Expression and function of membrane attack complex inhibitory proteins on thyroid follicular cells.

Human thyroid cells are resistant to lysis by the homologous membrane attack complex. By immunohistochemical staining we here show that normal thyroid cells and those in Graves' disease and Hashimoto's thyroiditis express two membrane attack complex-inhibiting proteins, CD59 antigen and membrane attack complex-inhibiting protein/homologous restriction factor (MIP/HRF). In vitro, the expression of both molecules was enhanced by interleukin-1 (IL-1), tumour necrosis factor (TNF) and interferon-gamma (IFN-gamma) and cytokine-treated thyroid cells were more resistant to lysis by homologous complement. Blocking experiments with monoclonal antibodies against CD59 antigen and MIP/HRF showed that both molecules contributed but CD59 antigen was the more important in mediating resistance to complement attack. Expression of these proteins may be an important determinant of the severity of tissue injury produced by complement-fixing thyroid peroxidase antibodies in autoimmune thyroid disease.     

Thyroid follicular cell function after non-lethal complement membrane attack

Terminal complement complexes have been identified around thyroid follicles in Graves' disease and Hashimoto's thyroiditis, and the concentrations of such complexes are increased in the sera of these patients, suggesting a role for complement activation and membrane attack complexes (MAC) in autoimmune thyroiditis. This has been investigated further using cultured human and rat thyroid cells. Thyrocytes were resistant to lysis by homologous complement, in contrast to the effects of heterologous (rabbit) complement. The formation of non-lethal amounts of MAC, using reactive lysis or classical pathway activation, significantly reduced cAMP production by these cells in response to thyroid-stimulating hormone (TSH) (P less than 0.01); similar effects were seen with thyroid-stimulating antibodies. Thyroid cells were able to recover rapidly from complement attack after washing and incubation for 30 min. Non-lethal MAC formation also resulted in reactive oxygen metabolite production, detected by luminol-dependent chemiluminescence in three out of five thyroid cell preparations tested. Ionomycin, but not TSH, also stimulated reactive oxygen metabolite production. These results suggest that repeated or continuous sub-lethal complement attack on thyroid cells may exacerbate hypothyroidism in Hashimoto's thyroiditis, or partially counter the effects of thyroid-stimulating antibodies in Graves' disease. Furthermore, the production of reactive oxygen metabolites in these circumstances could increase the intra-thyroidal inflammatory response; oxygen radical scavenging by anti-thyroid drugs (which are concentrated by thyrocytes) may account in part for the amelioration of thyroiditis observed with such treatment.     

Terminal complement complexes and C1/C1 inhibitor complexes in autoimmune thyroid disease.

The potential role of complement activation and the membrane attack complex in the pathogenesis of Graves' disease and Hashimoto's thyroiditis has been investigated by measuring serum concentrations of the C1r-C1s-C1 inhibitor complex (C1/C1-inh) and the terminal complement complex (TCC), and by studying the binding to thyroid tissue of monoclonal and polyclonal antibodies against TCC neoantigens. Serum C1/C1-inh and TCC concentrations were significantly increased in 29 patients with untreated Graves' disease compared with 47 healthy subjects (P less than 0.001 for both), and decreased significantly after carbimazole treatment in 18 of these patients for whom post-treatment samples were available (P less than 0.01 and P less than 0.02, respectively). The serum TCC concentration, but not that of C1/C1-inh, was also significantly increased in 15 patients with Hashimoto's thyroiditis compared with the 47 healthy subjects (P less than 0.001). TCCs were identified by immunohistochemical staining around the thyroid follicles in thyroidectomy specimens from patients with Graves' disease (six out of six) and Hashimoto's thyroiditis (two out of two); normal thyroid tissue from two subjects showed no staining. These results suggest a role for complement, in particular the membrane attack complex in the pathogenesis of autoimmune thyroid disease.     

Expression of intercellular adhesion molecule-1 (ICAM-1) on thyroid epithelial cells in Hashimoto's thyroiditis but not in Graves' disease or papillary thyroid cancer.

In order to study the possible role of antigen-independent adhesion systems in thyroid autoimmunity, we evaluated by indirect immunofluorescence the expression of lymphocyte functional antigen-1 (LFA-1) and its ligand ICAM-1 on mononuclear cell infiltrates (when present) and thyroid follicular cells of four patients with Hashimoto's thyroiditis, 30 with Graves' disease, five with papillary cancer, two with follicular adenoma, and two normal thyroid specimens. The expression of MHC class I and class II antigens was also evaluated. Most mononuclear infiltrates were LFA-1 positive, as expected. A positivity for ICAM-1 on follicular cells was observed in three out of four Hashimoto's thyroiditis specimens; such a phenomenon was totally absent in Graves' disease or any other pathological condition, or in normal tissue. MHC class II expression on thyrocytes was observed in all the patients with Hashimoto's thyroiditis, in 27 out of 30 with Graves' disease and in three out of five papillary cancer specimens.     

Vascular endothelial growth factor (VEGF), VEGF receptors expression and microvascular density in benign and malignant thyroid diseases

Angiogenesis is critical for the growth and metastatic spread of tumours. Vascular endothelial growth factor (VEGF) is the most potent inducer of neovasculature, and its increased expression has been related to a worse clinical outcome in many diseases. The purpose of this study was to evaluate the relation between VEGF, its receptors (VEGFR-1 and VEGFR-2) and microvessel density (MVD) in thyroid diseases. Immunostaining for VEGF and VEGF receptors was performed in 66 specimens of thyroid tissue, comprising 17 multinodular goitre (MNG), 14 Graves' disease, 10 follicular adenoma, 8 Hashimoto's thyroiditis, 7 papillary carcinoma and 10 normal thyroid specimens. Thyrocyte positivity for VEGF and VEGF receptors was scored 0-3. Immunohistochemistry for CD31, and CD34 on the same sections was performed to evaluate MVD. Immunohistochemical staining of VEGF in thyrocytes was positive in 92% of all the thyroid tissues studied. Using an immunostaining intensity cut off of 2, increased thyrocyte staining was seen in follicular adenoma specimens, MNG and normal thyroids compared with Hashimoto's thyroiditis and Graves' disease (P < 0.05). Similarly, VEGF thyrocyte expression in Graves' disease was less than other pathologies (P < 0.05). VEGFR-1 expression and the average MVD score did not differ between the different thyroid pathologies. VEGF expression was lower in autoimmune pathologies compared to autonomous growth processes. Conversely, both VEGFR-1 and VEGFR-2 were widely expressed in benign and neoplastic thyroid disease, suggesting that the up-regulation of VEGF and not its receptors occurs as tissue becomes autonomous. There was no clear relationship between MVD measurement and thyroid pathology.     

Detection of interleukin-6 and interleukin-1 production in human thyroid epithelial cells by non-radioactive in situ hybridization and immunohistochemical methods.

Human endocrine thyroid epithelial cells have been described to produce cytokines in vitro. In order to determine whether they do so in vivo during thyroiditis, parallel studies on mRNA expression with a non-radioactive in situ hybridization technique and immunohistochemical detection for the protein were performed on frozen sections of thyroid samples from autoimmune thyroiditis (Graves' disease and Hashimoto's thyroiditis), non-toxic goitre and normal thyroid tissue. cDNA probes were sulphonated and their hybridization with mRNA was detected with a sulphonyl-specific monoclonal antibody. This signal was amplified and visualized with the alkaline phosphatase-anti-alkaline phosphatase (APAAP) system. The protein products were detected with immuno-purified rabbit F(ab')2 antibody fragments recognizing recombinant human cytokines, visualized by the immunoperoxidase technique. Each sample was studied at the two levels. Both interleukin-6 mRNA and protein were found in the endocrine cells. There was no obvious difference between autoimmune thyroiditis and non-toxic goitre. However, normal thyroid epithelial cells produced less interleukin-6. Interleukin-1 alpha mRNA and its protein were found in epithelial cells from Hashimoto's thyroiditis samples, but not in the others, except one Graves' disease sample, in which only mRNA was detected. Interleukin-1 beta was not detected in these cells, its mRNA was only found in one of the Graves' disease samples. These cytokines were also detected in some infiltrating cells.     

Fas ligand gene polymorphisms are not associated with Hashimoto's thyroiditis and Graves' disease

Hashimoto's thyroiditis and Graves' disease represent the two most common autoimmune thyroid disorders. Whereas in Hashimoto's thyroiditis FasL expression causes thyrocytes to undergo apoptosis, additional anti-apoptotic molecules appear to protect these cells in Graves' disease. Mutations of the FasL gene were observed in systemic lupus erythematosus. Given its functional relevance for the pathogenesis of thyroid autoimmunity we wondered whether variants of the FasL gene play a role in Hashimoto's thyroiditis and Graves' disease. We genotyped families with at least one offspring affected by Hashimoto's thyroiditis (n = 86) and Graves' disease (n = 90) for two FasL gene polymorphisms (C -843 T in the promoter, A IVS2nt-124 G in intron 2). Extended transmission disequilibrium (ETDT) and chi(2) testing were performed. Neither polymorphism alone nor the promoter/intron 2 haplotypes (p = 0.91) were associated with Hashimoto's thyroiditis. No association with Graves' disease was observed for the promoter polymorphism (p = 0.91) and the intron 2 "A" allele (57.1%; p = 0.36) or the promoter/intron 2 haplotypes (p = 0.31). Moreover, intron 2 genotyping revealed no difference between an additional 251 patients with Graves' disease and 197 healthy controls (p = 0.37). Italian and German families did not differ for the studied polymorphisms. In conclusion, our data do not suggest common genetic FasL variants to significantly contribute to the pathogenesis of either Hashimoto's thyroiditis or Graves' disease.     

The expression and role in T cell adhesion of LFA-3 and ICAM-2 on human thyroid cells.

Thyroid follicular cells from patients with Graves' disease and Hashimoto's thyroiditis express intercellular adhesion molecule-1 (ICAM-1) and this is in part responsible for T cell adherence in vitro. To assess the potential role of other adhesion molecules in autoimmune thyroiditis, we investigated the expression and function of lymphocyte function-associated antigen-3 (LFA-3) and ICAM-2 on thyroid cells. Under basal culture conditions, a mean of 22.7% of Graves' thyroid cells (n = 8) expressed LFA-3 and this was enhanced by a mixture of T cell-derived cytokines and by IL-1, but not by TSH. LFA-3 was also demonstrated on Graves' (n = 4) and Hashimoto (n = 2) thyroid cells by immunohistochemical staining ex vivo. A small number of thyroid cells (mean 5.5%, n = 5) expressed ICAM-2 by flow cytometry but this was not altered by cytokines, and ICAM-2 could only be demonstrated on endothelial cells by immunohistochemical staining. It seems likely that contamination of primary thyroid cultures by such cells accounted for the small number of ICAM-2+ cells found using flow cytometry. Almost all of the cultured cells expressing LFA-3 or ICAM-2 also expressed ICAM-1, as assessed by dual staining. Blocking LFA-1, LFA-3, and ICAM-1 with monoclonal antibodies inhibited the adherence of T cells to thyroid follicular cells in assays of cell clustering; antibodies against ICAM-2 had no effect. These results show that two important adhesion receptor ligands, ICAM-1 and LFA-3, are expressed by thyroid cells in autoimmune thyroiditis and that these are likely to have functional importance in allowing T cells to bind to thyroid cell targets. This may play an important role in the initiation and maintenance of Graves' disease and Hashimoto's thyroiditis.     

In vitro production of interferon-gamma by peripheral blood from patients with Graves'' disease, Hashimoto''s thyroiditis and rheumatoid arthritis.

The production of interferon-gamma (IFN-gamma) by peripheral blood mononuclear cells (PBMC), CD4 cells, or CD8 cells in response to interleukin-2 (IL-2) stimulation has been studied; the samples were obtained from 12 healthy control subjects, 19 patients with Graves' disease (10 hyperthyroid and nine euthyroid), 13 patients with Hashimoto's thyroiditis (four hypothyroid and nine euthyroid), and 15 patients with rheumatoid arthritis (11 active and four inactive). A dose of IL-2 (25 U/ml) was utilized to induce IFN-gamma by PBMC from all four groups. The incremental increase in IFN-gamma values (with IL-2 stimulation minus without stimulation) was significantly less in PBMC from patients with Graves' disease, Hashimoto's thyroiditis, and rheumatoid arthritis than that in PBMC from control subjects. The values from PBMC in patients with Graves' disease in a euthyroid state were below normal but greater than those from patients with Graves' disease in a hyperthyroid state. The incremental increase in IFN-gamma values from Graves' disease PBMC correlated with the serum TSH values (r = 0.622, P less than 0.01), but not with thyroid autoantibodies (anti-thyroid microsomal antibodies, anti-thyroid microsomal antibodies, nor TSH-binding inhibitory immunoglobulin activities). The incremental increase in IFN-gamma from PBMC from both control subjects and Graves' disease was correlated with that from CD4 cells (r = 0.711, P less than 0.01), but not with that from CD8 cells. The production of IFN-gamma in response to IL-2 from PBMC in Graves' disease correlated inversely with thyroid function, appearing to reflect the very effect of hyperthyroidism in this process. The precise explanation of these phenomena remains unclear. The decreased response of IFN-gamma to IL-2 stimulation by PBMC from patients with Graves' disease, Hashimoto's thyroiditis, and rheumatoid arthritis seems to be a non-specific phenomenon occurring in both organ specific autoimmune disease and systemic autoimmune disease. It may be due to a down-regulation in autoimmune disease of CD4 cells in response to IL-2, a decreased level of IL-2 cellular receptors or a decreased receptor affinity, associated increased soluble IL-2 receptors, or a defect of the intra-CD4 cellular IL-2 signal to produce or release IFN-gamma in the conditions studied.     

Heterogeneity of thyroid autoantigens identified by immunoblotting

Autoimmune thyroid disease in man is commonly associated with autoantibodies against thyroglobulin, microsomes, and the TSH receptor, and the character and specificity of these antithyroid antibodies have been extensively utilized in investigating these conditions. In the present study we have asked whether other thyroid-related antigens exist, against which autoantibodies may be directed. A crude thyroid extract was separated by polyacrylamide gel electrophoresis followed by immunoblotting with serum obtained from patients with Graves' disease or Hashimoto's thyroiditis. Antibodies in sera from patients with Graves' disease and Hashimoto's thyroiditis reacted with many antigenic determinants in immunoblots of the thyroid membrane preparation (2000g supernatant). These determinants were disease specific in that sera from normals and patients with Addison's disease and rheumatoid arthritis did not react, but there was no difference between the patterns of reactivity with Graves' disease or Hashimoto's thyroiditis sera. Thyroglobulin produced two predominant bands of reactivity at 320 and 200 kDa, whereas purified microsomal antigen produced a triplet of bands around 105 kDa, when these preparations were reacted with appropriate autoimmune sera. Nonetheless, some sera produced additional bands with the microsomal antigen blots, indicating that some of the antigens which were detected using crude thyroid membrane remained in the microsome preparation to produce multiple antibody binding reactivities. We were unable to inhibit any of the antibody binding with TSH. Purification of individual thyroid antigens on the basis of their molecular weights should standardize current antibody assays and permit more detailed evaluation of the cellular immune responses in Graves' disease and Hashimoto's thyroiditis.     

Increase in peripheral natural killer cell activity in patients with autoimmune thyroid disease.

Changes in the activity and number of natural killer (NK) cells in peripheral blood in patients with autoimmune thyroid disease were examined. NK activity was measured in a 4-hr 51Cr-release assay and the number of NK cells was analyzed with FITC-conjugated monoclonal antibodies by use of an automated flow cytometer. NK activity in patients with untreated Graves' disease (n = 25, 39.7 +/- 13.5%, P less than 0.05) and Hashimoto's thyroiditis (n = 18, 41.0 +/- 14.2%, P less than 0.05) was high compared to the activity in non-pregnant controls (n = 61, 32.6 +/- 15.0%). NK activity in patients with postpartum Graves' thyrotoxicosis (n = 11, 48.6 +/- 18.9%) was markedly increased compared to the activity in non-pregnant controls (P less than 0.01) and in postpartum controls (n = 29, 33.8 +/- 15.2%, P less than 0.05), although the mean ages of each group did not differ significantly. Moreover, NK activities in the thyrotoxic state were significantly higher than those in the euthyroid state in the same patients with postpartum Graves' thyrotoxicosis or with postpartum destructive thyrotoxicosis. The number of CD16 positive cells increased in patients with postpartum Graves' thyrotoxicosis. However the number of CD16 and CD57 positive cells were normal in all other groups of patients. These results indicate that an increase of NK activity is associated with exacerbation of autoimmune thyroid disease both in Hashimoto's thyroiditis and in Graves' disease and suggest that NK cells might have an important role for the control of disease activity in autoimmune thyroid disease.     

Decreases in alpha beta T cell receptor negative T cells and CD8 cells, and an increase in CD4+ CD8+ cells in active Hashimoto''s disease and subacute thyroiditis.

We examined peripheral lymphocyte subsets in patients with autoimmune thyroid disease, or subacute thyroiditis, in the active stage when possible. During destructive thyrotoxicosis arising from alpha beta T cell receptor (TCR) negative T (WT31-CD3+) cells and CD8 (CD4-CD8+) cells decreased and those of CD4+CD8+ cells increased slightly, resulting in proportional increases in CD4 (CD4+CD8-) cells, non-T, non-B (CD5-CD19-) cells, and the CD4/CD8 cell ratio. Changes were similar in active subacute thyroiditis. During stimulative thyrotoxicosis in active Graves' disease, the numbers of such T lymphocyte subsets were not changed, but only the number of CD5+ B (CD5+CD19+) cells increased markedly, resulting in proportional decreases in total T (CD3+) cells, alpha beta+ TCR T (WT31+CD3+) cells, CD8 cells, and non-T, non-B cells. A serial study of some of the patients showed opposite changes in alpha beta TCR- T cells, the CD4/CD8 cell ratio, and CD5+ B cells between the active stages of Graves' and Hashimoto's diseases. alpha beta TCR- T cells were mostly gamma delta TCR+ T (IIF2+ CD3+) cells in these patients. These data suggest that alpha beta TCR-T (gamma delta TCR+ T), CD8, and CD4+ CD8+ cells are important in thyroid destruction in Hashimoto's disease and subacute thyroiditis, and that CD5+ B cells are important in thyroid stimulation in Graves' disease.     

Characterization of the natural killer cell activity in Hashimoto's and Graves' diseases

Natural killer (NK) cell activity and blood mononuclear cell subpopulations were characterized in patients with Hashimoto's thyroiditis ( n = 11), Graves' disease ( n = 20), non-toxic goitre ( n = 10) and in normal controls ( n = 22). NK cell activity against K 562 target cells and the capability of IFN-α, Il-2, and indomethacin to enhance NK cell activity in vitro did not differ significantly between the groups. The percentages of large granular lymphocytes, CD5 +, CD4 +, CD8 + and CD16 + cells were normal in patients with non-toxic goitre, Hashimoto's and Graves' diseases. There was no correlation between NK cell activities and TgAb, MAb and TSAb. Although NK cell activity is suppressed in several autoimmune diseases, NK cell function is normal in patients with autoimmune thyroid disorders.     

Marked increase of CD5 + B cells in hyperthyroid Graves' disease

We examined the proportions of B lymphocytes bearing CD5 cell surface antigen (CD5+ B cells), which are capable of making autoantibodies, in peripheral blood from patients with various thyroid diseases. The level of CD5+ B cells was markedly increased (>9.0%) above the normal range (0.5-7.7%) in untreated, hyperthyroid patients with Graves' disease, although about 10% of the patients had no detectable serum thyroid-stimulating hormone (TSH) receptor antibody (TRAb). However, the levels of CD5+ B cells were normal in untreated patients with destructive thyrotoxicosis due to aggravation of Hashimoto's thyroiditis or subacute thyroiditis. In patients with stimulated hyperthyroid Graves' disease the levels of CD5+ B cells were correlated with those of thyroid hormones and TRAb, all significantly increased. However, once hyperthyroidism was controlled by anti-thyroid drugs, CD5+ B cells were decreased, followed in turn by reduction of TRAb. We conclude that the proportion of CD5+ B cells is useful as a therapeutic index and for diagnosis of Graves' disease and its differentiation from destruction-induced thyrotoxicosis.     

The pathogenetic connection between Graves' disease and chronic lymphocytic thyroiditis. (The role and incidence of thyroid stimulating antibodies)

Antibody-positivity to thyroid specific antigens (Htg, microsomal) and/or lymphocytic infiltration of the gland's parenchyma were observed in 207 (55%) of 377 patients with Graves's disease. Only in 48 (12.7%) of the cases were the findings in agreement with the criteria of chronic lymphocytic thyroiditis. Human thyroid stimulating antibody (HTSab) was detected in 135 (65%) of these 207 patients. In cases of Graves' disease associated with chronic lymphocytic thyroiditis, this proportion was found to be as high as 89.6% and attained even 100% in cases of Hashitoxicosis (39 patients). The presence of HTSab thus seems to form one of the features of patients with Hashitoxicosis. Infiltrative ophthalmopathy also showed a remarkably high incidence (59%) in this porcess. The typical prevalence of Graves' disease in females in the present material attained a 15:1 female-to-male ratio when the disease was associated with chronic lymphocytic thyroiditis. The results of the present study suggest that chronic lymphocytic thyroiditis associated with Graves' disease promotes the formation of thyroid stimulating antibodies.     

The production and characterization of thyroid-derived T-cell lines in Graves' disease and Hashimoto's thyroiditis

Although the thyroid gland itself is a major site of the autoimmune response, the study of T-cell function in autoimmune thyroid disease has usually relied on peripheral blood as a source of cells. In this study, we have established thyroid-derived T-cell lines from six patients with Graves' disease and one patient with Hashimoto's thyroiditis by culturing the thyroid lymphocytes on an autologous thyroid follicular cell monolayer in the presence of exogenous interleukin 2 (IL-2). These T-cell lines have allowed in vitro investigation of thyroid-derived T-cell function, an approach which was previously limited by the number of lymphocytes obtained from the gland. The lines were predominantly OKT3, OKT4, and HLA-DR positive but showed heterogeneous proliferative responses. Some lines gave autologous or allogeneic mixed lymphocyte reactions but other did not. Only one of the seven lines responded well to the thyroid antigens thyroglobulin and microsomes presented by autologous monocytes. However, six of the lines proliferated in the presence of live but not dead autologous thyroid follicular cells, particularly when interferon-gamma (IFN-gamma) was added. This treatment has been shown to enhance HLA-DR and -DQ antigen expression by thyroid follicular cells in vitro. Furthermore, the proliferation induced by IFN-gamma-treated thyroid follicular cells was increased when thyroglobulin was also added. Together these results support the hypothesis that the expression of Ia antigens such as HLA-DR by thyroid follicular cells in autoimmune thyroid disease may be important in enhancing the autoimmune response, conferring on these cells the ability to present thyroid autoantigens to T cells. The use of thyroid-derived T-cell lines should permit a more detailed evaluation of the disordered immuno-regulation in Graves' disease and Hashimoto's thyroiditis than has been possible previously.     

Control of target cell survival in thyroid autoimmunity by T helper cytokines via regulation of apoptotic proteins

After autoimmune inflammation, interactions between CD95 and its ligand (CD95L) mediate thyrocyte destruction in Hashimoto's thyroiditis (HT). Conversely, thyroid autoimmune processes that lead to Graves' disease (GD) result in autoantibody-mediated thyrotropin receptor stimulation without thyrocyte depletion. We found that GD thyrocytes expressed CD95 and CD95L in a similar manner to HT thyrocytes, but did not undergo CD95-induced apoptosis either in vivo or in vitro. This pattern was due to the differential production of TH1 and TH2 cytokines. Interferon gamma promoted caspase up-regulation and CD95-induced apoptosis in HT thyrocytes, whereas interleukin 4 and interleukin 10 protected GD thyrocytes by potent up-regulation of cFLIP and Bcl-xL, which prevented CD95-induced apoptosis in sensitized thyrocytes. Thus, modulation of apoptosis-related proteins by TH1 and TH2 cytokines controls thyrocyte survival in thyroid autoimmunity.     

A differential association of interferon-gamma high-producing allele T and low-producing allele A (+874 A/T) with Hashimoto's thyroiditis and Graves' disease

Cytokines play a crucial role in the pathogenesis of autoimmune thyroid disease. The aim of this study was to investigate the relationship of the single base change polymorphic variants identified in the first intron of interferon-gamma (IFN-gamma) (+874 T/A) with susceptibility to thyroid dysfunctions. A total of 340 subjects were included in the study comprising of 190 patients (104 patients with Hashimoto's thyroiditis, 26 with non-Hashimoto's hypothyroidism and 60 Graves' disease) and 150 controls. Genotyping was done by amplification refractory mutation system-polymerase chain reaction using a set of sequence-specific primers. Statistical analysis revealed a significant association between high IFN-gamma-producing genotype TT and Hashimoto's thyroiditis compared to controls (P value < 0.001). On the other hand, the frequency of genotype TT was decreased in patients with Graves' hyperthyroidism with a significant increase in low IFN-gamma-producing genotype AA among this group (P = 0.03). To conclude the results of the study suggest a differential association of high- and low-producing alleles of IFN-gamma gene with Hashimoto's thyroiditis and Graves' disease. The high IFN-gamma-producing allele T was observed to be associated with Hashimoto's thyroiditis in the present study where as in Graves' hyperthyroidism the association was observed to be stronger with the low producing allele A.     

Heterogeneity of immunoregulatory T cells in human thyroid autoimmunity: influence of thyroid status.

Monoclonal antibodies of the OKT series were used to identify circulating T lymphocytes (OKT3+), their helper-inducer (OKT4+) and suppressor-cytotoxic (OKT8+) subsets and cells bearing Ia antigen (OKIa+) in 75 patients with thyroid autoimmune disorders, including 14 Graves' disease, 21 myxoedema, 20 asymptomatic thyroiditis, 12 Hashimoto's thyroiditis and eight simple goitre with superimposed thyroiditis. In the whole population of patients, a negative correlation was observed between the percentage of OKT8+ cells and serum free thyroxine levels whatever the type of thyroiditis. The percentage of OKT8+ cells was decreased in Graves' disease and increased in myxoedema while it reversed after adequate treatment of the two diseases. However, a trend to a decrease in the proportion of OKT8+ cells was still observed in treated Graves' disease and in all the other groups of thyroiditis with euthyroidism. The minor modifications observed for OKT3+ and OKT4+ cells were in relation with those of OKT8+ cells. There was an increased percentage of Ia+ cells in Graves' disease and in Hashimoto's thyroiditis partly reflecting the presence of activated lymphocytes. In conclusion, these data suggest first of all a direct influence of serum T4 on the distribution of circulating OKT8+ cells in addition to documenting the heterogeneity of T cell immunoregulatory factors.     

Clinical value of a bispecific antibody binding to thyroglobulin and thyroperoxidase (TGPO-aAb) in various thyroid diseases.

TGPO-aAb is a bispecific antibody which binds to thyroglobulin as well as thyroid peroxidase. It is supposed to be raised in some patients with autoimmune thyroid disease. We investigated 205 patients suffering from Graves' disease (n = 81), Hashimoto's thyroiditis (n = 36), toxic nodular goitre (n = 50), differentiated carcinoma of the thyroid (n = 10), and autoimmune thyropathy of unknown origin (n = 28). An immunoradiometric assay was used to measure serum TGPO-aAb. Eighty-nine of 205 patients had elevated titres of TGPO-aAb. If TGPO-aAb were raised then autoantibodies against thyroglobulin and thyroid peroxidase were always raised, too. This was, however, not true vice versa. We found TGPO-aAb in 61% of patients with Hashimoto's, 49% of patients with Graves', 64% of patients with autoimmune thyropathy, but only in 12% of patients with toxic nodular goitre. In patients with thyroid carcinoma TGPO-aAb was found only if there was evidence of paraneoplastic autoimmune thyroiditis. We re-examined 16 of 36 patients with Hashimoto's thyroiditis after 1 year: 8 patients had retained their raised TGPO-aAb, 4 patients showed no TGPO-aAb on both occasions, and 4 patients had 'lost' their previously raised TGPO-aAb on follow-up. We conclude that TGPO-aAb may provide additional information in Hashimoto's thyroiditis. Determination of TGPO-aAb does not allow to distinguish between various forms of autoimmune thyroid disease. Nevertheless, the presence of TGPO-aAb and its variation during the natural course of autoimmune thyroid disease remains to be understood which would give a better insight into its clinical significance.