The modulation of the human sodium iodide symporter activity by Graves' disease sera

The transport of iodide into the thyroid, catalyzed by the Na+/I- symporter (NIS), is the initial and rate-limiting step in the formation of thyroid hormones. To study the basic characteristics of the human (h) NIS, we have established a Chinese hamster ovary cell line stably expressing the hNIS (CHO-NIS9). In agreement with previous work on the rat NIS, iodide uptake in these cells was initiated within 2 min of the addition of 131I, reaching a plateau after 30 min. Both perchlorate and thiocyanate inhibited iodide uptake in a dose-dependent manner, with inhibition evident at concentrations of 0.01 and 0.1 micromol/L, respectively, and reaching complete inhibition at 20 micromol/L and 500 micromol/L, respectively. Ouabain, which blocks the activity of the Na+/K+ adenosine triphosphatase, also inhibited iodide uptake in a dose-dependent manner, starting at concentrations of 100 micromol/L and reaching maximum inhibition at 1600 micromol/L, indicating that iodide uptake in these cells is sodium dependent. CHO-NIS9 cells were further used to study 88 sera from patients with Graves' disease, for iodide uptake inhibitory activity, which were compared with sera from 31 controls. Significant iodide uptake inhibition was taken as any inhibition in excess of the mean + 3 SD of the results with the control sera. On this basis, 27 (30.7%) of the Graves' sera, but none of the controls, inhibited iodide uptake in CHO-NIS9. IgGs from these patients also inhibited iodide uptake, indicating that this inhibitory activity was antibody mediated. In summary, we have established a CHO cell line stably expressing the hNIS and shown that antibodies in GD sera can inhibit iodide uptake in these cells. This further emphasizes the role of NIS as a novel autoantigen in thyroid immunity.

Analysis of the T-cell receptor Valpha repertoire and cytokine gene expression in Sjögren's syndrome

The antigen receptor diversity of pathogenic T cells in Sjögren's syndrome (SS) may have important implications in the development of the disease; cytokines from these cells and other sources also play a role in the pathogenesis of this disease. Using a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) technique, we have attempted to correlate the presence of restriction in the T-cell receptor (TCR) repertoire with cytokine profiles. We have analysed TCR V alpha family usage, and the expression of interleukin-1alpha (IL-1alpha), IL-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-13, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), in labial biopsies from 12 patients with SS and compared these with samples from three patients with chronic sialadenitis (CS). Only one of the SS biopsies showed evidence of V alpha restriction (three out of 18 gene families). Apart from this, expression patterns were similar in both patient groups. Four of the 12 SS samples demonstrated a 'limited heterogeneity' of the V alpha repertoire with 3-4 families predominantly expressed, in particular V alpha1 and V alpha3. Peripheral blood lymphocytes were unrestricted. The cytokine profiles of the SS and CS biopsies were generally similar. However both IFN-gamma and IL-1alpha were absent from CS, but present in SS samples. The expression of IFN-gamma in the majority of the samples, together with a lack of IL-4 and IL-13 mRNA, suggests the predominance of a Th1 response in SS. There was no clear association between the repertoire of V alpha genes expressed and the cytokine profile observed. However, the V alpha restriction in one SS sample did correspond with a limited diversity of cytokines detected.

Profile of cytokine mRNA expression in peri-implantation human endometrium

The human embryo and subsequent fetus is a semi-allograft and immunologically foreign to the mother. Successful embryonic implantation and maintenance of normal pregnancy depends on intricate interactions between the invading embryo, maternal endometrium and maternal immune response. Cytokines are pivotal in determining the type of maternal T-helper immune response, which can be divided into T-helper 1 (TH1)-mediated delayed hypersensitivity and T-helper 2 (TH2)-mediated humoral immunity. We examined the pattern of TH1 [interleukin (IL)-2, IL-12 and interferon-gamma] and TH2 (IL-4 and IL-6) cytokine expression in the peri-implantation endometrium of 10 fertile, multiparous women. Endometrial samples were timed to the mid-cycle luteinizing hormone (LH) surge, with collection on days LH+7 to LH+9. Analysis for cytokine mRNA was by mRNA extraction and reverse transcription-polymerase chain reaction. The results show a lack of TH1 and predominant TH2 cytokine expression. We postulate that endometrial cytokines may contribute to the local modulation of maternal adaptive immune response in peri-implantation endometrium, to facilitate successful embryonic implantation and maintenance of pregnancy.

Cytokines and Graves' disease

Cytokines are an extraordinarily diverse group of molecules, with pleiotropic and often overlapping effects. They are crucial to the autoimmune response, and, in particular, regulation of CD4+ and CD8+ T-cell function depends on the balance of cytokines produced during an immune response. It is also now clear that cytokines are produced by a wide array of cells, including the thyroid follicular cells (TFCs). Intrathyroidal lymphocytes produce a heterogeneous pattern of cytokines and we have summarized the likely effects of these. In Graves' disease, TFCs can themselves express immunologically important molecules as the result of cytokine stimulation and these could contribute to the perpetuation of the autoimmune process. In addition, cytokines have a number of generally inhibitory effects on thyroid hormone production which would tend to counter the stimulatory effects of thyroid-stimulating hormone receptor antibodies in Graves' disease.

Detection of IL-12, IL-13, and IL-15 messenger ribonucleic acid in the thyroid of patients with autoimmune thyroid disease

IL-12, IL-13, and IL-15 are important cytokines that have not been studied previously in human autoimmune thyroid diseases. By applying RT-PCR on RNA extracted from tissue samples, we have investigated in vivo gene expression of these cytokines in multinodular goiter (MNG), Graves' disease (GD), and Hashimoto's thyroiditis (HT). In addition, in vitro studies were carried out using the transformed human thyroid cell line, HT-ori3, and primary thyroid cell cultures derived from patients with GD. These cells were used either unstimulated or stimulated for 12 h with TSH, IL-1, or interferon-gamma (IFN-gamma). IL-12 p40 gene expression was identified in 2 of 10 MNG samples, 6 of 12 GD, and 3 of 4 HT. HT-ori3 and primary thyroid cell cultures were positive for IL-12 p40 messenger RNA (mRNA) expression in both unstimulated and stimulated cell cultures. IL-13 mRNA was expressed in 2 MNG, 9 GD, and 1 HT sample. Both HT-ori3 and primary thyroid cultures expressed IL-13 after TSH, IL-1, or IFN-gamma stimulation; unstimulated primary cultures of thyroid cells, however, did not express IL-13. IL-15 gene expression was detected in 8 MNG, 8 GD, and 4 HT samples. HT-ori3 and primary thyroid cell cultures, stimulated with TSH, IL-1, or IFN-gamma, showed expression of this cytokine. Unstimulated cells showed only a weak expression. Our results indicate that the cytokine patterns in the various diseases studied are heterogeneous; that thyroid cells can express IL-12, IL-13, and IL-15 mRNA in culture, particularly after TSH, IL-1, or IFN-gamma stimulation; and that IL-15 is expressed in most of the tissue samples studied.

Intrathyroidal cytokine gene expression in Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) is an organ-specific autoimmune disease in which cytokines are likely to have a role in the initiation and perpetuation of the disease. Using the reverse transcription-polymerase chain reaction (RT-PCR) we analysed the cytokine profile in four HT tissue samples. Furthermore, cell fractionation was carried out on two tissue samples and cytokine profile was studied in CD4+ and CD8+ T cells, in addition to the residual cellular infiltrate composed of CD4- and CD8- cells. Our results showed IL-1 beta, IL-4 and IL-6 mRNA expression in three out of four tissue samples, whereas IL-1 alpha, IL-2, IL-8, IL-10, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) were expressed in all tissue samples studied. Expression of IL-1 alpha and IL-1 beta was absent in both CD4+ and CD8+ subsets. However, IL-2, IL-4, IL-6, IL-8, IFN-gamma and TNF-alpha mRNA were detected in both CD4+ and CD8+ subsets. IL-10 was expressed in the CD4+ subset in one sample, whereas it was negative in both CD8+ fractions. All the cytokines studied were expressed in the residual infiltrate. These results suggest a mixed Th1 and Th2 response in HT, both of which may have an important role in the pathophysiology of the thyroid destructive process through cell-mediated cytotoxicity, and/or humoral autoimmunity manifested by autoantibody production.

Cytokines and thyroid function

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