Human umbilical cord mesenchymal stem cells alleviate the imbalance of CD4+ T cells via protein tyrosine phosphatase non-receptor type 2/signal transducer and activator of transcription 3 signaling in ameliorating experimental autoimmune thyroiditis in rats.

This study aimed to investigate the therapeutic effect of human umbilical cord mesenchymal stem cells (hUCMSCs) on experimental autoimmune thyroiditis (EAT) and the underlying mechanisms by utilizing a porcine thyroglobulin-induced EAT rat model. The rats received four tail vein injections of vehicle or hUCMSCs at an interval of 7 days and were sacrificed on day 28 after the first injection. Hematoxylin and eosin staining and enzyme-linked immunosorbent assays (ELISAs) were used to assess the therapeutic effects of hUCMSCs on EAT. Splenic lymphocytes were isolated from rats, and the proportions of CD4+ T cell subsets were analyzed by flow cytometry. Splenic CD4+ T cells from EAT rats were cocultured with hUCMSCs. A loss-of-function assay for protein tyrosine phosphatase non-receptor type 2 (PTPN2) was performed to explore the involvement of PTPN2/signal transducer and activator of transcription 3 (STAT3) signaling on the therapeutic benefit of hUCMSCs in EAT. hUCMSC treatment significantly alleviated inflammation, reduced serum thyroid antibody levels, and decreased the ratios of IL-17α+/CD25+FOXP3+ cells and serum IFN-γ/IL-4 in EAT rats. Furthermore, hUCMSC treatment upregulated PTPN2 protein expression in splenic lymphocytes of EAT rats as well as enhanced the PTPN2 protein level and attenuated phosphorylation of STAT3 in CD4+ T cells in vitro. Importantly, knockdown of Ptpn2 significantly reversed hUCMSC-mediated suppression of cell proliferation and hUCMSC-induced alterations in the expression of inflammatory cytokines in CD4+ T cells. Thus, hUCMSC treatment alleviates thyroid inflammation and the CD4+ T cell imbalance in EAT via PTPN2/STAT3 signaling, serving as a promising therapeutic approach for autoimmune thyroiditis.

Levothyroxine and insulin requirement in autoimmune polyglandular type 3 syndrome: a real-life study.

PURPOSE: To evaluate factors influencing the insulin and levothyroxine requirement in patients with autoimmune polyglandular syndrome type 3 (APS-3) vs. patients with type 1 diabetes mellitus (T1DM) and autoimmune hypothyroidism (AH) alone, respectively. METHODS: Fifty patients with APS-3, 60 patients with T1DM and 40 patients with AH were included. Anthropometric, clinical and biochemical parameters were evaluated in all patients. Insulin requirement was calculated in patients with APS-3 and T1DM, while levothyroxine requirement was calculated in APS-3 and AH. RESULTS: Patients with APS-3 showed higher age (p = 0.001), age of onset of diabetes (p = 0.006) and TSH (p = 0.004) and lower total insulin as U/day (p < 0.001) and U/Kg (p = 0.001), long-acting insulin as U/day (p = 0.030) and U/kg (p = 0.038) and irisin (p = 0.002) compared to T1DM. Patients with APS-3 had higher waist circumference (p = 0.008), duration of thyroid disease (p = 0.020), levothyroxine total daily dose (p = 0.025) and mcg/kg (p = 0.006), triglycerides (p = 0.007) and VAI (p = 0.010) and lower age of onset of thyroid disease (p = 0.007) than AH. At multivariate analysis, levothyroxine treatment and VAI were associated with insulin and levothyroxine requirement in APS-3, respectively. VAI was independently associated with insulin requirement in T1DM. Circulating irisin levels were independently associated with levothyroxine requirement in AH. CONCLUSION: Patients with APS-3 show lower insulin requirement and higher levothyroxine requirement than T1DM and AH alone, respectively. Levothyroxine treatment and VAI affect insulin and levothyroxine requirement, respectively, in APS-3. In T1DM, adipose tissue dysfunction, indirectly expressed by high VAI, is associated with an increased insulin requirement, while circulating irisin levels influence the levothyroxine requirement in AH.

Thyroid complications of SARS and coronavirus disease 2019 (COVID-19).

We have reviewed the available literature on thyroid diseases and coronavirus disease 2019 (COVID-19), and data from the previous coronavirus pandemic, the severe acute respiratory syndrome (SARS) epidemic. We learned that both SARS and COVID-19 patients had thyroid abnormalities. In the limited number of SARS cases, where it was examined, decreased serum T3, T4 and TSH levels were detected. In a study of survivors of SARS approximately 7% of the patients had hypothyroidism. In the previous evaluation evidence was found that pituitary function was also affected in SARS. Others suggested a hypothalamic-pituitary-adrenal axis dysfunction. One result published recently indicates that a primary injury to the thyroid gland itself may play a key role in the pathogenesis of thyroid disorders in COVID-19 patients, too. Subacute thyroiditis, autoimmune thyroiditis and an atypical form of thyroiditis are complications of COVID-19. Thyroid hormone dysfunction affects the outcome by increasing mortality in critical illnesses like acute respiratory distress syndrome, which is a leading complication in COVID-19. Angiotensin-converting enzyme 2 is a membrane-bound enzyme, which is also expressed in the thyroid gland and the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) uses it for docking, entering as well as replication. Based on the available results obtained in the SARS-CoV-2 pandemic, beside others, we suggest that it is necessary to monitor thyroid hormones in COVID-19.

Triiodothyronine secretion in early thyroid failure: The adaptive response of central feedforward control.

BACKGROUND: Defined by thyroid-pituitary feedback control, clinical diagnosis of hypothyroidism and hyperthyroidism has become synonymous with TSH measurement. We combined in silico analysis and in vivo data to explore the central influences on thyroidal T3 production. MATERIALS & METHODS: A system of five coupled first-order nonlinear parameterised ordinary differential equations (ODEs) is used to model the feedback control of TSH and TRH by thyroid hormones together with the feedforward control of thyroidal T3 secretion and enzymatic T4-T3 conversion. Dependencies of the stable equilibrium solutions of this ODE system, that is the homeostasis of the underlying physiological process, on the system parameters were investigated whether they accounted for clinical observations. RESULTS: During the modelled transition to hypothyroidism, central control imposed an increasing influence in maintaining serum FT3 levels, compared to peripheral conversion efficiency. Numerical continuation analysis revealed dependencies of T3 production on different elements of TSH feedforward control. While T4-T3 conversion provided the main T3 source in euthyroidism, this was overtaken by increasing glandular T3 secretion when thyroid reserve declined. The computational results were in good agreement with data from untreated patients with autoimmune thyroiditis. CONCLUSIONS: Dependencies revealed in the expression of control differ in thyroid health and disease, using a physiologically based mathematical model of combined feedback-feedforward control of the hypothalamic-pituitary-thyroid regulation. Strong T3-protective mechanisms of the control system emerge with declining thyroid function, when glandular T3 secretion becomes increasingly influential over conversion efficiency. This has wide-ranging implications for the utility of TSH in clinical decision-making.

High iodine induces DNA damage in autoimmune thyroiditis partially by inhibiting the DNA repair protein MTH1.

This study aims to investigate the level of DNA damage in high iodine (HI)-induced autoimmune thyroiditis (AIT), and to explore the role of DNA repair protein MutT homolog-1 (MTH1) in this process. The levels of pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8 were measured using qRT-PCR and ELISA. The apoptosis was evaluated using TUNEL staining. The pathological changes of thyroid tissues were evaluated using hematoxylin and eosin (HE) staining. The DNA damage was assessed by determining the expression of 8-hydroxy-2'deoxyguanosine (8-OHdG; an indicator of oxidative DNA damage) and performing the Comet assay. Our results showed that both the HI-treated NOD.H-2h4 mice (experimental AIT mice) and the HI-treated mouse thyroid follicular epithelial cells showed enhanced inflammation, apoptosis, and DNA damage level, accompanied by decreased MTH1 expression. Importantly, overexpression of MTH1 effectively abrogated the HI-induced enhancement of inflammation, apoptosis, and DNA damage in mouse thyroid follicular epithelial cells. In conclusion, HI treatment induces DNA damage in AIT, at least in part, by inhibiting the DNA repair protein MTH1.

Reduced expression of PD-L1 in autoimmune thyroiditis attenuate trophoblast invasion through ERK/MMP pathway.

BACKGROUND: Autoimmune thyroiditis (AIT) with euthyroid is associated with miscarriage. But the exact mechanism remains unclear. Studies have shown that the programmed cell death-1 (PD-1)/programmed cell death -ligand 1 (PD-L1) pathway is essential for normal pregnancy. However, the expression of PD-L1 in gestational trophoblasts in mice with autoimmune thyroiditis and the mechanisms leading to miscarriage have not been fully investigated. METHODS: Immunofluorescence and Western blot were used to detect the expression of PD-L1, p-ERK, MMP-2 and MMP-9 in embryonic trophoblast cells of pregnant mice with AIT. The expression of PD-L1 in HTR-8/SVneo cells were silenced, and the expression of PD-L1, MMP-2, MMP-9, ERK and p-ERK1/2 was detected by Western blot analyses and immunofluorescence assays. Invasive assays were performed in PD-L1 silenced HTR-8/SVneo cells using a Transwell chamber. RESULTS: Compared with normal pregnancy, the expression of PD-L1, ERK, p-ERK, MMP-2 and MMP-9 in embryonic trophoblast cells was significantly lower in pregnant mice with AIT. Compared with the negative control (NC) group (cells transfected with negative control siRNA), phosphorylation of MMP-2, MMP-9 and P-ERK1/2 proteins was significantly reduced in HTR-8/SVneo cells transfected with PD-L1 siRNA, and the number of cells penetrating the membrane was reduced. CONCLUSION: AIT inhibits ERK/MMP-2 and MMP-9 pathways through PD-L1 reduction, attenuates embryonic trophoblast invasion and ultimalely induces miscarriage ultimately.

Promoter methylation and expression of intercellular adhesion molecule 1 gene in blood of autoimmune thyroiditis patients.

Growing data supported that epigenetic modifications, including altered DNA methylation have a potential role in the pathogenesis of autoimmune thyroid diseases (AITD). In the present study we aimed to investigate the methylation status of ICAM-1 gene promoter in patients with AITD. Forty patients with Graves' disease (GD), 40 patients with Hashimoto thyroiditis (HT) and 40 normal controls were included. DNA extraction from blood samples was done to analyze the ICAM-1 methylation status using methylation-specific PCR method. RNA was also extracted to determine the ICAM-1 expression values by real time PCR. We found that the differences in the frequency of ICAM-1 methylation status between GD or HT and healthy individuals were statistically significant (p = 0.04, 0.018 respectively) whereas there was no significant difference between GD and HT patients (p > 0.05). There was a correlation between decreased ICAM-1 methylation and exophthalmos (p = 0.01) and the high TSI level (p < 0.002) in GD patients. However, there was no correlation between ICAM-1 methylation and other clinicopathological features or other laboratory parameters in GD or HT. Furthermore, ICAM-1 mRNA expression showed significant up-regulation in ICAM-1 un-methylated samples compared to methylated samples in both GD and HT patients (p < 0.001 for each). Results provided the evidence of association of the hypo-methylation status of ICAM-1 gene promoter with GD and HT patients. In addition, DNA methylation may have a critical role in the ICAM-1 expression regulation of AITD patients.

[Effects of Bcl-2 family on the thyroid cell apoptosis of experimental autoimmune thyroiditis mice induced by iodine].

OBJECTIVE: To study the effect of Bcl-2 family members on experimental autoimmune thyroiditis(EAT) and explore the pathogenesis of autoimmune thyroiditis. METHODS: Twenty-four female 4-5 week old NOD-SCID mice were randomly divided into four groups(six mice in each group): control group, high iodine group, poly(I:C) group and high iodine combined with poly(I:C) group. Control group and poly(I:C) group were fed with distilled water, while the high iodine group and high iodine combined with poly(I:C) group were supplied with 0. 05% NaI in their drinking water for 16 weeks. Poly(I:C) group and high iodine combined with poly(I:C) group received intraperitoneal injection of 100 µL poly(I:C)(1 µg/µL) at monday, wednesday and friday of the 11 th and 15 th week. Serum and thyroid were obtained at the last day of the 16 th week. The EAT model was confirmed by ELISA method and pathological HE staining, the apoptosis of thyroid cell were detected by TUNEL method and Cyt-C immunocytochemistry assay, and the mRNA levels of Bcl-2 family members in thyroid were determined by real-time qPCR method. RESULTS: EAT model was established using NOD-SCID mice through high-iodine feeding combined with poly(I:C) intraperitoneal injection. The degree of cell apoptosis and the Cyt-C expression levels were positively correlated with inflammation in thyroid follicular epithelial cells. The mRNA levels of Noxa, PUMA and Bid of high iodine group and high iodine combined with poly(I:C) group were higher than those in control and poly(I:C) groups(P<0. 05). CONCLUSION: Mitochondrial apoptosis pathway is involved in the thyroid cell apoptosis of EAT induced by high iodine, and the apoptosis may be regulated by the up-regulation of Noxa, PUMA and Bid, which belong to the pro-apoptotic members of Bcl-2 family.

Estrogen receptor ß activation stimulates the development of experimental autoimmune thyroiditis through up-regulation of Th17-type responses.

Estrogens play important roles in autoimmune thyroiditis, but it remains unknown which estrogen receptor (ER) subtype mediates the stimulatory effects. Herein we treated ovariectomized mice with ERα or ERß selective agonist followed by thyroglobulin-immunization to induce experimental autoimmune thyroiditis (EAT), and observed the aggravation of EAT after diarylpropionitrile (DPN, ERß selective agonist) administration. The mRNA levels of interleukin(IL)-17A, IL-21 and RORγt and percentages of T helper (Th) 17 cells were up-regulated in the splenocytes of DPN-treated mice. Activated ERß was found directly binding to IL-17A and IL-21 gene promoters, and also indirectly promoting IL-21 and RORγt gene transcription through interaction with NF-κB. The expressions of co-stimulatory molecules were increased on antigen-presenting cells (APCs) after DPN administration. It suggests that ERß is the predominant ER subtype responsible for EAT development, and its activation may enhance Th17-type responses through genomic pathways and alteration of APCs' activities.

Myo-inositol in autoimmune thyroiditis, and hypothyroidism.

Myo-inositol (Myo-Ins) plays an important role in thyroid function and autoimmunity. Myo-Ins is the precursor for the synthesis of phosphoinositides, which takes part in the phosphatidylinositol (PtdIns) signal transduction pathway, and plays a decisive role in several cellular processes. In the thyroid cells, PtdIns is involved in the intracellular thyroid-stimulating hormone (TSH) signaling, via Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) (PIP-3). Moreover, the phosphatidyl inositol 3 kinases (PI3K) family of lipid kinases regulates diverse aspects of T, B, and Tregs lymphocyte behaviour. Different mouse models deficient for the molecules involved in the PIP3 pathway suggest that impairment of PIP3 signaling leads to dysregulation of immune responses and, sometimes, autoimmunity. Studies have shown that cytokines modulate Myo-Ins in thyroid cells. Moreover, clinical studies have shown that after treatment with Myo-inositol plus seleniomethionine (Myo-Ins + Se), TSH levels significantly declined in patients with subclinical hypothyroidism due to autoimmune thyroiditis. The treatment was accompanied by a decline of antithyroid autoantibodies. After treatment serum CXCL10 levels declined, confirming the immune-modulatory effect of Myo-Ins. Additional research is necessary in larger population to evaluate the effect on the quality of life, and to study the mechanism of the effect on chemokines.

Flexible peptide recognition by HLA-DR triggers specific autoimmune T-cell responses in autoimmune thyroiditis and diabetes.

Autoimmune polyglandular syndrome 3 variant (APS3v) refers to the co-occurrence of autoimmune thyroiditis (AITD) and type 1 diabetes (T1D) within the same individual. HLA class II confers the strongest susceptibility to APS3v. We previously identified a unique amino acid signature of the HLA-DR pocket (designated APS3v HLA-DR pocket) that predisposes to APS3v. We hypothesized that both thyroid and islet peptides can be presented by the unique APS3v HLA-DR pocket, triggering AITD + T1D together. To test this hypothesis we screened islet and thyroid peptides for their ability to bind to the APS3v HLA-DR pocket. Virtual screen of all possible thyroglobulin (Tg), thyroid-stimulating hormone receptor (TSHR), thyroid peroxidase (TPO), insulin (Ins), and glutamic acid decarboxylase 65 (GAD65) peptides identified 36 peptides that bound to this unique pocket. In vitro binding assays using baculovirus-produced recombinant APS3v HLA-DR identified 11 thyroid/islet peptides (of the 36 predicted binders) that bound with high affinity. By immunizing humanized HLA-DR3 mice carrying the APS3v HLA-DR pocket we identified 4 peptides (Tg.1571, GAD.492, TPO.758, TPO.338) that were presented by antigen presenting cells and elicited T-cell response. We conclude that both thyroid and islet peptides can bind to this flexible APS3v HLA-DR pocket and induce thyroid and islet specific T-cell responses. These findings set the stage to developing specific inhibitors of the APS3v HLA-DR pocket as a precision medicine approach to treating or preventing APS3v in patients that carry this genetic HLA-DR pocket variant.

Mechanisms and kinetics of proliferation and fibrosis development in a mouse model of thyrocyte hyperplasia.

IFN-γ(-/-) NOD.H-2h4 mice develop autoimmune disease with extensive hyperplasia and proliferation of thyroid epithelial cells (TEC H/P) and fibrosis. Splenic T cells from donors with severe TEC H/P transfer TEC H/P to SCID recipients. The goal of this study was to determine what factors control TEC H/P development/progression by examining T cells, markers of apoptosis, senescence and proliferation in thyroids of SCID recipients over time. At 28days, T cell infiltration was maximal, thyrocytes were proliferating, and fibrosis was moderate. At days 60 and 90, thyroids were larger with more fibrosis. T cells, cytokines and thyrocyte proliferation decreased, and cell cycle inhibitor proteins, and anti-apoptotic molecules increased. T cells and thyrocytes had foci of phosphorylated histone protein H2A.X, indicative of cellular senescence, when TEC H/P progressed and thyrocyte proliferation declined. Some thyrocytes were regenerating at day 90, with irregularly shaped empty follicles and ciliated epithelium. Proliferating thyrocytes were thyroid transcription factor (TTF1)-positive, suggesting they derived from epithelial cells and not brachial cleft remnants.

The sodium iodide symporter is unlikely to be a thyroid/breast shared antigen.

PURPOSE: Anti-thyroid peroxidase (TPO) autoantibodies (TPOAb) seem to be protective for patients with breast cancer (BC). Thyroid and breast tissues both express the sodium iodide symporter (NIS), similarly both have a peroxidase activity, TPO and lactoperoxidase (LPO) respectively. We hypothesize a common immune response to a thyroid/breast shared antigen suggesting three putative mechanisms: (1) TPOAb react to both TPO and LPO, (2) TPO could be expressed in BC and (3) patients with TPOAb could have autoantibodies to NIS (NISAb). Previous studies excluded NISAb that block NIS activity in sera of patients with thyroid autoimmunity (TA) and/or BC. This study investigates neutral NISAb (binding without affecting function). METHODS: Clones of CHO cells stably expressing human NIS (hNIS; CHO-NIS) were isolated following transfection of hNIS in pcDNA3 vector. Expression of hNIS mRNA and surface protein was confirmed by PCR and flow cytometry respectively using a hNIS-mouse-monoclonal-antibody. CHO-NIS and controls transfected with the empty pcDNA3 vector (CHO-Empty) were incubated with 42 heat-inactivated human sera followed by an anti-human-IgG-AlexaFluor488-conjugate: 12 with BC, 11 with TA, 10 with both BC and TA and 9 with non-autoimmune thyroid diseases. The Kolmogorov-Smirnov Test was used to compare the fluorescence intensity obtained with CHO-NIS and CHO-Empty, using sera from six young males as a negative control population. RESULTS: None of the 42 sera were positive for NISAb. CONCLUSIONS: NISAb are rare and NIS is unlikely to be a common thyroid/BC shared antigen. We have recently demonstrated TPO expression in BC tissue and are currently investigating TPOAb cross-reactivity with TPO/LPO.

Cytokeratin 5/6 and P63 immunophenotype of thyroid lymphoepithelial complexes.

Thyroid lymphoepithelial complexes (LECos) are rare, being reported in lymphoma, Graves-Basedow disease, Hashimoto thyroiditis, pericarcinomatous thyroid or in the context of branchial cleft-like cysts. Here we report immunohistochemical expression of cytokeratin 5/6, P63 and TTF1 in 6 cases of thyroid LECos. Two cases had carbimazole treatment for hyperthyroidia and Graves disease. Anti-thyroglobulin, -thyroperoxidase or -TSH antibodies were detected in 4 cases. NSAID or poviodone iodine allergy were present in 2 cases. The treatment consisted in total thyroidectomy or lobectomy. Microscopy showed nodular goiter and focal lymphocytic thyroiditis. Basaloid LECos were seen in all thyroids while squamoid LECos in 2. Associated lesions were papillary thyroid microcarcinoma (2 cases), solid cell nest, thyroglosal duct remnant, lymphoepithelial cyst and thymus-parathyroid unit (one case each). Cytokeratin 5/6 was expressed in both squamoid and basaloid LECos along with P63. TTF1 expression was faint or absent. In conclusion LECos may occur in the context of autoimmune thyroiditis or of a specific immune susceptibility background. The expression of CK5/6 and of P63 suggests a squamous differentiation including in the basaloid LECos. The etiologic relevance of these immunostainings remains limited although rather suggestive of a metaplastic process than of migration-abnormalities.

[Vitamin D and autoimmune thyroid diseases]. / Vitamin D a autoimunitní tyreopatie.

From the recent literature data it may be concluded that vitamin D deficiency is associated with increased risk of thyroid autoimmunity development and thus should be considered as an additional important risk factor for both chronic autoimmune thyroiditis (postpartum thyroiditis including) and Graves´ disease. A higher risk of Graves´ disease development is also associated with several polymorphisms in the gene encoding for vitamin D binding protein and for the specific receptor of active form of vitamin D - 1,25-(OH)2D3 in the respective target cells. Whether careful supplementation with vitamin D aimed to normalize low 25(OH)D levels brings preventive or therapeutic effect is subject to further research.Key words: autoimmune thyroiditis - D vitamin deficiency - D vitamin supplementation - Graves´disease.

Regulatory T cells in B-cell-deficient and wild-type mice differ functionally and in expression of cell surface markers.

NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) with chronic inflammation of thyroids by T and B cells. B-cell deficient (B(-/-) ) mice are resistant to SAT but develop SAT if regulatory T (Treg) cells are transiently depleted. We established a transfer model using splenocytes from CD28(-/-)  B(-/-) mice (effector cells and antigen-presenting cells) cultured with or without sorted Treg cells from Foxp3-GFP wild-type (WT) or B(-/-) mice. After transfer to mice lacking T cells, mice given Treg cells from B(-/-) mice had significantly lower SAT severity scores than mice given Treg cells from WT mice, indicating that Treg cells in B(-/-) mice are more effective suppressors of SAT than Treg cells in WT mice. Treg cells from B(-/-) mice differ from WT Treg cells in expression of CD27, tumour necrosis factor receptor (TNFR) II p75, and glucocorticoid-induced TNFR-related protein (GITR). After transient depletion using anti-CD25 or diphtheria toxin, the repopulating Treg cells in B(-/-) mice lack suppressor function, and expression of CD27, GITR and p75 is like that of WT Treg cells. If B(-/-) Treg cells develop with B cells in bone marrow chimeras, their phenotype is like that of WT Treg cells. Addition of B cells to cultures of B(-/-) Treg and T effector cells abrogates their suppressive function and their phenotype is like that of WT Treg cells. These results establish for the first time that Treg cells in WT and B(-/-) mice differ both functionally and in expression of particular cell surface markers. Both properties are altered after transient depletion and repopulation of B(-/-) Treg cells, and by the presence of B cells during Treg cell development or during interaction with effector T cells.

Association of Hashimoto's thyroiditis and thyroid cancer.

PURPOSE OF REVIEW: The association of Hashimoto's thyroiditis and thyroid cancer remains an active focus of research and controversy. Since it was first proposed in 1955, numerous studies have explored the epidemiology and etiology of these concurrent disease processes. RECENT FINDINGS: The lymphocytic infiltration of Hashimoto's thyroiditis is frequently encountered in thyroid glands resected for a neoplasm. The most frequent association is noted with papillary thyroid cancer. Several recent studies performed on patients undergoing thyroidectomy with coexisting Hashimoto's thyroiditis report an increased prevalence of papillary thyroid cancer, with a favorable disease profile and an improved prognosis, particularly in women. Conversely, some population-based studies using fine-needle aspiration biopsy data report no linkage between serologic Hashimoto's thyroiditis and thyroid cancer, yet they are limited by the lack of definitive pathology. On the other hand, the significantly increased incidence of primary thyroid lymphomas in patients with Hashimoto's thyroiditis strongly suggests a pathogenetic link between this autoimmune disorder and malignant thyroid lymphoma. SUMMARY: The lymphocytic infiltration of Hashimoto's thyroiditis is frequently associated with papillary thyroid cancer and may indeed be a risk factor for developing this type of cancer. Nonetheless, a pathogenesis linking these diseases remains unclear. The relationship between thyroid lymphoma and Hashimoto's thyroiditis appears to be well established.

The Role of Iodine and Selenium in Autoimmune Thyroiditis.

Iodine and selenium (Se) are both essential elements to thyroid hormone economy, while they represent key players in the development of autoimmune thyroiditis.Chronic high iodine intake has been associated in various studies with increased frequency of autoimmune thyroiditis. In susceptible individuals, iodine excess increases intra-thyroid infiltrating Th17 cells and inhibits T regulatory (TREG) cells development, while it triggers an abnormal expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in thyrocytes, thus inducing apoptosis and parenchymal destruction. As was shown in a mouse model, high iodine supply leads to changes in the immunogenicity of the thyroglobulin molecule, upregulation of vascular intercellular adhesion molecule-1 (ICAM-1), and reactive oxygen species (ROS) generation in the thyrocytes. Serum Se levels were found decreased in Hashimoto thyroiditis and especially in Graves' disease as well as in thyroid-associated ophthalmopathy patients, the levels being related to the pathogenesis and outcome. Selenium is strongly involved, via the variable selenoproteins, in antioxidant, redox, and anti-inflammatory processes. Selenium enhances CD4+/CD25 FOXP3 and T regulatory cells activity while suppressing cytokine secretion, thus preventing apoptosis of the follicular cells and providing protection from thyroiditis. Selenium supplementation may be useful in autoimmune thyroid diseases, though, while usually well-tolerated, it should not be universally recommended, and it is also likely to be helpful for those with low Se status and autoimmunity. Broadly speaking, the achievement and maintenance of "selenostasis" as well as adequate urinary iodine excretion are mandatory to control disease, while, putatively, they may additionally be critical to preventing disease.

Identification of pathogenic T cell epitopes near cathepsin cleavage sites in thyroglobulin.

Experimental autoimmune thyroiditis, induced in mice after challenge with thyroglobulin (Tg), is known to be under the genetic control of the H2A(k) locus. Because cathepsins are known to influence proteolytic processing of Tg in vivo, we examined in this study whether putative H2A(k)-binding Tg epitopes, located near cathepsin cleavage sites within mouse Tg, have immunopathogenic properties. Cathepsin L, B, and D cleavage sites in mouse Tg were predicted based on homology with known cathepsin cleavage sites in rabbit Tg. We used an algorithm-based approach to identify H2A(k)-binding motifs within 20-aa residue segments adjacent to cathepsin cleavage sites, and five 12mer peptides encompassing these sequences were synthesized. Two of them, p2369 (aa 2369-2380) and p2439 (aa 2439-2450) were immunogenic, eliciting significant proliferative T cell responses using lymph node cells from peptide-primed mice and production of IL-2 and IFN-γ in recall assays in vitro. Both peptides induced experimental autoimmune thyroiditis upon direct challenge of CBA/J mice with peptide in CFA and by adoptive transfer of peptide-primed lymph node cells into naive recipient hosts, but neither peptide was characterized as dominant.

OX40L/Jagged1 cosignaling by GM-CSF-induced bone marrow-derived dendritic cells is required for the expansion of functional regulatory T cells.

Earlier, we had demonstrated that treatment with low dose of GM-CSF can prevent the development of experimental autoimmune thyroiditis (EAT), experimental autoimmune myasthenia gravis, and type 1 diabetes, and could also reverse ongoing EAT and experimental autoimmune myasthenia gravis. The protective effect was mediated through the induction of tolerogenic CD11C(+)CD8α(-) dendritic cells (DCs) and consequent expansion of Foxp3(+) regulatory T cells (Tregs). Subsequently, we showed that GM-CSF acted specifically on bone marrow precursors and facilitated their differentiation into tolerogenic dendritic cells (DCs; GM-CSF-induced bone marrow-derived DCs [GM-BMDCs]), which directed Treg expansion in a contact-dependent manner. This novel mechanism of Treg expansion was independent of TCR-mediated signaling but required exogenous IL-2 and cosignaling from DC-bound OX40L. In this study, we observed that OX40L-mediated signaling by GM-BMDCs, although necessary, was not sufficient for Treg expansion and required signaling by Jagged1. Concurrent signaling induced by OX40L and Jagged1 via OX40 and Notch3 receptors expressed on Tregs was essential for the Treg expansion with sustained FoxP3 expression. Adoptive transfer of only OX40L(+)Jagged1(+) BMDCs led to Treg expansion, increased production of IL-4 and IL-10, and suppression of EAT in the recipient mice. These results showed a critical role for OX40L- and Jagged1-induced cosignaling in GM-BMDC-induced Treg expansion.