Suppressor T lymphocyte dysfunction is important in the pathogenesis of autoimmune thyroid disease: a perspective

The Underestimated Impact of Hashimoto Thyroiditis on Thyroid Papillary Carcinoma

It is stated that Hashimoto's Thyroiditis (HT) is a risk factor for the development of Papillary Thyroid Cancer (PTC). However, the effect of HT on the coexistence of HT and PTC is still controversial. In this study, our aim is to investigate the effect of the presence of HT on clinicopathological data in patients with PTC. All 356 patients whose pathology was reported as PTC who were operated between 2015 and 2023 were included in the study. PTC patients were divided into 2 groups as those with and without HT. The effect of HT association on clinicopathological features was investigated. In 356 PTC patients, the rate of HT was 31.2%. PTC patients with HT had less multifocality (p < 0.05), more lymph node metastases (LNM) (p < 0.01) compared to PTC patients without HT. The presence of HT did not affect the bilaterality of the tumor, tumor diameter, lymphovascular invasion, or capsule invasion. While multifocality was observed less frequently in PTC patients with HT, lymph node metastasis rates were higher.

[Сhronic autoimmune thyroiditis is a «signal disease» in the multiorgan autoimmune syndrome]

The current century has been declared by the WHO as the «century of autoimmune diseases», of which there are more than a hundred today. The natural course of any autoimmune disease is characterized by progression from a latent and subclinical to a clinical stage and is associated with the presence of specific circulating autoantibodies. During the life of a person with one verified autoimmune disease, there is a high probability of consecutive manifestation of other autoimmune pathologies. Every fourth patient with chronic autoimmune thyroiditis develops autoimmune non-thyroid pathologies during his life, and vice versa, chronic autoimmune thyroiditis is present among people with non-thyroid autoimmune diseases. Modern ideas about the pathogenetic mechanisms of the development and progression of autoimmune diseases make it possible to consider chronic autoimmune thyroiditis as a «signal pathology» in the multiorgan autoimmune syndrome.

From Mysterious Supernatant Entity to miRNA-150 in Antigen-Specific Exosomes: a History of Hapten-Specific T Suppressor Factor

Soon after the discovery of T suppressor cells by Gershon in 1970, it was demonstrated that one subpopulation of these lymphocytes induced by i.v. hapten injection suppresses contact sensitivity response mediated by effector CD4+ or CD8+ T cells in mice through the release of soluble T suppressor factor (TsF) that acts antigen specifically. Our experiments showed that biologically active TsF is a complex entity consisting of two subfactors, one antigen specific and other non-specific, produced by differently induced populations of cells. In following years, we found that the antigen-specific subfactor is a light chain of IgM antibody that is produced by B1a lymphocytes. However, the exact nature of non-specific part remained a mystery for about 30 years. Our current studies characterized TsF as regulatory miRNA-150 carried by T suppressor cell-derived exosomes that are antigen specific due to a surface coat of IgM antibody light chains produced by B1a cells. The present communication briefly summarizes our studies on TsF that led to discovery of regulating miRNA that acts antigen specifically to suppress immune response.

The Pathogenesis of Hashimoto's Thyroiditis: Further Developments in our Understanding

Hashimoto's thyroiditis (HT) is part of a spectrum of thyroid autoimmune conditions and this review provides an update on the latest developments in the field. HT has a genetic predisposition with a number of immune-related and thyroid-specific genes conferring disease susceptibility. However, disentangling genes with protective and predisposing effect is a complex process that requires further work. The recent increase in the incidence of HT implicates environmental factors in disease pathogenesis including improved hygiene, increased dietary iodine intake, new treatment modalities and chemical agents. Additional unmodifiable predisposing factors include stress, climate, age and gender. Both cellular and humoral immunity play a role in HT pathogenesis. Defects in T regulatory cells and increased activation of follicular helper T cells may have a role in disease initiation/perpetuation. Infiltrating lymphocytes can be directly cytotoxic to thyroid follicular cells (TFC) or may affect cell viability/function indirectly through cytokine production, which alters TFC integrity and modulates their metabolic and immune function. Thyroid peroxidase and thyroglobulin antibodies are present in the majority of HT patients and help with management decisions. Antibodies against the sodium iodide symporter and pendrin are present in a minority with little known about their clinical relevance. In addition to immune cells, recent work has identified DNA fragments, generated following cell death, and micro RNA as potential factors in HT pathogenesis. Despite the large number of studies, the mechanistic pathways in HT are still not fully understood and further work is required to enhance our knowledge and identify novel preventative and therapeutic clinical targets.

CD4+CD25+Foxp3+ Treg cells and liver transplant tolerance

Several subgroups of regulatory T (Treg) cells play crucial roles in both induction and maintenance of immune tolerance to self-antigens and alloantigens. The most extensively and comprehensively studied regulatory T cell subgroup is CD4⁺CD25⁺Foxp3⁺ Treg cells. Numerous studies indicate that insufficiency or dysfunction of CD4⁺CD25⁺Foxp3⁺ Treg cells is responsible for the development of many autoimmune diseases and rejections after organ transplantation. Therefore, harnessing CD4⁺CD25⁺Foxp3⁺ Treg cells may provide a promising approach for inducing and maintaining liver transplant tolerance. In this review, we will focus on the history and classification of regulatory T cells, the mechanisms by which regulatory T cells induce transplant tolerance and their roles in liver transplant tolerance.

Comparative Study of Angiogenesis in Thyroid Glands With Graves Disease and Hashimoto's Thyroiditis

Angiogenesis entails the sprouting of new vessels from pre-existing vasculature. In adults, angiogenesis occurs in the thyroid gland during disease processes such as hyperplastic goiter, Graves disease, thyroiditis, and cancer. In the present study multiple morphologic characteristics of microvessels were measured in and compared between 18 cases of Graves disease, 29 cases of Hashimoto's thyroiditis, and 15 control cases. All histologic sections were immunostained for CD31. Quantification of microvessel density (MVD), major axis length, minor axis length, area, perimeter and shape factor was performed by image analysis. MVD was increased significantly in both forms of autoimmune thyroid disease. Significantly higher values were found in Graves disease in comparison to Hashimoto's thyroiditis. In contrast, major axis length, minor axis length, and area had significantly higher values in Hashimoto's thyroiditis than in Graves disease. The statistical analysis revealed MVD as the unique significant morphometric factor discriminating the two autoimmune entities.

New insights into antibody-mediated hyperthyroidism

The most common cause of hyperthyroidism is Graves' disease, which represents a typical example of an organ-specific autoimmune condition. The exact triggers for the disease remain unknown, but are likely to involve a complex interaction between multiple environmental factors in a genetically predisposed individual. The main feature of the condition is the presence of thyroid-stimulating antibodies, which activate the thyroid- stimulating hormone receptor, resulting in hyperthyroidism. These antibodies may also be involved in the extrathyroidal complications of the disease. The recent generation of thyroid-stimulating antibodies in animal models and the isolation of monoclonal thyroid-stimulating antibodies from a patient with Graves' disease should allow the detailed study of thyroid-stimulating antibodies-thyroid-stimulating hormone receptor interactions. This will help to shed more light on disease pathogenesis and may offer new treatment strategies in difficult cases, particularly in patients with extrathyroidal complications.

The autoimmune endocrinopathies the complexities continue to ravel

The organ-specific autoimmune endocrinopathies constitute a group of disorders related to one another and to some other nonendocrine autoimmune organ-specific diseases. Although there are genetic links between these entities, there are genetic differences as well; the suggestion of autoantigenic crossreactivity has not borne fruit and does not appear to explain these associations. Each condition may be due to a defect(s) in specific antigen-presenting genes, with consequential effects on specific T lymphocyte activation. Genetic overlap may explain poly-endocrine autoimmune disease or the appearance of different maladies in other family members. The immune response is extremely complex, but the many elements involved, and molecules that can interdict them, provide some promise for potential new therapeutic immunomodulatory interventions. (Trends Endocrinol Metab 1997;8:59-63). (c) 1997, Elsevier Science Inc.

The effect of adding a surfeit of autologous CD8+ T cells to SCID mice after secondary rexenografts of Graves' thyroid tissue

To investigate the effect of adding a surfeit of CD8+ T cells as a potential immunoregulator in Graves' disease (GD), thyroid tissues from 4 patients with GD and 2 normal subjects (N) were initially xenografted into nude mice. Eight weeks after xenografting, the thyroid tissues, which were then devoid of lymphocytes and appeared normal, were retrieved from the nude mouse, and rexenografted (rexenografts) into severe combined immuno-deficient (SCID) mice; 20 x 10(6) of autologous peripheral blood mononuclear cells (PMBC) or 20 x 10(6) of CD8(+)-depleted PBMC ("non-CD8 cells," i.e., CD4-enriched PBMC) were simultaneously engrafted into SCID mice with thyroid rexenografts. In addition, 20 x 10(6) of CD8(+)-enriched PBMC ("CD8-doubled" cells, which were prepared to double the percentage of CD8+ T cells compared to that of PBMC) were engrafted into SCID mice with rexenografts from 2 GD and 2 N; finally, 20 x 10(6) of PBMC plus an extra 10 x 10(6) of CD8+ T cells ("extra-CD8 added" cells, total 30 x 10(6) of CD8-enriched cells) were engrafted into separate SCID mice with rexenografts from 2 GD. The reengraftment of GD rexenografts or N rexenografts alone did not result in the detection of thyroperoxidase (TPO)-antibodies (Abs), thyroglobulin (Tg)-Abs, thyroid-stimulating Ab (TSAb) production, human IgG, or lymphocytic infiltration in the xenografts. However, the engraftment of either autologous PBMC or non-CD8 cells from patients with GD and N into SCID mice with rexenografts caused human IgG to become detectable and then rise further in 10 of 17 SCID mice; when human IgG, TPO-Ab, Tg-Ab, and TSAb were quantitated, GD rexenografts plus non-CD8 cells engrafted into SCID mice showed a higher production of each antibody and human IgG than in GD rexenografts plus PBMC, or GD rexenografts plus CD8-doubled cells, or GD rexenografts plus extra "CD8-added" cells. Moreover, when CD8-doubled cells or extra CD8-added cells with rexenografts were engrafted to SCID mice with rexenografts, they showed generally lower production of human IgG and thyroid antibodies compared to SCID mice into which PBMC were engrafted with rexenografts, despite the fact that 50% more cells (30 x 10(6)) were engrafted in the preparations of extra CD8-added cells. In conclusion, CD8+ T cells from patients with GD appeared to suppress the induction of thyroid antibodies, TSAb, and human IgG. The CD8+ cells thus are acting as suppressor or regulatory T cells. Such cells might be important in the pathogenesis of autoimmune thyroid disease.

Metabolism of glucose and glutamine in lymphocytes from Graves' hyperthyroid patients: influence of methimazole treatment

Several studies have shown that thyroid hormones are able to influence selected immune responses such as cell mediated immunity, differentiation of B lymphocytes and the activity of NK cells. These hormones can also regulate the metabolism of glucose and glutamine in rat macrophages and their effects seem to occur mainly through the Krebs cycle. Alterations in the hexokinase, citrate synthase, glucose-6-phosphate dehydrogenase and glutaminase activities in lymphocytes from patients with Graves' disease, either untreated or on methimazole (MMI) therapy were investigated. Experiments were also done in vitro to determine the activities of these enzymes in normal lymphocytes cultured for 24 h in the presence of MMI T3 and T4 using concentrations close to the physiological. Changes in the conversion of [U-14C]-glucose and [U-14C]-glutamine to 14CO2 as caused by the addition of MMI, T3 or T4 to the culture medium were also evaluated. The results indicate that high levels of thyroid hormones might stimulate the metabolism of glucose and glutamine for a short period of time but, if the stimulus is maintained, the utilization of glutamine by lymphocytes is then suppressed. Moreover, MMI does affect lymphocyte metabolism but the significance of this finding for its immunosuppressive effect remains to be examined.

The Pathogenesis of Graves’ Disease

We have hypothesized over many years that Graves' disease (GD) and the other autoimmune thyroid diseases (AITD) are each due to antigen-specific defects in suppressor (regulatory) T lymphocyte function. There have been several reports dealing with the role of regulatory T lymphocyte subsets, ie., that will prevent autoimmune disease in these and other organ-specific autoimmune diseases. In AITD, suppressor T cells have been shown to be less well activated by relevant antigen, but are normally activated by irrelevant antigen; suppressor T cells from normal persons react equally well to both. In GD, these cells have been shown to be inadequately activated by TSH receptor antigen, but are normally activated by irrelevant autoantigen. This reduction is partial only, and insufficient itself to precipitate the autoimmune disease; further insults from the environment are necessary to further reduce generalized regulatory cell activity, adding to the genetically induced specific regulatory cell dysfunction, which appears in turn to be due to a specific defect in the presentation of a specific antigen. This, in turn, may relate to abnormalities of the genes responsible for antigen presentation. The end result is activation of appropriate helper and effector T cells, the stimulation by these of appropriate B lymphocytes, and the concurrent production of cytokines. These events lead to functional changes within the target cell which itself will express Class II antigens, heat shock proteins, and intercellular adhesion molecules, all of which amplify the immune response. Moreover, the activation of helper T lymphocytes by specific antigen depends on the availability of normal amounts of antigen being presented to them by antigen-presenting cells. Thus, there is no need to invoke any primary abnormality or infection of the thyroid cell, or any cross-reacting antigen of microorganismic origin to initiate this process. What is required is an abnormality of antigen-presentation such that regulatory cells are not properly activated, plus some additive environmental disturbance acting on the immune system. GD specifically results from the production by B lymphocytes of an antibody directed against the TSH receptor which stimulates the thyrocyte in a manner similar to TSH, but for a much longer interval. There are also antibodies to the thyrotrophin (TSH) receptor which block the action of TSH. Thyroid stimulating antibody is typical of GD and is detectable in about 95% of cases, but is also seen in destructive thyroiditis transiently. It tends to decline with antithyoid drug therapy, and rises further (for several months) after 131 I treatment. It may slowly decline after subtotal thyroidectomy. It also declines in the third trimester of pregnancy but sometimes is sufficiently high to cause foetal and neonatal passive transfer GD. It tends to rebound in the mother after delivery and may result in postpartum GD. The blocking antibody may cause atrophic thyroiditis and hypothyroidism. Antimicrosomal antibody has now been shown to be antithyroperoxidase. It correlates moderately well with thyroid dysfunction in Hashimoto's thyroiditis (HT) and GD, while antithyroglobulin is of much less value. Graves' ophthalmopathy is still not well understood, and its precise relationship to Graves' hyperthyroidism has yet to be worked out. However the retroorbital fibroblast is now emerging as the most likely target cell, with retroorbital muscle involvement possibly secondary. A recent observation of a genomic point mutation on the TSH receptor on fibroblasts from patients with Graves' ophthalmopathy but not normal persons raises interesting possibilities.

The basis of autoimmunity: an overview

Autoimmune diseases represent a failure of control in the immune system. In recent years, our understanding of the mechanisms of action of both the innate and the specific immune responses has increased greatly. In particular, we now know much more about the nature of antigens recognized by lymphocytes, as well as how diversity of antigen receptors is generated, antigens and antigen receptors interact, and the cells of the immune system communicate. It is apparent that an inevitable consequence of the diversity of the potential response to antigen is self-reactivity. However, the relative infrequency with which pathological self-reactivity occurs implies the existence of effective control of immune responses. The conditions under which immune responses can be activated, and the factors which regulate their progression, have been subjected to detailed scrutiny. Several of the mechanisms involved in the removal or inactivation of self-reactive lymphocytes, the process of self-tolerance, are now understood. What is less clear are the conditions under which, and the mechanisms by which, this self-tolerance can break down, giving rise to autoimmunity. Several classes of explanation have been put forward to explain this failure of self-tolerance. Although they are of great theoretical interest, proof of their involvement in the pathogenesis of the major autoimmune diseases is largely lacking. A further expansion of our understanding of the mechanisms by which self-tolerance is normally maintained is still needed, in order to comprehend the pathways of breakdown of this tolerance in autoimmunity. Only then will sites and mechanisms for effective therapeutic intervention be identified.

Immunoregulation in autoimmune thyroid disease

We have postulated over many years that autoimmune thyroid diseases (AITD) are disorders of immunoregulation due to antigen specific defect(s) in suppressor (regulatory) T (Ts) lymphocyte function. Despite earlier skepticism, there is recent increased evidence to support this view. Several investigators working with animal models have demonstrated T lymphocyte subsets that are regulatory, i.e., will prevent AITD; conversely, depletion of these cells precipitates the lesion in the experimental models. These cells have been shown to be inadequately activated by specific antigen. In human AITD, recent studies have demonstrated that CD8+ (suppressor/cytotoxic) and CD8+CD11b+ ("pure suppressor") cells are activated by irrelevant antigen normally, but are significantly less well activated in response to thyroglobulin or thyroperoxidase. In further similar studies, CD8+ cells from patients with Graves' disease (GD) are induced normally in response to glutamic acid decarboxylase-65 (GAD-65), the putative beta cell antigen important in insulin-dependent diabetes mellitus (IDDM), but significantly less to synthetic TSH receptor (TSHR). Conversely, CD8+ cells from patients with IDDM are activated normally in response to TSHR, but significantly less to GAD-65. While these reductions in activation are partial only, and other additive factors playing on the immune system may be necessary to precipitate AITD, this disorder in the activation of Ts cells may be fundamental to the development of these disorders. This in turn may be due to molecular disturbances in MHC-related genes that dictate the mechanisms of presentation of specific antigen.