Why thyroid is major site of thyroid autoantibody synthesis in autoimmune thyroid disease

Analysis of T cell receptor Vbeta diversity in peripheral CD4 and CD8 T lymphocytes in patients with autoimmune thyroid diseases

Autoimmune thyroid diseases are characterized by intrathyroidal infiltration of CD4(+) and CD8(+) T lymphocytes reactive to self-thyroid antigens. Early studies analysing T cell receptor (TCR) Valpha gene usage have shown oligoclonal expansion of intrathyroidal T lymphocytes but not peripheral blood T cells. However, TCR Vbeta diversity of the isolated CD4(+) and CD8(+) T cell compartments in the peripheral blood has not been characterized fully in these patients. We performed complementarity-determining region 3 (CDR3) spectratyping as well as flow cytometric analysis for the TCR Vbeta repertoire in peripheral CD4(+) and CD8(+) T cells from 13 patients with Graves' disease and 17 patients with Hashimoto's thyroiditis. Polyclonal TCR Vbeta repertoire was demonstrated by flow cytometry in both diseases. In contrast, CDR3 spectratyping showed significantly higher skewing of TCR Vbeta in peripheral CD8(+) T cells but not CD4(+) T cells among patients with Hashimoto's thyroiditis compared with healthy adults. We found trends towards a more skewed CDR3 size distribution in those patients having disease longer than 5 years and requiring thyroid hormone replacement. Patients with Graves' disease exhibited no skewing both in CD4(+) and CD8(+) T cells. These findings indicate that clonal expansion of CD8(+) T cells in Hashimoto's thyroiditis can be detected in peripheral blood and may support the role of CD8(+) T cells in cell-mediated autoimmune attacks on the thyroid gland in Hashimoto's thyroiditis.

Balance of Th1/Th2 cytokines in thyroid autoantibody synthesis in vitro

Thyroid-infiltrating lymphocytes spontaneously synthesize IgG class thyroid autoantibodies while blood lymphocytes require activation to produce the same autoantibodies. Surprisingly, the stimulus commonly used to induce autoantibodies by blood lymphocytes, Pokeweed mitogen (PWM), inhibits autoantibody synthesis by thyroid lymphocytes. To address this dichotomy, we investigated the Th1: Th2 cytokine balance in relation to thyroid peroxidase (TPO) autoantibody production in cultures of thyroid, lymph node and blood lymphocytes. The characteristic PWM effect on TPO autoantibody production by thyroid and blood lymphocytes (10 day cultures) was confirmed. Cytokine measurements in these cultures revealed that PWM increased IFN-gamma production by thyroid, lymph node and blood lymphocytes. However, PWM enhanced IL-4 levels in lymphocytes from blood and lymph node but not in thyroid lymphocytes. Moreover, the IL-4: IFN-gamma ratios in short- and long-term cultures were higher for PBMC and lymph node lymphocytes than for thyroid lymphocytes. In summary, PWM shifts the cytokine balance towards Th2 for blood lymphocytes and towards Th1 for thyroid lymphocytes. The shift towards Th1 in the target organ is associated with reduced autoantibody synthesis. Our observations suggest that "immune deviation" towards Th2 as a form of therapy in Graves' disease could project the patient from the frying pan into the fire.

The pathology of autoimmune thyroid disease: a review

Lymphocytic infiltration of the thyroid gland is the pathologic hallmark of autoimmune thyroid disease. Lymphoid cells are seen in the stroma of glands affected by Graves' disease. However, large lymphoid infiltrates are characteristic of that spectrum of diseases conveniently termed chronic lymphocytic thyroiditis. In this review, the pathology of the various subtypes of chronic thyroiditis is enumerated, including recently defined lesions, i.e., painless thyroiditis, thyroiditis associated with interleukin chemotherapy, and peritumor thyroiditis are reviewed. The unifying morphologic characteristics seen in these conditions are discussed.

CD5+ B lymphocytes and CD4+ CD45RA+ T cells in Graves' disease

Fifteen patients affected by new-onset Graves' disease with ophthalmopathy have been examined for lymphocyte subset phenotypes by two-colour cytometric analysis. CD5+ B cells were significantly increased in comparison to the normal population (43.2 +/- 20.6% versus 19.5 +/- 6.9%; p < 0.0009); total T cells showed a normal amount (70.4 +/- 9.6%), but the levels of THLADR+ cells were significantly increased in comparison to the control group (13.7 +/- 10.5% versus 4.7 +/- 3.2%; p < 0.007). The characterization of the subset suppressor-inducer CD4+ CD45RA+, evaluated as percentage of the total CD4+ T cells, showed a significant decrease in comparison with the control group (43.8 +/- 13.5% versus 52.3 +/- 6.5%; p < 0.03). Serum immunoglobulin evaluation showed a statistically significant increase of IgM (p < 0.05) and a significant decrease of IgA (p < 0.02). A statistical correlation between IgM levels and percentage of CD5+ B cells has been found (p < 0.04). The defect of suppressor-inducer T cell subset, along with the increase of CD5+ B cells may contribute to the pathogenetic mechanism of the disease in patients with a genetically-induced aberrant immune response.

Graves' disease: phenotypic and functional analysis at the clonal level of the T-cell repertoire in peripheral blood and in thyroid

We have investigated at the clonal level the repertoire of intrathyroid and peripheral T lymphocytes in three patients with Graves' disease using a high efficiency cloning technique. Clonal efficiencies ranged from 10 to 31% for intrathyroid, and from 19 to 100% for peripheral T cells. In Graves' disease the phenotypic analysis showed similar percentages of CD3+ CD4+ CD8- and CD3+ CD4- CD8+ clones in thyroid infiltrates and peripheral blood. The functional evaluation showed similar or lower proportions of cytolytic clones in thyroid infiltrates with respect to peripheral blood. Furthermore, the proportions of intrathyroid and peripheral T-cell clones capable of releasing interleukin-2 and/or gamma-interferon in response to mitogen stimulation were similar. Finally, 44% of intrathyroid clones were neither cytolytic nor able to release IL-2 and gamma-interferon. These results are strikingly different from those obtained in Hashimoto's thyroiditis, where the large majority of intrathyroid T-cell clones are cytolytic and the proportions of clones able to release gamma-IFN are remarkably increased in thyroid infiltrates when compared to those obtained from peripheral blood. Taken together, these data suggest a different role for T lymphocytes in the pathogenesis of the two major human autoimmune thyroid diseases.

Autoimmune thyroid disease: immunological, pathological, and clinical aspects

Autoimmune thyroiditis, most notably Hashimoto's thyroiditis, appears to be increasing in prevalence and is now more easily detected by sensitive laboratory tests and more invasive procedures such as fine needle aspiration. During the last decade, marked progress has been made in the understanding of these diseases. There is a greater awareness of the interaction between the humoral and cell-mediated arms of the immune system in autoimmune thyroiditis. Recent studies implicate a subpopulation of suppressor T lymphocytes which have an antigen-specific defect, resulting in their suboptimal interaction with the helper T lymphocytes and subsequent autoimmune manifestations. There is some evidence that thyroid epithelial cells which inappropriately express HLA-DR may enhance presentation of thyroid antigens to the immune system, possibly significant in the initiation or enhancement of the autoimmune response. The presence of various antithyroid autoantibodies allows the use of laboratory assays to confirm the clinical diagnosis and predict the results of treatment. There appears to be predisposing genetic factors in the development of autoimmune thyroiditis, with some geographical and racial differences. Environmental factors, most notably dietary intake of iodine, have also been implicated in the pathogenesis of Hashimoto's thyroiditis. Several animal models have been developed addressing such issues. Ongoing studies in the areas of postpartum thyroiditis and childhood thyroiditis are helpful in clarifying their relationship with Hashimoto's thyroiditis. Graves' disease and postpartum thyroiditis are being investigated as possible causes of postpartum depression. The association of Hashimoto's thyroiditis and carcinoma of the thyroid gland is still controversial, but its relationship with malignant lymphoma is now well accepted. Thus, although the pathogenesis of autoimmune thyroiditis remains elusive, there has been significant refinement of the clinical diagnosis, and immunological abnormalities of specific intrathyroidal lymphocytes have been identified. Hopefully, these new areas of knowledge will assist in the treatment of these diseases and in the prevention of the development of malignant lymphomas of the thyroid gland.

Separation and analysis of mononuclear cells infiltrating the thyroid of patients with Graves' disease

A simple method was established for separating lymphocytes infiltrating the thyroid from thyroid epithelial cells. Namely, suspensions of minced thyroid from patients with Graves' disease were layered on a Percoll two-step density gradient (p = 1.050 and 1.077 g/ml) and centrifuged (400g, 30 min, 4 degrees C). In this way 0.1-18 X 10(5) lymphocytes/g of thyroid tissue with a purity of 65-95% were obtained. Thyroid lymphocytes were analyzed quantitatively with monoclonal antibodies by laser flow cytometry and compared with peripheral lymphocytes. The proportion of OKT3+ cells was decreased with increase in OKIa+ cells. The percentage of OKIa+ cells was significantly correlated with that of Leu12+ cells. The percentages of OKT4+ cells and OKIa+ cells were higher when analyzed with an extended gate window, which was arranged for detection of activated, large-sized lymphocytes. The percentages of OKT8+ and Leu7+ cells were not significantly different from those in peripheral blood. From these results it was concluded that the proportion of B lymphocytes is increased and that of T lymphocytes is decreased, the proportion of activated B lymphocytes is increased, some helper/inducer T cells are activated in the thyroid gland in Graves' disease, and these activated lymphocytes may be important in local production of antithyroid autoantibodies.

T cell subsets and thyroid-stimulating antibodies in patients with Graves' disease in clinical remission

Patients with active Graves' disease almost constantly show phenotypic alterations of T lymphocytes, such as an increase of "activated" cells recognized by various surface markers (e.g. la antigens). Such alterations are present in a certain number of apparently cured patients. The data herein reported refer to 25 patients with Graves' disease in clinical remission, in whom we have attempted to correlate T cell subset imbalances, the presence of thyroid-stimulating antibodies (TSAb) and the outcome of the subsequent relapse. The results obtained show a significant association between TSAb and the increase of la-positive T cells: no relationship was found between TSAb and other T lymphocyte subsets. One-year clinical follow-up of the patients enabled us to see relapses of hyperthyroidism in only two patients, who had shown in the first control both TSAb positivity and increased la-positive T cells. These results, in our opinion, suggest a role of la antigens expression on T lymphocytes in the clinical course of Graves' disease.

Proliferation of T8-positive cytolytic T lymphocytes in response to thyroglobulin in human autoimmune thyroiditis: analysis of cell interactions and culture requirements

These experiments were designed to analyze the involvement of T-lymphocyte subpopulations in autoimmune thyroid disorders such as Graves' Disease (GD) and Hashimoto's Disease (HD). In a first set of experiments, lymphocytes isolated from thyroid infiltrates or from peripheral blood of GD and HD patients were analyzed for the expression of various surface antigens. While HLA-DR + T cells were numerous among thyroid infiltrating T lymphocytes in both groups of patients, the proportions of T8 + cells (as defined by their reactivity with the B 9.4 monoclonal antibody specific for T8 surface molecule) were strikingly different in HD and GD. In the latter group of patients only 19% of infiltrating T cells were T8 +, whereas these cells represented approximately 50% in four HD patients. Given the previous demonstration that all T cells expressing T8 antigen are cytolytic T lymphocytes (CTL) or their precursors (CTL-P) in conjunction with the fact that lymphocytes from HD or GD patients are known to proliferate in vitro in response to human tg (Htg), we further analyzed the T-cell subset(s) responsible for in vitro proliferation to Htg. In these experiments, peripheral blood T lymphocytes purified from patients with GD or HD were cultured with 1 microgram/ml Htg and irradiated autologous T-depleted mononuclear cells as the source of antigen presenting cells (APC). The proportions of T8 + cells declined considerably during culture in GD patients, but at Days 6 to 9, T8 + cells represented as much as 51% of cultured T lymphocytes from patients with HD. Moreover, the majority of T8 + cells were medium-large size lymphoblasts. Removal of Htg at Day 6 resulted in both abrogation of proliferative responsiveness and in decreases of T8 + percentages. Further analysis of the cell interactions leading to T8 + cell proliferation in response to Htg showed that helper/inducer T cells, as defined by 5/9 antigen expression, were strictly required. Collectively, these features are reminiscent of the T-cell involvement in experimental autoimmune thyroiditis of mice and stress for the first time the potential role of CTL in tissue damage occurring in Hashimoto's thyroiditis.

Autoimmune thyroid disease: purification and phenotypic analysis of intrathyroid T cells

A phenotypic analysis of T cells infiltrating the thyroid of patients with autoimmune thyroid disease (both Graves' disease and Hashimoto's thyroiditis) was performed. T lymphocytes were purified from mononuclear cells extracted from surgically removed tissue. The following markers were evaluated: la antigens, MLR4 antigen (expressed on activated T cells) 5/9 antigen (expressed on a subset of lymphocytes containing the whole "helper-inducer" activity in vitro), Fc gamma-receptors, B9 antigen (expressed by cytotoxic, or precursor of cytotoxic, T cells). We observed increased percentages of 5/9-, MLR4- and la-positive T cells with respect to peripheral blood in both HT and GD: on the contrary, in specimens from nonautoimmune thyroid diseases mononuclear infiltrate was minimal, and even T cell evaluation was not possible. In addition, B9- and Fc gamma-positive T cells were increased in Hashimoto's, but not in Graves' thyroid tissue, thus suggesting a different role of cytotoxic effector mechanisms in the two diseases.

Thyroglobulin-induced T-cell in vitro proliferation in Hashimoto's thyroiditis: identification of the responsive subset and effect of monoclonal antibodies directed to Ia antigens

Recently it was reported that the peripheral blood and thyroid gland of patients with Hashimoto's thyroiditis contain activated (Ia+ and/or MLR4+) T cells and high levels of 5/9+ ("helper") T lymphocytes. In normal individuals the 5/9 monoclonal antibody recognizes a T-cell fraction that includes all T lymphocytes with inducer activities. Here, circulating 5/9+ and 5/9- T lymphocytes were isolated from patients with Hashimoto's disease, and the proliferative response induced by human thyroglobulin was investigated. The results show that the total thyroglobulin-induced lymphocyte DNA synthesis is confined to the 5/9+ T-cell fraction. Further subfractionation of 5/9+ into MLR4+ and MLR4- cells clearly indicates that no substantial differences exist in their proliferative capacities. Whether 5/9, MLR4, and Ia antigens, all expressed on the thyroglobulin-responsive T-cell subset, are involved in thyroglobulin-induced cell proliferation, was also analyzed. Although both 5/9 and MLR4 monoclonal antibodies had no effect, complete inhibition of antigen-induced blastogenesis was observed upon addition of monoclonal antibodies (D1/12 and BT2/9) directed to common determinants of Ia antigens. This inhibitory effect was also observed when T or non-T fractions were separately incubated with the monoclonal antibodies before culture. These results indicate that in humans, as in animals, the major histocompatibility complex may play a role in autoimmune thyroiditis. The data show that (a) the thyroglobulin-induced proliferative response is confined to a subset (5/9+) of T lymphocytes and (b) Ia antigens are involved in thyroglobulin-induced lymphocyte DNA synthesis in Hashimoto's disease.

Immunohistochemical characterization of intrathyroid lymphocytes in Graves' disease. Interstitial and intraepithelial populations

The phenotypic cell surface markers of the lymphocytes present in thyroid tissue from four patients with Graves' disease were quantitatively analyzed using the avidin-biotin immunoperoxidase technique. As control specimens, normal perinodular tissues from three patients who had benign thyroid nodules resected were also studied. In contrast to normal thyroid tissue, which contained very few T cells and no B cells, thyroid tissue of all four patients with Graves' disease contained a lymphocytic infiltrate, and this could be divided into two populations of lymphocytes. The first population was located in the follicular epithelium and expressed a cytotoxic-suppressor T cell marker (Leu2a). On the average, these cells were 4.2 times as numerous in Graves' tissues as in normal tissues (p less than 0.05). Most of these cells did not express Leu1, a pan-T cell marker. The second population was found in the interstitial tissues, often within lymphoid aggregates, and 70 to 83 percent of the cells expressed Leu1. The majority of these cells expressed a helper-inducer T cell marker, Leu3a; Leu3a/Leu2a ratios within aggregates ranged from 1.9 to 2.1. The number of B cells present was small, ranging from 5.8 to 12.1 percent of the interstitial lymphocytes. These findings are consistent with the involvement of both helper-inducer and suppressor-cytotoxic T cells in a localized autoimmune reaction directed, at least in part, against the thyroid follicular epithelial cells.

Incidence of T cell subset imbalance in relatives of Graves' disease patients

In previous reports we demonstrated imbalances of T cell subsets in patients with autoimmune thyroid disease. In the present investigation, we studied several T cell markers with different functional meaning (Fc gamma-receptors, HLA-Ia antigens, MLR4 and 5/9 antigens) in first degree relatives of Graves' disease patients. Our data suggest that imbalances of circulating T cell subpopulations are apparent only when abnormal hormone levels and/or thyroid autoantibodies are present.

Aberrant expression of HLA-DR antigen on thyrocytes in Graves' disease: relevance for autoimmunity

To investigate the expression of class II histocompatibility antigens HLA-DR in the thyrocytes in autoimmune thyroid diseases, 47 thyroidectomy specimens were examined by immunofluorescence with monoclonal antibodies to the nonpolymorphic region of the DR molecule. Aberrant DR expression was most marked in the Hashimoto gland, with the entire section being strongly stained. DR expression was seen in discrete groups of follicles in 20/26 thyroids from patients with Graves' disease, in 2/9 non-toxic nodular goitres, and in none of 11 specimens of "normal" thyroid. The presence of lymphoid foci, "activated" T-cells, and immune complexes on the follicular basement membrane were not regularly associated with the DR-positive thyroid acini. HLA-A,B,C expression was also increased in the diseased glands. Expression of HLA-DR thus seems to be one of the earliest manifestations of autoimmune lymphocytic thyroiditis.