Immunoglobulins of patients recovering from Yersinia enterocolitica infections exhibit Graves' disease-like activity in human thyroid membranes

The Role of the Microbiota in Graves' Disease and Graves' Orbitopathy

Graves' disease (GD) is a clinical syndrome with an enlarged and overactive thyroid gland, an accelerated heart rate, Graves' orbitopathy (GO), and pretibial myxedema (PTM). GO is the most common extrathyroidal complication of GD. GD/GO has a significant negative impact on the quality of life. GD is the most common systemic autoimmune disorder, mediated by autoantibodies to the thyroid-stimulating hormone receptor (TSHR). It is generally accepted that GD/GO results from complex interactions between genetic and environmental factors that lead to the loss of immune tolerance to thyroid antigens. However, the exact mechanism is still elusive. Systematic investigations into GD/GO animal models and clinical patients have provided important new insight into these disorders during the past 4 years. These studies suggested that gut microbiota may play an essential role in the pathogenesis of GD/GO. Antibiotic vancomycin can reduce disease severity, but fecal material transfer (FMT) from GD/GO patients exaggerates the disease in GD/GO mouse models. There are significant differences in microbiota composition between GD/GO patients and healthy controls. Lactobacillus, Prevotella, and Veillonella often increase in GD patients. The commonly used therapeutic agents for GD/GO can also affect the gut microbiota. Antigenic mimicry and the imbalance of T helper 17 cells (Th17)/regulatory T cells (Tregs) are the primary mechanisms proposed for dysbiosis in GD/GO. Interventions including antibiotics, probiotics, and diet modification that modulate the gut microbiota have been actively investigated in preclinical models and, to some extent, in clinical settings, such as probiotics (Bifidobacterium longum) and selenium supplements. Future studies will reveal molecular pathways linking gut and thyroid functions and how they impact orbital autoimmunity. Microbiota-targeting therapeutics will likely be an essential strategy in managing GD/GO in the coming years.

Thyroid Autoimmunity: Role of Anti-thyroid Antibodies in Thyroid and Extra-Thyroidal Diseases

Autoimmune diseases have a high prevalence in the population, and autoimmune thyroid disease (AITD) is one of the most common representatives. Thyroid autoantibodies are not only frequently detected in patients with AITD but also in subjects without manifest thyroid dysfunction. The high prevalence raises questions regarding a potential role in extra-thyroidal diseases. This review summarizes the etiology and mechanism of AITD and addresses prevalence of antibodies against thyroid peroxidase, thyroid-stimulating hormone receptor (TSHR), and anti-thyroglobulin and their action outside the thyroid. The main issues limiting the reliability of the conclusions drawn here include problems with different specificities and sensitivities of the antibody detection assays employed, as well as potential confounding effects of altered thyroid hormone levels, and lack of prospective studies. In addition to the well-known effects of TSHR antibodies on fibroblasts in Graves' disease (GD), studies speculate on a role of anti-thyroid antibodies in cancer. All antibodies may have a tumor-promoting role in breast cancer carcinogenesis despite anti-thyroid peroxidase antibodies having a positive prognostic effect in patients with overt disease. Cross-reactivity with lactoperoxidase leading to induction of chronic inflammation might promote breast cancer, while anti-thyroid antibodies in manifest breast cancer might be an indication for a more active immune system. A better general health condition in older women with anti-thyroid peroxidase antibodies might support this hypothesis. The different actions of the anti-thyroid antibodies correspond to differences in cellular location of the antigens, titers of the circulating antibodies, duration of antibody exposure, and immunological mechanisms in GD and Hashimoto's thyroiditis.

A possible link between the Epstein-Barr virus infection and autoimmune thyroid disorders

The Epstein-Barr virus (EBV), also known as human herpesvirus 4, is a member of the Herpesviridae virus family. EBV infection can cause infectious mononucleosis (IM) in the lytic phase of EBV's life cycle. Past EBV infection is associated with lymphomas, and may also result in certain allergic and autoimmune diseases. Although potential mechanisms of autoimmune diseases have not been clearly elucidated, both genetic and environmental factors, such as infectious agents, are considered to be responsible for their development. In addition, EBV modifies the host immune response. The worldwide prevalence of autoimmune diseases shows how common this pathogen is. Normally, the virus stays in the body and remains dormant throughout life. However, this is not always the case, and a serious EBV-related illness may develop later in life. This explains the chronic course of autoimmune diseases that is often accompanied by exacerbations of symptoms. Based on the present studies, EBV infection can cause autoimmune diseases, such as systemic lupus erythematosus (SLE), multiple sclerosis (MS), rheumatoid arthritis (RA), Sjögren's syndrome, and autoimmune hepatitis. The EBV has also been reported in patients with autoimmune thyroid disorders. Although EBV is not the only agent responsible for the development of autoimmune thyroid diseases, it can be considered a contributory factor.

H1N1 infection-induced thyroid storm

A thyroid storm is a life-threatening exacerbation of thyrotoxicosis, and is usually characterized by hyperthermia, tachycardia, severe agitation and altered mental status. A thyroid storm may be triggered by many causes, including systemic pulmonary infections. Delay in prompt diagnosis leads to high mortality. We present the first case of H1N1 infection triggering a thyroid storm. The delay in diagnosis because of preoccupancy with the H1N1 pandemic may have contributed to the poor outcome. When assessing cases with H1N1 infection, physicians should be more vigilant in order not to miss other important diagnoses.

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.

A case of Graves' disease combined with hantaan virus infection

Graves' disease (GD) is generally presented by thyrotoxicosis with hyperthyroidism, and it is an organ-specific autoimmune disease induced by thyroid-stimulating hormone receptor autoantibodies. However, among diverse etiologies, viral infections have been suggested to trigger or to be involved in the pathogenesis of GD. Hantaan virus infection causing hemorrhagic fever with renal syndrome (HFRS) is common in South Korea and its pathogenesis is suggested to be an immunologic mechanism. We have experienced a patient who was diagnosed as HFRS with thyrotoxicosis. So we herein report the case as GD combined with the hantaan virus infection.

Increased prevalence of antibodies to enteropathogenic Yersinia enterocolitica virulence proteins in relatives of patients with autoimmune thyroid disease

Infections have been implicated in the pathogenesis of a number of autoimmune diseases, and Yersinia enterocolitica (YE) might play a role in the development of autoimmune thyroid disease (AITD). Clinical evidence in support of this hypothesis has been inconclusive. We reasoned that looking earlier in the natural course of AITD might enhance chances of finding evidence for YE infection. Consequently, we determined seroreactivity against YE in subjects at risk of developing AITD, i.e. in 803 female relatives of AITD patients in self-proclaimed good health. As a comparison group we used 100 healthy women who participated in a program for reference values. IgG and IgA antibodies to virulence-associated outer membrane proteins (YOPs) of YE were measured by a specific assay. Serum thyroid peroxidase antibodies (TPO-Ab) as indicators of AITD were considered to be positive at levels of> 100 kU/l. The prevalence of YOP IgG-Ab was higher in AITD relatives than in controls (40.1% vs. 24%, P = 0.002), and the same was true for YOP IgA-Ab (22% vs. 13%, P < 0.05). Of the 803 AITD relatives, 44 had an increased or decreased plasma TSH, and 759 were euthyroid as evident from a normal TSH; the prevalence of YOP-Ab did not differ between these three subgroups. TPO-Ab were present in 10% of controls and in 27% of the AITD relatives (P < 0.001). The prevalence of TPO-Ab in the euthyroid AITD relatives was not different between YOP IgG-Ab positive and negative subjects (23.3% vs. 24.7%, NS), nor between YOP IgA-Ab positive and negative subjects (21.2% vs. 24.9%, NS). In conclusion, healthy female relatives of AITD patients have an increased prevalence of YOP antibodies, which, however, is not related to the higher prevalence of TPO antibodies in these subjects. The findings suggest a higher rate of persistent YE infection in AITD relatives. Susceptibility genes for AITD may also confer a risk for YE infection.

Relationship between thyroid autoimmunity and Yersinia enterocolitica antibodies

It has previously been proposed that subclinical Yersinia enterocolitica infection may play a role in autoimmune thyroid disease (AITD). In this study, we investigated the relationship between the thyroid autoantibodies and the antibodies that produced against different serotypes of Y. enterocolitica. A total of 215 subjects were included into the study (65 newly diagnosed Graves' disease [GD], 57 Hashimoto's thyroiditis [HT], 53 nontoxic diffuse goiter [NTDG], and 40 subjects for control group [CG]). Thyroid receptor antibodies (TRAb), thyroid and agglutinating antibodies against Y. enterocolitica serotype O:3, O:5, O:8, O:9 were measured in the blood samples. The highest incidence of Y. enterocolitica antibody positivity was measured in GD (53.8% for O:3, 29.2% for O:5, 44.6% for O:8, and 40% for O:9) and followed by HT. In patients with GD, TRAb levels were also higher than in patients with HT, NTDG, and CG. There was no difference between NTDG and CG in respect to the titer levels and the positivity of both TRAb and Y. enterocolitica antibodies. There was also a weak linear correlation between TRAb level and the titer of antibodies against Y. enterocolitica antigens. It can be concluded that Y. enterocolitica infection may play a role in etiology of GD in Turkey.

Chronic sequelae of foodborne disease

In the past decade the complexity of foodborne pathogens, as well as their adaptability and ability to cause acute illness, and in some cases chronic (secondary) complications, have been newly appreciated. This overview examines long-term consequences of foodborne infections and intoxications to emphasize the need for more research and education.

The Pathogenesis of Graves’ Disease

We have hypothesized over many years that Graves' disease (GD) and the other autoimmune thyroid diseases (AITD) are each due to antigen-specific defects in suppressor (regulatory) T lymphocyte function. There have been several reports dealing with the role of regulatory T lymphocyte subsets, ie., that will prevent autoimmune disease in these and other organ-specific autoimmune diseases. In AITD, suppressor T cells have been shown to be less well activated by relevant antigen, but are normally activated by irrelevant antigen; suppressor T cells from normal persons react equally well to both. In GD, these cells have been shown to be inadequately activated by TSH receptor antigen, but are normally activated by irrelevant autoantigen. This reduction is partial only, and insufficient itself to precipitate the autoimmune disease; further insults from the environment are necessary to further reduce generalized regulatory cell activity, adding to the genetically induced specific regulatory cell dysfunction, which appears in turn to be due to a specific defect in the presentation of a specific antigen. This, in turn, may relate to abnormalities of the genes responsible for antigen presentation. The end result is activation of appropriate helper and effector T cells, the stimulation by these of appropriate B lymphocytes, and the concurrent production of cytokines. These events lead to functional changes within the target cell which itself will express Class II antigens, heat shock proteins, and intercellular adhesion molecules, all of which amplify the immune response. Moreover, the activation of helper T lymphocytes by specific antigen depends on the availability of normal amounts of antigen being presented to them by antigen-presenting cells. Thus, there is no need to invoke any primary abnormality or infection of the thyroid cell, or any cross-reacting antigen of microorganismic origin to initiate this process. What is required is an abnormality of antigen-presentation such that regulatory cells are not properly activated, plus some additive environmental disturbance acting on the immune system. GD specifically results from the production by B lymphocytes of an antibody directed against the TSH receptor which stimulates the thyrocyte in a manner similar to TSH, but for a much longer interval. There are also antibodies to the thyrotrophin (TSH) receptor which block the action of TSH. Thyroid stimulating antibody is typical of GD and is detectable in about 95% of cases, but is also seen in destructive thyroiditis transiently. It tends to decline with antithyoid drug therapy, and rises further (for several months) after 131 I treatment. It may slowly decline after subtotal thyroidectomy. It also declines in the third trimester of pregnancy but sometimes is sufficiently high to cause foetal and neonatal passive transfer GD. It tends to rebound in the mother after delivery and may result in postpartum GD. The blocking antibody may cause atrophic thyroiditis and hypothyroidism. Antimicrosomal antibody has now been shown to be antithyroperoxidase. It correlates moderately well with thyroid dysfunction in Hashimoto's thyroiditis (HT) and GD, while antithyroglobulin is of much less value. Graves' ophthalmopathy is still not well understood, and its precise relationship to Graves' hyperthyroidism has yet to be worked out. However the retroorbital fibroblast is now emerging as the most likely target cell, with retroorbital muscle involvement possibly secondary. A recent observation of a genomic point mutation on the TSH receptor on fibroblasts from patients with Graves' ophthalmopathy but not normal persons raises interesting possibilities.

Seroreactivity to bacterial antigens is not a unique phenomenon in patients with autoimmune thyroid diseases in Canada

It has been suggested elsewhere that the enteric pathogen Yersinia enterocolitica (Y.e.) might be implicated etiologically in autoimmune thyroid disease (AITD). To reevaluate this hypothesis in the Canadian population, where the prevalence of anti-Y.e. antibodies in the general population is very low (< 1%), we have studied the occurrence of antibacterial reactivity (against Y.e. 0:3 and 0:9, Escherichia coli and Staphylococcus aureus) in the sera of patients with Hashimoto's thyroiditis (HT), Graves' disease (GD), nontoxic nodular goiter (NTG), and autoimmune rheumatic diseases (ARD) as well as normal controls (C). Using the tube agglutination method, no single positive sample was detected in these subjects. No differences in the mean levels of anti-Y.e. 0:3 or 0:9 by ELISA were observed between various groups of patients. Immunoreactivity in the course of medical therapy during 5-12 months did not show significant changes in any of 12 ARD and AITD patients. Some serological reactivity to the plasmid containing strain of Y.e. 0:3 was demonstrated in all subjects by the Western blotting technique. However, weaker signals and fewer bands were noticed in these sera compared to sera from patients with acute yersiniosis. Analysis of the pattern of reactivity did not show any difference in reactivity to any protein between the groups of subjects. The immunodominant antigen in Y.e. 0:3 to which IgG reacted in almost all subjects was the plasmid encoded 240-kDa protein. Our study favors the view that there is a merely coincidental incidence of seroreactivity to bacterial antigens, which appears to be irrespective of diagnosis.

Has the use of antithyroid drugs for Graves' disease become obsolete?

In spite of an experience of almost 50 years of use of antithyroid drugs and radioiodine for the treatment of Graves' disease, the rationale for choice is often obscure. Early reports of high remission rates during thiourea therapy were followed by less optimistic ones, which along with other factors may have fueled the current major shift toward use of radioiodine. This review examines whether or not the use of antithyroid drugs indeed may have become obsolete. The intrathyroidal and extrathyroidal mechanisms of action of the drugs are reviewed with emphasis on their potential immunosuppressive effects. The latter may involve a direct effect on thyroid follicular cells, a direct suppression of TSH receptor antibody formation, or indirect effects mediated via heat shock proteins, oxygen free radicals, and the immune system. Potential factors associated with success or failure with antithyroid drug therapy are discussed, such as the effects of dose and duration of treatment, iodine milieu, and concomitant L-thyroxine therapy. The risks inherent to radioiodine therapy are only briefly described with emphasis on the possible aggravation by radioiodine of preexistent ophthalmopathy. The reader must decide whether the evidence marshalled convincingly indicates that the use of the thiourea compounds should be abandoned. The author thinks not, and is optimistic that imminent discovery of the yet elusive and enigmatic pathogenesis of Graves' disease will permit new and innovative treatment or more effective use of currently available therapies.

Suppressor T lymphocyte dysfunction is important in the pathogenesis of autoimmune thyroid disease: a perspective

Over the past decade, there was considerable scepticism regarding the existence, nature, and function of suppressor T (Ts) lymphocytes, particularly antigen-specific Ts lymphocytes. The receptors of putative antigen-specific murine Ts hybrids revealed that most either lacked the T cell receptor beta (TCR beta) chain or had failed to properly rearrange them and thus could not make a functional receptor. Moreover, studies of the DNA of sequences of the MHC I-J region (considered an important determinant for suppression) fail to show evidence for a unique open reading frame capable of encoding the I-J restriction element. In addition, no molecular basis for suppression had been characterized. These criticisms have now been satisfactorily resolved and the pendulum is swinging in favor of participation by antigen-specific Ts lymphocytes in immune tolerance. Ts lymphocytes have now been cloned and cell lines have been found to be idiotypic-specific. Indeed, specific Ts lymphocytes in the periphery have been shown to prevent the appearance of autoreactivity. It is, therefore, legitimate to consider their control as part of the mechanisms of maintaining the integrity of the immune system. Moreover, all human primary Ts clones and the majority of murine Ts clones have now been shown to rearrange TCR alpha beta. Ts lymphocytes are induced by antigen via antigen-presenting cells (APCs), and may do so in the context of MHC class II antigens, a concept not previously accepted. Moreover, there is now considerable evidence that such cells many well be involved in various autoimmune disease states.(ABSTRACT TRUNCATED AT 250 WORDS)

A perspective on human autoimmune thyroid disease: is there an abnormality of the target cell which predisposes to the disorder?

It has been suggested recently that autoimmunity could be regarded as a physiological response of the normal immune system to autoantigens caught up in an inflammatory response to viral or bacterial antigen expressed in the target tissue. Other theories to explain autoimmunity include molecular mimicry whereby a viral or microbial hapten similar to an autoantigen initiates the production of autoantibodies that cross react with an autoantigen, with a subsequent immune response reacting with autologous cell structures which are homologous with the particular microorganism. There has also been a suggestion that there may be a genetic abnormality of the target cell which is necessary for the initiation of autoimmune thyroid disease. The present review examines these proposals and provides evidence against an antigen-driven origin for autoimmune thyroid disease (AITD). Currently, there is no valid evidence for viral involvement, and likewise the evidence for molecular mimicry as an initiating factor does not hold up to scrutiny. While a genetic abnormality of the thyrocyte may be important in certain animal models of AITD, in the human there is no evidence for such an abnormality. Evidence that AITD is derived from a disturbance of immunoregulatory mechanisms has been documented elsewhere and would appear to be the most appropriate explanation for these disorders. The immunoregulatory disturbance itself may be related to an abnormality of the mechanism of specific antigen (i.e. normal autoantigen) presentation to appropriately induce T lymphocytes and that theory will require further illumination.