Autoimmune murine thyroiditis VII: induction of the thyroid lesions by passive transfer of immune serum

Recognition of thyroglobulin by T cells: the role of iodine

Among known autoantigens, thyroglobulin (Tg) is unique in its capacity to store iodine, an element provided in our daily diet. Evolutionary pressure has sculpted Tg into a large molecular scaffolding to allow organification of iodide and its incorporation into thyroid hormones. The increase in molecular size and the posttranslational modification by iodine had to exact immunological consequences. Over the last 15 years, numerous Tg peptides-targets of thyroiditogenic T cells-have been mapped, raising questions regarding the mechanisms that maintain or abrogate immune tolerance against this large autoantigen. This review summarizes the work in this area and discusses the role iodine may play in these processes.

Newer insights into the pathogenesis of experimental autoimmune thyroiditis

Experimental autoimmune thyroiditis (EAT), produced in the mouse by immunization with murine thyroglobulin plus complete Freund's adjuvant, represents a valuable model for studying the pathogenesis of human chronic (Hashimoto's) thyroiditis. A major issue requiring clarification is the difference between benign autoimmunity, characterized solely by production of autoantibodies to thyroglobulin, and pathogenic autoimmunity where injury occurs to the thyroid cells. In this article, we describe the role of two key cytokines, IL12 and IFNgamma, in modifying the pathogenic immune response. EAT, defined by cellular infiltration of the thyroid and the development of thyroglobulin-specific autoantibodies, is a dynamic process. Consequently, a cytokine may exert a different effect at different times during the disease process. For purposes of discussion, we propose that there are three stages in the development of EAT: priming; initiation; and progression. Administration of anti-IL12 during the priming stage and initiation dramatically decreases disease and lowers autoantibody levels. In contrast, injection of recombinant IL12 after disease was established significantly decreases the severity of disease and reduces autoantibody levels. Unlike IL-12, IFNgamma was not essential for the priming of EAT. However, the severity of disease in the anti-IFNgamma-treated initiation- and progression-treated animals was higher than in controls, implying a regulatory role for IFNgamma. These findings emphasize that EAT involves a complex array of pathogenic mechanisms. The balance of cytokines produced during the early phase of the autoimmune reaction probably determines the progression from a harmless autoimmune response to autoimmune disease.

Suppression of murine thyroiditis via blockade of the CD40-CD40L interaction

The CD40 ligand (gp39) is transiently expressed on activated CD4+ T cells and mediates cognate helper function by interacting with CD40 on B cells. Increasing evidence suggests, however, critical involvement of gp39 not only in antibody-mediated responses but also in the development of effector T cells. Here, we have investigated the effect of in vivo gp39 blockade on the induction of murine experimental autoimmune thyroiditis (EAT), a T-cell-mediated disease. Over a 5-week period, EAT was induced in SJL mice with thyroglobulin (Tg) and adjuvant. Concomitantly, mice received intraperitoneal (i.p.) injections of MR1, a gp39-specific hamster monoclonal antibody (mAb), at 4-day intervals. Control mice were challenged with Tg but received equivalent doses of hamster immunoglobulin (HIg). It was observed that the control mice developed severe thyroiditis whereas the MR1-treated mice exhibited very low levels of infiltration that were mostly focal in nature. Blockade of gp39 was effective since the Tg-specific IgG titres were low or undetectable in all MR1-treated animals compared with the controls. In addition, upon restimulation with Tg in vitro, lymph node cells (LNC) from Tg-primed, MR1-treated mice proliferated less strongly and secreted significantly lower amounts of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) than LNC from untreated or HIg-treated controls. These results strongly suggest that in vivo blockade of gp39 suppresses EAT by inhibiting the priming of inflammatory Tg-specific T-helper type 1 cells.

The effect of soluble complement receptor 1 (sCR1) and human thyroid antibodies on the course of experimental autoimmune thyroiditis in rats

Experimental autoimmune thyroiditis (EAT), induced by immunisation of rats with thyroid extract and complete Freund's adjuvant, has been used as a model to study the effects of complement inhibition mediated by soluble complement receptor 1 (sCR1) administration during the initial phase of the disease. There was no effect of sCR1 on the severity of thyroiditis at day 28 after immunisation or on the levels of thyroid antibodies, whether sCR1 was given during the first or second week after immunisation. Human IgG containing high levels of thyroid peroxidase antibodies given to rats at the time of immunisation caused significant worsening of thyroiditis severity (P < 0.01 compared to animals receiving normal IgG) but sCR1 again had no effect in this variant of the EAT model. The results indicate that complement does not play a major role in the initial phase of tissue injury in EAT and complement inhibition does not impair the generation of an autoimmune response against the thyroid, although it remains possible that complement activation is important during the chronic phase of disease maintenance in human autoimmune thyroid disease.

Histological and functional changes in the thyroid glands of mice implanted with hybridomas secreting monoclonal autoantibody against mouse thyroglobulin

Mouse hybridoma cells secreting monoclonal antibody (mAb) against mouse thyroglobulin were established. The implantation of the hybridomas succeeded to induce high titers of circulating mAb against thyroglobulin in sera of mice. By using the implantation of the hybridomas in mice, the effect of autoantibody on the thyroid glands was studied histologically and functionally. In these mice the thyroid follicles were significantly swollen and warped, whereas there was no infiltration of inflammatory cells. The 125I-uptake in their thyroid glands was markedly decreased. There were no functional changes in control mice implanted with non-secreting P3U1 partner cells. Therefore, it was suggested that high titers of anti-thyroglobulin autoantibody could definitely cause the histological and functional damages in the thyroid glands.

Experimental autoimmune thyroiditis in mice chronically treated from birth with anti-IgM antibodies

The role of T lymphocytes in the pathogenesis of experimental autoimmune thyroiditis in mice is well established while the role of B lymphocytes is unclear. Mice with thyroid lesions have thyroglobulin antibodies whereas these antibodies can occur in mice immunized with Tg that do not develop thyroid lesions. To determine whether thyroglobulin antibodies are necessary for the development of the thyroid infiltrates with mononuclear cells, which are characteristic for experimental autoimmune thyroiditis, AKR mice chronically treated from birth with goat anti-mouse IgM antibodies were immunized with mouse thyroglobulin in Freund's complete adjuvant when they were 7 weeks old. Control mice, similarly immunized, were chronically injected from birth with normal goat gamma-globulin. Three weeks after immunization, all mice were sacrificed, thyroglobulin antibodies in the serum were measured by hemagglutination assay and enzyme-linked immunosorbent assay, and thyroid pathology was assessed. The serum concentration of IgG and IgM, the percentage of B and T lymphocytes in the spleen (flow cytometry), and the in vitro proliferative response of spleen lymphocytes to stimulation by PHA, LPS, and Tg were also measured. All mice treated with anti-IgM antibodies did not have detectable thyroglobulin antibodies but 63% of these mice and 88% of control mice (all of which had thyroglobulin antibodies) had thyroid lesions. Mice treated with anti-IgM antibodies that did not have thyroid lesions had a more pronounced depression of B lymphocytes than similarly treated mice that had thyroid lesions. These experiments suggest that thyroglobulin antibodies are not necessary for the development of thyroid infiltrates with mononuclear cells. B lymphocytes could still participate in the production of experimental autoimmune thyroiditis by presenting thyroglobulin to helper T lymphocytes.

Induction of experimental autoimmune thyroiditis in B cell-depleted mice

The effect of B cell depletion on the induction and severity of murine experimental autoimmune thyroiditis was investigated. Thirteen CBA mice were given repeated intraperitoneal doses of 700 micrograms purified rabbit anti-mouse Ig antibody from 24 hours to 8 weeks after birth. Controls were given normal rabbit IgG (14 mice) or were left uninjected (10 mice). At six weeks all mice received two doses of 70 micrograms murine thyroid extract in complete Freund's adjuvant. Only 2/13 of the anti-Ig treated mice were fully B cell-deficient as determined by serum IgM, spleen cell immunofluorescence and responsiveness to LPS; however, the levels of anti-thyroglobulin autoantibodies were very low in 7/13 mice. The results demonstrate that thyroiditis can be actively induced in the absence of B cells and autoantibodies but that B cells may play a role in increasing disease severity.

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.

Microbial adjuvant and autoimmunity. IV. The induction of thyroid lesions in syngeneic X-irradiated mice by the transfer of spleen cells from mice immunized with thyroid extract and Klebsiella O3 lipopolysaccharide

The role of humoral and cellular immune responses in the initiation and maintenance of autoimmune thyroiditis was investigated in mice immunized with syngeneic thyroid extract and Klebsiella O3 lipopolysaccharide (KO3 LPS) as an adjuvant. The transfer of spleen cells from hyperimmunized mice to 400R-irradiated syngeneic mice produced definite lesions in the thyroid glands, whereas the transfer of immune sera failed to do so. No lesions were induced in normal intact mice by the same transfer of sera and spleen cells from hyperimmunized mice. It was suggested that the induction of thyroiditis by immunization using KO3 LPS adjuvant is primarily due to cell-mediated immunity and that pretreatment of mice by X-irradiation is essential for production of the lesions. The role of X-irradiation in the induction of thyroiditis was discussed.

Cell-mediated immunity in autoimmune thyroid disease

The initiation of an autoimmune response requires the establishment of an appropriate microenvironment. This, in turn, involves several requirements, including antigen expression on the membrane surface of the target cells, class II antigen expression on the antigen-presenting cell or target cell, a relative systemic or local increase in the helper/inducer subset of T cells, and/or a relative decrease in the suppressor subset of T cells. All of these conditions have been described in the thyroid gland. Appropriate cellular interactions result in the appearance of activated T cells and the generation of cytotoxic T cells. The pathologic alterations may be produced by the local production of antibody and subsequent formation of immune complexes, by direct lymphocyte damage, or by lymphokine production. Autoimmune thyroid disease remains, to our minds, the most instructive paradigm of the organ-specific autoimmune endocrinopathies.

Influence of immunomodulators, niridazole and levamisole, on autoimmune murine thyroiditis

The pathogenesis of murine autoimmune thyroiditis, induced in mice by immunization with mouse thyroglobulin emulsified in Freund's complete adjuvant, is unclear. To investigate the role of cell-mediated immunity in the murine thyroiditis, niridazole (100 mg/kg) and levamisole (12.5 mg/kg) were administered in mice before or after the antigenic challenge. Niridazole decreased the severity of thyroid infiltrates when started before the antigenic challenge. A similar inhibitory effect was observed after administration of levamisole. These findings are consistent with the possibility of a direct involvement of T-lymphocytes in the pathogenesis of autoimmune murine thyroiditis.

Immunohistochemical and electron microscopic studies on Hashimoto's thyroiditis

The thyroid glands of nine patients with Hashimoto's thyroiditis were studied by immunoperoxidase method for immunoglobulin (Ig) and thyroid hormone, and of these four tissue specimens were further examined by electron microscope. Immunoperoxidase method for Ig revealed that about 63% of the infiltrating cells contained Ig, and that about 90% of such Ig-containing cells had IgG. IgG-containing cells seemed to secrete autoantibodies. Immunoperoxidase method for thyroid hormone and electron microscopy revealed that there was a good correlation between the morphological features of the thyroid follicle and its immunohistochemical staining pattern. In follicles composed of columnar cells, the colloid and cytoplasm of some epithelial cells were immunohistochemically stained. Dense deposits, regarded as immune complexes, were observed in the basement membrane of these follicles, and lymphocytes were seen between the adjacent cells. When similar deposits appeared in the basement membrane of such follicles, 4 or more lymphocytes per follicle could be seen among the epithelial cells. The present findings seem to indicate that antibody-dependent cell-mediated cytotoxicity plays an important role in the pathogenesis of Hashimoto's thyroiditis.

Humoral and cell-mediated immune mechanisms in the production of pathology in avirulent Semliki Forest virus encephalitis

Seven days after peripheral inoculation with an avirulent strain of Semliki Forest virus, the brains of CBA and nude mice exhibited a mononuclear inflammation and spongiform degeneration. Mice that had received cyclophosphamide (150 mg/kg) 24 h after infection showed no pathology until day 11. However, immunofluorescence studies of the brains of immunosuppressed, infected mice demonstrated viral antigen within the soma and processes of neurons at earlier periods. The brain lesions could be reconstituted on day 7 in immunosuppressed, infected recipients with 6-day immune spleen cells. Immune spleen cells depleted of T lymphocytes, the non-immunoglobulin-bearing population deficient in B lymphocytes, or immune sera plus nonimmune bone marrow cells could also reconstitute the lesions. However, inflammation and spongiform changes were reduced when donor immune cells were depleted of either T or B lymphocytes. When both T and B lymphocytes were removed from the donor immune population, recipient brains did not show pathology. The results demonstrate that either antibody or immune T cells can trigger pathology, but there is also participation of nonimmune bone marrow-derived mononuclear cells, probably of the monocyte-macrophage lineage.

H-2 gene products influence susceptibility of target thyroid gland to damage in experimental autoimmune thyroiditis

The restriction of the pathogenesis of experimental autoimmune thyroiditis (EAT) by H-2 gene products was investigated. EAT was induced by injecting thyroglobulin extract plus adjuvant into F1 hybrid mice that had been implanted under the kidney capsules with thyroid glands originating from either the EAT-susceptible or -resistant parental strain mice. We found relative H-2 restriction of thyroid damage to those glands originating from the H-2 susceptible parental strain. H-2 restriction of damage at the level of the target thyroid gland implicates cytotoxic effector T lymphocytes as a pathogenic agent of EAT.

Fc receptor-bearing lymphoid cells in the chicken. II. Relative increase of Fc(IgG) receptor bearing cells in obese strain-chickens

An EA rosette technique is used to study ontological development and organ distribution of Fc(IgG) receptor-bearing lymphoid cells in normal CS White Leghorn chickens, and in OS chickens with spontaneous autoimmune thyroiditis. During the embryonic period, no difference was seen between CS and OS in the tissue distribution of cells with Fc receptors. At the time of hatching and subsequently, the OS chickens possessed relatively more Fc receptor-bearing lymphoid cells than did CS chickens. The increase of Fc receptor-bearing lymphoid cells was most prominent among spleen cells. No difference in the affinity of Fc receptors between lymphocytes of the OS and CS chickens was demonstrated. The possible role of Fc receptor-carrying cells in the development of autoimmune thyroiditis is discussed.

Immune complex deposits in Graves' disease and Hashimoto's thyroiditis

The thyroid glands of four patients with Graves' disease and five patients with Hashimoto's thyroiditis were investigated to demonstrate in vivo immune complex deposition. By electron microscopy, electron-dense deposits were observed in the follicular basal lamina--basement membrane--(FBL) often associated with lymphocytic and plasma cell infiltration. A positive correlation was obtained with all cases by immunofluorescent studies using anti-IgG, IgA, IgM, C3 and antithyroglobulin conjugated serums. The staining was of a granular pattern and coincided to the FBL region. No discrepancies were noted in electron microscopic and immunofluorescent observations between patients with Graves' disease and Hashimoto's thyroiditis, and the occasional observation of immune complexes in areas devoid of infiltrate in some patients with Graves' disease. Morphologically, the deposits were found to be similar to those described in the Obese Strain chickens with spontaneous autoimmune thyroiditis.

Passive transfer of autoimmune disease with isologous IgG1 and IgG2 antibodies to the tubular basement membrane in strain XIII guinea pigs: loss of self-tolerance induced by autoantibodies

Initiation of an autoimmune tubulointerstitial disease was achieved in strain XIII guinea pigs by passive transfer of functionally pure IgG1 or IgG2 fractions of isologous anti-tubular basement membrane (TBM) serum. IgG2 appeared to be somewhat more effective than IgG1. The immunopathologic features in the IgG1 and IgG2 recipients were similar at the time of sacrifice, 14 days after transfer. The recipients that developed disease had higher than expected anti-TBM titers at 14 days. Furthermore, anti-TBM antibodies were of both IgG isotypes. In contrast, simultaneously administered IgG1 or IgG2 anti-BGG antibodies declined in titer in the recipients and were never found in the isotype fraction that had not been transferred. These findings indicate that the recipients of anti-TBM antibodies of either IgG1 or IgG2 isotype were stimulated to produce anti-TBM autoantibodies, which participated in the pathogenesis of the renal disease. The model demonstrates that autoantibodies may provide a mechanism (autoimmune amplification) for the intensification and perpetuation of antibody-mediated autoimmune diseases.

Autoimmune murine thyroiditis IX. Relationship of humoral and cellular immunity to thyroiditis in high and low responder mice

Good responder (C57/Br/cd) and poor responder (C57BL/10) mice were immunized with mouse thyroid extract in Freund's complete adjuvant. The good responder mice first showed antibody to thyroglobulin on the seventh day while the poor responder animals had slightly lower titers and antibody did not appear until day 12. The first signs of thyroid infiltration appeared on day 4 in the responder strain, and severe lesions were seen between the third and fifth week. In contrast, the poor responder mice showed almost no evidence of infiltration. The macrophage disappearance reaction, a measure of cell-mediated immunity, was similar in the responder and nonresponder strains.

Spontaneous autoimmune thyroiditis in the BUF rat

The inbred BUF rat develops autoimmune thyroiditis spontaneously. The incidence is related to the age of the animal and is increased by neonatal thymectomy and by treatment with methylcholanthrene. Autoantibodies to thyroglobulin can be demonstrated by indirect immunofluorescence and hemagglutination, but skin tests are negative. The "spontaneous" autoimmune disease may be due to the conjunction of an unusually vigorous immunological response to thyroglobulin and the loss of thymic suppressor function.