Development Of Autoimmune Thyroiditis Research Articles

Detection of enterovirus RNA in postoperative thyroid tissue specimens

Autoimmune thyroiditis is a very common disease. A genetic predisposition and environmental factors such as viruses are thought to contribute to the development of autoimmune thyroiditis. Enteroviruses, which are involved in other autoimmune diseases, are attractive candidates. To investigate the presence of enteroviral genome sequences in postoperative thyroid tissues with lymphocytic infiltration, a common histological feature of thyroiditis. Postoperative thyroid specimens collected prospectively from 86 patients were blindly frozen at -80 degrees C. The presence of EV genome sequences in the samples was blindly investigated by real-time RT-PCR. Clinical data, histological findings and levels of anti-TPO antibodies were collected. EV-RNA detection was positive (up to 36 cycles) or weakly positive (37-39 cycles) in 22 out of 86 patients (25%). EV-RNA (positive or weakly positive signal) was detected in 5 out of 27 (18.5%) thyroid specimens with lymphocytic infiltration, and in 17 out of 59 (29%) thyroid specimens without lymphocytic infiltration (P = 0.4). No correlation was observed between EV-RNA detection in thyroid and the presence of anti-TPOAb. EV-RNA was detected in 3 out of 11 patients histologically diagnosed as thyroiditis (27.3%) and in 18 out of 74 patients (24.3%) with thyroid tumours (multinodular goitre, adenoma and carcinoma) (P = 0.5) and in one patient with a normal thyroid. EV-RNA can be detected in thyroid tissue from patients with various thyroid diseases, but there is no relationship between the presence of EV-RNA and thyroiditis. Further studies are needed to clarify the role of EV in thyroid diseases.

Effects of interleukin-6 blockade on the development of autoimmune thyroiditis in nonobese diabetic mice

We explored the role of interleukin-6 (IL-6) in the development of autoimmune thyroiditis in nonobese diabetic (NOD) mice, an animal model of Hashimoto's thyroiditis, using anti-mouse IL-6 receptor antibody (MR16-1). Thyroiditis was induced by iodide ingestion or mouse thyroglobulin (Tg) immunization. Mice were injected intraperitoneally with saline, control rat IgG, or MR16-1 (2 or 8 mg). Iodide ingestion did not increase serum IL-6 levels and MR16-1 (2 mg) failed to prevent the development of thyroiditis. In contrast, Tg immunization induced a rapid and significant increase in serum IL-6 levels. While MR16-1 (2 mg) had no effect on Tg-induced thyroiditis, the severity, but not incidence, of thyroiditis was reduced in 8 mg MR16-1-treated mice compared with saline-injected mice. However, thyroiditis development in the 8 mg MR16-1-treated mice was indistinguishable from that in the control IgG-treated mice. MR16-1 (8 mg) did not affect serum anti-Tg antibody levels. These results suggest that IL-6 may play only a minor role in the development of autoimmune thyroiditis in NOD mice.

Autoimmune Thyroid Diseases in a Large Group of Hungarian Patients with Primary Sjögren's Syndrome

Previous studies on relatively small populations of patients with primary Sjögren's syndrome (pSS) suggested an association between pSS and Hashimoto's thyroiditis (HT). As some findings in the literature regarding the relationship between pSS and thyroid disease are contradictory, and there is little information on the sequence of pSS and HT, we conducted a study with a population of patients with pSS that was about three times larger than previously studied populations. Our objective was to determine the prevalence of HT and Graves' disease (GD) in patients with pSS and to assess the sequence of pSS and autoimmune thyroid diseases. A total of 479 patients with pSS were retrospectively studied. Thyroid ultrasound and scintigraphy were performed, and serum thyrotropin, free triiodothyronine, free thyroxine, antithyroid peroxidase antibody (TPOAb), and anti-thyroglobulin autoantibody (TgAb) measurements were carried out. Solitary thyroid nodules were investigated by fine-needle aspiration biopsy. Thyroid dysfunction was found in 95 patients (21.25%). Thirty of these patients had HT and 18 had GD. HT predated pSS in eight patients, developed at approximately the same time in seven patients, and followed pSS in 15 patients. Almost all (90%) patients with HT had persistently elevated serum TgAb or TPOAb titers. An association between HT and pSS was found based on the fact that the frequency of HT was greater among pSS patients (6.26%) than in the general population (1-2%). In contrast, no association between GD and pSS was found. We noted that both HT and GD can appear either before or after the onset of pSS. Since most cases of pSS predate the appearance of autoimmune thyroid diseases it is important to determine if pSS is a predisposing factor for the development of autoimmune thyroiditis.

Experimental study on the effects of chronic iodine excess on thyroid function, structure, and autoimmunity in autoimmune-prone NOD.H-2h4 mice

Iodine is an essential component of thyroid hormones; high intake may lead to thyroid disease. Epidemiologic researches have shown that exposure to iodine may be involved in the onset and development of autoimmune thyroiditis. Iodine may induce hypothyroidism in patients with autoimmune thyroiditis in a dose-dependent manner. The aim of the present study was to investigate the effects of dosages of iodine on thyroid autoimmunity, morphology, structure, and function in autoimmune-prone animals. NOD.H-2h4 mice were randomly divided into normal iodine, 5-fold, 10-fold, 100-fold, 1,000-fold iodine excess group, anesthetized by diethyl ether and bleed from eye socket vein at 4, 8, 16, and 24 weeks after the commencement of experiment. Iodine and thyroid hormone levels in the thyroid tissue and sera, serum thyroglobulin antibody levels, as well as thyroid gland histological appearance were measured. Excessive iodine caused thyroid goiter, and there was a positive correlation between the thyroid weight and the dosage of iodine (r = 0.64-0.92, P < 0.01). Iodine overdose ultrastructurally damaged thyroid epithelial cells in a dose-dependent manner. The incidence of thyroiditis, as well as the degree of lymphocytic infiltration in the thyroid gradually increased as the dosage increased (r = 0.87-0.98, P </= 0.05). Excessive iodine intake might induce goiter, lead to thyroiditis, worsen lymphocytic infiltration, as well as damage to the thyroid follicular structure in a dose-dependent manner in autoimmune-prone NOD.H-2h4 mice.

Environmental factors and autoimmune thyroiditis

Autoimmune thyroiditis, of which Hashimoto thyroiditis represents the most frequent form, is an inflammatory state of the thyroid gland that results from the interaction between genetic variants that promote susceptibility and environmental factors. High iodine intake, selenium deficiency, pollutants such as tobacco smoke, infectious diseases such as chronic hepatitis C, and certain drugs are implicated in the development of autoimmune thyroiditis, primarily in genetically predisposed people. Long-term iodine exposure leads to increased iodination of thyroglobulin, which increases its antigenicity and initiates the autoimmune process in genetically susceptible individuals. Selenium deficiency decreases the activity of selenoproteins, including glutathione peroxidases, which can lead to raised concentrations of hydrogen peroxide and thus promote inflammation and disease. Such environmental pollutants as smoke, polychlorinated biphenyls, solvents and metals have been implicated in the autoimmune process and inflammation. Environmental factors have not yet, however, been sufficiently investigated to clarify their roles in pathogenesis, and there is a need to assess their effects on development of the autoimmune process and the mechanisms of their interactions with susceptibility genes.

Effects of angiotensin II blockade on the development of autoimmune thyroiditis in nonobese diabetic mice

We evaluated the effects of angiotensin II (Ang II) blockers, losartan, an Ang II receptor blocker, and enalapril, an angiotensin converting enzyme inhibitor, on the development of autoimmune thyroiditis in nonobese diabetic (NOD) mice, an animal model of Hashimoto's thyroiditis (HT). Mice were assigned into three groups, untreated, losartan-treated (30 mg/kg/day), and enalapril-treated (10 mg/kg/day) groups. Thyroiditis was induced by iodide ingestion (experiment 1) or mouse thyroglobulin (Tg) immunization (experiment 2). Both procedures effectively induced thyroiditis. While iodide ingestion failed to induce anti-mouse Tg antibody (TgAb) production, Tg immunization resulted in a significant increase in serum TgAb levels. In both experiments, neither losartan nor enalapril interfered with the development of thyroiditis and TgAb production. These results suggest that Ang II may not be associated with the development of autoimmune thyroiditis in NOD mice. Thus, the Ang II blockade may not have therapeutic potential in HT.

Suppression of Iodide Uptake and Thyroid Hormone Synthesis with Stimulation of the Type I Interferon System by Double-Stranded Ribonucleic Acid in Cultured Human Thyroid Follicles

Although viral infection is thought to be associated with subacute thyroiditis and probably with autoimmune thyroid disease, possible changes in thyroid function during the prodromal period of infection or subclinical infection remain largely unknown. Recently, it was shown that pathogen-associated molecular patterns stimulate Toll-like receptors (TLR) and activate innate immune responses by producing type I interferons (IFN). Using a human thyroid follicle culture system, in which de novo synthesized thyroid hormones are released into the culture medium under physiological concentrations of human TSH, we studied the effects of polyinosinic-polycytidylic acid [Poly(I:C)], a chemical analog of viral double-stranded RNA (dsRNA), on TSH-induced thyroid function. Thyrocytes expressed ligands for dsRNA (TLR 3, CD14, and retinoic-acid-inducible protein-1) comparable with the TSH receptor. DNA microarray and real-time PCR analyses revealed that dsRNA increased the expression of mRNA for TLR3, IFN-beta, IFN-regulating factors, proinflammatory cytokines, and class I major histocompatibility complex (MHC), whereas genes associated with thyroid hormonogenesis (sodium/iodide symporter, peroxidase, deiodinases) were suppressed. In accordance to these data, Poly(I:C) suppressed TSH-induced 125I uptake and hormone synthesis dose dependently, accompanied by a decrease in the ratio of 125I-T3/125I-T4 released into the culture medium, whereas peptidoglycan, lipopolysaccharides, or unmethylated CpG DNA, ligands for TLR2, TLR4, and TLR9, respectively, had no significant effect. These inhibitory effects of Poly(I:C) were not blocked by a neutralizing antibody against TLR3 and an anti-IFN alpha/beta receptor antibody. These in vitro findings suggest that when thyrocytes are infected with certain viruses, dsRNA formed intracellularly in thyrocytes may be a cause for thyroid dysfunction, leading to development of autoimmune thyroiditis.

Hormonal change and cytokine mRNA expression in peripheral blood mononuclear cells during the development of canine autoimmune thyroiditis

To elucidate the hormonal change and alteration in cytokine expression in peripheral blood mononuclear cells (PBMC) during the early stage of autoimmune thyroiditis, we have developed a canine model of this disease, in which normal dogs were immunized with bovine thyroglobulin (Tg) and/or canine thyroid extract. Serum samples were collected weekly, anti-canine Tg antibody was measured by enzyme-linked immunosorbent assay (ELISA) and thyroid stimulating hormone (TSH) and total T4 levels by radioimmunoassay. We also assayed T lymphocyte proliferation in response to Tg, as well as measuring cytokine mRNA by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). All six dogs immunized with bovine Tg had both canine Tg autoantibody and anti-T4 antibody. When the sample from the highest TgAA titre time-point was compared with baseline the expression of mRNA encoding the Th1-type cytokine such as interferon (IFN)-gamma, interleukin (IL)-18 and IL-15 was increased during the development of autoimmune thyroiditis. Expression of the Th2-type cytokine, IL-6 showed minimal change and IL-4 expression was not detected in any of the samples. Expression of the T suppressive cytokine, IL-10 and transforming growth factor (TGF)-beta was increased in the presence of antigen stimulation. These findings suggest that, although autoimmune thyroiditis is an organ-specific autoimmune disease, systemic cytokine mRNA expression is also changed.

Coexistence of chronic lymphocytic leukemia and Hashimoto’s thyroiditis

Dear Editor,Autoimmune phenomena are seen frequently during thecourse of chronic lymphocytic leukemia (CLL). However,development of autoimmune thyroiditis is very rare. A 66-year-old male CLL patient was admitted to the hospital forhis regular controls. His complaints, including sweating andweight loss, were present for 6 months. Advanced CLL wasdiagnosed 3 years ago, and six courses of fludarabine(30 mg/m

Thyroid Autoantibodies in Cord Blood Sera from Children and Adolescents with Autoimmune Thyroiditis

Autoimmune thyroid disease is common among women of childbearing age. Thyroid autoantibodies are predominantly of the immunoglobulin G (IgG)-type and pass the placental barrier from mother to child. Recent studies have suggested a pathogenetic role for transplacentally transmitted autoantibodies in the development of autoimmune disease. The aim of the present study was to investigate if children and adolescents with autoimmune thyroiditis (AIT) have been exposed to thyroid autoantibodies already in utero. Cord blood sera taken at delivery from 34 newborns who had developed AIT during childhood and adolescence, and sera from 31 of their mothers, were analyzed for the presence of autoantibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TgAb), and compared to 233 randomly selected control children and their mothers. The prevalence of TPOAb in cord blood sera was elevated among the children and adolescents with AIT compared to controls (38% versus 14%; odds ratio [OR] 4.12, p < 0.001). An increased prevalence of TPOAb was also found among their mothers (29% versus 15%; OR 2.17, p < 0.048). No significant difference in the prevalence of TgAb was found either between children with AIT and the control children (18% versus 9%; OR 2.16, p < 0.15), or between their mothers and the control mothers (23% versus 12%; OR 2.17, p < 0.16). Most of the TPOAb-positive children had TPOAb-positive mothers, indicating the maternal origin of their TPOAb. In conclusion, a large proportion of children who later developed AIT had already been exposed to transplacentally transmitted TPOAb in utero. Whether these autoantibodies have any pathogenetic role in the development of AIT in offspring or if they simply mirror the inheritance of AIT, remains to be investigated.

Autoinduction of tumor necrosis factor-α in FRTL-5 rat thyroid cells

Tumor necrosis factor-alpha (TNFalpha) may play a role in the development of autoimmune thyroiditis such as Hashimoto's thyroiditis. In the present study, we examined whether TNFalpha induced its own expression in FRTL-5 rat thyroid cells. Lipopolysaccharide (LPS) markedly increased TNFalpha mRNA levels in FRTL-5 cells as assessed by semiquantitative RT-PCR. In addition, LPS-stimulated cells released TNFalpha protein into the culture medium. Similarly, TNFalpha induced its own gene and protein expression in FRTL-5 cells as assessed by RT-PCR and metabolic labeling and immunoprecipitation of TNFalpha. The autoinduction of TNFalpha gene was also observed in TNFalpha-stimulated human thyroid epithelial cells. TNFalpha induction was specific to LPS and TNFalpha since interferon-alpha or amiodarone failed to increase TNFalpha mRNA levels in FRTL-5 cells. Human TNFalpha induced rat TNFalpha gene expression, indicating that type 1 TNF receptor (TNF-R) is involved in the autoinduction. TNFalpha did not increase either type 1 or type 2 TNF-R mRNA levels, suggesting that upregulation of TNF receptors is not involved in the autoinduction of TNFalpha. Although the biological significance of autoinduction of TNFalpha remains unclear, our results suggest that thyroid epithelial cells may participate in the development of autoimmune thyroiditis through production of TNFalpha. Furthermore, inhibition of TNFalpha production in the thyroid may represent a novel approach to mitigating inflammation in autoimmune thyroiditis.

Death Ligand Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Inhibits Experimental Autoimmune Thyroiditis

The role of TNF-related apoptosis-inducing ligand (TRAIL) in autoimmune thyroiditis is unclear. We used experimental autoimmune thyroiditis to clarify the contribution of TRAIL to the development of autoimmune thyroiditis. CBA/J mice were immunized with murine thyroglobulin, and spleen cells from these mice were subsequently injected into irradiated recipient CBA/J mice. One week later, the recipient mice were treated with recombinant TRAIL or a control protein. Compared with control animals, TRAIL-treated mice developed a milder form of the disease with a significant decrease in mononuclear cell infiltration in the thyroid and less thyroid follicular destruction. Furthermore, the number of apoptotic thyrocytes and also thyroglobulin-specific T helper-1 cell responses in TRAIL-treated mice was lower than that in the control animals. This study suggests that exogenous TRAIL suppresses the development of autoimmune thyroiditis via altering the function of cells involved in the immune response. These findings may contribute toward a novel treatment autoimmune thyroiditis.

New Insights into the Conformational Dominant Epitopes on Thyroid Peroxidase Recognized by Human Autoantibodies

Human anti-thyroperoxidase (TPO) autoantibodies (aAbs) are a major hallmark of autoimmune thyroid diseases. Their epitopes are discontinuous and mainly restricted to an immunodominant region (IDR) consisting of two overlapping regions (IDR/A and B). To shed light on the relationship between these regions, we first performed competitive studies using all available reference anti-TPO antibodies. Interestingly, we showed that human IDR/A- and B-specific anti-TPO aAbs recognized essentially the same regions on the TPO molecule. However, our data also indicated that IDR/A-specific human aAbs strongly recognized the region containing residues 599-617, whereas the IDR/B-specific aAbs bind to several regions as well as region 599-617. Next, we scanned this key region to identify the residues involved in the immunodominant autoepitope. Using peptide spot technology together with competitive ELISA experiments, we demonstrated that residues (604)ETP-DL(609) play a major role in the anti-peptide P14 epitope and that IDR/A-specific human anti-TPO aAbs, either expressed as recombinant Fab or obtained from Graves' disease patients, specifically recognize the sequences (597)FCGLPRLE(604) and (611)TAIASRSV(618). All together our data emphasize that both the IDRs involve the same surface area on human TPO, but the differential usage of one or the other regions leads to different inhibition patterns in competitive experiments. In conclusion, our data help to resolve the long-sought issue on the molecular immunology of the two IDRs on TPO and provide new clues to design efficient peptides that may be part of a combinatorial treatment aiming at delaying development of autoimmune thyroiditis when used prophylactically.

Neonatal stimulation of the thyroid gland with iodine or suppression during adolescence with triiodothyronine changes the prevalence of autoimmune thyroiditis in BB rats.

Changes in the functional state of beta cells by neonatal stimulation or adolescent suppression have reduced the incidence of type 1 diabetes mellitus in animal models. The aim of this study was to evaluate the effect of manipulation of the activity of the thyroid gland by neonatal stimulation or by adolescent suppression on the prevalence of spontaneous autoimmune thyroiditis (AIT) in rats. Bio-Breeding/Worcester (BB) rats were treated neonatally with sodium iodine (NaI) or thyroid stimulating hormone (TSH), or during adolescence by triiodothyronine (T(3)), and the lymphocytic infiltration in the thyroid gland was evaluated. Neonatal treatment with NaI decreased the prevalence of AIT to 32+/-9% compared with 66+/-5% in the controls (P<0.002), mainly caused by a reduction among the female rats (13+/-9% vs 52+/-8%, P<0.006). TSH had no effect. Post neonatal suppression of the thyroid gland by T(3) had a biphasic response. Early in adolescence the overall prevalence was 14+/-7% compared with 66+/-5% in the controls (P<10(-5)); for female rats AIT was prevented (0+/-0%) compared with 52+/-8% in the controls (P<0.0003) and in male rats the values were 29+/-13% compared with 80+/-6% in the controls (P<0.001). Treatment with T(3) later in adolescence increased the overall prevalence to 81+/-7% compared with 66+/-5% in the controls (not significant). For female rats the prevalence increased to 78+/-9% compared with 52+/-8% in the controls (P=0.04). The degree of thyroiditis among the affected animals was similar in all groups. Neonatal stimulation of the thyroid gland by iodine or early adolescent suppression by T(3) reduced the prevalence of AIT whereas T(3) given later increased the prevalence of thyroiditis in rats. Thyroid activity at various ages seems to be of importance for the development of autoimmune thyroiditis.

Prevalence of 20S proteasome, anti-nuclear and thyroid antibodies in young patients at onset of type 1 diabetes mellitus and the risk of autoimmune thyroiditis.

Patients with type 1 diabetes mellitus (DM1) are at high risk to develop further autoimmune disorders, which are mostly characterized by the presence of organ-specific antibodies in serum and a subclinical disease course. Diabetes-related (glutamic acid decarboxylase, tyrosine phosphatase, IA-2) and thyroid-specific (thyroperoxidase, thyroglobulin) as well as antibodies to 20S proteasome, and anti-nuclear antibodies, were measured at DM1 onset in 147 children and adolescents. Patients were followed prospectively for the development of autoimmune thyroiditis (TSH elevation and/or sonographic thyroid gland enlargement in the presence of thyroid antibodies) up to 12 years, median observation time 4.4 years. Eight of 147 (5.4%) patients developed autoimmune thyroiditis. The cumulative incidence (+/-SE) at 5 years was 0.08+/-0.03. The prevalence of thyroid antibodies was 16.7%, of DM-related 88.4%, 20S proteasome 21.9%, and anti-nuclear antibodies 20.0%. There was a positive correlation between thyroid and anti-nuclear antibodies (p <0.001). Clinical course of DM1 and remission duration were not influenced by the presence of autoantibodies. However, in contrast to patients without antibodies, those with positive antibodies had significantly (p <0.001) elevated cumulative incidence of autoimmune thyroiditis at 5 years: thyroperoxidase 0.40+/-0.13, thyroglobulin 0.38+/-0.15, and anti-nuclear antibodies 0.29+/-0.12, respectively. These data underline that autoimmunity in patients with DM1 is not only restricted to beta-cell antigens at the onset of disease. In particular, patients with positive thyroid and anti-nuclear antibodies are at high risk to develop autoimmune thyroiditis during the first 5 years of DM1.

Intrauterine exposure to maternal enterovirus infection as a risk factor for development of autoimmune thyroiditis during childhood and adolescence.

Maternal intrauterine enterovirus infection during pregnancy increases the risk for the offspring to develop type 1 diabetes mellitus. Type 1 diabetes mellitus and autoimmune thyroiditits (AIT) are closely linked. A common pathogenetic factor is possible. The objective of this study was to investigate a possible association between maternal enterovirus infection during pregnancy and the development of AIT in the offspring. Sera taken at delivery from 31 mothers whose children subsequently developed AIT was analyzed for immunoglobulin (Ig)A, IgG, and IgM antibodies against enterovirus, and compared to a control group comprising 233 randomly selected maternal sera. Of the mothers whose children developed AIT, 5 of 31 (16%) were enterovirus IgM-positive, compared to 17 of 233 (7%) in the control group (p = 0.16). The age at diagnosis of AIT was significantly lower in the group of children with IgM-positive mothers compared to children with IgM-negative mothers (p < 0.05). In addition, 3 children (60%) in the IgM-positive group were overtly hypothyroid at diagnosis of AIT, compared to no child (0%) in the IgM-negative group (p < 0.01). No significant differences were found in IgA and IgG antibody titers between the mothers whose children developed AIT and the control group. Although this study did not have enough power to reveal intrauterine exposure to maternal enterovirus infection during pregnancy as a risk factor for development of AIT during childhood and adolescence, it suggested an association with earlier onset of clinical disease in children to enterovirus IgM-seropositive mothers.

The effects of alpha interferon on the development of autoimmune thyroiditis in the NOD H2h4 mouse.

Alpha interferon (αIFN) therapy is known to induce thyroid autoimmunity in up to 40% of patients. The mechanism is unknown, but Th1 switching has been hypothesized. The aim of our study was to examine whether αIFN accelerated the development of thyroiditis in genetically susceptible mice. We took advantage of NOD-H2h4, a genetically susceptible animal model, which develops thyroiditis when fed a high iodine diet. Six to eight week old male NOD H2h4 mice were injected with mouse αIFN (200 units) or with saline three times a week for 8 weeks. All mice drank iodinated water (0.15%). Mice were sacrificed after 8 weeks of injection. Their thyroids were examined for histology and blood was tested for antithyroglobulin antibody levels. T4 and glucose levels were also assessed. In the IFN-injected group, 6/13 (46.2%) developed thyroiditis and/or thyroid antibodies while in the saline-injected group, only 4/13 (30.8%) developed thyroiditis and/or thyroid antibodies (p=0.4). The grade of thyroiditis was not different amongst the two groups. None of the mice developed clinical thyroiditis or diabetes mellitus. Our results showed that αIFN treatment did not accelerate thyroiditis in this mouse model. This may imply that αIFN induces thyroiditis in a non-genetically dependent manner, and this would not be detected in a genetically susceptible mouse model if the effect were small. Alternatively, it is possible that αIFN did not induce thyroiditis in mice because, unlike in humans, in mice αIFN does not induce Th1 switching.

Interleukin-1 beta inhibits rat thyroid cell function in vivo and in vitro by an NO-independent mechanism and induces hypothyroidism and accelerated thyroiditis in diabetes-prone BB rats.

Interleukin-1 beta has been implicated as a pathogenic factor in the development of autoimmune thyroiditis. When given for 5 days to normal non-diabetes-prone Wistar Kyoto rats, it decreased plasma concentrations of total tri-iodothyronine and thyroxine and increased plasma TSH. These effects were not prevented by co-injection of nitroarginine methyl ester or aminoguanidine, inhibitors of NO synthases. Exposure to interleukin-1 beta dose-dependently reduced iodine uptake in FRTL-5 cells, but had no effect on thyroglobulin secretion. Nitrite was not detected in the FRTL-5 cell culture media after exposure to interleukin-1 beta. However, reverse transcription PCR analysis of mRNA isolated from interleukin-1 beta-exposed FRTL-5 cells revealed a transitory expression of the inducible NO synthase, which was markedly lower than inducible NO synthase induction in interleukin-1 beta-exposed isolated rat islets of Langerhans. Co-incubation with the NO synthase inhibitor NG-monomethylarginine did not ameliorate the effect of interleukin-1 beta on FRTL-5 cell iodine uptake. Furthermore, we demonstrate that daily injections of interleukin-1 beta for 13 weeks aggravated spontaneous thyroiditis and induced severe hypothyroidism in non-diabetic diabetes-prone BB rats. The data suggest that NO does not mediate interleukin-1 beta-induced inhibition of rat thyroid function in vivo or in vitro in FRTL-5 cells, and the induction of hypothyroidism by interleukin-1 beta in diabetes-prone BB rats is speculated to be due to exacerbation of recruitment and activation of intrathyroidal mononuclear cells.

Mouse models of autoimmune disease suggest that self-tolerance is maintained by unresponsive autoreactive T cells.

Multiple organ-localized autoimmune diseases, such as thyroiditis and gastritis, spontaneously develop in BALB/c nu/nu (nude) mice receiving embryonic rat thymus grafts (TG) under their renal capsules (TG nude mice). When thyroid was grafted into the rat thymus of TG nude mice, development of autoimmune thyroiditis, but not other diseases, was completely prevented. However, when such mice received thyroid antigen plus complete Freund's adjuvant (CFA), severe autoimmune thyroiditis developed, suggesting that some thyroid-specific autoreactive T cells migrate into the periphery, but remain unresponsive. Development of autoimmune diseases, including thyroiditis, in TG nude mice was prevented by a single intraperitoneal injection of splenic CD4+ cells from normal BALB/c mice and also from mice with intrathymic thyroid grafts, indicating that thyroid-specific suppressor T cells are present in normal mice and that such T cells are neither deleted nor inactivated by the intrathymic thyroid grafts, in contrast to autoreactive T cells. Thus clonal deletion in the thymus, and clonal anergy and/or ignorance in the periphery, of autoreactive cells is important to maintain immune tolerance to organ-specific antigen, but CD4 suppressor T cells may play a more important role in tolerance, and the failure of education of this population may cause autoimmune diseases in the TG nude mouse model.

Effects of interleukin-1β on scanning electron microscopic appearance and thyroid peroxidase content of human thyrocytes in monolayer culture

Interleukin (IL-1), an inflammatory cytokine that is detected in the thyroid tissues of patients with autoimmune thyroiditis, is believed to be involved in the disease process. To clarify the role of IL-1 in the development of autoimmune thyroiditis, we investigated the effects of interleukin-1β (IL-1β) on the morphology of human thyrocytes in monolayer culture as well as the effect on thyroid peroxidase (TPO) content of these cells. Human normal thyrocytes were cultured with IL-1β for 4 days in the presence and absence of TSH. In morphologic studies, cultured cells were fixed for examination by scanning electron microscopy and for immunofluorescent staining of actin filaments. IL-1 produced striking morphologic changes in the cultured thyrocytes, including the cytoplasmic retraction and dissociation and/or depolymerization of actin filaments. These changes were unrelated to TSH stimulation. For detection of TPO, cultured cells were stained by an immunofluorescent technique and analyzed by fluorescence photometry. IL-1 reduced the TPO content and inhibited the TSH-induced increase in TPO in a concentration-dependent manner. These morphological changes and the reduction in TPO content of cultured thyrocytes suggest that IL-1 modulates the pathophysiology of autoimmune thyroiditis.