Antibodies producing complement-mediated thyroid cytotoxicity in patients with atrophic or goitrous autoimmune thyroiditis

Changes in TgAb and TPOAb titers are greater in thyrotoxicosis than isolated hypothyroidism induced by PD-1 blockade

Anti-thyroglobulin antibodies (TgAb) and/or anti-thyroid peroxidase antibodies (TPOAb) positivity at baseline is a risk marker for thyroid immune-related adverse events (thyroid-irAEs) in anti-programmed cell death-1 antibody (PD-1-Ab) treatment; however, it is unknown if TgAb and TPOAb titers are associated with clinical characteristics of thyroid-irAEs. Among 586 patients treated with PD-1-Ab at Nagoya University Hospital between 2 November 2015 and 30 September 2021, 57 patients developed thyroid-irAEs (thyrotoxicosis [n = 38]; hypothyroidism without prior thyrotoxicosis {isolated hypothyroidism} [n = 19]) in whom thyroid function, and TgAb and TPOAb titers were determined at baseline and at the onset. The changes in TgAb (median, 54.8 vs. 0.2 IU/mL; p = 0.002) and TPOAb titers (31.6 vs. 0 IU/mL; p = 0.032) from baseline to onset of developing thyroid-irAEs were greater in patients with thyrotoxicosis than patients with isolated hypothyroidism. Higher TgAb and TPOAb titers, and the TgAb titer at baseline were associated with an earlier onset of thyrotoxicosis and higher peak free thyroxine levels, respectively. Twenty-eight patients who developed hypothyroidism after thyrotoxicosis had higher TgAb (54.5 vs. 10.7 IU/mL; p = 0.011) and TPOAb titers at baseline (46.1 vs. 9.0 IU/mL; p < 0.001) and greater changes in TgAb (61.7 vs. 7.8 IU/mL; p = 0.025) and TPOAb titers (52.8 vs. -0.8 IU/mL; p < 0.001) than patients who did not develop hypothyroidism. The TgAb titer at baseline and changes in the TgAb and TPOAb titers were greater in patients with thyrotoxicosis than patients with isolated hypothyroidism, suggesting that the magnitude of the thyroid autoimmune response reflects the clinical types of thyroid-irAEs.

Peripheral immunophenotyping of AITD subjects reveals alterations in immune cells in pediatric vs adult-onset AITD

Autoimmune thyroid disease (AITD) is caused by aberrant activation of the immune system allowing autoreactive B and T cells to target the thyroid gland leading to disease. Although AITD is more frequently diagnosed in adults, children are also affected but rarely studied. Here, we performed phenotypic and functional characterization of peripheral blood immune cells from pediatric and adult-onset AITD patients and age-matched controls using mass cytometry. Major findings indicate that unlike adult-onset AITD patients, pediatric AITD patients exhibit a decrease in anergic B cells (B_ND) and DN2 B cells and an increase in immature B cells compared to age-matched controls. These results indicate alterations in peripheral blood immune cells seen in pediatric-onset AITD could lead to rapid progression of disease. Hence, this study demonstrates diversity of AITD by showing differences in immune cell phenotypes and function based on age of onset, and may inform future therapies.

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Penetrance of high-risk HLA-DR3 haplotype is higher in pediatric AITD patients

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Pediatric AITD patients display altered frequency of autoreactive B cell subsets

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Immune cell subset frequency and function is similar in adult AITD and controls

Relationship of the platelet distribution width/platelet count ratio with thyroid antibody levels in patients with Hashimoto's thyroiditis

Objective

I investigated whether the platelet distribution width/platelet count (PDW/PC) ratio, which is an inexpensive and simple test performed for almost all patients, is applicable in the follow-up of patients with Hashimoto’s thyroiditis and examined the relationship of this ratio with thyroperoxidase and thyroglobulin antibody levels.

Materials and methods

The study groups consisted of 67 patients with Hashimoto’s thyroiditis and 17 controls. All participants were aged 20 to 75 and treated the Internal Medicine outpatient clinic of my institution. The PDW/PC ratio and thyroid antibody levels were retrospectively evaluated in patients with normal liver and renal function and normal white blood cell counts, hemoglobin levels, and hematocrit levels.

Results

Thyroid antibody levels were significantly higher in patients with Hashimoto’s thyroiditis than in controls. PC was higher in patients with Hashimoto’s thyroiditis, whereas the PDW/PC ratio was lower. However, these differences were not statistically significant.

Conclusion

In this study, I did not find a statistically significant relationship between thyroid antibody levels and PDW/PC. However, a weak correlation between these variables was identified.

Multiple Autoimmune Syndrome With Alopecia Universalis and Immune Thrombocytopenic Purpura

Multiple autoimmune syndrome (MAS) is a condition characterized by three or more autoimmune disorders in the same individual. The development of MAS involves genetic, immunological, and infectious factors. Here we report a case of a 40-year-old man who presented with four autoimmune diseases, namely autoimmune hypothyroidism, alopecia universalis, celiac disease, and immune thrombocytopenic purpura (ITP), which leads to a diagnosis of MAS. However, the patient does not fit in any category of MAS classification. In addition to the need for continued surveillance for the development of new autoimmune disease in predisposed patients, this case report suggests an additional fourth category of the classification of MAS that includes autoimmune hypothyroidism, alopecia universalis, celiac disease, and ITP.

The Contribution of IgG Glycosylation to Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) and Complement-Dependent Cytotoxicity (CDC) in Hashimoto's Thyroiditis: An in Vitro Model of Thyroid Autoimmunity

Antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) are involved in destruction of thyroid tissue in Hashimoto’s thyroiditis (HT). N-glycosylation of the Fc fragment affects the effector functions of IgG by enhancing or suppressing the cytotoxicity effect. The aim of the present study was to assess the impact of HT-specific IgG glycosylation in ADCC and CDC, using in vitro models. The normal thyroid Nthy-ori 3-1 cell line and thyroid carcinoma FTC-133 cells were used as the target cells. Peripheral blood mononuclear cells (PBMCs) from healthy donors and the HL-60 human promyelotic leukemia cell line served as the effector cells. IgG was isolated from sera of HT and healthy donors and then treated with α2-3,6,8-neuraminidase to cut off sialic acids (SA) from N-glycans. We observed more intensive cytotoxicity in the presence of IgG from HT patients than in the presence of IgG from healthy donors. Removal of SA from IgG N-glycans increased ADCC intensity and reduced CDC. We conclude that the enhanced thyrocyte lysis resulted from the higher anti-TPO content in the whole IgG pool of HT donors and from altered IgG glycosylation in HT autoimmunity.

Thyrotropin Receptor Blocking Antibodies

Autoantibodies (Ab) against the thyroid-stimulating hormone receptor (TSHR) are frequently found in autoimmune thyroid disease (AITD). Autoantibodies to the TSHR (anti-TSHR-Ab) may mimic or block the action of TSH or be functionally neutral. Measurement of anti-TSHR-Ab can be done either via competitive-binding immunoassays or with functional cell-based bioassays. Antibody-binding assays do not assess anti-TSHR-Ab functionality, but rather measure the concentration of total anti-TSHR binding activity. In contrast, functional cell-based bioassays indicate whether anti-TSHR-Ab have stimulatory or blocking activity. Historically bioassays for anti-TSHR-Ab were research tools and were used to study the pathophysiology of Graves' disease and Hashimoto's thyroiditis. In the past, bioassays for anti-TSHR-Abs were laborious and time-consuming and varied widely in performance from laboratory to laboratory. Recent advances in the development of cell-based assays, including the application of molecular engineering, have led to significant improvements that have enabled bioassays to be employed routinely in clinical laboratories. The prevalence and functional significance of TSHR blocking autoantibodies (TBAb) in autoimmune hypothyroidism has been less well investigated compared to TSHR stimulating Ab. There is an increasing body of data, however, that demonstrate the clinical utility and relevance of TBAb, and thus the importance of TBAb bioassays, in the diagnosis and management of patients with AITD. In the present review, we summarize the different methods used to measure TBAb, and discuss their prevalence and clinical relevance.

The Evolving Story of Autoantibodies in Pemphigus Vulgaris: Development of the "Super Compensation Hypothesis"

Emerging data and innovative technologies are re-shaping our understanding of the scope and specificity of the autoimmune response in Pemphigus vulgaris (PV), a prototypical humorally mediated autoimmune skin blistering disorder. Seminal studies identified the desmosomal proteins Desmoglein 3 and 1 (Dsg3 and Dsg1), cadherin family proteins which function to maintain cell adhesion, as the primary targets of pathogenic autoAbs. Consequently, pathogenesis in PV has primarily considered to be the result of anti-Dsg autoAbs alone. However, accumulating data suggesting that anti-Dsg autoAbs by themselves cannot adequately explain the loss of cell-cell adhesion seen in PV, nor account for the disease heterogeneity exhibited across PV patients has spurred the notion that additional autoAb specificities may contribute to disease. To investigate the role of non-Dsg autoAbs in PV, an increasing number of studies have attempted to characterize additional targets of PV autoAbs. The recent advent of protein microarray technology, which allows for the rapid, highly sensitive, and multiplexed assessment of autoAb specificity has facilitated the comprehensive classification of the scope and specificity of the autoAb response in PV. Such detailed deconstruction of the autoimmune response in PV, beyond simply tracking anti-Dsg autoAbs, has provided invaluable new insights concerning disease mechanisms and enhanced disease classification which could directly translate into superior tools for prognostics and clinical management, as well as the development of novel, disease specific treatments.

Is only Thyroid Peroxidase Antibody Sufficient for Diagnosing Chronic Lymphocytic Thyroiditis?

Objectives:

Recently, only anti-thyroid peroxidase (anti-TPO) has been suggested as an autoantibody in the diagnosis of chronic lymphocytic thyroiditis (CLT). In contrast, anti-thyroglobulin (anti-Tg) positivity has also been reported to be important. To evaluate this relationship more clearly, we planned to retrospectively investigate the autoantibody levels of the patients who underwent thyroid surgery for various reasons and those with CLT in postoperative pathology.

Methods:

We evaluated 670 patients who underwent thyroid surgery (total/subtotal thyroidectomy) for various reasons at our hospital between January 2015 and March 2017. Patients with indications of Graves’ disease, toxic multinodular goiter, and all malignancies except for thyroid papillary carcinoma (TPC) were excluded. Eighty-nine patients whose pathology findings were compatible with CLT and preoperative thyroid autoantibodies were identified enrolled in to the study. Patients with absence and presence of thyroid antibodies were included in the seronegative CLT group and seropositive CLT group, respectively. In addition, patients were divided into thyroid papillary carcinoma (TPC) and benign groups.

Results:

According to the study criteria, 89 (83 females, six males) (mean age, 46.08±11.19 years) patients who had preoperatively identified autoantibodies were detected. Anti-TPO positivity was found in 47 (52.8%) cases, whereas anti-Tg positivity was found in 49 (55.1%). Only anti-TPO positivity was found in 18 (20.2%) cases, whereas only anti-Tg positivity was detected in 20 (22.5%). Twenty-two (24.7%) of the patients were seronegative. On comparing the seronegative and seropositive groups, seronegativity was more frequent in male patients (p=0.03). Thyroid-stimulating hormone was found to be significantly higher in the seropositive group (p=0.01). TPC was detected in 36 (40.4%) of all cases. No difference regarding age, thyroid function tests, and antibody levels was found between the benign and TPC groups.

Conclusion:

Although all of our cases were histopathologically diagnosed with CLT, serologically, 75.3% of thyroid autoimmunities could be shown when both antibodies were evaluated together. When only anti-TPO was considered, this rate decreased to 52.8%. Therefore, anti-Tg appears to be still important in showing autoimmunity. Prospective studies are needed to evaluate this relationship more clearly.

Immunological changes of T helper cells in flow cytometer-sorted CD4+ T cells from patients with Hashimoto's thyroiditis

Recent incidence rates for Hashimoto's thyroiditis (HT) and hypothyroidism are higher than those of previous studies. Previous studies indicated that T helper cells may have a major role in the pathogenesis and development of HT, but there is no consensus in the literature. The aim of the present study was to explore the peripheral T helper cell response in the different stages of HT. In this cross-sectional study, we performed flow cytometry analysis to determine the various T cell subsets of 389 patients with HT (34 patients with HT who developed overt hypothyroidism, and 148 patients with HT who developed subclinical hypothyroidism), as well as 51 healthy controls. Anti-thyroid antibodies, and thyroid function were measured. The findings demonstrated that the proportion of peripheral Th1 cells was significantly lower in patients with HT than in healthy euthyroid controls (P<0.001), and the proportion of peripheral Th2, Treg cells was significantly higher in patients with HT than in healthy euthyroid controls (P<0.001). Therefore the Th1/Th2 ratio was significantly lower in HT patients than in healthy euthyroid controls (P<0.001). The Th17/Treg ratio in HT patients was significantly lower than that control subjects (P<0.001). Th1 proportions in patients with overt hypothyroidism HT were significantly higher than in subclinical hypothyroidism HT patients (P=0.031). In conclusion, the findings of the present study demonstrated that there is an increased immune deviation of Th1 lymphocytes and compensatory accelerating activity of Treg cells in HT, and the peripheral Th1 cells from the HT patients correlated to the developmental stage of hypothyroidism.

IL-34 Expression Is Reduced in Hashimoto's Thyroiditis and Associated With Thyrocyte Apoptosis

Hashimoto's thyroiditis (HT) is a common autoimmune disease accompanied by lymphocyte infiltration and thyroid tissue destruction. IL-34 was first described in 2008, and its involvement in the development of many autoimmune diseases has been recently identified. However, whether IL-34 is a regulatory factor in HT is unclear. Here, we demonstrate that IL-34 is expressed on thyroid follicular epithelial cells and that IL-34 expression is significantly reduced in thyroid tissue in patients with HT and spontaneous autoimmune thyroiditis (SAT) models. Serum IL-34 levels in patients with HT are also significantly reduced. In addition, IL-34 is associated with thyroid autoantibodies in both thyroid tissue and serum. Furthermore, our data show that IL-34 participates in the apoptosis resistance of thyrocytes in HT induced by CSF-1R and may be a potential indicator for evaluating thyrocyte damage.

Thyroid peroxidase (TPO) expressed in thyroid and breast tissues shows similar antigenic properties

BACKGROUND

Thyroid peroxidase (TPO) is essential for physiological function of the thyroid gland. The high prevalence of thyroid peroxidase antibodies (TPOAbs) in patients with breast cancer and their protective role had previously been demonstrated, indicating a link between breast cancer and thyroid autoimmunity. Recently, TPO was shown to be present in breast cancer tissue samples but its antigenicity has not been analyzed.

METHODS

In this study, we investigated TPO expression levels in a series of fifty-six breast cancer samples paired with normal (peri-tumoral) tissue and its antigenic activity using a panel of well-characterized murine anti-human TPOAbs.

RESULTS

We have shown that TPO transcripts were present in both normal and cancer tissue samples, although the amounts in the latter were reduced. Additionally, we observed that TPO levels are lower in more advanced cancers. TPO protein expression was confirmed in all tissue samples, both normal and cancerous. We also found that the antigenicity of the immunodominant regions (IDRs) in breast TPO resembles that of thyroid TPO, which is crucial for effective interactions with human TPOAbs.

CONCLUSIONS

Expression of TPO in breast cancer together with its antigenic activity may have beneficial effects in TPOAb-positive breast cancer patients. However, further studies are needed to confirm the beneficial role of TPOAbs and to better understand the underlying mechanism.

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.

The relationship between procalcitonin and thyroid autoantibodies in patients with autoimmune thyroiditis

BACKGROUND

The aim of this study is to investigate the serum levels of procalcitonin and its association with autoantibodies in patients with euthyroid Hashimoto's thyroiditis.

METHODS

A total of 80 participants were included in the study; 40 of which were newly diagnosed with Hashimoto's thyroiditis, aged over 18, and 40 of which were healthy volunteers. The serum levels of procalcitonin were measured by enzyme-linked immunosorbent assay kit. Thyroid function tests were analyzed in hormone laboratory with Electro-chemiluminescence immunoassay.

RESULTS

Hashimoto's thyroiditis patients had higher median procalcitonin levels than those of the control group (34.3 pg/mL vs 27.8 pg/mL respectively; P=.037). Also, male patients had higher median procalcitonin levels as compared to female patients (37 pg/mL vs 27 pg/mL respectively; P=.013). In the Hashimoto's thyroiditis group, procalcitonin level was positively correlated with anti-thyroglobulin and anti-thyroid peroxidase levels (r=.559, P<.001; r=634, P<.001, respectively). The procalcitonin and anti-thyroid peroxidase levels were identified to be an independent predictor in diagnosis of Hashimoto's thyroiditis.

CONCLUSIONS

The fact that procalcitonin was found to be correlated with thyroid autoantibodies and found to be an independent risk factor for Hashimoto's thyroiditis in the regression analysis in the framework of this study urges us to think that procalcitonin may be associated with the autoimmunity.

Modelling of Thyroid Peroxidase Reveals Insights into Its Enzyme Function and Autoantigenicity

Thyroid peroxidase (TPO) catalyses the biosynthesis of thyroid hormones and is a major autoantigen in Hashimoto's disease--the most common organ-specific autoimmune disease. Epitope mapping studies have shown that the autoimmune response to TPO is directed mainly at two surface regions on the molecule: immunodominant regions A and B (IDR-A, and IDR-B). TPO has been a major target for structural studies for over 20 years; however, to date, the structure of TPO remains to be determined. We have used a molecular modelling approach to investigate plausible modes of TPO structure and dimer organisation. Sequence features of the C-terminus are consistent with a coiled-coil dimerization motif that most likely anchors the TPO dimer in the apical membrane of thyroid follicular cells. Two contrasting models of TPO were produced, differing in the orientation and exposure of their active sites relative to the membrane. Both models are equally plausible based upon the known enzymatic function of TPO. The "trans" model places IDR-B on the membrane-facing side of the myeloperoxidase (MPO)-like domain, potentially hindering access of autoantibodies, necessitating considerable conformational change, and perhaps even dissociation of the dimer into monomers. IDR-A spans MPO- and CCP-like domains and is relatively fragmented compared to IDR-B, therefore most likely requiring domain rearrangements in order to coalesce into one compact epitope. Less epitope fragmentation and higher solvent accessibility of the "cis" model favours it slightly over the "trans" model. Here, IDR-B clusters towards the surface of the MPO-like domain facing the thyroid follicular lumen preventing steric hindrance of autoantibodies. However, conformational rearrangements may still be necessary to allow full engagement with autoantibodies, with IDR-B on both models being close to the dimer interface. Taken together, the modelling highlights the need to consider the oligomeric state of TPO, its conformational properties, and its proximity to the membrane, when interpreting epitope-mapping data.

Immune disorders in Hashimoto's thyroiditis: what do we know so far?

This review of literature attempts to identify the factors that are involved in the pathogenesis of Hashimoto thyroiditis, an immune defect in an individual with genetic susceptibility accompanied with environmental factors. The frequency of Hashimoto's disease is a growing trend and among Caucasians it is estimated at approximately 5%. The dysfunction of the gland may be clinically evident (0.1-2% of the population) or subclinical (10-15%). The pathology is diagnosed five to ten times more often in women than men and its incidence increases with the age (the peak of the number of cases is between 45 and 65); however, it can also be diagnosed in children. The pathogenesis of Hashimoto's thyroiditis is still not fully comprehended. In the etiology of Hashimoto thyroiditis excessively stimulated T CD4+ cells are known to play the most important role. Recent research has demonstrated an increasing role of newly discovered cells such as Th17 (CD4+IL-17+) or T regulatory cells (CD4+CD25+(high)FoxP3+) in the induction of autoimmune disorders. The process of programmed cell death also plays an equally important role in the pathogenesis and the development of hypothyroidism.

Autoimmune thyroid disorders

Purpose of Review. Studies have been published in the field of autoimmune thyroid diseases since January 2005. The review is organized into areas of etiology, autoimmune features, autoantibodies, mechanism of thyroid cell injury, B-cell responses, and T-cell responses. Also it reviews the diagnosis and the relationship between autoimmune thyroid disease, neoplasm, and kidney disorders. Recent Findings. Autoimmune thyroid diseases have been reported in people living in different parts of the world including North America, Europe, Baalkans, Asia, Middle East, South America, and Africa though the reported figures do not fully reflect the number of people infected per year. Cases are unrecognized due to inaccurate diagnosis and hence are treated as other diseases. However, the most recent studies have shown that the human autoimmune thyroid diseases (AITDs) affect up to 5% of the general population and are seen mostly in women between 30 and 50 years. Summary. Autoimmune thyroid disease is the result of a complex interaction between genetic and environmental factors. Overall, this review has expanded our understanding of the mechanism involved in pathogenesis of AITD and the relationship between autoimmune thyroid disease, neoplasm, and kidney disease. It has opened new lines of investigations that will ultimately result in a better clinical practice.

Autoimmune thyroid disorders-An update

BACKGROUND

Autoimmune thyroid disease (AITD), a common organ specific autoimmune disorder is seen mostly in women between 30-50 yrs of age. Thyroid autoimmunity can cause several forms of thyroiditis ranging from hypothyroidism (Hashimoto's thyroiditis) to hyperthyroidism (Graves'Disease). Prevalence rate of autoimmune mediated hypothyroidism is about 0.8 per 100 and 95% among them are women. Graves' disease is about one tenth as common as hypothyroidism and tends to occur more in younger individuals. Both these disorders share many immunologic features and the disease may progress from one state to other as the autoimmune process changes. Genetic, environmental and endogenous factors are responsible for initiation of thyroid autoimmunity. At present the only confirmed genetic factor lies in HLA complex (HLA DR-3) and the T cell regulatory gene (CTLA 4). A number of environmental factors like viral infection, smoking, stress & iodine intake are associated with the disease progression. The development of antibodies to thyroid peroxidase (TPO) thyroglobulin (TG) and Thyroid stimulating hormone receptor (TSH R) is the main hallmark of AITD. Circulating T Lymphocytes are increased in AITD and thyroid gland is infiltrated with CD4+ and CD8+ T Cells. Wide varieties of cytokines are produced by infiltrated immune cells, which mediate cytotoxicity leading to thyroid cell destruction. Circulating antibodies to TPO and TG are measured by immunofluorescense, hemagglutination, ELISA & RIA. TSHR antibodies of Graves' disease can be measured in bioassays or indirectly in assays that detect antibody binding to the receptor.

Human recombinant anti-thyroperoxidase autoantibodies: in vitro cytotoxic activity on papillary thyroid cancer expressing TPO

Background:

Thyroid cancers are difficult to treat due to their limited responsiveness to chemo- and radiotherapy. There is thus a great interest in and a need for alternative therapeutic approaches.

Results:

We studied the cytotoxic activity of anti-thyroperoxidase autoantibodies (anti-TPO aAbs, expressed in baculovirus/insect cell (B4) and CHO cells (B4′) or purified from patients' sera) against a papillary thyroid cancer (NPA) cell line. Anti-TPO aAbs from patients' sera led to a partial destruction of NPA cell line by complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC) and exhibited an anti-proliferative activity. Comparison of the cytotoxic activity of anti-TPO aAbs shows that B4′ induced an anti-proliferative effect and a better ADCC than B4, but a lower one than anti-TPO aAbs from patients' sera. Antibody-dependent cell-mediated cytotoxicity was increased when human peripheral blood mononuclear cells were used as effector cells, suggesting that FcγRs, CD64, CD32 and CD16 are involved. Indeed, anti-TPO aAbs from patients' sera, but not B4 and B4′, exhibited CDC activity.

Conclusions:

These data indicate that anti-TPO aAbs display moderate ADCC and anti-proliferative activities on NPA cells; IgG glycosylation appears to be important for cytotoxic activity and ADCC efficiency depends on FcγR-bearing cells. Finally, recombinant human anti-TPO aAbs cannot yet be considered as an optimal tool for the development of a novel therapeutic approach for thyroid cancer.

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.

Distribution of immunoglobulin G subclasses of anti-thyroid peroxidase antibody in sera from patients with Hashimoto's thyroiditis with different thyroid functional status

The mechanism of disease progression in Hashimoto's thyroiditis (HT) is still unclear. Anti-thyroid peroxidase antibody (TPOAb), a diagnostic hallmark of HT, is principally of the immunoglobulin G (IgG) isotype, and it appears to be a response to thyroid injury. The aim of our study was to evaluate the distribution of IgG subclasses of TPOAb in sera from patients with HT with different thyroid functional status. Sera from 168 patients with newly diagnosed HT were collected and divided into three groups according to thyroid function: patients with hypothyroidism (n = 66), subclinical hypothyroidism (n = 60) and euthyroidism (n = 42). Antigen-specific enzyme-linked immunosorbent assay was used to detect the distribution of TPOAb IgG subclasses. The prevalence of TPOAb IgG subclasses in all patients' sera with HT was IgG1 70.2%, IgG2 35.1%, IgG3 19.6% and IgG4 66.1% respectively. The prevalence of IgG2 in sera from patients with hypothyroidism (51.5%) was significantly higher than that of subclinical hypothyroidism (33.3%) (P < 0.05), and the latter was also significantly higher than that of euthyroidism (11.9%) (P < 0.05). The positive percentage of IgG2 subclass in sera from patients with hypothyroidism and subclinical hypothyroidism was significantly higher than that of euthyroidism (P < 0.05), the prevalence and positive percentage of IgG4 subclass in sera from patients with hypothyroidism and subclinical hypothyroidism was significantly higher than that of euthyroidism respectively (P < 0.05). The predominant TPOAb IgG subclasses in sera from patients with HT were IgG1 and IgG4. Patients with high levels of TPOAb IgG2, IgG4 subclasses might be at high risk of developing overt hypothyroidism.

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.

Localization of the immunodominant region on human thyroid peroxidase in autoimmune thyroid diseases: an update

Recent studies in the field of autoimmune thyroid diseases have largely focused on the delineation of B-cell auto-epitopes recognized by the main autoantigens to improve our understanding of how these molecules are seen by the immune system. Among these autoantigens which are targeted by autoantibodies during the development of autoimmune thyroid diseases, thyroid peroxidase is a major player. Indeed, high amounts of anti-thyroid peroxidase autoantibodies are found in the sera of patients suffering from Graves' disease and Hashimoto's thyroiditis, respectively hyper and hypothyroidism. Since anti-thyroid peroxidase autoantibodies from patients'sera mainly recognize a discontinuous immunodominant region on thyroid peroxidase and due to the complexity of the three dimensional structure of human thyroid peroxidase, numerous investigations have been necessary to closely localize this immunodominant region. The aim of the present review is to summarize the current knowledge regarding the localization of the immunodominant region recognized by human thyroid peroxidase-specific autoantibodies generated during the development of autoimmune thyroid diseases.

Fas-FasL in Hashimoto's thyroiditis

Hashimoto's thyroiditis is a common chronic autoimmune disease characterized by the loss of thyroid follicular cells (thyrocytes) that are gradually replaced by lymphocytic infiltration and diffuse fibrosis. These morphological findings suggested that autoreactive T-cell clones were responsible for thyrocyte destruction and hypothyroidism through effector-target cytotoxic recognition. Later, autonomous interaction between thyrocyte Fas and FasL has been proposed as a major mechanism of thyrocyte depletion in Hashimoto's thyroiditis. Here, we analyze the possible role of Fas and FasL in the pathogenesis of Hashimoto's thyroiditis. We suggest that the Fas-FasL system dictates the outcome of the autoimmune response by acting on both immune and target cells.

Status of antithyroid antibodies in Bangladesh

To study autoimmunity among thyroid diseases, 397 thyroid patients (age 30 (13) years; M/F 75/322) from two referral centres in Bangladesh and 94 healthy controls (age 30 (13) years; M/F 24/70) were studied for antimicrosomal and antithyroglobulin antibodies. Thyroid patients were clinically grouped as suspected autoimmune thyroid disease (AITD), non-autoimmune, or indeterminate groups (where no decision could be reached). Antimicrosomal antibody was strongly positive in 19.4% and weakly positive in 7.3% of patients but only 4.3% and 2.1% respectively in the controls (chi(2) = 17.852; p = 0.000) whereas strong and weak positivity were 27.2% and 6. 8% in patients compared with 8.5% and 4.3% respectively in the controls (chi(2) = 16.916; p = 0.000) for antithyroglobulin antibody. Antibodies were positive in 63.0% with Hashimoto's thyroiditis, 36.4% with Graves' disease, and 44.7% with atrophic thyroiditis among the autoimmune group. In the non-autoimmune group antibodies were positive in 100% with multinodular hypothyroidism, 46.7% with subacute thyroiditis, 40.0% with suspected iodine deficiency goitre, 31.3% with toxic multinodular goitre, 30.8% with non-toxic solitary nodules, and 19.4% with simple diffuse goitre. None was positive for antimicrosomal antibody without being positive for antithyroglobulin antibody. The two antibodies strongly correlated in both patients (r = 0.977, p = 0.000) and controls (r = 0.986, p = 0.000). About 9% (36/397) of patients were mismatched with the final diagnosis on antibody measurement; most of them had Hashimoto's thyroiditis (33/36). Prevalence of AITD among thyroid patients was 48.36%. Specificity of antimicrosomal and antithyroglobulin antibodies were 93% and 87%. It was concluded that AITD is not uncommon in Bangladesh; antimicrosomal antibody is a useful marker for AITD and unless antibodies are checked, an appreciable number of patients with AITDs will remain undetected.