Expression of HLA-DR antigens by thyroid cells: the effect of Graves' IgG

We have investigated factors which influence HLA-DR expression on thyroid cells. While bTSH (100 mU/ml) did not enhance HLA-DR expression, it increased when brought about by IFN-gamma. Graves' IgG showed a dose-dependent (0.1-2 mg/ml) increase in DR expression and at a concentration of 2 mg/ml prolonged the time for which DR was expressed. The pathway of DR induction by Graves' IgG apparently differs from that by IFN-gamma. The humoral response in Graves' disease, by inducing DR expression, may be instrumental in propagating thyroid specific autoimmunity.     

Induction of circulating activated suppressor-like T cells by methimazole therapy for Graves' disease

Thyrostatic drug treatment of Graves' disease suppresses excessive thyroid hormone synthesis and causes a parallel decrease in serum thyroid autoantibody levels. The mechanism of this immunosuppression is unknown. We studied methimazole-induced immunoregulatory effects prospectively in 14 patients with Graves' disease treated for up to six months. The numbers of circulating activated, HLA-DR-positive T helper/inducer cells decreased gradually, from 8.3+1.7 percent (+SD) to 1.0+1.7 percent (P less than 0.001). HLA-DR-positive T suppressor/cytotoxic cells increased transiently at one month, from 2.0+1.9 percent to 12.6+6.4 percent (P less than 0.001), and returned to 2.9+3.7 percent at six months. Methimazole did not alter the HLA-DR expression of T cells in vitro. In two patients, the helper activity of T cells in inducing autoantibody secretion in vitro was substantially reduced after one month of methimazole treatment. Before treatment, large proportions of thyroid-infiltrating T-cell subsets expressed the activation markers HLA-DR, interferon-gamma, and interleukin-2 receptors, which were partially lost during therapy. Methimazole treatment was accompanied by a gradual reduction in circulating levels of thyrotropin-receptor, microsomal, and thyroglobulin autoantibodies. These results are compatible with the view that methimazole-induced immunoregulation in Graves' disease is mediated by a direct inhibitory effect on thyrocytes. This inhibition is in turn accompanied by marked changes in the proportions of activated T helper-like and T suppressor-like cells. This altered T-cell activation profile reflects, at least in part, the functional suppression of autoantibody production observed in methimazole-treated patients with Graves' disease.     

Modulation of Fas-mediated apoptosis of human thyroid epithelial cells by IgG from patients with Graves' disease (GD) and idiopathic myxoedema

The expression of two autoimmune thyroid diseases, GD and idiopathic myxoedema, is associated with antibodies to the thyroid-stimulating hormone (TSH) receptor. Thyroid stimulating antibodies (TSAb) in GD are TSH agonists and cause hyperthyroidism as well as goitre, whereas thyroid stimulation blocking antibodies (TSBAb) in idiopathic myxoedema are TSH antagonists and cause hypothyroidism and thyroid atrophy. We investigated the effect of antibodies to TSH receptor on Fas-mediated apoptosis of thyroid epithelial cells (thyrocytes). Human IgG was isolated from healthy donors, patients with GD and idiopathic myxoedema. Human thyrocytes were obtained from surgical specimens. Thyrocytes were cultured in the presence or absence of human IgG with or without interferon-gamma (IFN-γ) or IL-1β for a specified time. After incubation, we examined the level of cAMP in cultured supernatants and both Fas and Bcl-2 expression on thyrocytes. In addition, we examined anti-Fas-mediated apoptosis of thyrocytes. Fas expression on thyrocytes was significantly down-regulated by Graves' IgG and TSH, although idiopathic myxoedema IgG did not affect Fas expression on thyrocytes. Idiopathic myxoedema IgG abrogated the effect of TSH on both cAMP production and inhibition of Fas expression on thyrocytes. Treatment of thyrocytes with IL-1β or IFN-γ caused a marked augmentation of Fas expression on thyrocytes. The increase of Fas expression of thyrocytes induced by IL-1β or IFN-γ was significantly suppressed in the presence of TSH or Graves' IgG. Anti-Fas-induced apoptosis of thyrocytes was observed in thyrocytes treated with IL-1β or IFN-γ, but was markedly inhibited in the presence of TSH or Graves' IgG. Furthermore, idiopathic myxoedema IgG abrogated most of the inhibitory effect of TSH on Fas-mediated apoptosis of thyrocytes treated with IL-1β or IFN-γ. Bcl-2 expression of thyrocytes did not change after stimulation with TSH, Graves' IgG, idiopathic myxoedema IgG, IL-1β or IFN-γ. These results suggest that TSAb found in Graves' patients may be potentially involved in the development of goitre by inhibition of Fas-mediated apoptosis of thyrocytes. In addition, TSBAb inhibit the action of TSH and increase the sensitivity toward Fas-mediated apoptosis of thyrocytes, inducing thyroid atrophy seen in patients with idiopathic myxoedema.     

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.     

Inhibition of the receptor for interleukin-2 induced by carbimazole: relevance for the therapy of autoimmune thyroid disease.

Evidence has been accumulated that the anti-thyroid drugs used in the treatment of Graves' disease may have immunosuppressive properties but the exact mechanism of action is still unclear. In the present study, we have investigated the in vitro effect of carbimazole (CBZ) on the expression of lymphocyte differentiation antigens and on suppressor cell activity. The incorporation of radiolabelled methimazole (35S-MMI, the active metabolite of CBZ) by resting and mitogen stimulated lymphocytes was also investigated. CBZ at concentrations of 60 microM significantly inhibited the expression of the receptor for interleukin-2 (as defined by the anti-TAC monoclonal antibody [MoAb]) by lymphocytes stimulated with phytohaemagglutinin. The expression of an early activation antigen (as characterized by the 4F2 MoAb) was not affected. Twenty-four hour pre-incubation of cells with different concentrations of CBZ or medium alone did not change the lymphocyte response to mitogenic stimulation, thus suggesting no effect of the compound on suppressor cell function. Finally, there were no significant differences in the uptake of 35S-MMI between resting and stimulated lymphocytes. These data suggest that the immunosuppressive effect of CBZ may be due to its effect of reducing the expression of the receptor for interleukin-2 on lymphocytes undergoing full activation. This property of CBZ could be of relevance in the therapy of autoimmune thyroid diseases (not only Graves' disease) which are characterised by the presence of activated T cells in the thyroid and in circulation.     

Interferon-gamma induces HLA-DR expression by thyroid epithelium.

We recently showed that human thyroid epithelial cells, which are normally negative for HLA-DR molecules, express HLA-DR in thyroid autoimmunity. Furthermore, induction of HLA-DR on normal thyroid cells can be achieved by culture with plant lectins. We have now found that recombinant human interferon-gamma (IFN-gamma) induces expression of HLA-DR molecules on cultured human thyroid cells, whereas Namalva IFN-alpha, recombinant IFN-beta or recombinant interleukin-2 (IL-2) do not. All three IFN, but not IL-2, enhanced thyroid cell HLA-A,B,C expression. The results strongly implicate T cells (which are the source of IFN-gamma) in the aberrant induction of DR on thyroid epithelial cells which is proposed to be a central feature of the immunopathological processes leading to autoimmunity.     

Synergy in antigen presentation by thyroid epithelial cells and monocytes from patients with graves'' disease

The present study was undertaken to examine the ability of thyrocytes from Graves' patients to present purified protein derivative (PPD) to autologous peripheral blood T cells. Normal human thyrocytes which were pre-cultured with interferon-gamma were able to induce the proliferation of T cells in response to PPD antigen, but unstimulated thyrocytes failed to do. Thyrocytes from Graves' patients on which HLA-DR antigens were expressed have an ability to induce the proliferation of T cells. Thyrocytes from Graves' patients which were pulsed with PPD antigen for 4 h were capable of stimulating proliferation of the T cells. However, the stimulation index of T cells co-cultured with thyrocytes and PPD were significantly lower than that of T cells co-cultured with monocytes and PPD. Sub-optimal numbers of monocytes which by themselves were unable to support T-cell proliferation synergistically augmented antigen presentation by thyrocytes. These results suggest that cellular interactions among thyrocytes, monocytes and T cells may perpetuate immune or autoimmune responses in thyroid tissues from Graves' patients.     

Tumour necrosis factor synergises with gamma interferon on the induction of mRNA for DR alpha chain on thyrocytes from Graves' disease and non toxic goitre

In both thyroid autoimmune diseases Graves' and Hashimoto's thyroiditis, the epithelial thyroid follicular cells (TFC) have been shown to express HLA class II molecules, and can restimulate autoreactive T cells cloned from the diseased tissue. This aberrant class II expression is important in the mechanism of perpetuation of the disease process, therefore we have compared the effect of interferon gamma (IFN gamma) and tumour necrosis factor (TNF alpha) on the HLA-DR alpha mRNA expression of thyroid follicular cells derived from Graves' disease (GD) and a non autoimmune disease, non toxic goitre (NTG). Our results indicate that TNF alpha synergises with IFN gamma in the induction of HLA class II mRNA. There was no consistent difference in DR alpha mRNA expression between the GD and NTG thyroid follicular cell preparations in response to induction by a combination of these lymphokines at various concentrations. Our data suggest that the differences in the level of expression of class II molecules observed in vivo in Graves' disease and non toxic goitre, which is much higher in the former, is probably due to local release of lymphokines by infiltrating T lymphocytes, although other factors may be involved.     

Studies on thyroid cell surface antigens using cultured human thyroid cells.

Human thyroid cells in primary culture were used for studies of thyroid cell surface antibodies in patients with thyroid autoimmune disorders. Radioiodinated IgG preparations containing thyroid microsomal antibody (TMAb), thyroid stimulating antibody (TSAb) and/or thyroglobulin antibody (TgAb) were tested for binding to thyroid cells. Binding was observed with radioiodinated IgG from patients with Graves' disease, Hashimoto's thyroiditis and idiopathic myxoedema containing TMAb, irrespective of the presence of TSAb and TgAb, while negative results were obtained with normal IgG. A dose-dependent inhibition of binding to thyroid cells was produced by the addition of the corresponding unlabelled IgG preparations. Evidence for tissue specificity was provided by the absence of binding to human skin fibroblasts used as controls. Preabsorption with human thyroid microsomes completely abolished the binding to thyroid cells of a radioiodinated TMAb positive IgG preparation, while only incomplete removal of the reactivity to thyroid microsomes was produced by preabsorption with thyroid cells. These data suggest that some but not all microsomal antigenic determinants are expressed on the thyroid cell surface. Binding to thyroid cells was also observed with purified TgAb, indicating that thyroglobulin antigenic determinants are present on the surface of thyroid cells. No evidence of binding was obtained with a TSAb positive Graves' IgG preparation with undetectable TMAb and TgAb. Unlabelled IgG preparations containing TMAb from patients with either Hashimoto's thyroiditis or idiopathic myxoedema were shown to inhibit the binding to thyroid cells of radioiodinated TMAb positive Graves' IgG and vice versa. These data indicate that antibodies present in these thyroid autoimmune disorders share common thyroid cell surface antigens. However, the binding of radioiodinated IgG from a patient with idiopathic myxoedema was only partially inhibited by Graves' or Hashimoto's IgG, suggesting that some of the thyroid cell surface antibodies of idiopathic myxoedema may not be detectable in other thyroid autoimmune disorders.     

MHC class II antigen expression in human vascular smooth muscle cells is induced by interferon-gamma and modulated by tumour necrosis factor and lymphotoxin

Arterial smooth muscle cells (SMC) express major histocompatibility complex (MHC) class II antigens in experimental vasculitis and in the human atherosclerotic plaque. We have therefore studied the regulation of expression of MHC antigens in cultured human arterial SMC, using immunofluorescence, radioimmunoprecipitation and a quantitative cell-surface immunoradiometric assay. SMC expressed class I, but not class II, antigens on their cell surfaces under basal conditions. Treatment of SMC with recombinant or natural interferon-gamma (IFN-gamma) induced expression of class II antigens in the following order of intensity, DR greater than DP greater than DQ. HLA-DR protein in SMC showed the same MW as that synthesized by B-lymphoblastoid cells. Antibodies to IFN-gamma blocked all HLA-DR-inducing activity in mixed leucocyte reaction (MLR) supernatants and PHA-stimulated peripheral blood mononuclear cell (PBMC)-conditioned media, indicating that IFN-gamma is the only lymphokine secreted under these conditions that is capable of de novo induction of HLA-DR expression in SMC. Treatment of SMC with recombinant human tumour necrosis factor-alpha (TNF) or lymphotoxin (LT) did not per se induce class II antigen expression. However, both TNF and LT substantially enhanced IFN-gamma-induced expression of HLA-DQ while decreasing that of HLA-DP. TNF, but not LT, increased HLA-DR expression. Also, in dermal fibroblasts, IFN-gamma-induced HLA-DP expression was significantly inhibited in the presence of TNF. These data demonstrate that TNF and LT differentially modulate IFN-gamma-induced MHC antigen expression in mesenchymal cells. The fact that SMC can express MHC class II antigens suggests that this cell type may serve as an accessory cell in the initiation of the immune response.     

Comparative study on IgG and IgA antibodies against human thyroid and eye-muscle antigens in Graves' ophthalmopathy.

Circulating IgG and IgA anti-thyroid and anti-eye muscle antibodies were investigated in 87 patients with Graves' disease (60 cases with ophthalmopathy). The ELISA method was used. Both IgG and IgA antibodies were demonstrated against human thyroid and eye-muscle membrane or cytosol antigens. Anti-eye-muscle antibodies of the IgA type were observed more frequently than those of the IgG type (25 cases vs. 18 were demonstrated with membrane antigens and 37 cases vs. 23 with cytosol antigens). The respective distributions for thyroid antigens the cytosol fraction were 55 cases vs. 13 and 18 cases vs. 36. A significant difference was observed in the anti-thyroid IgG levels and the anti-eye-muscle membrane or cytosol levels between the patients with Graves' disease and those in control group (P less than 0.001). The difference in the IgA antibody to thyroid and eye-muscle antigens was significant between the patients with and without ophthalmopathy (P less than 0.002). The strong correlation between the levels of IgA antibodies to thyroid and those to the eye-muscle cytosol fractions might be connected with the theory of the common aetiology of the thyroid and eye diseases in Graves' ophthalmopathy (P less than 0.001). Circulating IgA anti-human thyroid and eye-muscle antibodies seemed to have a diagnostic relevance in the development of ophthalmopathy in Graves' ophthalmopathy.     

Intercellular adhesion molecule-1 (ICAM-1) in Graves' disease: contrast between in vivo and in vitro results.

We have reassessed the possible role of the adhesion molecule ICAM-1 in the pathogenesis of thyroid autoimmunity. In order to do that, we have investigated its expression in eight Graves' thyroids both in vivo (i.e. on cryostat sections and on cell suspensions), and in vitro (i.e. on cells cultured in monolayers for 3 days), and the results were compared with those obtained with similar preparations from four normal glands. On cryostat sections, the expression of ICAM-1, and for comparison that of HLA Class I and Class II molecules, was studied by immunofluorescence (IFL), but the former were also assessed by a distinct immunohistochemical technique. ICAM-1 was not detected in thyrocytes in vivo of both normal and Graves' glands, but solely in endothelial cells and antigen-presenting cells (APC). This selective reaction was confirmed by a four-layer technique using specific markers which identify endothelial cells and thyrocytes. HLA Class II molecules were confirmed to be inappropriately expressed in thyrocytes of Graves' glands, but there was no co-expression of these products and ICAM-1 in the same cells. In contrast, ICAM-1 appeared de novo in a proportion of Graves' and normal thyrocytes soon after the attachment and spreading of these cells in monolayer cultures (36-48 h). Graves' thyrocytes showed a quantitatively higher degree of expression compared with that detected on normal thyroid cells (40-70% versus 12-20%). Under these experimental conditions, the four-layer staining with thyroid microsomal antibodies confirmed that thyrocytes were indeed the positive cells which expressed ICAM-1. Blocking experiments with cultured thyrocytes from two Graves' glands and MoAbs to tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) did not prevent the occurrence of ICAM-1 expression. As a result of our study, we failed to demonstrate that Graves' thyrocytes express ICAM-1 in vivo. The unexpected case of inducing ICAM-1 on thyroid cells under certain in vitro conditions remains intriguing. The phenomenon could be the simple consequence of a mechanical effect rather than exerted by specific biological processes. Further investigations are, therefore, needed to establish whether ICAM-1 is really involved in the pathogenesis of Graves' disease.     

Functional analysis of intercellular adhesion molecule-1-expressing human thyroid cells

We have tested the potential role of thyroid cell intercellular adhesion molecule-1 (ICAM-1) expression by in vitro assays of cell clustering and cytotoxicity. Increased ICAM-1 appeared within 24 h of thyroid cell stimulation with cytokines and was not inhibited by the antithyroid drug methimazole. Autologous and allogeneic lymphocyte-thyroid cell cluster formation, assessed by flow cytometry, was reduced by about one-third in the presence of a monoclonal antibody against ICAM-1, regardless of whether thyroid cells were expressing basal levels of ICAM-1 or had been stimulated with interferon-gamma. The cytotoxicity produced by interleukin 2-stimulated allogeneic lymphocytes was not consistently inhibited by anti-ICAM-1 antibody, but phytohemagglutinin-stimulated lymphocytes showed a reduction of 23%-28% in cytotoxicity against untreated or interferon-gamma stimulated thyroid cells when the anti-ICAM-1 monoclonal antibody was present. Finally, thyroid cells could be infected by rhinovirus, confirming the presence of fully functional ligand. These results show that ICAM-1 expression by thyroid cells may enhance immune cell recognition and play some role in cytotoxicity, features which could be important in the initiation or perpetuation of autoimmune thyroiditis.     

Inhibitory effects of nicotinamide on intercellular adhesion molecule-1 expression on cultured human thyroid cells.

We investigated the effects of nicotinamide and 3-aminobenzamide (3-AB), inhibitors of poly (ADP ribose) synthetase, on phytohaemagglutinin (PHA)- or interferon-gamma (IFN-gamma)-induced intercellular adhesion molecule-1 (ICAM-1) expression on cultured thyroid cells from patients with Graves' disease. Primary cultured thyroid cells were incubated for 3 days with IFN-gamma (10-800 U/ml) or PHA (1-50 micrograms/ml) in the presence of nicotinamide, 3-AB, superoxide dismutase or catalase. The surface expression of ICAM-1 was measured by flow cytometry. Nicotinamide and 3-AB dose-dependently inhibited the induction of ICAM-1 expression by IFN-gamma or PHA on thyroid cells. Neither catalase nor superoxide dismutase, which are free-radical scavengers, inhibited the expression of ICAM-1 on thyroid cells. Our data suggest that the mechanism of the suppression of ICAM-1 expression on thyroid cells by nicotinamide is not likely to be due to the free radical scavenging. Further studies are indicated to elucidate whether the inhibition of ICAM-1 by these drugs may result in the suppression of autoimmune reaction in the thyroid gland.     

Detection of HLA-DR antigens in paraffin-embedded thyroid epithelial cells with a monoclonal antibody.

The human Class II major histocompatibility (MHC) antigens, or Ia antigens, which are thought to regulate immune cell interaction, can be detected in paraffin-embedded tissues by immunoperoxidase staining with a recently developed monoclonal antibody (LK8D3). HLA-DR antigens were observed in lymphoid tissues, Langerhans cells of the skin, some epithelial cells, and pulmonary alveolar macrophages. The expression of HLA-DR antigens was analyzed in formalin-paraffin sections by immunoperoxidase in 86 normal and abnormal thyroid epithelial tissues. All patients with Hashimoto's disease (8/8) and most patients with Graves' disease (6/8) expressed HLA/DR antigens in the thyroid epithelial cells and in adjacent inflammatory cells. Most papillary carcinomas (12/18), including 3 of 5 follicular variant of papillary thyroid carcinomas, had HLA-DR antigens detected in epithelial cells; whereas medullary thyroid carcinomas (0/5), follicular carcinomas (0/5), and multinodular goiters (0/4) did not have detectable HLA-DR immunoreactivity. A few other thyroid lesions had HLA-DR antigens detected in epithelial cells, including anaplastic carcinomas (2/5), Hurthle-cell tumors (1/16), and thyroid lymphomas (2/2). Monoclonal antibody LK8D3 and two other commercially available monoclonal antibodies against HLA-DR-stained tissues equally well in cryostat sections, but only antibody LK8D3 was effective in formalin-fixed paraffin-embedded tissue sections. These results indicate that epithelial cells from thyroids of patients with autoimmune diseases commonly express HLA-DR antigens. The presence of HLA-DR antigens in most papillary thyroid carcinomas may be helpful diagnostically in cases of follicular variants of papillary carcinomas. The role of HLA-DR expression in autoimmune thyroid disease and in papillary thyroid carcinoma remains to be determined.     

Modulation of expression of class II histocompatibility antigens by secretion of a cellular inhibitor in K562 leukemic cells

In this report we show that it is possible to induce the expression of HLA-DR antigens on K562 cells, previously reported to be unresponsive to interferon-gamma (IFN-gamma). However, only low cell concentrations and a high dose of IFN-gamma allowed the induction of HLA-DR antigens. Furthermore, the recombinant glycosylated IFN-gamma is 100-fold more efficient than the unglycosylated form. This induction of HLA-DR antigens on K562 was not related to a stage of differentiation or to the presence of cells subsets specifically sensitive to IFN-gamma, since repeated sorting of K562 HLA-DR-positive and negative cells did not lead to the selection of a cell subset with a different potential of induction for HLA-DR. The difficulty in obtaining induction is due to the production of a soluble endogenous inhibitor of proteic nature, whose action is not restricted to the K562 cell line since it operates also on both epithelial and fibroblastic cells. Treatment of normal human epithelial and fibroblastic cells with conditioned medium from K562 cultures caused a marked decrease in the expression of HLA class II antigens (DR and DP) induced by IFN-gamma (10,000 U/ml), but had no effect on cell growth; however, it also affected expression of HLA class I antigens. This inhibition is not mediated by prostaglandin or an IFN-alpha or IFN-beta-dependent mechanism. Production of this inhibitor by pluripotent human leukemic cells could cause an unbalance in the complex control exerted by the immunological system during hematopoietic differentiation or leukemic progression.     

Decrease of HLA-DR antigen expression by human monocytes during cultivation in absence of exogenous or endogenous interferon-gamma

The kinetics of HLA-DR antigen expression by human peripheral blood monocytes during cultivation in vitro was studied. Immediately after separation by glass adherence, about 60% of monocytes expressed DR antigens as judged by indirect fluorescence staining with a monoclonal antibody (BL-DR/1). Monocytes carefully depleted of lymphocytes, gradually lost their DR antigens during cultivation in the absence of exogenous interferon-gamma (IFN-gamma). However, addition of a few lymphocytes to the adherent cells prevented the decrease of DR antigen expression. Furthermore, it was shown that doses as low as 1 IU/ml of IFN-gamma are sufficient to induce DR antigen expression by cultured monocytes. Experiments with cyclosporin A suggest that lymphocytes contaminating the monocyte preparations can produce spontaneously sufficient amounts of IFN-gamma for maintenance of the DR antigens on monocytes.     

HLA-D subregion expression by thyroid epithelium in autoimmune thyroid diseases and induced in vitro.

Human thyroid epithelial cells (thyrocytes) express HLA Class II molecules in autoimmune thyroid diseases (ATD). Normal thyrocytes do not express Class II, but can be induced to do so by culture with interferon-gamma (gamma-IFN). We have examined HLA-D subregion expression in sections and monolayers of thyroid by indirect immunofluorescence using appropriate monoclonal antibodies. The results indicate that, in ATD, the incidence and intensity of Class II subregion expression by thyrocytes varies between patients, and follows the pattern DR greater than DP greater than DQ. The same hierarchy is observed in cultured normal thyrocytes treated with gamma-IFN: strong induction of Class II, and of DP and DQ in particular, requires relatively high concentrations of gamma-IFN or additional factors such as thyroid stimulating hormone. These findings suggest that HLA-D subregion expression by thyrocytes in on-going ATD is determined by the levels of disease related factors in the affected tissue.     

Immunomodulation by methimazole therapy in Graves' disease: rapid changes in activation stage of circulating regulatory T cell subsets, B cells and NK cells

In patients with Graves' disease, initiation of thyrostatic therapy with methimazole causes a selective reduction of thyroid but not other autoantibody levels. The mechanism of this immunosuppressive effect is unknown. In the present study, methimazole (20 mg daily) induced very rapid changes in the surface antigen expression of several circulating lymphocyte subpopulations in six patients with Graves' disease. Within 1 to 3 days of therapy, the proportions of HLA-DR+ cells within the CD8+(Leu 2+) subset (activated 'suppressor/cytotoxic' T cells), CD11+(Leu 15+) cells out of CD8+ cells ('suppressor' T cells), and CD45+R (Leu 18+) cells out of CD4+(LEU 3+) cells ('suppressor/inducer' T cells) increased significantly from 4.7 +/- 3.9% to 9.5 +/- 6.0%, from 7.5 +/- 1.5% to 17 +/- 5.8% and from 49 +/- 17% to 73 +/- 19%, respectively. In parallel, the percentages of DR+ cells within the CD4+(Leu 3+) subset (activated 'helper' T cells), 4F2+ cells out of CD19+(Leu 12+) cells (activated B cells) and 4F2+ cells out of CD16+(Leu 11+) cells (activated 'natural killer'-like cells) declined significantly from 7.2 +/- 5.6% to 2.8 +/- 2.1%, from 7.2 +/- 1.5% to 4.0 +/- 2.8% and from 5.5 +/- 3.5% to 2.8 +/- 4.9% at 3 days, respectively. In contrast, no consistent phenotypic changes occurred in lymphocytes drawn from six healthy subjects during 7 days of methimazole medication. Direct in vitro effects of methimazole on lymphocyte markers were not observed when blood mononuclear cells from untreated patients were incubated with either the drug (10(-4) and 10(-6)M) or with autologous pre/post treatment serum for 1 to 4 days. Methimazole thus induces rapid alterations in the subclass and activation marker expression of circulating lymphocyte populations in Graves' disease. These alterations are compatible with a down-regulation of B cell activity. Indirect evidence suggests that the thyroid gland is the source of secondary signals for these changes to take place.