Autoimmune thyroiditis: predisposition and pathogenesis

The Role of Nuclear Medicine in Benign Thyroid Disease

Since the mid-twentieth century, the radionuclide thyroid scan has been utilized in the management of benign thyroid disorders. In current medical practice, patients with hyperthyroidism are referred for thyroid scintigraphy, while patients with goiters and thyroid nodules are most often evaluated by ultrasound or computed tomography. Since thyroid scintigraphy reflects the functional state of the gland, it provides information that anatomical imaging lacks. Therefore, radionuclide imaging of the thyroid is the imaging modality of choice in the evaluation of the hyperthyroid patient. In addition, patients with so-called subclinical hyperthyroidism often present a diagnostic dilemma to the clinician since the causative factor must be determined for proper patient management. The aim of this manuscript is to illustrate the imaging characteristics of thyroid disorders commonly seen in clinical practice resulting in thyrotoxicosis or pending thyrotoxicosis, so that correlation with clinical presentation and pertinent laboratory data will lead to the correct diagnosis.

B cells from anti-thyroid antibody positive, infertile women show hyper-reactivity to BCR stimulation

Anti-thyroid antibody (ATA) positivity affects 1 out of 9 women in childbearing age and presents a significant risk for infertility. Emerging evidence indicates that alterations in the B cell receptor induced calcium (Ca2+) signaling could be key in the development of autoimmunity. We aimed to investigate the Ca2+ flux response of B lymphocyte subsets to BCR stimulation in Hashimoto’s thyroiditis and related infertility. We collected peripheral blood samples from ATA+, infertile, euthyroid patients (HIE), hypothyroid, ATA+ patients before (H1) and after levothyroxine treatment (H2), and age-matched healthy controls (HC). All B cell subsets of ATA+, infertile, euthyroid patients showed elevated basal Ca2+ level and hyper-responsivity to BCR ligation compared to the other groups, which could reflect altered systemic immune function. The Ca2+ flux of hypothyroid patients was similar to healthy controls. The levothyroxine-treated patients had decreased prevalence of CD25+ B cells and lower basal Ca2+ level compared to pre-treatment. Our results support the role of altered Ca2+ flux of B cells in the early phase of thyroid autoimmunity and infertility.

High Prevalence of Antithyroid Antibodies in a New Zealand Cohort of Patients With Systemic Sclerosis

BACKGROUND

Autoimmune thyroid disease affects 1% of the general population, and autoimmune thyroid antibodies are noted in up to 15%.

OBJECTIVE

We hypothesized systemic sclerosis (SSc) is associated with higher prevalence of antithyroglobulin (anti-Tg) and anti-thyroid peroxidase (anti-TPO) antibodies) to justify monitoring of thyroid function for earlier detection and treatment.

METHODS

Waikato Hospital SSc clinic patients were prospectively tested for thyroid function tests and antithyroid antibodies (ATAs).

RESULTS

Of the 75 patients with SSc and 10 patients with SSc overlap syndrome (SOS) followed up in the SSc clinic, anti-Tg and anti-TPO were prospectively tested in 61 (70.6%) of the 85 patients. The cohort comprised 38 patients with limited cutaneous SSc (lcSSc), 15 with diffuse cutaneous SSc, and 8 with SOS.Anti-Tg and anti-TPO antibodies were found in 34.2% in lcSSc patients and 33.3% in diffuse cutaneous SSc patients, whereas in SOS they were found in 25% (Tg) and in 12.5% (TPO) of patients.At baseline, 10 patients (11.7%) had thyroid dysfunction: 8 (9.4%) with subclinical hypothyroidism and 1 each (1.2%) with subclinical hyperthyroidism and with clinical hyperthyroidism.After 18 months, 1 woman with lcSSc, positive for both ATAs, developed clinical hypothyroidism.

CONCLUSIONS

There is a higher prevalence of ATAs in SSc and SOS compared with the general population. Screening these patients for ATAs is a reasonable measure.

131I-Induced Graves' disease in patients treated for toxic multinodular goitre: systematic review and descriptive analysis

BACKGROUND

Graves' disease (GD) arising after the treatment of toxic multinodular goitre (TMNG) with radioiodine has long been described but it remained unclear whether GD was in fact iodine induced, its incidence, risk factors, natural history and treatment outcomes.

METHODS

A systematic search using The Cochrane Library, Medline and PubMed Central allowed the pooling of data from 3633 patients with thyroid autonomy, 1340 patients with TMNG, to fill gaps in knowledge, regarding the clinical expression of iodine-induced GD (131I-IGD) in adults.

RESULTS

131I-IGD developed in 0-5.3% of those with thyroid autonomy (first year) and in 5-5.4% of those with TMNG, 3-6 months after treatment. Patients with toxic adenoma were less affected. 131I-IGD was more common in patients with pre-treatment direct or indirect signs of autoimmunity: positive anti-TPO (p < 0.05), glandular hypoechogenicity, TRAbs within reference range, diffuse uptake on 99mTc-pertechnetate scans (p < 0.05), findings that may increase the risk tenfold. 131I-IGD manifested 3 months after 131I, justifying 15.4-29% of cases of relapse. The rate of spontaneous remission was 17-20% (6 months) and the rate of relapse after a second 131I treatment 22-25%. The use of an uptake-based administered 131I activity led to a greater proportion of euthyroid patients (78% compared to 25-50% with the mass-based approach).

CONCLUSIONS

GD may be triggered by 131I. The incidence of the condition is low. Several risk factors were consistently identified; some have shown to raise the risk significantly. 131I-IGD seems more treatment resistant than iodine-independent GD and the best resolution rates were achieved with uptake-based selected iodine activities.

The relationship between thyroid antibody titer and levothyroxine dose in patients with overt primary hypothyroidism

BACKGROUND

Both excess and insufficient thyroid hormone replacement may produce adverse effects in various target tissues; therefore, understanding factors that affect achievement of target TSH levels is crucial.

OBJECTIVE

Investigate the relationship between antibody titers and levothyroxine dose.

DESIGN

Retrospective, review of data in medical records.

SETTING

Thyroid center of Fatih Sultan Mehmet Education and Research Hospital, Istanbul, Turkey.

PATIENTS AND METHODS

The study population consisted of patients that had been diagnosed as having overt primary hypothyroidism and were taking levothyroxine for at least one year. The serum TSH level for an euthyroid state was between 0.5-4 mIU/L. The levels of anti-thyroid peroxidase (TPOAb) considered positive for antibodies were < 5.6 IU/mL and for anti-thyroglobulin (TgAb) autoantibodies < 4.10 IU/ mL.

MAIN OUTCOME MEASURE

Daily levothyroxine doses of antibody-positive and negative patients and association of daily drug requirement with antibody titers.

RESULTS

The study population consisted of the 303 patients (273 females and 30 males with the mean [SD] age of 46.6 [13.2] years). In the antibody-positive group (n=210) average daily levothyroxine dose was statistically significantly higher than in the antibody-negative group (n=93) (mean of 78.8 [36.7] vs 64.2 [27.1] mg/day, P=.001, respectively). There was a low but statistically significant positive relationship between the TPOAb (r=0.217, P < .01) and TgAb levels (r=0.158, P < .05) and levothyroxine doses in the antibody-positive group.

CONCLUSION

Antibody titers are positively associated with larger levothyroxine (LT-4) replacement dosing in patients with autoimmune thyroiditis.

LIMITATION

Unknown antibody titers before starting levothyroxine use.

[Biochemical and immunological markers of autoimmune thyroiditis]

Correlations between biochemical and immunological markers of programmed cell death (apoptosis), and the functional state of the thyroid gland (hyperthyroidism, euthyroidism, hypothyroidism) have been investigated in autoimmune thyroiditis (AT) (also known as chronic autoimmune thyroiditis). Annexin V, TRAIL and TNF-a, as well as DNA-hydrolyzing antibodies were used as the main markers. Increased levels of TRAIL were found in the serum of AT patients (hyperthyroidism>hypothyroidism>euthyroidism) compared with healthy individuals. The highest frequency of antibodies to denatured DNA (Abs-dDNA) had the highest frequency in AT patients (97%) compared with healthy controls. Among these patients, 75% had hyperthyroidism, 85% had hypothyroidism, and 84.7% had euthyroidism. Abs hydrolyzing activity demonstrated correlation dependence with symptoms of the thyroid dysfunction.

Genetic variants of interleukin-4 gene in autoimmune thyroid diseases: an updated meta-analysis

Autoimmune thyroid diseases (AITDs) including Graves' disease (GD) and Hashimoto's thyroiditis (HT) are common autoimmune endocrine disorders. Interleukin-4 (IL-4), a cytokine secreted by T cells, plays a critical role in antigen-specific Th2 responses. The IL-4 gene is highly polymorphic and it has been reported that the polymorphism at -590 (T/C, rs2243250) in the promoter region of IL-4 may contribute to the development of AITDs. Recently, several case-control studies have examined the association of genetic variants of IL-4 with AITDs. However, the results of these studies remain conflicting. To systematically study the role of IL-4 in the pathogenesis of AITDs, we conducted a meta-analysis including 11 eligible studies (1847 cases and 2068 healthy controls). Fixed-effect or random-effect models were used to calculate pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs). Our results revealed a significant association between the IL-4 genetic variant (-590, T/C, rs2243250) and the risk of developing AITDs (TC + TT versus TT genotype: OR = 1.83, 95% CI = 1.083-3.091, p = 0.024). These findings demonstrate that the IL-4 rs2243250 genetic variant might play a key role in the development of AITDs.

Thyroid status two decades after salt iodization: country-wide data in school children from India

OBJECTIVE

Country-wide evaluation of thyroid disorders in school children following two decades of universal salt iodization (USI) has not been carried out till date. This study was planned with aim to assess thyroid status of school children two decades after the launch of USI programme.

DESIGN

Population survey.

PATIENTS

We collected data from 25 schools in 19 cities across five different geographical zones of India. Those children who were evaluated for anthropometry, and goitre status by palpation formed 'total population'. Children who consented to give blood samples were defined as 'study population'.

MEASUREMENTS

Serum free T3, free T4, TSH, anti-TPO antibody and thyroid ultrasound.

RESULTS

A total of 38,961 children aged 5-15 years formed total population. Goitre rate was 15.5% while thyroid hypoechogenicity was found in 4404 (11.3%) children. In the study population (13,790 children), 2258 (16.4%) had goitre, 505 (3.7%) had positive anti-TPO antibody titres, 1001 (7.3%) had hypothyroidism (TSH > 5.2 μIU/ml) and 41 (0.3%) had thyrotoxicosis (TSH < 0.1 μIU/ml). Among goitrous children, 203 (9.0%) had anti-TPO positivity, 365 (16.1%) had hypoechogenicity of thyroid and either of these were present in 488 (21.6%) children.

CONCLUSIONS

Endemic goitre in school children persisted nationwide, despite more than two decades of USI programme. Thyroid autoimmunity only partially explains the increase in goitre prevalence.

Fine epitope mapping within the pathogenic thyroglobulin peptide 2340-2359: minimal epitopes retaining antigenicity across various MHC haplotypes are not necessarily immunogenic

We have previously reported that the 20-mer peptide p2340 (amino acids 2340-2359), of human thyroglobulin (Tg) has the unique feature that it causes experimental autoimmune thyroiditis (EAT) in mouse strains bearing high-responder (HR) or low-responder (LR) MHC haplotypes in Tg-induced EAT. In this study, we have employed fine epitope mapping to examine whether this property of p2340 is the result of recognition of distinct or shared minimal T-cell epitopes in the context of HR or LR MHC class II molecules. Use of overlapping peptides showed that a core minimal 9-mer epitope (LTWVQTHIR, amino acids 2344-2352) was recognized by p2340-primed T cells from both HR (H2(k,s) ) and LR (H2(b,d) ) strains, whereas a second 9-mer epitope (HIRGFGGDP, amino acids 2350-2358) was antigenic only in H2(s) hosts. Truncation analysis of LTWVQTHIR and HIRGFGGDP peptides delineated them as the minimal epitopes recognized by p2340-primed T cells from the above strains. Subcutaneous challenge of all mouse strains with the 9-mer core peptide LTWVQTHIR in adjuvant elicited specific lymph node cell proliferative responses and mild EAT only in HR hosts, highlighting this sequence as a minimal pathogenic Tg peptide in EAT. The 9-mer peptide HIRGFGGDP was not found to be immunogenic in H2(s) hosts. These data demonstrate that minimal T-cell epitopes, defined as autoantigenic in hosts of various MHC haplotypes, are not intrinsically immunogenic. Activation of naive autoreactive T cells may require contributions from flanking residues within longer peptide sequences encompassing these epitopes.

Diagnostic approach to goitre in children

Thyroid disease is a common paediatric disorder that affects up to 3.7% of school-aged children, and it usually presents with a goitre. By far, the most frequent cause of a goitre is autoimmune thyroid disease, although a benign colloid goitre is also a common cause. The present review focuses on the diagnostic approach to a child with a hypothyroid, hyperthyroid or euthyroid goitre.

Amiodarone and thyroid dysfunction

Amiodarone is a potent antiarrhythmic drug associated with thyroid dysfunction. Its high iodine content causes inhibition of 5'-deiodinase activity. Most patients remain euthyroid. Amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH) may occur depending on the iodine status of individuals and prior thyroid disease. AIT is caused by excess iodine-induced thyroid hormone synthesis (type I AIT) or by destructive thyroiditis (type II AIT). If the medical condition allows it, discontinuation of the drug is recommended in type I AIT. Otherwise, large doses of thioamides are required. Type II AIT is treated with corticosteroids. Mixed cases require a combination of both drugs. Potassium perchlorate has been used to treat resistant cases of type I AIT but use is limited by toxicity. Thyroidectomy, plasmapheresis, lithium, and radioiodine are used in select cases of AIT. AIH is successfully treated with levothyroxine. Screening for thyroid disease before starting amiodarone and periodic monitoring of thyroid function tests are advocated.

[Occurrence of diabetic ketoacidosis and autoimmune thyroiditis in a patient treated with pegylated interferon-alpha 2b and ribavirin for chronic hepatitis C]

Combined pegylated interferon and ribavirin therapy for chronic hepatitis C infection cause a wide range of side effects, including flu-like syndrome, hematological abnormalities, cardiovascular symptoms, gastrointestinal symptoms, pulmonary dysfunction, depression, and retinopathy. Interferon-alpha has been shown to be related to the development of various autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, autoimmune thyroid disease, and type 1 diabetes mellitus (DM). Type 1 DM and thyroid disease respectively develop in 0.08-2.61% and 10-15% of patients treated with combined interferon-alpha and ribavirin for chronic hepatitis C. The coexistence of type 1 DM and autoimmune thyroiditis was rarely reported. We report a case of a 33-year-old female patient with chronic hepatitis C who simultaneously developed diabetic ketoacidosis and autoimmune thyroiditis after treatment with pegylated interferon-alpha 2b and ribavirin.

Acute myeloid leukemia with infiltration of thyroid gland complicating Hashimoto's thyroiditis

We describe a case of acute myeloid leukemia with infiltration of thyroid gland complicating Hashimoto's thyroiditis. In Hashimoto's thyroiditis, the leukocyte function-associated antigen-1 (LFA-1)/intercellular vascular cell adhesion molecule-1 (ICAM-1) and very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1) pathways in T lymphocytes and the vascular endothelium both play a role in the initiation and enhancement of lymphocyte recruitment to the thyroid glands during an autoimmune attack. The leukemic blast cells were positive for VLA-4 and negative for LFA-1 by immunohistochemistry. The presence of VLA-4 in blast cells might play a key role in the migration of blast cells to the thyroid glands.

p53 codon 72 proline/arginine polymorphism and autoimmune thyroid diseases

p53 protein participates in the processes of apoptosis, which is involved in a number of immunological reactions. In order to test whether the p53 gene could be used as a genetic marker for the prediction of the development of autoimmune thyroid diseases (AITD), we screened, by using polymerase chain reaction (PCR) analysis, for the C (CCC)/G (CGC) polymorphism at the p53 codon 72 (Pro 72/Arg 72) to determine the genotypes of 107 Hashimoto's thyroiditis (HT) and 90 Graves' disease (GD) patients, and 105 normal controls. The data demonstrated that, for the genotype analysis, HT patients featured an enhanced numerical ratio for the Arg/Arg homozygous genotype (33.7%) and a diminished ratio for the Arg/Pro heterozygous genotype (41.1%) at the p53 codon 72 than was the case for normal controls (Arg/Arg: 17.1% and Arg/Pro: 61.9%; P=0.005). The odds ratio for the risk of the Arg/Arg genotype's appearance, compared with that of the Arg/Pro and Pro/Pro genotypes combined, for the HT patient group was 2.450 (95% confidence interval: 1.274-4.716). With respect to allelic analysis, we did not observe significant difference in the frequency of appearance of the Arg allelic variant and the Pro allelic variant for the p53 codon 72 when comparing the HT patient group with the control group (P=0.208). On the other hand, GD patients presented no significant difference in distribution for both genotype and allelic frequencies (P=0.344 and 0.245, respectively) when compared with normal controls. In conclusion, HT patients feature a greater ratio of arginine homozygosity at p53 codon 72 than in the case for normal subjects. The p53 codon 72 proline/arginine polymorphism may be a genetic marker to predict the increased susceptibility of development of HT.

First Observation of an Hashimoto Thyroiditis-Like Disease in Horses from Eastern Europe: Histopathological and Immunological Findings

Among 622 slaughtered horses from eastern Europe, 156 thyroid glands were selected on the basis of macroscopic alterations (e.g., determination of volume and weight). In the 80% of these thyroids, microscopic alterations consistent with a diagnosis of Hashimoto thyroiditis-like disease were found. In particular, a subverted architecture of the thyroid gland with colloid rarefaction, lymphocytic infiltration, and fibrosis was noted. The confirmation of the histopathological diagnosis of an equine Hashimoto thyroiditis-like disease was provided by the increased serum concentration of thyroglobulin, of antithyroglobulin, and of antithyroid peroxidase autoantibodies. Despite evidence consistent with an Hashimoto thyroiditis-like disease in eastern European horses, the etiopathogenesis of this autoimmune disorder deserves further investigation. In this respect, in some horses histopathological alterations in the pituitary gland may suggest an as-yet-unidentified disorder within the hypothalamus-pituitary adrenal axis associated with Hashimoto thyroiditis.

Lack of association between interleukin-4 gene polymorphisms and autoimmune thyroid diseases amongst Taiwanese Chinese

Graves' disease (GD) and Hashimoto's thyroiditis (HT) are both common autoimmune diseases of the thyroid gland (AITD). The IL-4 is involved in both humoral and cellular immunity. The aim of this study was to test whether the IL-4 gene could be used as a genetic marker to predict the development of AITD amongst the Chinese population of Taiwan. For this study, a normal control group of 105 healthy subjects and two experimental groups featuring individuals afflicted with either GD (104 patients) or HT (109 patients) were examined. Polymerase chain reaction (PCR) was used to analyze the variable number of tandem repeats (VNTRs) polymorphism for the IL-4 gene intron 3 and PCR-based restriction analysis using endonuclease BsmFI was undertaken for the same gene at the promoter -590 position. We found no significant difference in the frequencies of presence of genotype and allelic variants for the IL-4 gene at both the intron 3 and the promoter regions between the normal control group and each of the two patient groups. These findings suggest that the IL-4 gene polymorphisms that arise at either intron 3 or promoter -590 positions are not suitable genetic markers for AITD among Taiwanese Chinese.

Proinflammatory cytokine gene polymorphisms among Hashimoto's thyroiditis patients

Proinflammatory cytokines are involved in the pathogenesis of Hashimoto's thyroiditis (HT). To test whether certain specific proinflammatory cytokine gene polymorphisms could be genetic markers for an individual's susceptibility to HT, we investigated single-site polymorphisms of certain proinflammatory cytokine genes of interest for 107 HT sufferers and 163 controls, subsequent to preparing the necessary experimental genomic DNA from peripheral blood, using a polymerase chain reaction (PCR)-based restriction analysis. The polymorphisms we detected were as follows: 1) C/T and E1/E2 polymorphisms for the interleukin (IL)-1beta gene at promoter (-511) and exon 5, respectively; 2) a variable number of tandem repeats (VNTRs) for the IL-1 receptor antagonist (IL-1Ra) gene at intron 2; 3) a C/G polymorphism for the IL-6 gene at promoter (-572); and 4) an A/G polymorphism for the tumor necrosis factor (TNF)-alpha gene at promoter (-308). The data demonstrated an increased ratio of CG genotype and decreased ratios of CC and GG genotypes (chi-squared test; P = 0.025) for the IL-6 gene promoter for HT patients when compared with normal controls. The odds ratio (OR) for the CG genotype, as compared to the GG genotype, for HT patients was shown to be 4.065 (95% confidence interval (CI): 1.268-13.032). Comparison of the genotype analysis for the remaining gene polymorphisms and the allelic analysis for all of the screened gene polymorphisms, however, all revealed no statistically significant difference between the two study groups as regards frequency of genotype. In conclusion, we suggest that an IL-6 gene promoter (-572) C/G polymorphism could represent a potential "candidate" genetic marker to predict an individual's susceptibility to HT.

The codon 620 single nucleotide polymorphism of the protein tyrosine phosphatase-22 gene does not contribute to autoimmune thyroid disease susceptibility in the Japanese

The etiology of the autoimmune thyroid diseases (AITDs), Graves' disease (GD), and Hashimoto's thyroiditis (HT) is largely unknown. However, genetic susceptibility is believed to play a major role. The lymphoid tyrosine phosphatase (LYP), encoded by the protein tyrosine phosphatase-22 (PTPN22) gene, is a powerful inhibitor of T cell activation. Recently, a single-nucleotide polymorphism (SNP), encoding a functional arginine to tryptophan residue change at PTPN22 codon 620 in Caucasians has been shown to be associated with GD and other autoimmune diseases. We have used a polymerase chain reaction (PCR)-restriction fragment (XcmI) assay to examine genotypes at the codon 620 polymorphism in 334 unrelated patients with AITD and 179 controls. None of the patients with AITD and controls had the tryptophan allele. These data suggest that the codon 620 polymorphism of the PTPN22 gene does not have a causal role for AITD in the Japanese. However, we cannot exclude the PTPN22 region as harboring another susceptibility locus for AITD in linkage disequilibrium with the Trp/Arg SNP.

Association of a CTLA-4 3' untranslated region (CT60) single nucleotide polymorphism with autoimmune thyroid disease in the Japanese population

The etiology of the autoimmune thyroid diseases (AITDs), Graves' disease (GD) and Hashimoto's thyroiditis is largely unknown. However, genetic susceptibility is believed to play a major role. The cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene, encoding a negative regulator of the T-lymphocyte immune response, had been reported to be associated and/or linked to AITD. Recently, AITD susceptibility in the Caucasians was mapped to the 6.1-kb 3'UTR of the CTLA-4 gene, in which the single-nucleotide polymorphism (SNP), CT60, was most strongly associated with AITD. In order to determine the association of the CTLA-4 gene with AITD in the Japanese, case-control association analysis for the CT60 of the CTLA-4 gene using 264 AITD patients and 179 healthy controls was done. The frequency of the disease-susceptible G allele of the CT60 of the Japanese control was higher than that of the Caucasians (72.6 vs. 52.3%). However, the G allele of the CT60 was associated with GD (84.0 vs. 72.6%, P=0.0008) and AITD (80.1 vs. 72.6%, P=0.009) in the Japanese. Furthermore, the G allele of the CT60 was associated with the increased risk for GD [P=0.004, odds ratio (OR)=2.0] and AITD (P=0.03,OR=1.6) in a recessive model. These results suggested that the CTLA-4 gene is involved in the susceptibility for GD and AITD in the Japanese.

Effects of prophylactic thyroid hormone replacement in euthyroid Hashimoto's thyroiditis

Hashimoto's thyroiditis is the most frequent autoimmune thyroid disease. L-thyroxine therapy can reduce the incidence and alleviate the symptoms of this disease. The aim of this study was to evaluate the effects of prophylactic L-thyroxine treatment on clinical and laboratory findings of patients who were euthyroid at the time of diagnosis. Thirty-three patients who had diagnosis of euthyroid Hashimoto's thyroiditis were randomized to two groups, one group received prophylactic L-thyroxine treatment and the other was followed-up without treatment. Initial thyroid function tests, autoantibodies, ultrasonography, fine needle aspiration biopsy and peripheral blood lymphocyte subsets were similar in the two study groups. After 15 months of L-thyroxine treatment, there was a significant increase in free T4 and a significant decrease in TSH and anti-thyroglobulin antibody anti-thyroid peroxidase antibody levels. CD8+ cell counts increased in both groups, CD4/CD8 levels decreased significantly because of the increase in CD8+ cell count levels. Though there was no change in cytological findings, ultrasonography showed a decrease in thyroid volume in L-thyroxine receiving patients whereas an increase was detected in patients who were followed without treatment. In conclusion, prophylactic thyroid hormone therapy can be used in patients with Hashimoto's thyroiditis even if they are euthyroid.

Hashitoxicosis in children: clinical features and natural history

OBJECTIVE

To determine the incidence, natural history, and clinical characteristics of Hashitoxicosis (Htx) in pediatric patients with autoimmune thyroiditis.

STUDY DESIGN

Medical records of children diagnosed with Hashimoto thyroiditis between 1993 and 2002 were reviewed. The clinical course of patients presenting with hyperthyroidism was determined. Variables including sex, age, family history, thyroid hormone levels, anti-thyroid antibody titers, 123 I thyroid scan results, and presenting features were investigated as possible predisposing factors for the development of Htx.

RESULTS

Out of 69 patients with autoimmune thyroiditis, 8 were diagnosed with Htx. The duration of hyperthyroidism ranged from 31 to 168 days. Three patients became hypothyroid after an average of 46.3 +/- 13.2 days, and 5 patients became euthyroid after an average of 112.8 +/- 59.8 days. Additional findings included an elevated thyroid stimulating immunoglobulin (TSI) titer in 3 of the 8 patients with Htx, and increased uptake on 123 I scan in 2 patients.

CONCLUSION

Htx is an uncommon yet important cause of hyperthyroidism in children that has a variable clinical course. The diagnosis may be complicated, as presenting features sometimes exhibit significant overlap with Graves' disease. No factors predisposing to the development of Htx were identified.

Resistance to thyroid hormone associated with autoimmune thyroid disease in a Turkish family

The syndrome of resistance to thyroid hormone (RTH) is characterized by impaired tissue responses to thyroid hormone. Hashimoto's thyroiditis is the most common thyroid autoimmune disease. We present a Turkish family with both RTH and Hashimoto's thyroiditis. RTH was detected through the presence of point mutation in thyroid hormone receptor (TR), and Hashimoto's thyroiditis was diagnosed due to the presence of thyroid autoantibodies. The proposita, her affected mother as well as her unaffected sister have thyroid autoantibodies consistent with Hashimoto's thyroiditis, and a heterozygous point mutation in exon 10 encoding the ligand (3,3',5-L-T3)-binding domain of the TRbeta gene was detected in both the proposita and the mother. The mutation is a replacement of cytosine for guanine in codon 453 (CCT->GCT) producing a missense mutation substituting a normal proline with an alanine (P453A), which reduces the affinity for T3 to 17% of that of the normal TRbeta. Both also have modest elevation of serum TSH levels. In severe RTH, marked elevation of thyroid hormone concentrations in the absence of suppressed TSH supports the laboratory diagnosis of RTH. However, when RTH is mild and associated with thyroiditis, even a modest thyroid gland insufficiency can obliterate the serum T4 and T3 elevations, typical of RTH. This will manifest as elevated serum TSH. Demonstration of TRbeta gene mutation is then necessary to establish the diagnosis. In addition, under these circumstances, treatment with thyroid hormone should be considered.

The synergistic effect of phytohemagglutinin and interferon-gamma on the expression of tumor necrosis factor-alpha from RAW 264.7 cells

Tumor necrosis factor-alpha (TNF-alpha) is a major cytokine of host immune reaction by foreign agents. Phytohemagglutinin (PHA) is a dynamic contributor to mitogenic stimulation and augmentation of host immune defense. Interferon-gamma (IFN-gamma) induces induction of cytokines in macrophages and lymphocytes. The aim of this study was to examine the synergistic effects of PHA plus low dose IFN-gamma on TNF-alpha mRNA production, cytosolic levels, and secretion in RAW 264.7 cells. The cells were stimulated with PHA or IFN-gamma using various concentrations for various times. The effects of PHA on TNF-alpha expression appeared in dose- and time-dependent manners. The maximum doses of PHA and IFN-gamma to produce them were 300 microg/ml PHA and 10 ng/ml IFN-gamma. The optimum time of PHA for the TNF-alpha mRNA production and release were 6 and 7 h after stimulation, respectively, whereas the time of IFN-gamma on them was achieved at 3 and 8 h. Although the TNF-alpha mRNA production, cytosolic levels, and secretion from the cells were slightly detected under 10 microg/ml PHA and 1 ng/ml IFN-gamma, the combination of PHA (10 microg/ml) and IFN-gamma (1 ng/ml) greatly increased them, indicating the synergistic effect of PHA plus low dose IFN-gamma on TNF-alpha expression.

Interactions of HLA-DRB4 and CTLA-4 genes influence thyroid function in Hashimoto's thyroiditis in Japanese population

Hashimoto's thyroiditis (HT) is an autoimmune disease of the thyroid gland, and like many other autoimmune diseases, it is associated with the HLA and CTLA-4 gene. We have examined the distribution of the HLA DRB4*0101 allele and a CTLA-4 exon 1 A/G polymorphism in Japanese HT patients and controls and investigated possible interactions of these genes with thyroid function. Seventy Japanese HT patients and 105 controls were included in this study. HT was diagnosed on the basis of positivity for thyroid peroxidase (TPO) autoantibodies and the presence of a palpable diffuse goiter. Genotyping was performed by polymerase chain reaction (PCR)-based methods. CTLA-4-GG or -AG was more prevalent in the patients, and the odds ratio for the G allele was 4.95. The frequency of DRB4*0101-positive individuals was significantly higher in HT (odds ratio=2.17). The TSH values of HT patients at the time of diagnosis were compared to CTLA-4 genotype and HLA-DRB4*0101 positivity. They were slightly higher in the CTLA-4-AG group than in the -GG group and significantly higher in the HLA-DRB4*0101-positive group than in the -negative group (p<0.01). When the TSH values were compared in 4 groups based on positivity or negativity for HLA-DRB4*0101 and CTLA-4 GG or AG, they were found to be significantly higher in the CTLA-4-AG and HLA-DRB4*0101-positive group than in the 3 other groups (F=5.75, 3 degrees of freedom, p<0.01). These findings suggest that the interaction between the HLA-DRB4 and CTLA-4 genes determines the thyroid function of TPO-positive goitrous Japanese HT patients.

Amino acid substitutions in the thyroglobulin gene are associated with susceptibility to human and murine autoimmune thyroid disease

The 8q24 locus, which contains the thyroglobulin (Tg) gene, was previously shown to be strongly linked with autoimmune thyroid disease (AITD). We sequenced all 48 exons of the Tg gene and identified 14 single-nucleotide polymorphisms (SNPs). Case control association studies demonstrated that an exon 10-12 SNP cluster and an exon 33 SNP were significantly associated with AITD (P < 0.01). Haplotype analysis demonstrated that the combination of these two SNP groups was more significantly associated with AITD (P < 0.001). Gene-gene interaction studies provided evidence for an interaction between HLA-DR3 and the exon 33 SNP, giving an odds ratio of 6.1 for Graves' disease. We then sequenced exons 10,12, and 33 of the mouse Tg gene in 19 strains of mice. Fifty percent of the strains susceptible to thyroiditis had a unique SNP haplotype at exons 10 and 12, whereas none of the mouse strains that were resistant to thyroiditis had this SNP haplotype (P = 0.01). We concluded that Tg is a susceptibility gene for AITD, both in humans in and in mice. A combination of at least two Tg SNPs conferred susceptibility to human AITD. Moreover, the exon 33 SNP showed evidence for interaction with HLA-DR3 in conferring susceptibility to Graves' disease.

Correlation of number of intrathyroid lymphocytes with antimicrosomal antibody titer in Hashimoto's thyroiditis

The variants of Hashimoto's thyroiditis (classic, florid, and fibrotic types) differ in clinical manifestations, laboratory tests, and morphology. The titers of autoantibodies correlate with the degree of thyroidal lymphocytic infiltration (Wislon et al., 1998(5)) It appears that the density of lymphocytes is inversely proportional to antimicrosomal antibody (AMA) titer. The aim of the present study is to determine the precise relationship between the number of lymphocytes and AMA titer. It may be useful to predict the onset of the disease in subclinically hypothyroid patients. In 62 cases of cytologically confirmed Hashimoto's thyroiditis, the number of lymphocytes per high-power field was counted and correlated with AMA titer. The grading of lymphocytes was done as 1 (<10/HPF), 2 (11-20/HPF), and 3 (>/=21/HPF). The results showed no correlation between lymphocyte number and AMA titer.

Scintigraphic features of autoimmune thyroiditis

The term autoimmune thyroiditis encompasses multiple inflammatory conditions of the thyroid gland, each with variable clinical manifestations. The more acute forms, silent (painless) thyroiditis and postpartum thyroiditis, are associated with transient hyperthyroidism and are sometimes mistaken for Graves disease. The chronic form, Hashimoto thyroiditis (chronic autoimmune thyroiditis), results in goiter and eventual hypothyroidism unless it is recognized and treated promptly. Thyroid uptake measurements and scintigraphic findings (usually obtained with technetium-99m or iodine-123) play a complementary role along with thyroid function testing in differentiating autoimmune thyroiditis from other thyroid diseases, thereby influencing treatment. In some cases, histologic evaluation of biopsy specimens is required to yield the definitive diagnosis. Knowledge of the entire spectrum of these disorders is essential for appropriate case management.

Demystifying autoimmune thyroid disease. Which disorders require treatment?

The term "autoimmune thyroid disease" encompasses all of the autoimmune thyroid conditions, including Hashimoto's thyroiditis, Graves' disease, most cases of silent thyroiditis, and postpartum thyroiditis. Extrathyroidal manifestations (e.g., ophthalmopathy, dermopathy) can occur in Graves' disease and, less commonly, Hashimoto's thyroiditis. Spontaneous hypothyroidism is common in patients with Hashimoto's thyroiditis, and when it develops, life-long therapy with levothyroxine is needed. In the United States, most adult patients with Graves' disease are initially or eventually treated with radioiodine thyroid ablation. For transient thyroiditis involving hypothyroidism or hyperthyroidism, short-term or symptomatic therapy is adequate.

Enhancing or Suppressive Effects of Antibodies on Processing of a Pathogenic T Cell Epitope in Thyroglobulin

Thyroglobulin (Tg)-specific Abs occur commonly in thyroid disease, but it is not clear to what extent they affect Tg processing and presentation to T cells. Here we show that generation of the nondominant pathogenic Tg epitope (2549–2560), containing thyroxine (T4) at position 2553 (T4(2553)), is augmented by Tg-specific IgG mAbs that facilitate FcR-mediated internalization of Tg. However, other mAbs of the same (IgG1) subclass enhanced Tg uptake by APC but had no effect on the generation of this peptide. Treatment of APC with chloroquine or glutaraldehyde abrogated enhanced generation of T4(2553). The boosting effect was selective, since the enhancing mAbs did not facilitate generation of the neighboring cryptic (2495–2511) peptide, which is also pathogenic in mice. When Tg was simultaneously complexed to a mAb reactive with T4(2553) and to a mixture of boosting mAbs, the presentation of this epitope was totally suppressed. These results suggest that Tg-specific Abs alter Tg processing and may boost or suppress the presentation of nondominant pathogenic determinants during the course of disease.

Involvement of Epitope Mimicry in Potentiation But Not Initiation of Autoimmune Disease

We have examined whether the peptide (368–381) from the murine adenovirus type 1 E1B sequence, exhibiting a high degree of homology with the known pathogenic thyroglobulin (Tg) T cell epitope (2695–2706), can induce experimental autoimmune thyroiditis (EAT) in SJL/J mice. The viral peptide was a poor immunogen at the T or B cell level and did not elicit EAT either directly or by adoptive transfer assays. Surprisingly, however, the viral peptide was highly antigenic in vitro, activating a Tg2695–2706-specific T cell clone and reacting with serum IgG from mice primed with the Tg homologue. The viral peptide also induced strong recall responses in Tg2695–2706-primed lymph node cells, and subsequent adoptive transfer of these cells into naive mice led to development of highly significant EAT. These data demonstrate that nonimmunogenic viral peptides can act as agonists for preactivated autoreactive T cells and suggest that epitope mimicry may at times play a potentiating rather than a precipitating role in the pathogenesis of autoimmune disease.

Transition of nodular toxic goiter to autoimmune hyperthyroidism triggered by 131I therapy

The use of 131I treatment in nodular toxic goiter is widely accepted. In this article, we describe transition of nodular toxic goiter into an autoimmune toxic goiter with development of thyrotropin receptor antibodies (TRAb) as a side effect of 131I treatment. In this retrospective study, 149 patients with nodular toxic goiter (100 with multinodular goiter, 49 with a solitary autonomously functioning toxic nodule) were studied. Of these 149 patients 100 became permanently euthryoid after 1 dose of 131I, and due to persistent hyperthyroidism, 32 patients needed 2-5 doses to became euthyroid. After becoming euthyroid, none of these 132 patients had relapse of hyperthyroidism in the follow-up period. Based on evaluation of the thyroid hormone variables, 17 of 149 patients had a distinctly different pattern in the changes in thyroid hormones. They developed an increase in FT4I 3-6 months posttreatment after an initial fall in FT4I. Twelve of these 17 patients were treated with antithyroid drugs before the initial 131I dose. On samples of frozen sera (-20 degrees C) anti-thyroid peroxidase (TPO) and TRAb were followed for 6 months after 131I treatment in these 17 patients. A similar follow-up was done in 20 patients (10 with and 10 without antithyroid drug pretreatment), randomly selected from the patients who did not relapse. In the remaining 112 patients, anti-TPO and TRAb levels were measured only before the 131I treatment. Of the 17 patients with relapse, 6 developed TRAb concomitant with recurrence of hyperthyroidism (4% of the study group). In 5 of the 17 patients TRAb values remained absent throughout the follow-up period. The remaining 6 patients had elevated TRAb values before 131I treatment. Among the 132 patients who did not relapse, an additional 7 cases with presence of TRAb were found. A total of 9% of the study group was found to have TRAb before 131I pretreatment. Anti-TPO was found in 20 of 149 patients (13%) before 131I treatment. Complications, either hypothyroidism or TRAb-associated hyperthyroidism, were seen in 8 of 20 patients (40%) with anti-TPO before 131I treatment, compared to 9 of 129 (7%) without (p<0.005). In conclusion, TRAb and a Graves' like hyperthyroidism can be triggered by 131I treatment in patients with nodular toxic goiter. The presence of anti-TPO seem to be a marker of an increased risk of development of TRAb-associated hyperthyroidism as well as hypothyroidism, but both side effects can be seen despite the absence of anti-TPO autoantibodies.

HLA-DMB expression by thyrocytes: indication of the antigen-processing and possible presenting capability of thyroid cells

Expression of HLA class II molecules on thyrocytes is a characteristic feature of autoimmune thyroid disease and may lead the thyroid cells to present autoantigens to CD4+ T lymphocytes. Since HLA-DM is a critical molecule in class II-restricted antigen processing and presentation, we assessed the expression of HLA-DMB, -invariant chain (Ii), class II transactivator (CIITA) and DRA in an untransformed, pure thyrocyte strain HTV-59A. Here we report that both HLA-DMB mRNA and the protein are expressed in thyrocytes and that CIITA expression is enhanced by interferon-gamma (IFN-gamma) treatment and occurs before DMB, Ii and DRA up-regulation, suggesting CIITA expression is a requirement for antigen processing in thyrocytes. These results indicate that thyrocytes are capable of antigen processing and possibly antigen presentation to T cells.

Recombinant interferon alpha (rIFN-alpha) does not potentiate the effect of iodine excess on the development of thyroid abnormalities in patients with HCV chronic active hepatitis

OBJECTIVE

To determine whether the administration of pharmacological quantities of iodine during interferon-alpha (rIFN-alpha) treatment of chronic viral hepatitis B and C (HCV) would exacerbate the potential adverse effects of rIFN alpha on thyroid function.

DESIGN

Thyroid function tests were carried out in 48 euthyroid patients before and during rIFN-alpha therapy of HCV. Twenty-one of these patients were also treated with 10 drops saturated solution of potassium iodine (SSKI, approximately 350 mg iodine daily). Eight patients with HCV but not treated with rIFN-alpha received 10 drops SSKI.

PATIENTS

All patients were enthyroid prior to rIFN-alpha therapy for HCV or iodine and thyroid function tests were similar in the three groups.

MEASUREMENTS

Serum free T4, free T3, and TSH concentrations were measured prior to and at 30 and 60 days of rIFN-alpha therapy in the three groups of patients. The serum TSH response to TRH was assessed before rIFN-alpha therapy and on day 60. Thyroid peroxidase antibodies were measured before and during therapy.

RESULTS

During the 2-month study period, similar small but significant decreases in serum FT4 and FT3 and compensatory small significant increases in TSH concentrations were observed in the patients treated with rIFN-alpha + iodine and iodine alone but not in the patients receiving rIFN-alpha alone. Abnormal thyroid function tests were observed more frequently in patients receiving rIFN-alpha + iodine and iodine alone compared to those receiving rIFN-alpha alone.

CONCLUSIONS

Excess iodine administered to patients treated with rIFN-alpha induced small changes in thyroid function similar to those observed in patients treated with iodine alone. Thus, rIFN-alpha and iodine do not appear to be synergistic in the development of abnormal thyroid function tests over a 2-month treatment period.

Thyrocyte class I and class II upregulation is a secondary phenomenon and does not contribute to the pathogenesis of autoimmune thyroid disease

It has been proposed elsewhere that thyrocyte (TEC) class I expression plays a central role in the pathogenesis of autoimmune thyroid disease (AITD). We have studied thyroid xenografts from patients with Graves' disease (GD) and normal (paranodular) (N) tissues in nude and severe combined immunodeficient (SCID) mice. TEC class I and II expression are markedly increased in GD, as compared with N thyroids. When these tissues are transplanted to nude mice in which the immune environment is deleted from the thyroid grafts, TEC class I and class II expression decline to low levels; interferon-gamma (IFN-gamma) but not interferon-alpha (IFN-alpha) will then upregulate TEC class I and class II expression in these N and GD nude xenografts. In SCID mouse xenografts, GD tissue shows higher TEC class I and II expression compared with N. In these SCID mice, both IFN-alpha and IFN-gamma will stimulate TEC class I and II expression further in both GD and N. However, only IFN-alpha increases thyroid antibody (TAb) production from GD SCID grafts, whereas IFN-gamma causes a rise in GD TEC class I and II expression, but no significant increase in TAb. Moreover, in N SCID grafts, despite a rise in TEC class I and II expression induced by both IFNs, no TAb could be detected. Because an immune environment is necessary for TEC class I and II upregulated expression, we conclude that such upregulation is a secondary phenomenon. Because there was dissociation between the stimulation of TEC class I and II expression versus the production of TAb, then at least under these experimental conditions, there is no support for a role for TEC class I and class II upregulation in the pathogenesis of AITD.

Amiodarone and the thyroid: a practical guide to the management of thyroid dysfunction induced by amiodarone therapy

Amiodarone induces predictable changes in thyroid function tests that are largely explicable in terms of the physiological effects of iodide excess and inhibition of deiodinase activity. Clinically relevant thyroid dysfunction is not uncommon during amiodarone therapy, and requires careful diagnosis and treatment. The diagnosis and management of thyrotoxicosis is probably best supervised by a specialist endocrinologist. Control of hypothyroidism can generally be achieved simply by the addition of T4 to the therapeutic regimen, ideally after an initial assessment by an endocrinologist. The frequency with which amiodarone causes thyroid and other complications serves to emphasize the need for rational prescribing and long-term cardiological follow up.

Analysis of susceptibility of NOD mice to spontaneous and experimentally induced thyroiditis

Beside diabetes, non-obese diabetic (NOD) mice develop sporadic lymphoid infiltration of the thyroid gland, mimicking Hashimoto's thyroiditis. We have examined the prevalence of those manifestations in NOD mice, the influence of the major histocompatibility complex (MHC) and the association with autoantibodies. The incidence at 1 year is of 14.3% in wild-type NOD mice versus 19.6% in congenic NOD.H2k mice. The moderate, but statistically significant difference, based on the analysis of 161 NOD and 169 NOD.H2k mice, suggests that MHC genes partially control spontaneous NOD thyroiditis. Autoantibodies against thyroglobulin (Tg) are mouse specific and their presence correlates closely with thyroiditis. The strong correlation between cellular and humoral anomalies therefore resembles Hashimoto's thyroiditis. NOD and NOD.H2k mice actively immunized against Tg develop severe chronic lesions with epithelium necrosis and interstitial tissue fibrosis. Most interestingly, those lesions do not regress spontaneously as in CBA/J mice. Paradoxically, the response to Tg of lymph node cells from NOD mice is weaker both in proliferation and cytokine production. The defect is most evident for interferon-gamma-producing T cells and is reflected in the marked deficit in IgG2a antibodies. Thus a moderate anti-Tg response seems to favor chronicity of thyroiditis. In conclusion, NOD and NOD.H2k mice offer a unique opportunity of analyzing the factors leading to immune chronicity in a genetic context which promotes autoimmune endocrinopathies.

Cytokines and thyroid function

Cytokines play a crucial role in autoimmune thyroid disease (ATD) through various mechanisms. They are produced in the thyroid by intrathyroidal inflammatory cells, in particular lymphocytes, as well as by the thyroid follicular cells (TFC) themselves and may thus act in a cascade to enhance the autoimmune process (Fig. 1). Cytokines upregulate the inflammatory reaction through stimulation of both T and B cells, resulting in antibody production and tissue injury. In addition, intrathyroidal cytokines induce immunological changes in TFC including enhancement of both major histocompatibility complex (MHC) class I and class II molecule expression, and upregulation of adhesion and complement regulatory molecule expression. Cytokines can also modulate both growth and function of TFC and have a role in extrathyroidal complications of ATD, most importantly thyroid-associated ophthalmopathy (TAO), where they induce fibroblast proliferation and enhance the production of glycosaminoglycans (GAG), resulting in proptosis and the other clinical features of the disease. In addition to these effects, exogenous administration of cytokines has been associated with impairment of thyroid function ranging from the appearance of autoantibodies alone to the development of frank thyroid dysfunction. Cytokines have also been implicated in subacute thyroiditis (SAT) and amiodarone-induced thyroid dysfunction, as well as in thyroid function abnormalities occurring in patients with non-thyroidal illnesses (NTI). Genetic variations in cytokine genes represent potential risk factors for ATD, and disease associations have been described for polymorphisms in IL-1ra and TNF beta genes. Recent experimental evidence suggests the possibility of novel cytokine-based therapeutic approaches for ATD and its complications, in particular TAO.

Mouse thyroglobulin: conservation of sequence homology in C-terminal immunogenic regions of thyroglobulin

cDNA encoding 287 amino acids of the C-terminus of mouse thyroglobulin was cloned and sequenced. The amino acid homology between mouse and rat thyroglobulin was 96%, and was 78% between mouse and human. It was found that mouse thyroglobulin completely shared homology with two thyroiditogenic peptides described by other investigators. These findings are consistent with our hypothesis that in murine experimental thyroiditis, the primary thyroiditogenic epitopes are encoded by mouse-specific regions of thyroglobulin.

Natural course of subclinical hypothyroidism in Down's syndrome: prospective study results and therapeutic considerations

Pathogenesis, natural course and therapeutic management of subclinical hypothyroidism (SH) in Down's syndrome (DS) remain object of debate in literature. In the present study thyroid function, antithyroid antibody (ATA) prevalence and serum lipid concentrations were investigated in a group of 344 Down patients (DP) and data were compared with those obtained from a control group of 257 age and sex matched healthy subjects. Thyroid function and ATA prevalence were also studied in 120 parents of DP. SH prevalence was clearly higher in DP (32.5% of cases) than in controls (1.1%) and parents (0%). Similarly, ATA prevalence was higher in DP (18% of cases) than in controls (5.8%) and parents (6.6%). In spite of this, no correlation was found in DP between SH and ATA prevalences, since ATA were detected in 18.7% of SH-DP and in 15.8% of euthyroid DP. Thus, circulating ATA were not detected in the majority of SH-DP. No significant differences regarding T4, FT4, T3 and serum lipid levels among SH and euthyroid DP and controls were found. Moreover, TSH levels were only slightly increased, generally less than 10 microU/ml, in most cases of SH-DP. Follow-up was longer than 24 months (range 2-7 years, mean 3.1) in a group of 201 DP: two different patterns of SH course were observed, mainly depending on the presence or the absence of circulating ATA. In particular, 35.7% of ATA-positive SH-DP developed a clinically evident thyroid disease (overt hypothyroidism or hyperthyroidism), while no similar case was recorded among ATA-negative SH-DP.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroglobulin-reactive T lymphocytes in thyroiditis-prone BB/Wor rats

Autoimmune lymphocytic thyroiditis (LT) is a common cause of primary hypothyroidism. Autoreactive T lymphocytes are clearly associated with this disorder, but their pathogenic role in spontaneously occurring LT remains to be established. In the present study, thyroglobulin-reactive T lymphocytes were cultured from young, unprimed LT-prone BB/Wor rats before the age of spontaneously-occurring LT. Although similar investigations have been conducted in animal models for experimental autoimmune thyroiditis (EAT), this study is unique because it examines a mammalian model for spontaneous LT. Splenic T lymphocytes were isolated from unprimed 30 to 45-day-old Fisher and LT-prone BB/Wor rats before the onset of LT, then tested for activation by normal (NL), iodine-poor (LI), and iodine-rich (HI) rat thyroglobulin (Tg) in bulk proliferation assay. BB/Wor rat lymphocytes were activated by all three Tg preparations, but Fisher lymphocytes were unresponsive (BB/Wor vs Fisher; p < 0.0001, Student's t-test). There was no difference between BB/Wor rat responses to the three preparations (p > 0.05, ANOVA). Based on these results, we conclude that Tg-responsive T lymphocytes can be cultured from young, unprimed LT-prone BB/Wor rats. Isolating such lymphocytes before the onset of histologically demonstrable LT strengthens the argument that antigen-specific T cells have a pathogenic role in the development of spontaneous autoimmune thyroid disease. The fact that these lymphocytes recognized normal, iodine-rich and iodine poor preparations of rat Tg equally well suggest that unlike the EAT model, spontaneously-occurring Tg-reactive T cells are not influenced by thyroglobulin's iodine content.

Perforin expression by thyroid-infiltrating T cells in autoimmune thyroid disease

Infiltration of the thyroid gland by lymphocytes is a hall-mark of autoimmune thyroid disease; it is particularly evident in Hashimoto's thyroiditis but is also seen in most patients with Graves' disease. Infiltrating cells are comprised primarily of T lymphocytes, of which only a minority appears to be activated. Their precise pathogenic role is largely unknown. Since perforin has been a marker for functionally activated cytotoxic T cells in situ we elected to assess the presence of perforin-containing cells in thyroid-infiltrating lymphocytes and establish their phenotype. Cells were isolated from seven subtotal thyroidectomy specimens, five from patients with Graves' disease and two with Hashimoto's thyroiditis. The novel findings were as follows: CD4+ perforin-containing T cells occurred only in Hashimoto's glands, suggesting a class II-restricted component of cytotoxicity; in Graves' disease, and to a lesser extent in Hashimoto's, perforin-expressing cells were primarily T cell receptor alpha beta- CD4-CD8- (double negative); double negative perforin-containing cells in peripheral blood of normal individuals were largely gamma delta + T cells. In Hashimoto's samples, the predominant population of T cells expressing perforin was CD8+. By comparison, in studies of the synovial fluid of knee joints from patients with rheumatoid arthritis only a minor population of the perforin-containing cells was double-negative. The data suggest significant differences in cytotoxic autoimmune mechanisms between the two autoimmune thyroid diseases. Functional characterization of double-negative T cells is necessary to define their role in autoimmunity.

Adhesion molecules from the LFA-1/ICAM-1,3 and VLA-4/VCAM-1 pathways on T lymphocytes and vascular endothelium in Graves' and Hashimoto's thyroid glands

Lymphocytic infiltration of the thyroid gland in autoimmune thyroid disorders requires, as a first step, their attachment to endothelial cells (EC) and subsequently, their interaction with thyrocytes and extracellular matrix proteins. A number of different ligand molecules have been identified to mediate the interaction between EC and leukocyte subpopulations. In this study, we examined by flow cytometry and immunohistochemical techniques, the expression of integrin receptors and their counter-receptors by infiltrating lymphocytes and vascular endothelium in thyroid glands from patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT). A high proportion of GD intrathyroidal T lymphocytes expressed the CD69 and gp95/85 (Ea2) activation antigens as well as an increased number of LFA-alpha L, VLA-alpha 1, -alpha 4, -alpha 5, and beta 1 integrin receptors, as compared with peripheral blood T lymphocytes from the same patients. The expression of intercellular adhesion molecule (ICAM)-1 was increased in EC from GD and HT thyroids. In addition, an up-regulated de novo expression of vascular cell adhesion molecule (VCAM)-1 was found in EC in GD and HT thyroids, with no reactivity in control thyroids. Dendritic cells in thyroid lymphoid follicles were also positive for ICAM-1 and VCAM-1. In addition, most of intrathyroidal mononuclear cells expressed the ICAM-3 adhesion molecule. This enhanced expression of ICAM-1 and VCAM-1 by thyroid EC in GD and HT may reflect their ability to regulate leukocyte trafficking and activation by means of the expression of specific ligand molecules. Our data suggest that both the LFA-1/ICAM-1, ICAM-3 and VLA-4/VCAM-1 pathways could play a relevant role in localizing and perpetuating the autoimmune response in the thyroid gland in autoimmune thyroid disorders.