Newer insights into the pathogenesis of experimental autoimmune thyroiditis

Dynamic changes in the histomorphological structure of the thyroid gland of rats against the background of experimental autoimmune thyroiditis

In preclinical studies, which are conducted to study the therapeutic effectiveness and pharmacological safety of biologically active compounds for the correction of autoimmune thyroiditis, various experimental models of this pathology are used in the experiment. In this work, we analyzed various models of thyroiditis that have been used for the past fifty years. Such an analysis made it possible to choose the most optimal model for the study of autoimmune pathology of the thyroid gland as well as for the correction of this condition. The analysis of known and the search for new pathogenetically justified models of autoimmune diseases of endocrine organs is a very urgent task. The aim of the work was to study the dynamics of changes in the histomorphological structure of the thyroid gland when modeling autoimmune thyroiditis in rats using an allogeneic antigen isolated from the human thyroid gland. The postoperative thyroid gland of a person was used as an antigen. Morphological changes in the thyroid gland were studied one, three and six months after the end of the simulation. It was found that the use of this type of immunization led to changes in the parenchyma of the gland, characteristic of autoimmune thyroiditis. Already one month after modeling, Gürtle cells, fibrosis, areas of lymphoid infiltration of the parenchyma were registered. These pathological changes persisted and worsened three and six months after the end of the simulation. The investigated type of model of experimental autoimmune thyroiditis is easily reproduced. Pathological changes in the gland deepen over time and are comparable to those that occur in people with Hashimoto's thyroiditis

A Chinese Patent Medicine JiaYanKangTai Alleviates Inflammatory Lesions of Experimental Autoimmune Thyroiditis by Regulating Interleukin-17 Signaling

OBJECTIVE

This study was aimed to investigate the effects of JiaYanKangTai (JYKT) on regulating interleukin-17 (IL-17) signaling in rats with autoimmune thyroiditis.

METHODS

Lewis rats were administrated with JYKT for eight weeks after a seven-week subcutaneous injection of thyroglobulin with adjuvant and feeding iodine water. Ultrasonography was performed and total volume of thyroid was calculated. The expressions of autoantibodies and hormones were detected. Morphological changes of thyroid were observed. Metabolomics profile and metabolic network analysis were conducted. IL-17 signaling was detected by polymerase chain reaction and immunohistochemistry separately.

RESULTS

JYKT reduced the mean volumes of thyroid, decreased both levels of TPOAb and TGAb, and alleviated lymphocytic infiltration of the thyroid. Metabolic network analysis of metabolomics proved IL-17 signaling pathway as a critical pathway in JYKT administration for autoimmune thyroiditis. JYKT downregulated expressions of IL-17A, TRAF6, p-ERK1/2 and TNF-α.

CONCLUSION

JYKT alleviated inflammatory lesions of experimental autoimmune thyroiditis by regulating IL-17 signaling.

LPS-matured CD11c+ bone marrow-derived dendritic cells can initiate autoimmune pathology with minimal injection site inflammation

The pathogenesis of human autoimmune disorders is incompletely understood. This has led to the development of numerous murine models in which the pathogenesis of autoimmunity can be probed and the efficacy of novel therapies can be tested. One of the most widely-used murine models of autoimmunity is experimental autoimmune encephalomyelitis (EAE). To induce autoimmune pathology, mice are often immunized with an autoantigen alongside an adjuvant, typically complete Freund's adjuvant (CFA). Unfortunately, CFA causes significant inflammation at the site of administration. Despite the well-recognized complication of injection site inflammation, CFA with autoantigen immunization is widely used to induce central nervous system autoimmunity. We performed a literature review which allowed us to estimate that over 10,000 mice were immunized with CFA in published EAE studies in 2013. In this study, we demonstrated that subcutaneously administered myelin basic protein (MBP)-pulsed CD11c+ bone marrow-derived dendritic cells (BMDC) were as effective at inducing EAE as subcutaneously administered MBP plus CFA. Importantly, we also discovered that the CD11c+ BMDC caused significantly less injection site inflammation than MBP plus CFA immunization. This study demonstrated that the use of CD11c+ BMDC can enable the development of autopathogenic T-cells to be studied in vivo without the unwanted side-effects of long-lasting injection site inflammation. This model represents a significant refinement to existing EAE models and may lead to the improvement of the welfare of experimental mice used to study the development of autoimmunity in vivo.

cDNA immunization of mice with human thyroglobulin generates both humoral and T cell responses: a novel model of thyroid autoimmunity

Thyroglobulin (Tg) represents one of the largest known self-antigens involved in autoimmunity. Numerous studies have implicated it in triggering and perpetuating the autoimmune response in autoimmune thyroid diseases (AITD). Indeed, traditional models of autoimmune thyroid disease, experimental autoimmune thyroiditis (EAT), are generated by immunizing mice with thyroglobulin protein in conjunction with an adjuvant, or by high repeated doses of Tg alone, without adjuvant. These extant models are limited in their experimental flexibility, i.e. the ability to make modifications to the Tg used in immunizations. In this study, we have immunized mice with a plasmid cDNA encoding the full-length human Tg (hTG) protein, in order to generate a model of Hashimoto's thyroiditis which is closer to the human disease and does not require adjuvants to breakdown tolerance. Human thyroglobulin cDNA was injected and subsequently electroporated into skeletal muscle using a square wave generator. Following hTg cDNA immunizations, the mice developed both B and T cell responses to Tg, albeit with no evidence of lymphocytic infiltration of the thyroid. This novel model will afford investigators the means to test various hypotheses which were unavailable with the previous EAT models, specifically the effects of hTg sequence variations on the induction of thyroiditis.

GM-CSF-induced, bone-marrow-derived dendritic cells can expand natural Tregs and induce adaptive Tregs by different mechanisms

In our earlier work, we had shown that GM-CSF treatment of CBA/J mice can suppress ongoing thyroiditis by inducing tolerogenic CD8α(-) DCs, which helped expand and/or induce CD4(+)Foxp3(+) Tregs. To identify the primary cell type that was affected by the GM-CSF treatment and understand the mechanism by which Tregs were induced, we compared the effect of GM-CSF on matured spDCs and BMDC precursors in vitro. Matured spDCs exposed to GM-CSF ex vivo induced only a modest increase in the percentage of Foxp3-expressing T cells in cocultures. In contrast, BM cells, when cultured in the presence of GM-CSF, gave rise to a population of CD11c(+)CD11b(Hi)CD8α(-) DCs (BMDCs), which were able to expand Foxp3(+) Tregs upon coculture with CD4(+) T cells. This contact-dependent expansion occurred in the absence of TCR stimulation and was abrogated by OX40L blockage. Additionally, the BMDCs secreted high levels of TGF-β, which was required and sufficient for adaptive differentiation of T cells to Foxp3(+) Tregs, only upon TCR stimulation. These results strongly suggest that the BMDCs differentiated by GM-CSF can expand nTregs and induce adaptive Tregs through different mechanisms.

Toxicology of autoimmune diseases

Susceptibility to most autoimmune diseases is dependent on polygenic inheritance, environmental factors, and poorly defined stochastic events. One of the significant challenges facing autoimmune disease research is in identifying the specific events that trigger loss of tolerance and autoimmunity. Although many intrinsic factors, including age, sex, and genetics, contribute to autoimmunity, extrinsic factors such as drugs, chemicals, microbes, or other environmental factors can also act as important initiators. This review explores how certain extrinsic factors, namely, drugs and chemicals, can promote the development of autoimmunity, focusing on a few better characterized agents that, in most instances, have been shown to produce autoimmune manifestations in human populations. Mechanisms of autoimmune disease induction are discussed in terms of research obtained using specific animal models. Although a number of different pathways have been delineated for drug/chemical-induced autoimmunity, some similarities do exist, and a working model is proposed.

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.

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

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

Contrasting roles of IFN-gamma in murine models of autoimmune thyroid diseases

Interferon-gamma (IFN-gamma), a prototypic proinflammatory cytokine produced by several different cell types, including the Th1 subset of CD4(+) T cells, plays an important role in inflammation and autoimmune diseases. This review focuses on the varied and often contrasting roles of IFN-gamma in three murine models of autoimmune thyroid disease, experimentally induced autoimmune thyroiditis, the model of iodine-induced spontaneous autoimmune thyroiditis in NOD.H-2h4 mice and several different murine models of Graves' disease.

The genetic basis of thyroid autoimmunity

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. AITDs arise due to interplay between environmental and genetic factors. In the past decade, significant progress has been made in our understanding of the genetic contribution to the etiology of AITDs. Excitingly, several AITD susceptibility genes have been identified and characterized. Some of these susceptibility genes are specific to either GD or HT, while others confer susceptibility to both conditions. The first AITD susceptibility gene locus identified was the Human-Leukocyte-Antigen DR (HLA-DR) gene locus. Subsequently, a quintet of non-HLA genes, including the cytotoxic T lymphocyte antigen (CTLA-4), CD40, protein tyrosine phosphatase-22 (PTPN22), thyroglobulin, and thyroid-stimulating hormone receptor (TSHR) gene, has been shown to contribute to the susceptibility to AITDs. Recently, the mechanisms by which these new AITD genes predispose to AITDs have been dissected. In this review, we overview and highlight the recent data on the genes predisposing to AITDs and the putative mechanisms by which they confer susceptibility to disease.

The CD40, CTLA-4, thyroglobulin, TSH receptor, and PTPN22 gene quintet and its contribution to thyroid autoimmunity: back to the future

Autoimmune thyroid diseases (AITD) are common autoimmune diseases, affecting up to 5% of the general population. Thyroid-directed autoimmunity is manifested in two classical autoimmune conditions, Hashimoto's thyroiditis, resulting in hypothyroidism and Graves' disease resulting in hyperthyroidism. Autoimmune thyroid diseases arise due to an interplay between environmental and genetic factors. In the past decade significant progress has been made in our understanding of the genetic contribution to the etiology of AITD. Indeed, several AITD susceptibility genes have been identified. Some of these susceptibility genes are specific to either Graves' disease or Hashimoto's thyroiditis, while others confer susceptibility to both conditions. Both immunoregulatory genes and thyroid specific genes contribute to the pathogenesis of AITD. The time is now ripe to examine the mechanistic basis for the contribution of genetic factors to the etiology of AITD. In this review, we will focus on the contribution of non-MHC II genes.

Thyrocytes responding to IFN-gamma are essential for development of lymphocytic spontaneous autoimmune thyroiditis and inhibition of thyrocyte hyperplasia

IFN-gamma promotes the development of lymphocytic spontaneous autoimmune thyroiditis (L-SAT) in NOD.H-2h4 mice and inhibits the development of thyrocyte hyperplasia and proliferation (TEC H/P). The precise mechanisms by which IFN-gamma promotes L-SAT and inhibits TEC H/P are unknown. To determine whether responsiveness of lymphocytes or thyrocytes to IFN-gamma is important for the development of these lesions, IFN-gammaR-/- mice, which develop TEC H/P similar to IFN-gamma-/- mice, were used as recipients for adoptive cell transfer. Wild-type (WT) splenocytes or bone marrow induced L-SAT and inhibited TEC H/P in IFN-gamma-/-, but not IFN-gammaR-/- recipients. IFN-gammaR-/- recipients of WT cells developed severe TEC H/P, but did not develop L-SAT, suggesting that thyrocytes responding to IFN-gamma are important for inhibition of TEC H/P. Unexpectedly, IFN-gammaR-/- splenocytes or bone marrow did not induce L-SAT in IFN-gamma-/- or WT mice even though IFN-gammaR-/- lymphocyte donors produced as much IFN-gamma as lymphocytes from WT donors, and thyrocytes could respond to IFN-gamma. Real-time PCR indicated that recipients of IFN-gammaR-/- bone marrow expressed less mRNA for IFN-gamma-inducible chemokines compared with recipients of WT bone marrow. This might limit the migration of IFN-gammaR-/- lymphocytes to thyroids. Few IFN-gammaR-/- lymphocytes infiltrated thyroids even in the presence of WT lymphocytes, suggesting that lymphocytes unable to respond to IFN-gamma are not induced to migrate to thyroids. These results suggest that thyrocytes must be able to respond to IFN-gamma for the development of L-SAT and inhibition of TEC H/P, and lymphocytes must be able to respond to IFN-gamma to induce L-SAT.

IL-10-producing CD4+CD25+ regulatory T cells play a critical role in granulocyte-macrophage colony-stimulating factor-induced suppression of experimental autoimmune thyroiditis

Our earlier study showed that GM-CSF has the potential not only to prevent, but also to suppress, experimental autoimmune thyroiditis (EAT). GM-CSF-induced EAT suppression in mice was accompanied by an increase in the frequency of CD4(+)CD25(+) regulatory T cells that could suppress mouse thyroglobulin (mTg)-specific T cell responses in vitro, but the underlying mechanism of this suppression was not elucidated. In this study we show that GM-CSF can induce dendritic cells (DCs) with a semimature phenotype, an important characteristic of DCs, which are known to play a critical role in the induction and maintenance of regulatory T cells. Adoptive transfer of CD4(+)CD25(+) T cells from GM-CSF-treated and mTg-primed donors into untreated, but mTg-primed, recipients resulted in decreased mTg-specific T cell responses. Furthermore, lymphocytes obtained from these donors and recipients after adoptive transfer produced significantly higher levels of IL-10 compared with mTg-primed, untreated, control mice. Administration of anti-IL-10R Ab into GM-CSF-treated mice abrogated GM-CSF-induced suppression of EAT, as indicated by increased mTg-specific T cell responses, thyroid lymphocyte infiltration, and follicular destruction. Interestingly, in vivo blockade of IL-10R did not affect GM-CSF-induced expansion of CD4(+)CD25(+) T cells. However, IL-10-induced immunosuppression was due to its direct effects on mTg-specific effector T cells. Taken together, these results indicated that IL-10, produced by CD4(+)CD25(+) T cells that were probably induced by semimature DCs, is essential for disease suppression in GM-CSF-treated mice.

Immunogenetics of Hashimoto's thyroiditis

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

Hypothyroidism

Hypothyroidism is common, potentially serious, often clinically overlooked, readily diagnosed by laboratory testing, and eminently treatable. The condition is particularly prevalent in older women, in whom autoimmune thyroiditis is common. Other important causes include congenital thyroid disorders, previous thyroid surgery and irradiation, drugs such as lithium carbonate and amiodarone, and pituitary and hypothalamic disorders. Worldwide, dietary iodine deficiency remains an important cause. Hypothyroidism can present with nonspecific constitutional and neuropsychiatric complaints, or with hypercholesterolaemia, hyponatraemia, hyperprolactinaemia, or hyperhomocysteinaemia. Severe untreated hypothyroidism can lead to heart failure, psychosis, and coma. Although these manifestations are neither specific nor sensitive, the diagnosis is confirmed or excluded by measurements of serum thyrotropin and free thyroxine. Thyroxine replacement therapy is highly effective and safe, but suboptimal dosing is common in clinical practice. Patient noncompliance, drug interactions, and pregnancy can lead to inadequate treatment. Iatrogenic thyrotoxicosis can cause symptoms, and, even when mild, provoke atrial fibrillation and osteoporosis. We summarise present understanding of the history, epidemiology, pathophysiology, and clinical diagnosis and management of hypothyroidism.

A polymorphism of interferon-gamma gene associated with changes of anti-thyrotropin receptor antibodies induced by antithyroid drug treatment for Graves' disease in Japanese patients

Graves' disease (GD) is an autoimmune disorder with genetic predisposition. Interferon-gamma (IFN-gamma) is an important mediator of inflammatory and immune responses. The aim of the present study was to investigate whether the polymorphism of IFN-gamma gene is associated with the development of GD or with clinical course during the antithyroid drug therapy. We have studied the CA repeat polymorphisms in the first intron of IFN gamma gene in Japanese patients with GD (n = 162) and healthy control subjects without antithyroid autoantibodies or family history of autoimmune disorders (n = 133). There was no difference in allele frequency of IFN-gamma gene polymorphism between patients with GD and control subjects. However, the allele 4 (15 CA repeats) frequency was significantly greater in patients whose antithyrotropin receptor antibody (TRAb) became negative within 3 years by antithyroid drug treatment than those with consistently positive TRAb for more than 3 years (34.1% vs. 15.7%, chi2 = 8.545, p = 0.0035, pc = 0.049). The in vitro production of IFN-gamma by concanavalin A-stimulated peripheral blood mononuclear cells was significantly smaller in control subjects with the allele 4 compared to those with the other alleles. In conclusions, the CA repeat polymorphism of the IFN-gamma gene might be associated with the outcome of anti-thyroid drug treatment.

Thyroid-specific expression of IFN-gamma limits experimental autoimmune thyroiditis by suppressing lymphocyte activation in cervical lymph nodes

The role of IFN-gamma in the pathogenesis of autoimmune disease is controversial, being described as immunostimulatory in some studies and immunosuppressive in others. To determine the contribution of local expression of IFN-gamma, we derived NOD.H-2(h4) transgenic mice overexpressing IFN-gamma in a thyroid-restricted manner. Transgenic mice, which had serum IFN-gamma levels similar to wild-type littermates, showed up-regulation of MHC class II on thyrocytes, but did not develop spontaneous thyroiditis. Upon immunization with murine thyroglobulin, transgenic mice developed milder disease and reduced IgG1 responses compared with wild type. The milder disease was associated with decreased frequency of activated CD44(+) lymphocytes in the cervical lymph nodes. This suppressive effect was confirmed by showing that blockade of systemic IFN-gamma with mAb enhanced disease and increased IgG1 responses. The study supports a disease-limiting role of IFN-gamma in autoimmune thyroiditis. Furthermore, it provides the first evidence that local IFN-gamma activity in the thyroid is sufficient for disease suppression.

Selective induction of dendritic cells using granulocyte macrophage-colony stimulating factor, but not fms-like tyrosine kinase receptor 3-ligand, activates thyroglobulin-specific CD4+/CD25+ T cells and suppresses experimental autoimmune thyroiditis

Fms-like tyrosine kinase receptor 3-ligand (Flt3-L) and GM-CSF cause expansion of different subsets of dendritic cells and skew the immune response toward predominantly Th1 and Th2 type, respectively. In the present study, we investigated their effects on experimental autoimmune thyroiditis in CBA/J mice. Relative to mouse thyroglobulin (mTg) immunized controls, mTg-immunized mice treated with Flt3-L showed more severe thyroiditis characterized by enhanced lymphocytic infiltration of the thyroid, and IFN-gamma and IL-2 production. In contrast, mice treated with GM-CSF, either before or after immunization with mTg, showed suppressed T cell response to mTg and failed to develop thyroiditis. Lymphocytes from these mice, upon activation with mTg in vitro, produced higher levels of IL-4 and IL-10. Additionally, GM-CSF-treated mice showed an increase in the frequency of CD4(+)/CD25(+) T cells, which suppressed the mTg-specific T cell response. Neutralization of IL-10, but not IL-4, or depletion of CD4(+)/CD25(+) cells resulted in increased mTg-specific in vitro T cell proliferation suggesting that IL-10 produced by the Ag-specific CD4(+)/CD25(+) regulatory T cells might be critical for disease suppression. These results indicate that skewing immune response toward Th2, through selective activation of dendritic cells using GM-CSF, may have therapeutic potential in Th1 dominant autoimmune diseases including Hashimoto's thyroiditis.

Kinetics of mononuclear cell infiltration and cytokine expression in iodine-induced thyroiditis in the NOD-H2h4 mouse

Mononuclear cell infiltration of the thyroid gland is a common histologic feature of chronic lymphocytic thyroiditis. Although the infiltrating mononuclear cells have been implicated in the destruction of the thyroid, information concerning the progression of infiltration into the thyroid is limited. In this report, we examine the composition and kinetics of mononuclear cell infiltration in the thyroid and the expression of major histocompatibility complex class II (I-Ak), IL-12, and IFN-gamma in the thyroid of the NOD-H2h4 mouse, a model of spontaneous autoimmune thyroiditis accelerated by the administration of excess dietary iodine. Mice were given a low dose of 0.015% NaI in their drinking water for 2, 4, 6, 8, and 16 weeks, and thyroids were removed, serially sectioned, and stained in an avidin-biotin peroxidase assay. The thyroid infiltrate included CD4+ and CD8+ T cells, F4/80+ macrophages, and B220+ B cells. After 2 weeks of iodine treatment, CD4+ T cells were the first seen in the thyroid, followed by CD8+ T cells and F4/80+ macrophages. B220+ B cells entered the thyroid after 4 weeks of iodine treatment. IL-12 and IFN-gamma positive cells were located in the thyroid early in disease and were up-regulated in the focal accumulations of infiltrating cells. Thyrocytes clearly expressed I-Ak after 4 weeks of iodine treatment near the location of mononuclear cell infiltration.

Effect of iodide on Fas, Fas-ligand and Bcl-w mRNA expression in thyroid of NOD mice pretreated with methimazole

Nonobese diabetic (NOD) mice and a derived strain, NOD.H.2h4, have been used as a model for experimental spontaneous thyroiditis and thyroiditis induced by iodide excess after a goiter-inducing period. Some authors have proposed that iodide, given after methimazole or propylthiouracil, is capable of inducing apoptosis in thyroid cells and that anti-thyroid drugs can modulate the expression of apoptosis components such as Fas and its ligand (Fas-L). Here we evaluated the effect of potassium iodide (20 microg/animal for 4 days, i.p.) given to NOD mice at the 10th week of life after exposure to methimazole (1 mg/ml) in drinking water from the 4th to the 10th week of life. Fas, Fas-L and Bcl-w expression were analyzed semiquantitatively by RT-PCR immediately after potassium iodide administration (group MI44D) or at week 32 (MI32S). Control groups were added at 10 (C10) and 32 weeks (C32), as well as a group that received only methimazole (CM10). An increase in the expression of Fas-L and Bcl-w (P<0.01, ANOVA) was observed in animals of group MI44D, while Fas was expressed at higher levels (P = 0.02) in group C32 (72.89 +/- 47.09 arbitrary units) when compared to group C10 (10.8 +/- 8.55 arbitrary units). Thus, the analysis of Fas-L and Bcl-w expression in the MI44D group and Fas in group C32 allowed us to detect two different patterns of expression of these apoptosis components in thyroid tissue of NOD mice.

Identification of alpha-tropomyosin as a target self-antigen in Behçet's syndrome

Behçet's syndrome is a multi-system inflammatory disease affecting mainly the oral and urogenital mucosa and the uveal tract. The etiology and pathogenesis of Behçet's syndrome are unknown, but autoimmune mechanisms are implicated. We initiated this work to identify self-antigens targeted by patients with Behçet's syndrome. We used patient sera to immuno-blot tissue lysates, and we found that some patients manifest antibodies to a 37-kDa band. The 37-kDa band was detected in extracts of skin, tongue, vagina, muscle and heart but not in brain, kidney, lung, liver, intestine and thymus. In-gel digestion and mass spectrometry revealed the band to be alpha-tropomyosin. Autoimmunity to alpha-tropomyosin can be pathogenic; immunized Lewis rats developed lesions in the uveal tract and skin, with features of Behçet's disease.

Iodine: an environmental trigger of thyroiditis

Like most autoimmune diseases of humans, chronic lymphocytic (Hashimoto's) thyroiditis results from the combination of a genetic predisposition and an environmental trigger. A body of clinical and epidemiologic evidence points to excessive ingestion of iodine as an environmental agent. In genetically determined thyroiditis in animals, iodine enrichment has been shown to increase the incidence and severity of disease. Its mechanism of action is still uncertain. Using a new animal model of autoimmune thyroiditis, the NOD.H2(h4) mouse, we have been able to show that iodine enhances disease in a dose-dependent manner. Immunochemical studies suggest that iodine incorporation in the thyroglobulin may augment the antigenicity of this molecule by increasing the affinity of its determinants for the T-cell receptor or the MHC-presenting molecule either altering antigen processing or by affecting antigen presentation.