimmune thyroid disease, systemic lupus erythematosus and rheumatoid arthritis. In this review, we present concomitant autoimmune disorders associated with the different MG subgroups, and show how this influences treatment and prognosis. Concomitant MG should always be considered in patients with an autoimmune disorder and developing new neuromuscular weakness, fatigue or respiratory failure. When a second autoimmune disorder is suspected, MG should be included as a differential diagnosis.

Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity

Thyroid autoimmunity involves loss of tolerance to thyroid proteins in genetically susceptible individuals in association with environmental factors. In central tolerance, intrathymic autoantigen presentation deletes immature T cells with high affinity for autoantigen-derived peptides. Regulatory T cells provide an alternative mechanism to silence autoimmune T cells in the periphery. The TSH receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (Tg) have unusual properties ("immunogenicity") that contribute to breaking tolerance, including size, abundance, membrane association, glycosylation, and polymorphisms. Insight into loss of tolerance to thyroid proteins comes from spontaneous and induced animal models: 1) intrathymic expression controls self-tolerance to the TSHR, not TPO or Tg; 2) regulatory T cells are not involved in TSHR self-tolerance and instead control the balance between Graves' disease and thyroiditis; 3) breaking TSHR tolerance involves contributions from major histocompatibility complex molecules (humans and induced mouse models), TSHR polymorphism(s) (humans), and alternative splicing (mice); 4) loss of tolerance to Tg before TPO indicates that greater Tg immunogenicity vs TPO dominates central tolerance expectations; 5) tolerance is induced by thyroid autoantigen administration before autoimmunity is established; 6) interferon-α therapy for hepatitis C infection enhances thyroid autoimmunity in patients with intact immunity; Graves' disease developing after T-cell depletion reflects reconstitution autoimmunity; and 7) most environmental factors (including excess iodine) "reveal," but do not induce, thyroid autoimmunity. Micro-organisms likely exert their effects via bystander stimulation. Finally, no single mechanism explains the loss of tolerance to thyroid proteins. The goal of inducing self-tolerance to prevent autoimmune thyroid disease will require accurate prediction of at-risk individuals together with an antigen-specific, not blanket, therapeutic approach.

Autoimmune thyroid diseases in children

The two major autoimmune thyroid diseases (ATDs) include Graves' disease (GD) and autoimmune thyroiditis (AT); both of which are characterized by infiltration of the thyroid by T and B cells reactive to thyroid antigens, by the production of thyroid autoantibodies and by abnormal thyroid function (hyperthyroidism in GD and hypothyroidism in AT). While the exact etiology of thyroid autoimmunity is not known, it is believed to develop when a combination of genetic susceptibility and environmental encounters leads to breakdown of tolerance. It is important to recognize thyroid dysfunction at an early stage by maintaining an appropriate index of suspicion.

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.

Graves' disease associated with infectious mononucleosis due to primary Epstein-Barr virus infection: report of 3 cases

Although the etiology of Graves' disease is still not clear, it is generally suggested that environmental factors such as infections contribute to the development of Graves' disease. We report here three cases of Graves' disease which presented simultaneously with infectious mononucleosis due to primary EBV infection. Acute EBV infection might play an important role in the onset of Graves' disease. These three women complained of a sore throat or neck pain, resembling subacute thyroiditis. In the case of thyrotoxicosis accompanied by sore throat or neck pain, Graves' disease must be distinguished from subacute thyroiditis.

The etiology of autoimmune thyroid disease: a story of genes and environment

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT) are prevalent autoimmune diseases, affecting up to 5% of the general population. Autoimmune thyroid diseases arise due to complex interactions between environmental and genetic factors. Significant progress has been made in our understanding of the genetic and environmental triggers contributing to AITD. However, the interactions between genes and environment are yet to be defined. Among the major AITD susceptibility genes that have been identified and characterized is the HLA-DR gene locus, as well as non-MHC genes including the CTLA-4, CD40, PTPN22, thyroglobulin, and TSH receptor genes. The major environmental triggers of AITD include iodine, medications, infection, smoking, and possibly stress. Recent data on the genetic predisposition to AITD lead to novel putative mechanisms by which the genetic-environmental interactions may lead to the development of thyroid autoimmunity.

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

CONTEXT

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

OBJECTIVE

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

DESIGN/SETTING/PARTICIPANTS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSION

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

Acetylcholine receptor antibodies in myasthenia gravis are associated with greater risk of diabetes and thyroid disease

OBJECTIVE

Myasthenia gravis (MG) may be associated with the presence of acetylcholine receptor antibodies (AChRAb) [seropositive MG (SPMG)] or their absence [seronegative MG (SNMG)]. Along with features of MG, the presence of the AChRAb may relate to the existence of other immune-mediated diseases. We sought to determine the association of SPMG with other potential autoimmune diseases.

METHODS

A retrospective evaluation of prospectively identified MG patients at a tertiary care center was performed, with patients separated into SPMG and SNMG. Prevalence of other immune-mediated disorders, as well as the epidemiology, sensitivity of diagnostic testing, and thymic pathology, was contrasted between both patient groups.

RESULTS

Of the 109 MG patients identified, 66% were SPMG. SPMG was associated with a greater likelihood of significant repetitive stimulation decrement, the presence of either thymoma or thymic hyperplasia, and the presence of thyroid disease. In addition, all patients with a diagnosis of diabetes, concurrent with MG, were found to be SPMG.

CONCLUSIONS

AChRAb and SPMG impart not only a distinctive clinical and electrophysiological phenotype of MG, but are also associated with the heightened presence of endocrinological disease.

Autoimmune thyroid diseases: etiology, pathogenesis, and dermatologic manifestations

Autoimmune thyroid disease (AITD) including Graves' disease, Hashimoto's thyroiditis, and idiopathic hypothyroidism (atrophic Hashimoto's thyroiditis) is of vital concern to the dermatologist. This article reviews the cutaneous manifestations of Graves' disease and Hashimoto's thyroiditis. Recognition of dermatologic manifestations of AITD may alert practitioners to investigate for these disorders. The immune response involved in the pathogenesis of AITD is detailed. Current understanding of the role of genetic and environmental factors, antigens, and apoptosis are elaborated. The future holds exciting insight into the etiology, pathogenesis, and treatment of AITD.

Molecular aspects of allergy

Atopic diseases such as asthma, rhinitis, eczema and food allergies have increased in most industrialised countries of the world during the last 20 years. The reasons for this increase are not known and different hypotheses have been assessed including increased exposure to sensitising allergens or decreased stimulation of the immune system during critical periods of development. In allergic diseases there is a polarisation of the Th2 response and an increase in the production of type 2 cytokines which are involved in the production of immunoglobulin E and the development of mast cells, basophils and eosinophils leading to inflammation and disease. The effector phase of atopy is initiated by interaction with Fc epsilon RI expressed on effector cells such as mast cells and basophils but also found on an ever increasing list of cells. Binding of a polyvalent allergen to the variable part of IgE leads to a cross-link of the receptor that triggers the cell to release histamine and pharmacological mediators of the symptomatic allergic response. Cross-linking of Fc epsilon RI by autoantibodies against the alpha-chain of the Fc epsilon RI, causing subsequent histamine release is thought to be involved in the pathogenesis of other diseases such as chronic idiopathic urticaria (CIU). To date, most therapeutic strategies are aimed at inhibiting and controlling components of the inflammatory response. Recently, new treatment strategies have emerged that focus on the development of preventive and even curative treatments. The most promising therapeutic approaches are aimed at inhibiting the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic anti-IgE or anti-Fc epsilon RIalpha autoantibodies. Clinical trials in humans using an humanised anti-IgE antibody showed that this antibody was well tolerated and reduced both symptoms and use of medication in asthma and allergic rhinitis. Thus interruption of the atopic cascade at the level of the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic antibodies is effective and represents an attractive therapy for the treatment of atopic disease.

Association of the HLA-DRB1*0301 and HLA-DQA1*0501 alleles with Graves' disease in a population representing the gene contribution from several ethnic backgrounds

Graves' disease (GD) is the most frequent cause of hyperthyroidism. Although the etiology is not completely elucidated, there are several lines of evidence suggesting multifactorial mechanisms. Genetic, constitutional, and environmental factors are involved in its pathogenesis. Major histocompatibility complex (MHC) class II alleles have been associated with GD in several populations of distinct ethnic backgrounds and there is increasing evidence supporting an association between GD and HLA-DR3 in Caucasian populations. The MHC class II alleles were evaluated in 75 Brazilian patients presenting with GD and in 166 control individuals from the same geographic area. HLA-DRB, DQB, and DQA alleles were identified using polymerase chain reaction (PCR)-amplified DNA hybridized with sequence-specific probes. The HLA-DRB1*0301 allele was significantly increased in patients (34/75, 45.3%) as compared with controls (37/166, 22.3%, p = 0.009), conferring a relative risk (RR) of 2.8 and an etiologic fraction (EF) of 0.287. The HLA-DQA1*0501 allele was also overrepresented in patients (48/71, 67.6%) in relation to controls (24/71, 33.8%; p = 0.004), conferring an RR of 3.74 and an EF of 0.351. The susceptibility conferred by HLA-DQA1*0501 was independent of the HLA-DRB1*0301 allele. On the other hand, the HLA-DQB1*0602 allele was significantly decreased in patients (6/75, 8.0%) in relation to controls (53/166, 31.9%, p = 0.0008), conferring an RR of 0.18 and a preventive fraction of 0.267. Although the Brazilian population comprises individuals of several ethnic backgrounds, these results corroborate the participation of the HLA-DRB1*0301 and HLA-DQA1*0501 alleles as susceptibility markers for GD, and emphasize the participation of the HLA-DQB1*0602 allele as conferring protection against the development of the disease.

Thyroid-associated ophthalmopathy: clinical features, pathogenesis, and management

Thyroid-associated ophthalmopathy (TAO) is a progressive eye disorder characterized by immune-mediated inflammation of the extraocular muscles and orbital connective tissue. TAO is linked, in a unique way, with thyroid autoimmunity, in particular Graves' hyperthyroidism. Our working hypothesis for the pathogenesis of TAO is that recognition of a thyrotropin receptor (TSHR)-like protein in the orbital preadipocytes by antibodies may be the initial event leading to homing of lymphocytes into the orbital tissues. In the course of thyroid inflammation, antibodies and T cells reactive against G2s expressed in thyroid membranes cross-react with the protein in the eye muscle fiber, leading to eye muscle damage and dysfunction. Those patients with anti-G2s antibodies develop ocular myopathy. Antibodies against flavoprotein, the 64-kDa protein, which are produced in the context of eye muscle fiber damage and mitochondrial rupture, are sensitive markers of immune-mediated fiber necrosis in patients with ophthalmopathy but do not directly damage the eye muscle. Antibodies against type XIII collagen, which is localized in the plasma membranes of orbital fibroblast, may be a new marker for the congestive ophthalmopathy subtype of TAO. The measurement of antibodies against key eye muscle and orbital connective tissue autoantigens may have a role in the management of active ophthalmopathy and its prediction in patients with Graves' hyperthyroidism.

Evaluation of enterovirus serological tests IgM-EIA and complement fixation in patients with meningitis, confirmed by detection of enteroviral RNA by RT-PCR in cerebrospinal fluid

An enzyme immunoassay (EIA) for detection of anti-enterovirus IgM antibodies was compared with complement fixation test in 43 patients with confirmed enterovirus meningitis by RT-PCR of cerebrospinal fluids (CSF). In 34% of patients with enterovirus meningitis, IgM antibodies could be found, whereas complement fixation tests were positive in only 20%. The specificity was determined with sera of 105 patients with non-enterovirus meningitis. Specificity of IgM EIA and of complement fixation was 94% and 85%, respectively. In four patients with meningitis but without enterovirus detection in CSF, RT-PCR and virus isolation from stools were positive. In three of these patients, IgM antibodies were detected, giving a strong indication of an enterovirus-associated disease. Because of the high specificity of IgM EIA, diagnosis of enterovirus-associated diseases can be carried out in a single serum sample, whereas by complement fixation tests, only fourfold increases in antibody titres in paired sera indicate an acute infection. The application of IgM EIA is especially important in cases of meningitis when CSF samples are not available and for diagnosis of enterovirus diseases with other clinical symptoms such as fever, enteritis, and hand-foot-and-mouth disease.

Celiac disease associated with familial chronic urticaria and thyroid autoimmunity in a child

An 11-year-old girl presented with chronic urticaria (CU), antithyroid antibodies, and anemia. Celiac disease was diagnosed. The family history was positive for maternally derived CU and thyroid autoimmunity in three generations. Human leukocyte antigen typing disclosed human leukocyte antigen DQA1*0501 DQB1*0201 in both mother and child. CU was unresponsive to a gluten-free diet despite clinical and laboratory resolution of celiac disease in contrast to previous reports in adults. We believe that this is the first report of this association in a child, highlighting that CU may be a part of the spectrum of autoimmune phenomenon related to celiac disease.