Immunological of the Thyrotropin Receptor

Antibodies to the thyrotropin receptor appear to he responsible for hyperthyroidism in Graves disease. The antibodies, described as thyroid-stimulating antibodies (TSAb) mimic the effects of thyrotropin (TSH) by binding to the TSH receptor and activating adenylate cyclase. TSAb consist of an electrophoretically heterogeneous population of IgG and the thyroid-stimulating site is formed by combination of heavy and light chains in the Fab part of the molecule. Binding studies indicate that the TSAb molecule interacts monovalently with membrane bound TSH receptors and that TSAb consists of an antibody population which shows a restricted heterogeneity with regard to TSH receptor affinity. Studies in patients with Graves disease and hyperthyroidism indicate that the levels of TSAb correlate well with thyroidal iodine uptake and the absence of pituitary control of thyroid function. However in some patients with ophthalmic Graves' disease or autoimmune thyroiditis there is evidence of serum antibodies which interact with the TSH receptor but are unable to stimulate thyroid function.     

Immunological of the Thyrotropin Receptor

Antibodies to the thyrotropin receptor appear to he responsible for hyperthyroidism in Graves disease. The antibodies, described as thyroid-stimulating antibodies (TSAb) mimic the effects of thyrotropin (TSH) by binding to the TSH receptor and activating adenylate cyclase. TSAb consist of an electrophoretically heterogeneous population of IgG and the thyroid-stimulating site is formed by combination of heavy and light chains in the Fab part of the molecule. Binding studies indicate that the TSAb molecule interacts monovalently with membrane bound TSH receptors and that TSAb consists of an antibody population which shows a restricted heterogeneity with regard to TSH receptor affinity. Studies in patients with Graves disease and hyperthyroidism indicate that the levels of TSAb correlate well with thyroidal iodine uptake and the absence of pituitary control of thyroid function. However in some patients with ophthalmic Graves' disease or autoimmune thyroiditis there is evidence of serum antibodies which interact with the TSH receptor but are unable to stimulate thyroid function.     

Immunology of the thyrotropin receptor.

Antibodies to the thyrotropin receptor appear to be responsible for hyperthyroidism in Graves' disease. The antibodies, described as thyroid-stimulating antibodies (TSAb) mimic the effects of thyrotropin (TSH) by binding to the TSH receptor and activating adenylate cyclase. TSAb consist of an electrophoretically heterogeneous population of IgG and the thyroid-stimulating site is formed by combination of heavy and light chains in the Fab part of the molecule. Binding studies indicate that the TSAb molecule interacts monovalently with membrane bound TSH receptors and that TSAb consists of an antibody population which shows a restricted heterogeneity with regard to TSH receptor affinity. Studies in patients with Graves' disease and hyperthyroidism indicate that the levels of TSAb correlate well with thyroidal iodine uptake and the absence of pituitary control of thyroid function. However in some patients with ophthalmic Graves' disease or autoimmune thyroiditis there is evidence of serum antibodies which interact with the TSH receptor but are unable to stimulate thyroid function.     

Adenovirus encoding the thyrotropin receptor A-subunit improves the efficacy of dendritic cell-induced Graves' hyperthyroidism in mice

Stimulating the immune system by in vivo expression of the thyrotropin receptor (TSHR) is an efficient means to induce Graves' disease experimentally. For example, BALB/c mice injected with dendritic cells (DCs) infected with adenovirus encoding the full-length TSHR (AdTSHR) develop hyperthyroidism, albeit at a low incidence (36%). Recent observations suggest that the shed TSHR A-subunit, rather than the full-length receptor, is the autoantigen responsible for initiating/enhancing immune responses leading to thyroid stimulating antibodies (TSAb) and hyperthyroidism. Therefore, we attempted to improve the efficacy of the DC-based approach for Graves' disease using adenovirus encoding the TSHR A-subunit (AdTSHR289). Three injections of DCs infected with AdTSHR289 induced hyperthyroidism in 70% of BALB/c mice, approximately twice the disease induction rate with AdTSHR. TSAb activity was detected in most hyperthyroid mice, whereas virtually all immunized mice developed antibodies that inhibit [125I]TSH binding to the TSHR or recognize linear or conformational epitopes on the TSHR. TSHR antibodies were of IgG1 and IgG2a, indicating mixed T-helper type 1 (Th1)/Th2 immune responses. In conclusion, immunization with DC infected with adenovirus expressing the TSHR A-subunit is a highly efficient protocol to induce Graves' hyperthyroidism in BALB/c mice. This improved model will permit studies of the pathogenic role and therapeutic potential of DCs in Graves' hyperthyroidism.     

Induction of hyperthyroidism in mice by intradermal immunization with DNA encoding the thyrotropin receptor

Intramuscular injection with plasmid DNA encoding the human thyrotropin receptor (TSHR) has been known to elicit symptoms of Graves' disease (GD) in outbred but not inbred mice. In this study, we have examined, firstly, whether intradermal (i.d.) injection of TSHR DNA can induce hyperthyroidism in BALB/c mice and, secondly, whether coinjection of TSHR- and cytokine-producing plasmids can influence the outcome of disease. Animals were i.d. challenged at 0, 3 and 6 weeks with TSHR DNA and the immune response was assessed at the end of the 8th or 10th week. In two experiments, a total of 10 (67%) of 15 mice developed TSHR-specific antibodies as assessed by flow cytometry. Of these, 4 (27%) mice had elevated thyroxine (TT4) levels and goitrous thyroids with activated follicular epithelial cells but no evidence of lymphocytic infiltration. At 10 weeks, thyroid-stimulating antibodies (TSAb) were detected in two out of the four hyperthyroid animals. Interestingly, in mice that received a coinjection of TSHR- and IL-2- or IL-4-producing plasmids, there was no production of TSAbs and no evidence of hyperthyroidism. On the other hand, coinjection of DNA plasmids encoding TSHR and IL-12 did not significantly enhance GD development since two out of seven animals became thyrotoxic, but had no goitre. These results demonstrate that i.d. delivery of human TSHR DNA can break tolerance and elicit GD in inbred mice. The data do not support the notion that TSAb production is Th2-dependent in murine GD but they also suggest that codelivery of TSHR and Th1-promoting IL-12 genes may not be sufficient to enhance disease incidence and/or severity in this model.     

Modulation of Fas-mediated apoptosis of human thyroid epithelial cells by IgG from patients with Graves' disease (GD) and idiopathic myxoedema

The expression of two autoimmune thyroid diseases, GD and idiopathic myxoedema, is associated with antibodies to the thyroid-stimulating hormone (TSH) receptor. Thyroid stimulating antibodies (TSAb) in GD are TSH agonists and cause hyperthyroidism as well as goitre, whereas thyroid stimulation blocking antibodies (TSBAb) in idiopathic myxoedema are TSH antagonists and cause hypothyroidism and thyroid atrophy. We investigated the effect of antibodies to TSH receptor on Fas-mediated apoptosis of thyroid epithelial cells (thyrocytes). Human IgG was isolated from healthy donors, patients with GD and idiopathic myxoedema. Human thyrocytes were obtained from surgical specimens. Thyrocytes were cultured in the presence or absence of human IgG with or without interferon-gamma (IFN-γ) or IL-1β for a specified time. After incubation, we examined the level of cAMP in cultured supernatants and both Fas and Bcl-2 expression on thyrocytes. In addition, we examined anti-Fas-mediated apoptosis of thyrocytes. Fas expression on thyrocytes was significantly down-regulated by Graves' IgG and TSH, although idiopathic myxoedema IgG did not affect Fas expression on thyrocytes. Idiopathic myxoedema IgG abrogated the effect of TSH on both cAMP production and inhibition of Fas expression on thyrocytes. Treatment of thyrocytes with IL-1β or IFN-γ caused a marked augmentation of Fas expression on thyrocytes. The increase of Fas expression of thyrocytes induced by IL-1β or IFN-γ was significantly suppressed in the presence of TSH or Graves' IgG. Anti-Fas-induced apoptosis of thyrocytes was observed in thyrocytes treated with IL-1β or IFN-γ, but was markedly inhibited in the presence of TSH or Graves' IgG. Furthermore, idiopathic myxoedema IgG abrogated most of the inhibitory effect of TSH on Fas-mediated apoptosis of thyrocytes treated with IL-1β or IFN-γ. Bcl-2 expression of thyrocytes did not change after stimulation with TSH, Graves' IgG, idiopathic myxoedema IgG, IL-1β or IFN-γ. These results suggest that TSAb found in Graves' patients may be potentially involved in the development of goitre by inhibition of Fas-mediated apoptosis of thyrocytes. In addition, TSBAb inhibit the action of TSH and increase the sensitivity toward Fas-mediated apoptosis of thyrocytes, inducing thyroid atrophy seen in patients with idiopathic myxoedema.     

Graves病小鼠模型发病中调节性B细胞的表达变化

目的:观察Graves病(GD)小鼠模型脾脏调节性B细胞(regulatory B cells,Bregs)及相关细胞因子表达量的变化,探讨Bregs在GD发生、发展中的免疫调节作用。方法:将6周龄BALB/c雌性小鼠随机分为对照组(肌注空载腺病毒)、GD组(肌注TSHR-A亚单位-腺病毒建立GD小鼠模型)。每3周免疫1次,第3次免疫3周后处死。留取小鼠血清,化学发光法检测FT4水平,细胞培养生物学方法检测TSAb活性。取甲状腺,制备石蜡切片行HE染色。取脾脏,部分制成单个核细胞悬液,行三标记免疫荧光染色、流式细胞分析CD1dhiCD5+CD19+Bregs比例;部分脾脏提取总RNA,实时定量RT-PCR检测Bregs相关细胞因子白细胞介素10(IL-10)mRNA和转化生长因子-β(TGF-β)mRNA的表达水平。结果:发生GD的小鼠甲状腺滤泡细胞增生肥大,且血清FT4及TSAb水平升高。小鼠血清TSAb与FT4水平呈显著正相关(r=0.90,P<0.01);TSHR-A亚单位-腺病毒免疫组发生GD的小鼠脾脏CD19+B细胞较对照组明显升高(P<0.05),B细胞中CD1dhiCD5+CD19+Bregs所占比例和脾组织IL-10 mRNA、TGF-βmRNA表达量较对照组明显降低(P<0.05);且血清TSAb活性与CD1dhiCD5+CD19+Bregs占脾脏B细胞比例、脾组织IL-10 mRNA、TGF-βmRNA表达量均呈显著负相关(P<0.05)。结论:TSHR-A亚单位-腺病毒免疫建立的GD模型中Bregs表达存在缺陷,提示Bregs表达可能在GD的发生及发展中发挥免疫调节作用,且GD疾病严重程度可能与Bregs缺乏程度有关。     

A novel mouse model of Graves' disease: implications for a role of aberrant MHC class II expression in its pathogenesis

Mice immunized with fibroblasts expressing an MHC class II molecule and human thyrotropin receptor (TSHR), but not either alone, develop major features characteristic of Graves' disease (GD), such as thyroid-stimulating autoantibodies directed against TSHR, increased serum thyroid hormone levels, and enlarged thyroid glands. The results indicate the need for the simultaneous expression of a class II molecule and the TSHR on the surface of the fibroblasts to develop stimulating anti-TSHR antibodies and full-blown GD in our model. A T cell line established from a mouse with hyperthyroidism proliferates in response to fibroblasts expressing a class II molecule and TSHR, but not to the fibroblasts expressing only TSHR, indicating that the class II molecules on the fibroblasts present TSHR-derived peptide(s) to T cells. These results strongly suggest that the acquisition of antigen-presenting ability by thyrocytes can lead to the induction or progression of GD. We identified a T cell epitope of TSHR by the proliferative response of spleen cells from mice immunized with fibroblasts expressing a class II molecule and TSHR to 80 overlapping peptides spanning the extracellular domain of human TSHR. The identification of a major T cell epitope provides an important clue to a novel therapy of GD.     

A novel hypothesis for the etiology of Graves' disease: TSAb may be thyroid stimulating animal IgG-like hormone and TBAb may be the precursor of TSAb

There are doubtful points about the theory that autoimmunity with auto-antibody (Ab) to TSH receptor (R) causes hyperthyroidism in Graves' disease (GD). A main doubtful point is no curative effect of corticosteroid on Graves' hyperthyroidism in spite of curative effect of corticosteroid for all autoimmune diseases. Recently we demonstrated the immunological similarity of TSAb and TBAb-IgG to animal IgGs, except for human (h)IgG, by neutralization and purification of TSAb and TBAb-IgG using (1) heterophilic Ab to animal IgG in GD sera and (2) experimentally generated anti-animal IgG Abs [such as dog (d), bovine (b), porcine (p), and rabbit (rb)]. Furthermore, greater immunological similarity of Fab- and F(ab')(2)-portion of TSAb- and TBAb-IgG to bovine Fab, compared to hFab, was demonstrated using goat anti-bovine F(ab')(2) Ab. Existence of b and p TSH-like portions in the LATS-IgG molecule (probably Fab portion) was suggested by a previous report of neutralization of LATS activity by anti-b- or anti-p-TSH Ab. We suggested the existence of a mammalian animal-TSH-like structure, excepting hTSH, in the TSAb-IgG molecule (probably Fab portion), by discovery of anti-mammalian TSH Ab (such as d, b, p, guinea-pig, rat, whale, except h) in sera of GD. Lately, similar TSHR binding of H- and L-chain of human stimulating monoclonal TSHR Ab (M22)-Fab with TSH-α and-β subunit was reported. This evidence suggests that Fab portion of TSAb has a structure like mammalian TSH, but not hTSH. IgG-λ type of d, horse, b, p, goat, ovine is 95% and IgG-κ type is 5%, while human κ and λ chain is 60:40. Previous report that LATS (TSAb)-IgG composed of predominant λ type is supporting evidence that TRAb-IgG has immunological similarity with these animal IgGs compared to hIgG. We speculate that TSAb-IgG may be referred as a mermaid consisted in face (Fab) and trunk-leg (Fc). Face may be a kind of hormone with animal TSH-like structure and trunk-leg has animal IgG-like structure (in spite of no antibody function). There are many reports for co-existence of TSAb and TBAb-IgG in sera of GD. We reported conversion from TBAb (non-thyroid stimulating type IgG) to TSAb by co-incubation of anti-hIgG Ab (containing anti-animal IgG Ab as a cross-reaction) with TBAb-bound porcine thyroid cells. Thus, we suggest that TBAb may be the precursor form of TSAb.     

A Novel Mouse Model of Graves’ Disease: Implications for a Role of Aberrant MHC Class II Expression in its Pathogenesis

Mice immunized with fibroblasts expressing an MHC class II molecule and human thyrotropin receptor (TSHR), but not either alone, develop major features characteristic of Graves’ disease (GD), such as thyroid-stimulating autoantibodies directed against TSHR, increased serum thyroid hormone levels, and enlarged thyroid glands. The results indicate the need for the simultaneous expression of a class II molecule and the TSHR on the surface of the fibroblasts to develop stimulating anti-TSHR antibodies and fullblown GD in our model. A T cell line established from a mouse with hyperthyroidism proliferates in response to fibroblasts expressing a class II molecule and TSHR, but not to the fibroblasts expressing only TSHR, indicating that the class II molecules on the fibroblasts present TSHR-derived peptide(s) to T cells. These results strongly suggest that the acquisition of antigen-presenting ability by thyrocytes can lead to the induction or progression of GD. We identified a T cell epitope of TSHR by the proliferative response of spleen cells from mice immunized with fibroblasts expressing a class II molecule and TSHR to 80 overlapping peptides spanning the extracellular domain of human TSHR. The identification of a major T cell epitope provides an important clue to a novel therapy of GD.     

Antibodies to TSH-receptor in thyroid autoimmune disease interact with monoclonal antibodies whose epitopes are broadly distributed on the receptor

The hyperthyroidism of Graves' disease (GD) is caused by TSH-receptor (TSH-R) stimulating autoantibodies (TSAb), leading to overproduction of thyroid hormones. We present evidence for TSAb interaction with three distinct regions of the TSH-R, one in immediate vicinity of the carboxy terminal serpentine. Three murine monoclonal antibodies (MoAbs 28.1, A9 and 31.7) directed to amino acids 36-40, 147-228 and 382-415 were labelled and tested for their binding to human recombinant TSH-R on solid phase. All MoAbs bound to TSH-R with a K(d) of 8-12 nm and showed no competition among themselves. We tested 114 sera from euthyroid controls, 118 TBII positive sera from patients with GD (containing TSAb confirmed by bioassays), 16 TBII positive sera from patients with autoimmune thyroid disease (AIT), who were hypothyroid and had TSH blocking antibodies (TBAb), and 20 patients with AIT, who were hypothyroid but negative for all TRAb. Mid-regional MoAb A9 tracer achieved the highest sensitivity in the GD group (72.0%), whereas C-terminal MoAb 31.7 found most sera positive in the AIT group (87.5%). Surprisingly, the N-terminal MoAb 28.1 had the lowest sensitivity in the GD (10.4%) and AIT group (43.8%). Using a mixture of all three tracer MoAbs did not increase the sensitivity in the GD or AIT group, compared to the best single MoAb alone. Median inhibition of MoAb A9 was significantly (P < 0.001) higher than inhibition of MoAbs 28.1 or 31.7 in the group of GD patients but not in other groups. Almost all patient sera with positive reactivity in the MoAb tracer assays had TBII values in the higher range. However, there were many highly TBII positive sera, which did not show a displacement of the MoAb tracers. We conclude that, contrary to some reports, the binding of TSAb and TBAb to the TSH-R is not restricted to distinct and distant epitopes. The middle part of the TSH-R seems to be more relevant for TSAb binding than the N-terminal part, while a proportion of TSAb autoantibodies also binds to a C-terminal epitope of the TSH-R. The method described here is a TSH independent competitive assay for the detection of TSH-R autoantibodies.     

Thyroid function tests

About 80% of thyroid disease consists of thyroid-specific autoimmune diseases, Hashimoto's disease and Grave's disease. To diagnose thyroid diseases, testings for (1) thyroid function and (2) pathogenetic autoantibodies are indispensable. To assess thyroid function, serum hormone concentrations, such as TSH, FT4 and FT3 are measured. Among these hormones, serum TSH concentrations are the most reliable and informative regarding thyroid function, correcting indicating a hyperthyroid, euthyroid or hypothyroid state. Therefore, TSH measurement appears to be the first choice in selecting the hormone determination. Reference intervals for normal healthy subjects of TSH are around 0.4-5.0 microU/ml. The second choice for thyroid function assessment are FT4 which supersedes total T4(TT4). TT4 is affected by changes in serum thyroid hormone binding proteins(TBG, TTR, Albumin). For example, euthyroid pregnant women whose serum TBG are physiologically higher than those of non-pregnant women show augmentation of TT4. However, FT4 depicts within reference intervals, although measurement of FT4 alone is unable to detect any abnormality of thyroid hormone binding proteins. According to its plasma concentration and binding affinity, FT3 measurement deserves no more significance than T3. Another important test for thyroid diseases is to detect serum autoantibodies against thyroid tissues, such as TgAb, TPOAb. Much more important is TSH receptor antibody which differentiates Graves' disease from Hashimoto's thyroiditis. In patients who show hyperthyroidism and some very uncommon hypothyroidism, TSH receptor antibodies should be measured. Three indicators are available as routine tests; TRAb measured by radioreceptor assay; TSAb determined by bioassay using cultured porcine thyroid cells. Usually, TRAb activity clinically correlates well with TSAb. TSBAb was initially discovered in patients with severe hypothyroidism with atrophic thyroid gland. TSBAb blocks thyroid stimulating activity of TSH and consequently causes severe hypothyroidism. TRAb and TSAb are very useful to diagnose and follow patients with Grave's disease.     

Graves病小鼠模型IL-10水平与Th17细胞功能的检测和意义

目的 研究Th17细胞及相关细胞因子IL-17 mRNA与IL-10 mRNA在实验性Graves小鼠体内变化.方法 利用TSHR-E(胞外区)的腺病毒免疫小鼠方法建立Graves疾病模型,化学发光法检测血清FT4水平,细胞培养生物学方法检测TSAb活性,流式细胞术(FCM)分析小鼠脾脏细胞中Th17细胞的比例,qRT-PCR检测小鼠脾脏细胞中IL-17和IL-10mRNA水平.结果 小鼠血清FT4及TSAb水平升高,TSAb与FT4水平呈显著正相关(r=0.90,P＜0.01);Graves小鼠脾细胞中Th17细胞的比例为(2.56±0.43)％,明显高于正常对照组小鼠(1.07±0.27％)％(P＜0.05);Graves小鼠脾细胞中IL-17 mRNA的含量明显高于正常对照组(P＜0.05),而IL-10 mRNA的含量明显低于正常对照组(P＜0.05);且IL-17和IL-10水平变化存在明显的负相关(r=-0.564,P＜0.01).结论 TSHR-E(胞外区)的腺病毒免疫建立的GD模型中,IL-17mRNA增加和IL-10 mRNA则明显下降;提示两者可能在GD的发生及发展中发挥免疫调节作用.     

Autoantibodies against complement C1q correlate with the thyroid function in patients with autoimmune thyroid disease

Autoantibodies against complement C1q (anti-C1q) have been well described in patients with systemic lupus erythematosus, where they correlate with the occurrence of severe lupus nephritis. However, data on anti-C1q in organ-specific autoimmune diseases are scarce. In order to determine the prevalence of anti-C1q in patients with autoimmune thyroid disorders (AITD) and a possible association with thyroid function, we measured prospectively anti-C1q in 23 patients with Graves' disease (GD) and 52 patients with Hashimoto's thyroiditis (HT). Anti-C1q levels were correlated with parameters of thyroid function and autoantibodies against thyroperoxidase, thyroglobulin and thyroid stimulating hormone (TSH) receptor. Twenty-one patients with multi-nodular goitre and 72 normal blood donors served as controls. We found elevated concentrations of anti-C1q more frequently in patients with AITD than in controls: seven of 23 (30%) patients with GD and 11 of 52 (21%) patients with HT, compared with one of 21 (5%) patients with multi-nodular goitre and six of 72 (8%) normal controls. Anti-C1q levels did not correlate with thyroid autoantibodies. However, in GD absolute levels of anti-C1q correlated negatively with TSH and positively with free thyroxine (FT4) and triiodothyronine (FT3). In contrast, in HT, anti-C1q correlated positively with TSH levels. No correlation between TSH and thyroid autoantibodies was found. In conclusion, we found an increased prevalence of anti-C1q in patients with AITD and their levels correlated with the thyroid function in both GD and HT. This correlation seems to be independent of thyroid autoantibodies. Therefore, anti-C1q might point to a pathogenic mechanism involved in the development of AITD that is independent of classical thyroid autoantibodies.     

Administration of thyroxine in treated Graves' disease. Effects on the level of antibodies to thyroid-stimulating hormone receptors and on the risk of recurrence of hyperthyroidism

BACKGROUND. Antibodies to thyroid-stimulating hormone (TSH) receptors that stimulate the thyroid gland cause hyperthyroidism in patients with Graves' disease, and their production during antithyroid drug treatment is an important determinant of the course of the disease. One factor that might contribute to the persistent production of antibodies to TSH receptors is stimulation of the release of thyroid antigens by TSH during antithyroid drug therapy. We therefore studied the effect of the suppression of TSH secretion by thyroxine on the levels of antibodies to TSH receptors after thyroid hormone secretion had been normalized by methimazole. METHODS AND RESULTS. The levels of antibodies to TSH receptors were measured during treatment with methimazole, either alone or in combination with thyroxine, in 109 patients with hyperthyroidism due to Graves' disease. The patients first received 30 mg of methimazole daily for six months. All were euthyroid after six months, and their mean (+/- SD) level of antibodies to TSH receptors decreased from 64 +/- 9 percent to 25 +/- 15 percent (P less than 0.01; normal, 2.9 +/- 1.4 percent). Sixty patients then received 100 micrograms of thyroxine and 10 mg of methimazole and 49 received placebo and 10 mg of methimazole daily for one year. In the thyroxine-treated group, the mean serum thyroxine concentration increased from 108 +/- 16 nmol per liter to 145 +/- 11 nmol per liter (P less than 0.01), and the level of antibodies to TSH receptors decreased from 28 +/- 10 percent to 10 +/- 3 percent after one month of combination therapy. In the patients who received placebo and methimazole, the mean serum thyroxine concentration decreased and the level of antibodies to TSH receptors did not change. Methimazole, but not thyroxine or placebo, was discontinued in each group 1 1/2 years after the beginning of treatment. The level of antibodies to TSH receptors further decreased (from 6.6 +/- 3.2 percent at the time methimazole was discontinued to 2.1 +/- 1.2 percent one year later) in the patients who continued to receive thyroxine, but it increased (from 9.1 +/- 4.8 percent to 17.3 +/- 5.8 percent during the same period) in the patients who received placebo. One patient in the thyroxine-treated group (1.7 percent) and 17 patients in the placebo group (34.7 percent) had recurrences of hyperthyroidism within three years after the discontinuation of methimazole. CONCLUSIONS. The administration of thyroxine during antithyroid drug treatment decreases both the production of antibodies to TSH receptors and the frequency of recurrence of hyperthyroidism.     

Thyroid-stimulating antibodies in patients with long-term remission of Graves' hyperthyroidism

Summary The persistence of TSH receptor antibodies in Graves' disease despite the remission of hyperthyroidism has been described. Our study was designed to evaluate whether this extends to functionally active stimulators of the thyroid, since the occurrence of thyroid-stimulating antibodies (TSAb) in a euthyroid patient could well have important implications on our understanding of the pathogenetic role of such autoantibodies. Forty-four patients with a previous history of Graves' hyperthyroidism were reexamined after having been in long-lasting remission for 3 to 35 years (mean 8 years). Of the patients 16 had been treated by radioiodine, 17 by surgery, and 11 exclusively by antithyroid drugs. The determination of TSAb was based on T3 release from thyroid tissue in vitro to document the final response to these immunoglobulins. TSH-binding inhibiting immunoglobulins (TBII) were evaluated by a radioreceptor assay.TSAb were highly elevated in three of the 44 patients. These three patients showed a normal TSH response to i.v. TRH, suffered from endocrine ophthalmopathy, and had been treated by radioiodine for hyperthyroidism. TBII were found positive in seven patients including the three patients mentioned. The majority of patients positive for TSAb or TBII had been treated by radioiodine and none exclusively by antithyroid drugs.In conclusion, not only TBII but also T3 release-stimulating antibodies may occur in a minority of patients with long-term remission of Graves' hyperthyroidism. However, an absence of hyperthyroidism in these patients despite the presence of such thyroid stimulators seems to be only possible in association with a lack of functional responsiveness of the target organ due to previous administration of destructive therapies. Moreover, a major role of TBII in the absence of TSAb representing stimulatory inactive autoantibodies to the maintenance of remission was not apparent.Abbreviations cAMP cyclic adenosine monophosphate - T3 triiodothyronine - T4 tetraiodothyronine - TBII TSH-binding inhibiting immunoglobulins - TRH TSH-releasing hormone - TSAb thyroid-stimulating antibodies - TSH thyroidstimulating hormone     

Graves病患者治疗前、后血清甲状腺刺激抗体和TSH结合抑制免疫球蛋白活性的观察

本文研究了Ｇｒａｖｅｓ病（ＧＤ）患者在抗甲状腺药物（ＡＴＤ）治疗前、后血清甲状腺刺激抗体（ＴＳＡｂ）和ＴＳＨ结合抑制免疫球蛋白（ＴＢＩＩ）的变化，发现治疗前ＴＳＡｂ和ＴＢＩＩ的检出率分别为９１．７％和７９．２％，治疗后两抗体的活性及阳性率均显著下降，表明抗甲状腺药可改善ＧＤ患者的免疫异常。ＴＳＡｂ和ＴＢＩＩ活性不相关，提示ＴＳＨ受体抗体（ＴＲＡｂ）具有异质性。ＴＳＡｂ和ＴＢＩＩ活性与血清甲状腺激素水平无相关关系，说明体外测定的ＴＳＡｂ或／和ＴＢＩＩ活性并不能完全反映甲亢的严重程度。     

Prognostic value of thyroid stimulating antibodies and TSH-binding inhibiting immunoglobulins in the follow-up of Graves' disease

Summary The prognostic value of the determinations of autoantibodies in Graves' disease is still questionable. So far, the role of different assay procedures used has not been intensively investigated. We simultaneously applied two different techniques, a radioreceptor assay and a T3 releasing in vitro assay, in the follow-up of patients with Graves' disease to directly compare the course of the antibody activities determined by these assays and to find out a prognostic significance of the composition of the antibody spectrum present. The initial activities of thyroid stimulating antibodies (TSAb) and TSH-binding inhibiting immunoglobulins (TBII) were not significantly correlated in patients before treatment. During a 12-month antithyroid medication antibody titres showed a concordant course in the majority of patients. In 6 of 25 patients, however, a discordant behaviour was clearly documented including dose-response curves. At the end of treatment, the patients could be divided into three groups: group I included 5 patients positive for both TSAb and TBII, group II 6 patients positive for TBII and negative for TSAb and group III 14 patients negative for both of them. During the following survey of 18 months all patients of group I, 2 patients of group II and 6 patients of group III experienced a relapse of hyperthyroidism. In conclusion, TSAb and TBII activities dissociate in some patients during antithyroid drug therapy. For the individual patient, the disappearance of both TSAb and TBII was no certain indicator for a longstanding remission of Graves' hyperthyroidism. The persistence of TSAb seems to be more reliably associated with persisting or rapidly relapsing disease than the persistence of TBII.Abbreviations cAMP Cyclic Adenosine Monophosphate - GD Graves' disease - T3 Triiodothyronine - T4 Tetraiodothyronine - TBII TSH-binding inhibiting immunoglobulins - TRH TSH releasing hormone - TSAb Thyroid stimulating antibodies - TSH Thyroid stimulating hormone     

Unaltered thyroid function in mice responding to a highly immunogenic thyrotropin receptor: implications for the establishment of a mouse model for Graves' disease.

Grave's disease (GD) is a common disorder characterized by the presence of autoantibodies to the thyrotropin receptor. In the past, the exceedingly low expression of the thyrotropin receptor on thyrocytes has not allowed its purification in quantities sufficient to investigate the establishment of an animal model for this disease. In this study, we have purified the 398-amino acid, extracellular region of the human thyrotropin receptor (TSH-R.E) from insect cells using recombinant baculovirus, and explored its immunopathogenic properties in H-2b,d,q,k,s strains of mice. The receptor preparation was highly immunogenic since it elicited strong specific proliferative T cell responses as well as IgG responses in all strains tested. In addition, hyperimmunization with TSH-R.E induced (i) serum antibodies that blocked the binding of 125I-TSH to its receptor, a common feature of GD autoantibodies; and (ii) IgG that reacted with a synthetic peptide (residues 32-54) from the N-terminus of the receptor, a region implicated in the binding of thyroid stimulating antibodies. In SJL animals only, a weak antibody response to two other thyroid antigens, thyroglobulin and thyroid peroxidase, was also observed. The presence of these antibodies, however, was not accompanied by a detectable alteration in thyroid function as assessed by the measurement of serum TSH, T4 and iodine levels. Also mononuclear infiltration of the thyroid gland or morphological changes compatible with an activation state of thyrocytes were not apparent in TSH-R-challenged mice. In contrast, mice treated with the anti-oxidant aminotriazole showed a dramatic increase in serum TSH levels and an activated follicular epithelium. These data demonstrate that a highly immunogenic TSH-R.E in mice does not necessarily provide a proper stimulus for the induction of a hyper- or hypothyroid status as defined by hormonal or histological criteria. Main reasons for the inability to induce receptor-specific antibodies that affect thyroid function such as those generated in GD are likely to be the inappropriate folding of the recombinant extracellular domain of the receptor, or the xenogeneic nature of the autoantigen.     

Serum levels of thyroid-stimulating hormone receptor antibodies during IFN-alpha2a treatment of chronic hepatitis C.

Twenty chronic hepatitis C patients with baseline levels of thyroid hormones, antithyroglobulin, and antimicrosomal antibodies within the normal range were monitored by thyroid testing during a 26-week treatment with interferon-alpha2a (IFN-alpha2a). The present study was aimed at retrospectively analyzing thyroid-stimulating hormone (TSH) receptor antibodies, employing stored serum samples obtained from these patients at baseline, at 12 weeks, and at the end of IFN-alpha2a treatment. Ten patients (group A) received IFN-alpha2a at a total dose of 474 million units (MU), and 10 patients (group B) at a total dose of 774 MU. None of the patients produced antithyroglobulin and antimicrosomal antibodies. Two patients in group A exhibited elevated TSH levels without free thyroid hormone alterations while on the treatment. At baseline, 1 patient in group A had a positive TSH binding inhibitory immunoglobulin, and 1 patient in group B was positive for thyroid-stimulating antibody at the end of treatment. Both patients remained euthyroid throughout the treatment. Treatment with IFN-alpha2a may infrequently induce the production of TSH receptor antibodies in chronic hepatitis C patients provided preexisting autoimmune thyroid disease is precluded.