Animal models of thyroid-associated ophthalmopathy.

Thyroid-associated ophthalmopathy (TAO) is an autoimmune condition most frequently associated with Graves' disease (GD). The thyrotropin receptor (TSHR) is an important target of the autoimmune response in both disorders. The last 5 years have seen some progress in the development of animal models, induced with TSHR preparations and reproducing some or all of the features of GD and TAO with variable incidence. The most promising approaches have used: (1) treatment of AKR/N mice with cells transfected with the homologous major histocompatibility complex class II molecule to the recipients and the full-length human or murine TSHR. Approximately 20% of mice develop thyroid-stimulating antibodies (TSAB) and increased thyroxine levels but no thyroiditis; (2) transfer of TSHR primed T cells to naive syngeneic recipients. Approximately 65% of BALBc mice develop thyroiditis and orbital changes similar to TAO; (3) genetic immunization of NMRI outbred mice with the full-length human TSHR. Approximately 20% of mice develop TSAB, hyperthyroidism, and orbital changes.     

The link between Graves' disease and Hashimoto's thyroiditis: a role for regulatory T cells

Hyperthyroidism in Graves' disease is caused by thyroid-stimulating autoantibodies to the TSH receptor (TSHR), whereas hypothyroidism in Hashimoto's thyroiditis is associated with thyroid peroxidase and thyroglobulin autoantibodies. In some Graves' patients, thyroiditis becomes sufficiently extensive to cure the hyperthyroidism with resultant hypothyroidism. Factors determining the balance between these two diseases, the commonest organ-specific autoimmune diseases affecting humans, are unknown. Serendipitous findings in transgenic BALB/c mice, with the human TSHR A-subunit targeted to the thyroid, shed light on this relationship. Of three transgenic lines, two expressed high levels and one expressed low intrathyroidal A-subunit levels (Hi- and Lo-transgenics, respectively). Transgenics and wild-type littermates were depleted of T regulatory cells (Treg) using antibodies to CD25 (CD4(+) T cells) or CD122 (CD8(+) T cells) before TSHR-adenovirus immunization. Regardless of Treg depletion, high-expressor transgenics remained tolerant to A-subunit-adenovirus immunization (no TSHR antibodies and no hyperthyroidism). Tolerance was broken in low-transgenics, although TSHR antibody levels were lower than in wild-type littermates and no mice became hyperthyroid. Treg depletion before immunization did not significantly alter the TSHR antibody response. However, Treg depletion (particularly CD25) induced thyroid lymphocytic infiltrates in Lo-transgenics with transient or permanent hypothyroidism (low T(4), elevated TSH). Neither thyroid lymphocytic infiltration nor hypothyroidism developed in similarly treated wild-type littermates. Remarkably, lymphocytic infiltration was associated with intermolecular spreading of the TSHR antibody response to other self thyroid antigens, murine thyroid peroxidase and thyroglobulin. These data suggest a role for Treg in the natural progression of hyperthyroid Graves' disease to Hashimoto's thyroiditis and hypothyroidism in humans.     

Identification of thyroglobulin in orbital tissues of patients with thyroid-associated ophthalmopathy.

Thyroid-associated ophthalmopathy (TAO) is thought to have an autoimmune pathogenesis because of its association with autoimmune thyroid disease, in particular with Graves' disease. Nevertheless, the nature of the autoimmune reaction is unclear, and a target orbital autoantigen has not been conclusively identified. A widely discussed hypothesis is that antigens constitutively shared by the thyroid and orbital tissues are targets of an autoimmune reaction. It has been also postulated that a thyroid-soluble antigen, namely thyroglobulin (Tg), is transported to orbital tissues through the lymphatics, where it accumulates and elicits autoimmune damages in susceptible individuals. Here we have investigated whether Tg is present in orbital tissues from patients with TAO. Retrobulbar tissue specimens were obtained from three patients with Graves' disease and TAO who underwent decompressive orbitotomy, and at autopsy from two patients with no thyroid or eye disease. All patients with TAO had been previously treated with radioiodine to control Graves' hyperthyroidism. Western blot analysis with a monoclonal anti-Tg antibody showed the presence of intact Tg, both in soluble and membrane-associated fractions of orbital tissue extracts from the patients with TAO, in amounts estimated to range from approximately 320 to approximately 900 pg/microg of tissue protein. In contrast, Tg was not detected in orbital tissue extracts from patients with no thyroid or eye disease. Tg was also demonstrated in orbital tissue extracts from two of three patients with TAO by enzyme-linked immunosorbent assay (ELISA), in amounts estimated to range from approximately 450 to approximately 1000 pg/microg of protein. In addition, Tg in orbital tissue extracts from patients with TAO was immunoprecipitated by a rabbit anti-Tg antibody, suggesting that it retained its native conformation. An anti-thyroxine (T4) antibody captured in solid-phase Tg from orbital tissue extracts, showing that it contained thyroid hormone residues and had therefore originated in the thyroid. Tg-anti-Tg immune complexes were not found in orbital tissues, suggesting that if an autoimmune reaction to Tg occurs in TAO, it is likely to be cell mediated.     

Reduced expression of stromal-derived factor 1 in autonomous thyroid adenomas and its regulation in thyroid-derived cells.

Stromal-derived factor 1 (SDF-1) and CXCR4 comprise a unique chemokine/chemokine receptor pair, exhibiting important functions in morphogenesis and growth regulation as well as attractant properties on T lymphocytes. No data are available on SDF-1 and CXCR4 in normal or pathological thyroid tissues. SDF-1, CXCR4, and CD18 messenger ribonucleic acid (mRNA) as a marker of leukocytic infiltration were quantified in tissues affected by thyroid adenoma (n = 11) and Graves' disease (GD; n = 16) using competitive RT-PCR. SDF-1 mRNA levels differed significantly between autonomous adenomas and the corresponding normal tissue, but not in GD between patients with low or high leukocyte infiltration, thyroid peroxidase, and TSH receptor autoantibodies, respectively. We found a strong correlation between CXCR4 and CD18 mRNA, which indicates CXCR4 expression by leukocytes. To define the cellular source of SDF-1 and CXCR4 in thyroid tissue, we examined various thyroid-derived cells. Fibroblasts are the most potent producers of SDF-1, although thyrocytes also secrete SDF-1 in vitro. Leukocytes showed very weak SDF-1 mRNA levels and no secretion of the chemokine. Immunohistology confirmed and extended these results; SDF-1 expression was found in fibroblasts, but not or very weakly in CD45(+) leukocytes and thyrocytes. Only leukocytes were CXCR4(+). As examined by flow cytometry, the number of CD3(+) T cells expressing CXCR4 is significantly higher in the thyroid than in peripheral blood. SDF-1 seems to be involved in thyroid tissue homeostasis in thyroid adenoma, but not in the maintenance of lymphocytic infiltration in GD.     

甲状腺相关眼病治疗新进展

甲状腺相关眼病(TAO)是临床常见、发病率高的自身免疫性眼眶疾病,糖皮质激素是一线主流用药,鉴于使用者对其不良反应的忌惮以及部分患者对糖皮质激素治疗的不敏感,目前,已有诸多可改善TAO进程的药物在研发和临床应用前期中:从拮抗白细胞介素(IL)-6受体和肿瘤坏死因子(TNF)-α等免疫靶向治疗,到阻滞促甲状腺激素(TSH)受体产生甲状腺自身抗体;从拮抗胰岛素样生长因子(IGF)-1受体减少眼眶成纤维细胞活化,到锝-亚甲基二磷酸盐注射液(99Tc-MDP)、他汀类等调节自身免疫炎性反应,甚至从有效治疗Graves病的免疫疗法中也可以寻找到有望解决TAO的方法。     

Relation of CD30 molecules on T-cell subsets to the severity of autoimmune thyroid disease.

The prognosis of patients with autoimmune thyroid disease (AITD) varies. To clarify the immunologic differences among patients with various severities of AITD, we examined two types of molecules on peripheral T lymphocytes: CD195 (CCR5), which express dominantly on CD4(+) type 1 helper T (T(H)1) cells, and CD30, which is known as a marker of CD4(+) type 2 helper T (T(H)2) cells and a regulatory molecule of CD8(+) autoreactive cytotoxic T cells. We found presence of patients with high proportion (> 9%) of CD30 expression in CD4(+) cells in a group of patients with Graves' disease (GD) in remission compared to the patients with intractable GD and a decrease in the intensity of CD30 expression on CD8(+) cells from patients with severe Hashimoto's disease (HD) treated for hypothyroidism compared to patients with untreated and euthyroid HD. There was no difference in CD195 expression between these patients with GD or HD with different severities, but there was a decreased intensity of CD195(+) cells in thyrotoxic patients with GD. These results indicate that CD30 molecules on CD4(+) and CD8(+) cells may be related to the severities of GD and HD, respectively.     

Clinical associations of the genetic variants of CTLA‐4, Tg,TSHR, PTPN22, PTPN12 and FCRL3 in patients with Graves’ disease

Objective Graves’ disease (GD) is an organ‐specific autoimmune disorder. Both immune‐modulating genes and thyroid‐specific genes are involved in its genetic pathogenesis. It remains unclear, however, how the interactions of various susceptibility genes contribute to the pathogenesis and clinical severity of the disease. The purpose of this study was to investigate the relationships between GD and single nucleotide polymorphisms (SNPs) from CTLA‐4, PTPN22, PTPN12, FCRL3 (general autoimmunity genes regulating T and B cells) and the TSHR and Tg genes (disease‐specific genes). Furthermore, we evaluated the influences these SNPs have on the risk and severity of GD. Design and methods This cross‐sectional clinical study was performed in 436 GD patients and 316 healthy, gender‐matched individuals. Twenty‐eight SNPs from CTLA‐4, PTPN22, PTPN12, FCRL3, TSHR and Tg genes were genotyped and their associations with the risk and severity of GD were analysed. Results The CTLA‐4 rs231779, Tg rs2069550 and PTPN22 rs3789604 SNPs were associated with GD, with additive risk effects present in rs231779 and rs2069550. The ACACC and ACGCT haplotypes, composed of five SNPs in the CTLA‐4 gene (rs4553808, rs5472909, rs231775, rs231777 and rs231779), were protective and risk haplotypes respectively. The AA genotype of PTPN22 rs3789604 and AA genotype of FCRL3 rs7528684 were correlated with a reduced risk of GD, while the CC genotype of TSHR rs2239610 was associated with higher serum concentrations of FT4 and TRAb. Logistic analysis confirmed the contribution of CTLA‐4 rs231779 to the development of GD. Conclusions These preliminary results demonstrate that the immune‐regulatory gene CTLA‐4 and the thyroid‐specific gene Tg contribute to the risk of Graves’ disease with additive effects, while PTPN22 rs3789604 and FCRL3 rs7528684 polymorphisms are protective against the disease. In addition, the TSHR rs2239610 SNP is related to the severity of Graves’ disease.     

Animal models of Graves' disease

Graves' disease (GD) is an autoimmune condition in which goitre and hyperthyroidism are induced by thyroid stimulating antibodies (TSAB) which mimic the action of thyrotrophin (TSH). The target of the autoimmune response is the thyrotrophin receptor (TSHR) and, since its cloning, a number of differing approaches have been adopted in an attempt to develop an animal model of GD. Methods in which synthetic peptides or fragments of the receptor produced in bacteria or insect cells have been injected into animals together with immunological adjuvants have had only limited success in inducing some of the signs and symptoms of GD. Genetic immunisation resulted in thyroiditis in the majority, but TSAB formation in only a minority, of treated inbred mice. Transfer of receptor in vitro primed T cells to syngeneic naive recipients, with priming either using a bacterial fusion protein or genetic immunisation, induced destructive thyroiditis in non-obese diabetic (NOD) mice but lymphocytic thyroiditis in BALBc mice. Furthermore, the orbits of 17/22 of the BALBc animals, but not the NOD animals, with thyroiditis had orbital changes similar to those seen in thyroid eye disease. TSAB and elevated thyroxine levels were induced in AKR/N mice injected with fibroblasts expressing the full length human TSHR and murine major histocompatibility complex (MHC) class II homologous to the recipient mice. No thyroiditis was induced but preliminary results from a different group using the same protocol suggest that receptor autoantibodies and thyroid dysfunction could be transferred using T cells primed in vitro with the receptor and MHC-II expressing cells. The majority of the studies described above have studied inbred mouse strains. In a novel departure, the NMR outbred strain has been treated by genetic immunisation with very promising results, including the induction of increased thyroxine levels in 4/30 female mice, accompanied by TSAB in addition to thyroiditis, and with signs of hyperactivity and orbital pathology. This review discusses the various protocols together with the information regarding the pathogenesis of GD which each has contributed, and concludes with an evaluation of how close we are to mimicking this polygenic, multifactorial disease.     

Demonstration of immunoglobulin G, A, and E autoantibodies to the human thyrotropin receptor using flow cytometry

Human TSH receptor (TSHR) autoantibodies with biological activity result in thyroid dysfunction, but antibodies that simply bind do not. We have applied flow cytometry to the measurements of IgG, IgA, and IgE immunoreactivity to the TSHR in patients with Graves' disease (GD) and thyroid eye disease (TED) and in normal controls. CHO cells stably expressing the extracellular domain of the TSHR with a glycophosphatidylinositol anchor were produced and found to express approximately 4 times as many receptors, but of similar affinity, as JP09 in TSH binding studies. Substantial increases in median fluorescence and peak channel fluorescence were obtained by flow cytometry using TSHR monoclonal antibodies on the glycophosphatidylinositol cells. IgG autoantibodies were demonstrated in 55 of 65 untreated GD patients, 3 of 25 normal subjects, and 4 of 8 atypical TED sera (negative for TSHR autoantibodies with biological activity) by flow cytometry and correlated poorly with thyroid-stimulating antibodies. IgA antibodies were present in 1 of 12 normal, 1 of 7 treated GD with TED, and 3 of 8 atypical TED sera. IgE binding was observed in 1 of 12 normal, 2 of 8 treated GD without TED, 1 of 6 treated GD with TED, and 0 of 8 atypical TED sera. In conclusion, we have demonstrated autoantibodies that bind directly to the TSHR in the majority of GD patients and in 50% of patients with atypical TED and a small number of normal controls lacking TSHR antibodies that affect function. Although predominantly IgG lambda, TSHR autoantibodies of the IgA and IgE isotypes are also detectable.     

Interleukin-6 stimulates thyrotropin receptor expression in human orbital preadipocyte fibroblasts from patients with Graves' ophthalmopathy.

The thyrotropin receptor (TSHR) is the thyroid autoantigen against which stimulating autoantibodies are directed in Graves' hyperthyroidism. Recent evidence suggests that TSHR may also serve as an orbital autoantigen in Graves' ophthalmopathy (GO) and that expression of this protein is increased in the fatty connective tissues of the orbit in this condition. It has been shown that orbital fibroblasts from patients with GO increase thyrotropin (TSH)-dependent cyclic adenosine monophosphate (cAMP) production and TSHR gene expression when cultured under conditions known to stimulate adipocyte differentiation. In the current study, we wanted to determine whether treatment of these cells with particular cytokines (each 1 ng/mL) during differentiation might further augment TSHR expression. We found that exposure to interleukin (IL)-6 increased TSHR expression above control levels in cells from patients with GO. In contrast, this cytokine did not affect TSHR expression in normal orbital cells. Neither IL-4 nor IL-1alpha had a significant stimulatory effect in either normal or Graves' cultures. These findings suggest that IL-6 may play a role in the pathogenesis of GO by increasing expression of the putative autoantigen within the adipose/connective tissues of the orbit.     

Increased intensities of fas expression on peripheral T-cell subsets in severe autoimmune thyroid disease.

Fas (CD95)-Fas ligand (FasL; CD178)-induced apoptosis is necessary for the maintenance of self-tolerance. To clarify whether or not any abnormalities in the Fas-FasL system exist in patients with autoimmune thyroid disease (AITD), we examined the expression of Fas and FasL on peripheral T lymphocytes by three-color flow cytometry in 113 patients with AITD and 49 healthy controls. The intensities of Fas expression in both CD4(+) and CD8(+) T cells decreased in thyrotoxic patients with Graves' disease (GD), but increased in both patients with severe Hashimoto's disease (HD) undergoing treatment and seriously intractable patients with GD continuously positive for thyrotropin (TSH) receptor antibody despite treatment with antithyroid drugs for more than 5 years. The proportion of Fas expression was increased in CD4(+) T cells from patients with untreated GD, and in CD8(+) T cells from patients with severe HD. The proportion of CD8(+) T cells decreased in patients with severe HD. FasL were not expressed on T cells in controls and patients with AITD. These results indicate that (1). the intensities of Fas expression on peripheral T cells increase in severe autoimmune thyroid diseases and (2). both the intensity and the proportion of Fas expression may be important for the induction of apoptosis.     

Autoimmune thyrotoxicosis: diagnostic challenges

Autoimmune thyrotoxicosis or Graves' disease (GD) is the most common cause of hyperthyroidism in the United States (full text available online: http://education.amjmed.com/pp1/249). GD occurs more often in women (ratio 5:1) and has a population prevalence of 1-2%. A genetic determinant to the susceptibility to GD is suspected because of familial clustering of the disease, a high sibling recurrence risk, and the familial occurrence of thyroid autoantibodies. GD is a systemic autoimmune thyroid disorder characterized by the infiltration of immune effector cells and thyroid-antigen-specific T cells into the thyroid and thyroid stimulating hormone receptor (TSHR) expressing tissues, i.e. orbit, skin, with the production of autoantibodies to well-defined thyroidal antigens. Stimulatory autoantibodies in GD activate the TSHR leading to thyroid hyperplasia and unregulated thyroid hormone production and secretion. Diagnosis of GD is straightforward in a patient with a diffusely enlarged, heterogeneous, hypervascular (increased Doppler flow on neck ultrasound) thyroid gland, associated orbitopathy, biochemically confirmed thyrotoxicosis, positive TSHR autoantibodies, and often a family history of autoimmune disorders.     

Serum concentrations of adiponectin and resistin in hyperthyroid Graves' disease patients

This study was undertaken to determine whether serum adiponectin and resistin levels are influenced by hyperthyroidism and autoimmune factors and to find out whether their levels are dependent on the presence of ophthalmopathy. We measured serum concentrations of adiponectin and resistin in 76 patients (63 women, 13 men) with Graves' disease (GD) and compared them with levels of the control group which consisted of 30 healthy subjects. Patients were separated into two groups according to the presence or the absence of thyroid-associated ophthalmopathy (TAO). TAO (-) group consisted of 26 subjects without eye signs of GD and TAO (+) group included 50 subjects with ophthalmopathy. The latter group was further divided into 2 subgroups: with active TAO [26 patients, clinical activity score (CAS)> or =4] and with inactive TAO (24 patients, CAS<4). Groups did not differ in age, sex, body mass index (kg/m2) and smoking habits. Compared with euthyroid subjects, hyperthyroid GD patients had elevated mean serum adiponectin concentrations (19.96+/-4.97 microg/ml vs 15.01+/-3.99 microg/ml, p<0.001). However we did not observe any disparity between the TAO (-) and TAO (+) groups (20.60+/-5.06 microg/ml vs 19.63+/-4.94 microg/ml, p=ns). Comparing patients with a CAS> or =4 and patients with a CAS<4, we found similar mean serum concentrations of adiponectin (20.04+/-5.01 microg/ml vs 18.74+/-4.83 microg/ml, p=ns). Serum levels of resistin did not differ between the hyperthyroid patients and control subjects (13.11+/-4.26 ng/ml vs 12.82+/-4.75 ng/ml, p=ns). Serum resistin levels did not differ between TAO (+) and TAO (-) groups nor in patients with active and inactive TAO. Serum adiponectin correlated significantly with free T4 (FT4), free T3 (FT3), and TSH-R antibodies (TRAb) in GD patients (r=0.40, 0.41, and 0.37, respectively; p<0.001 for each). Serum resistin levels were not correlated with thyroid hormones and thyroid antibodies. The variables that in simple linear regression analyses were found to be correlated with serum adiponectin were then used in multiple regression analysis. In a model including adiponectin as dependent variable and FT4, FT3 and TRAb levels as independent variables, FT3 and TRAb remained as parameters independently related to adiponectin level (R2=0.35, p<0.001). CONCLUSIONS: Elevated serum adiponectin levels in GD patients are related to the degree of hyperthyroidism and autoimmune process. The presence and activity of ophthalmopathy is not a modifier of serum adiponectin and resistin.     

Induction of Graves-like disease in mice by immunization with fibroblasts transfected with the thyrotropin receptor and a class II molecule.

Graves disease is an autoimmune thyroid disease characterized by the presence of antibodies against the thyrotropin receptor (TSHR), which stimulate the thyroid to cause hyperthyroidism and/or goiter. By immunizing mice with fibroblasts transfected with both the human TSHR and a major histocompatibility complex class II molecule, but not by either alone, we have induced immune hyperthyroidism that has the major humoral and histological features of Graves disease: stimulating TSHR antibodies, thyrotropin binding inhibiting immunoglobulins, which are different from the stimulating TSHR antibodies, increased thyroid hormone levels, thyroid enlargement, thyrocyte hypercellularity, and thyrocyte intrusion into the follicular lumen. The results suggest that the aberrant expression of major histocompatibility complex class II molecules on cells that express a native form of the TSHR can result in the induction of functional anti-TSHR antibodies that stimulate the thyroid. They additionally suggest that the acquisition of antigen-presenting ability on a target cell containing the TSHR can activate T and B cells normally present in an animal and induce a disease with the major features of autoimmune Graves.