Induction of severe granulomatous experimental autoimmune thyroiditis in mice by effector cells activated in the presence of anti-interleukin 2 receptor antibody

Edaravone ameliorates experimental autoimmune thyroiditis in rats through HO-1-dependent STAT3/PI3K/Akt pathway

Autoimmune thyroiditis is among the most prevalent of all the autoimmunities in population. It is characterized as both cellular immune responses with T, B cells infiltrating to the thyroid gland followed by hypothyroidism as a result of destruction of the thyroid follicles and fibrous replacement of the parenchymal tissue, as well as immune response for TPO and Tg-antibody production. Experimental autoimmune thyroiditis (EAT) has been proven to be an ideal model to study autoimmune thyroiditis. In the present study, we induced an EAT model in rats and examined the effect of edaravone, a hydroxyl radical scavenging agent, on EAT severity and explored the mechanism. The results showed that edaravone reduced the severity score of thyroiditis dose-dependently and the levels of serum TPOAb, TgAb, T3 and T4. Edaravone significantly decreased the mRNA level of IL-17, but increased the mRNA level of IL-10, IL-4, TNF-α and IFN-γ. EAT model significantly induced oxidative stress, which was inhibited by the treatment of 10 mg/kg, 20 mg/kg or 40 mg/kg of edaravone. The EAT model significantly increased the Akt and STAT3 phosphorylation, but when rats were treated with 20 mg/kg or 40 mg/kg edaravone, they were significantly inhibited. The HO-1 expression was greatly increased by 20 mg/kg or 40 mg/kg edaravone. The PI3K inhibitor LY294002, Akt inhibitor triciribine or STAT3 inhibitor WP1066 all significantly decreased the severity score of thyroiditis in the EAT model group, while the HO-1 inhibitor ZnPP-IX increased the severity score of thyroiditis. These results confirm the invlovment of ROS and HO-1-dependent STAT3/PI3K/Akt pathway in the process of Hashimoto's thyroiditis and suggest the potential usage of edaravone in the therapy of it.

Effect of transgenic overexpression of FLIP on lymphocytes on development and resolution of experimental autoimmune thyroiditis

In our previous studies, resolution of granulomatous experimental autoimmune thyroiditis (G-EAT) was promoted when thyroid epithelial cells were protected from Fas-mediated apoptosis due to transgenic overexpression of FLIP. We hypothesized that if FLIP were overexpressed on lymphocytes, CD4(+) effector cells would be protected from Fas-mediated apoptosis, and resolution would be delayed. To test this hypothesis, we generated transgenic (Tg) mice overexpressing FLIP under the CD2 promoter. Transgenic FLIP was expressed on CD4(+) and CD8(+) T cells and B cells. Transgenic overexpression of FLIP protected cultured splenocytes from Fas-mediated, but not irradiation-induced, apoptosis in vitro. Unexpectedly, Tg(+) donor cells transferred minimal G-EAT, which was partially overcome by depleting donor CD8(+) T cells. When Tg(+) and Tg(-) donors transferred equivalent disease, G-EAT resolution was delayed in FLIP transgenic mice. However, CD2-FLIP Tg(+) donors often transferred less severe G-EAT, even after depletion of CD8(+) T cells. This influenced the rate of G-EAT resolution, resulting in little difference in G-EAT resolution between groups. Tg(+) mice always had reduced anti-mouse thyroglobulin autoantibody responses, compared with Tg(-) littermates, presumably because of FLIP overexpression on B cells. These results suggest that effects of transgenic FLIP on a particular autoimmune disease vary, depending on what cells express the transgene and whether those cells are effector cells or if they function to modulate disease.

Eosinophils infiltrate thyroids, but have no apparent role in induction or resolution of experimental autoimmune thyroiditis in interferon-gamma(-/-) mice

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin (MTg)-sensitized splenocytes activated with MTg and interleukin (IL)-12. Our previous studies showed that, when used as donors and recipients, interferon (IFN)-gamma(-/-) and wild-type (WT) DBA/1 mice both develop severe G-EAT. Thyroid lesions in IFN-gamma(-/-) mice have many eosinophils and few neutrophils, while those in WT mice have extensive neutrophil infiltration and few eosinophils. Thyroid lesions in IFN-gamma(-/-) mice consistently resolve by day 40-50, whereas those in WT mice have ongoing inflammation and fibrosis persisting for more than 60 days. To determine if the extensive infiltration of eosinophils in thyroids of IFN-gamma(-/-) mice contributes to thyroid damage and/or early resolution of G-EAT, anti-IL-5 was used to inhibit migration of eosinophils to thyroids. G-EAT severity was compared at day 20 and day 40-50 in IFN-gamma(-/-) recipients given anti-IL-5 or control immunoglobulin G (IgG). Thyroids of anti-IL-5-treated IFN-gamma(-/-) mice had few eosinophils and more neutrophils at day 20, but G-EAT severity scores were comparable to those of control IgG-treated mice at both day 20 and day 40-50. Expression of chemokine (C-X-C motif) ligand 1 (CXCL1) mRNA was higher and that of chemokine (C-C motif) ligand 11 (CCL11) mRNA was lower in thyroids of anti-IL-5-treated IFN-gamma(-/-) mice. IL-5 neutralization did not influence mRNA expression of most cytokines in IFN-gamma(-/-) mice. Thus, inhibiting eosinophil migration to thyroids did not affect G-EAT severity or resolution in IFN-gamma(-/-) mice, suggesting that eosinophil infiltration of thyroids occurs as a consequence of IFN-gamma deficiency, but these cells have no apparent pathogenic role in G-EAT.

A critical role for TRAIL in resolution of granulomatous experimental autoimmune thyroiditis

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin (MTG)-sensitized splenocytes activated in vitro with MTG and IL-12. Thyroid lesions reach maximal severity 20 days after cell transfer, and usually resolve or progress to fibrosis by day 60 depending on the extent of thyroid damage at day 20. Our previous studies indicated that neutralization of TNF-alpha or FasL had no effect on G-EAT induction, but neutralization of TNF-alpha promoted, while neutralization of FasL inhibited, G-EAT resolution. TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily. This study was undertaken to define the role of endogenous TRAIL in G-EAT development and/or resolution. Neutralization of endogenous TRAIL had little effect on G-EAT induction, but significantly inhibited G-EAT resolution and increased thyroid fibrosis. This correlated with higher expression of pro-inflammatory cytokines and preferential expression of the pro-apoptotic molecule TRAIL, and anti-apoptotic molecules FLIP and Bcl-xL on inflammatory cells in thyroids of anti-TRAIL-treated recipients. The results suggest that endogenous TRAIL is not required for G-EAT development in recipients, but is critical for G-EAT resolution. Endogenous TRAIL might promote resolution, at least in part, through modulation of the balance between pro- and anti-inflammatory cytokines, and the expression pattern of pro- and anti-apoptotic molecules of thyroid epithelial cells (TECs) and inflammatory cells.

Interleukin-10 promotes resolution of granulomatous experimental autoimmune thyroiditis

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin-sensitized splenocytes activated in vitro with mouse thyroglobulin and interleukin (IL)-12. Thyroid lesions reach maximal severity 20 days after cell transfer, and inflammation either resolves or progresses to fibrosis by day 60 depending on the extent of thyroid damage at day 20. Depletion of CD8(+) T cells inhibits G-EAT resolution. Our previous studies indicated that IL-10 was generally higher in G-EAT thyroids that resolved. Using both wild-type and IL-10(-/-) CBA/J mice, this study was undertaken to determine whether G-EAT resolution would be inhibited in the absence of IL-10. The results showed that either depletion of CD8(+) T cells or IL-10 deficiency increased fibrosis and inhibited resolution of inflammation. We also found a correlation between higher expression levels of proinflammatory cytokines and preferential expression levels of proapoptotic molecules, such as FasL and TRAIL, and antiapoptotic molecules, such as FLIP and Bcl-xL, in inflammatory cells from thyroids of both CD8-depleted and IL-10-deficient mice. Furthermore, many of the CD8(+) T cells were also IL-10(+). These results suggest that IL-10 plays an important role in G-EAT resolution and might promote resolution, at least in part, through its production in CD8(+) T cells. Further understanding of the mechanisms that promote the resolution of inflammation will facilitate the development of novel strategies for treating autoimmune diseases.

Expression of transgenic FLIP on thyroid epithelial cells inhibits induction and promotes resolution of granulomatous experimental autoimmune thyroiditis in CBA/J mice

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by transfer of thyroglobulin-primed in vitro activated splenocytes. Thyroid lesions reach maximal severity 20 d later, and inflammation resolves or progresses to fibrosis by d 60, depending on the extent of thyroid damage at d 20. Depletion of CD8+ T cells inhibits G-EAT resolution. We showed that expression of Fas-associated death domain-like IL-1beta-converting enzyme inhibitory protein (FLIP) transgene (Tg) on thyroid epithelial cells (TECs) of DBA/1 mice had no effect on G-EAT induction but promoted earlier resolution of G-EAT. However, when CBA/J wild-type donor cells were transferred to transgenic CBA/J mice expressing FLIP on TECs, they developed less severe G-EAT than FLIP Tg- littermates. Both strains expressed similar levels of the FLIP Tg, but endogenous FLIP was up-regulated to a greater extent on infiltrating T cells during G-EAT development in DBA/1 compared with CBA/J mice. After transient depletion of CD8+ T cells, FLIP Tg+ and Tg- CBA/J recipients both developed severe G-EAT at d 20. Thyroid lesions in CD8-depleted Tg+ recipients were resolving by d 60, whereas lesions in Tg- littermates did not resolve, and most were fibrotic. FLIP Tg+ recipients had increased apoptosis of CD3+ T cells compared with Tg- recipients. The results indicate that transgenic FLIP expressed on TECs in CBA/J mice promotes G-EAT resolution, but induction of G-EAT is inhibited unless CD8+ T cells are transiently depleted.

Contrasting roles of IFN-gamma in murine models of autoimmune thyroid diseases

Interferon-gamma (IFN-gamma), a prototypic proinflammatory cytokine produced by several different cell types, including the Th1 subset of CD4(+) T cells, plays an important role in inflammation and autoimmune diseases. This review focuses on the varied and often contrasting roles of IFN-gamma in three murine models of autoimmune thyroid disease, experimentally induced autoimmune thyroiditis, the model of iodine-induced spontaneous autoimmune thyroiditis in NOD.H-2h4 mice and several different murine models of Graves' disease.

Murine FLIP transgene expressed on thyroid epithelial cells promotes resolution of granulomatous experimental autoimmune thyroiditis in DBA/1 mice

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin-sensitized splenocytes activated in vitro with mouse thyroglobulin and interleukin-12. In wild-type (WT) DBA/1 recipients of WT donor splenocytes, thyroid lesions reach maximal severity at day 20, with ongoing inflammation and extensive fibrosis at day 60. Our previous studies indicated the site of expression of FLIP and Fas ligand [thyroid epithelial cells (TECs) versus inflammatory cells] differed in mice when lesions would resolve or progress to fibrosis. To test the hypothesis that expression of FLIP by TECs would promote earlier G-EAT resolution in DBA/1 mice, transgenic (Tg) DBA/1 mice expressing FLIP on TECs were generated. In FLIP Tg(+) and Tg(-) littermate recipients of WT donor splenocytes, G-EAT severity was comparable at day 20, but fibrosis was decreased, and many lesions resolved by day 60 in Tg(+) but not Tg(-) recipients. FLIP and Fas ligand were primarily expressed by TECs in Tg(+) recipients and by inflammatory cells in Tg(-) recipients at day 60. Apoptosis of inflammatory cells was greater, and expression of proinflammatory cytokines was decreased in thyroids of Tg(+) compared with Tg(-) recipients. These results are consistent with the hypothesis that transgenic expression of FLIP on thyroid epithelial cells promotes earlier resolution of granulomatous experimental autoimmune thyroiditis.

Fas ligand is required for resolution of granulomatous experimental autoimmune thyroiditis

We previously suggested that CD8(+) T cells promoted resolution of granulomatous experimental autoimmune thyroiditis (G-EAT) at least in part through regulation of Fas ligand (FasL) expression on thyroid epithelial cells. To directly evaluate the role of the Fas pathway in G-EAT resolution, Fas- and FasL-deficient mice on the NOD.H-2h4 background were used as recipients of activated G-EAT effector cells. When MTg-primed wild-type (WT) donor splenocytes were activated and transferred to WT recipients, thyroid lesions reached maximal severity on day 20 and resolved on day 50. Fas, FasL, and FLIP were up-regulated, and many apoptotic inflammatory cells were detected in recipient thyroids on day 20. Fas was predominantly expressed by inflammatory cells, and FasL and FLIP were mainly expressed by thyroid epithelial cells. After depletion of CD8(+) T cells, G-EAT resolution was delayed, FLIP and FasL were predominantly expressed by inflammatory cells, and few inflammatory cells were apoptotic. When WT donor splenocytes were transferred to gld recipients, disease severity on day 20 was similar to that in WT recipients, but resolution was delayed. As in CD8-depleted WT recipients, there were few apoptotic inflammatory cells, and FLIP and FasL were expressed primarily by inflammatory cells. These results indicated that the expression of functional FasL in recipient mice was critical for G-EAT resolution. WT cells induced minimal disease in lpr recipients. This was presumably because donor cells were eliminated by the increased FasL on lpr recipient cells, because donor cells were not eliminated, and the mice developed G-EAT if lpr recipients were given anti-FasL mAb.

FLIP and FasL expression by inflammatory cells vs thyrocytes can be predictive of chronic inflammation or resolution of autoimmune thyroiditis

Spontaneous autoimmune thyroiditis (SAT) in NOD.H-2h4 mice is a model of chronic inflammation of the thyroid, while granulomatous experimental autoimmune thyroiditis (G-EAT) is a model with spontaneous resolution of inflammation. In chronic inflammation (SAT), Fas, FasL, and FLIP were upregulated and predominant in inflammatory cells. There were few apoptotic cells, and low expression of active caspase-8 and -3. In resolving G-EAT in CBA/J and NOD.H-2h4 mice, FasL and FLIP were predominantly expressed by thyrocytes. There were many apoptotic inflammatory cells, and increased expression of active caspase-8 and -3. Depletion of CD8+ T cells inhibited G-EAT resolution and resulted in chronic inflammation. FLIP was expressed predominantly by inflammatory cells, and apoptosis of inflammatory cells and expression of active caspase-3 was reduced as in chronic SAT. Thus, differences in expression of pro- or antiapoptotic molecules in SAT or G-EAT were apparently related to the acute vs chronic nature of the inflammatory response rather than the method of disease induction. Upregulation of FLIP by inflammatory cells may block Fas-mediated apoptosis, contributing to chronic inflammation, whereas increased FLIP expression by thyrocytes in resolving G-EAT may protect thyrocytes from apoptosis, and FasL expression by thyrocytes may induce apoptosis of inflammatory cells, contributing to resolution.

Inhibition of TGFbeta1 by anti-TGFbeta1 antibody or lisinopril reduces thyroid fibrosis in granulomatous experimental autoimmune thyroiditis

In this study, a murine model of granulomatous experimental autoimmune thyroiditis (G-EAT) was used to determine the role of TGFbeta1 in fibrosis initiated by an autoimmune inflammatory response. The fibrotic process was evaluated by staining thyroid tissue for collagen, alpha-smooth muscle actin, TGFbeta1, and angiotensin-converting enzyme (ACE), and measuring serum thyroxine in mice given anti-TGFbeta1 or the ACE inhibitor lisinopril. The role of particular inflammatory cells in fibrosis was tested by depletion experiments, and the cytokine profile in thyroids was examined by RT-PCR. Neutralization of TGFbeta1 by anti-TGFbeta1 or lisinopril resulted in less collagen deposition and less accumulation of myofibroblasts, and levels of active TGFbeta1 and ACE were reduced in thyroids of treated mice compared with those of untreated controls. Other profibrotic molecules, such as platelet-derived growth factor, monocyte chemotactic protein-1, and IL-13, were also reduced in thyroids of anti-TGFbeta1- and lisinopril-treated mice compared with those of controls. Confocal microscopy showed that CD4(+) T cells and macrophages expressed TGFbeta1. Fibrosis was reduced by injection of anti-CD4 mAb on day 12, when G-EAT was very severe (4-5+). Together, these results suggest a critical role for TGFbeta1 in fibrosis initiated by autoimmune-induced inflammation. Autoreactive CD4(+) T cells may contribute to thyroid fibrosis through production of TGFbeta1. This G-EAT model provides a new model to study how fibrosis associated with autoimmune damage can be inhibited.

Expression and regulation of Fas and Fas ligand on thyrocytes and infiltrating cells during induction and resolution of granulomatous experimental autoimmune thyroiditis

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin-sensitized spleen cells activated in vitro with mouse thyroglobulin, anti-IL-2R, and IL-12. G-EAT lesions reach maximal severity 19-21 days after cell transfer, and lesions almost completely resolve by day 35. Depletion of CD8+ cells delays resolution and reduces Fas ligand (FasL) mRNA expression in thyroids. This study was undertaken to analyze Fas and FasL protein expression in the thyroid during induction and resolution of G-EAT and to determine whether CD8+ cells might regulate Fas or FasL expression in the thyroid. Fas and FasL expression was analyzed by immunohistochemical staining or in situ hybridization in thyroids of mice with or without depletion of CD8+ cells. Fas and FasL proteins were not detectable in normal thyroids, but expression of both proteins increased during development of G-EAT. Fas was expressed primarily by inflammatory cells; some enlarged thyrocytes were also Fas+. Thyrocytes had intense FasL immunoreactvity, and many CD8+ cells were also FasL positive. Depletion of CD8+ cells resulted in decreased FasL expression by thyrocytes and inflammatory cells, but had no effect on Fas expression. TUNEL assay detected many apoptotic inflammatory cells in proximity to thyrocytes. CD8-depleted thyroids had ongoing inflammation with fewer apoptotic infiltrating cells at day 35. Administration of a neutralizing anti-FasL mAb had no apparent effects on development of G-EAT, but anti-FasL was as effective as anti-CD8 in preventing G-EAT resolution. These results suggested that CD8+ T cells and thyrocytes may kill inflammatory cells through the Fas pathway, contributing to G-EAT resolution.

Transforming growth factor-beta has contrasting effects in the presence or absence of exogenous interleukin-12 on the in vitro activation of cells that transfer experimental autoimmune thyroiditis

Mouse thyroglobulin (MuTg)-sensitized spleen cells activated in vitro with MuTg induce experimental autoimmune thyroiditis (EAT) in recipient mice with a thyroid infiltrate consisting primarily of lymphocytes. A more severe and histologically distinct granulomatous form of EAT (G-EAT) is induced when donor cells are activated with MuTg together with anti-interferon-gamma (IFN-gamma), anti-interleukin-2 receptor (IL-2R) monoclonal antibody (mAb), and IL-12. Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that can both suppress and exacerbate autoimmune diseases and often has inhibitory effects on lymphocytes. To determine if TGF-beta could modulate the in vitro activation of effector cells for G-EAT, TGF-beta was added to cultures of MuTg-sensitized donor spleen cells together with MuTg. Cells activated in the presence of 2 ng/ml TGF-beta induced moderately severe G-EAT in recipient mice. G-EAT induced by cells activated in the presence of TGF-beta was histologically similar but less severe than the G-EAT induced by cells activated in the presence of IL-12. IL-12 and TGF-beta modulate the activation of G-EAT effector cells by distinct mechanisms, as cells activated by TGF-beta could induce G-EAT in the presence of anti-IL-12, and TGF-beta inhibited the effects of IL-12 on EAT effector cells. TGF-beta exerted its activity during the first 24 h of the 72-h culture, whereas IL-12 functioned primarily during the final 24 h of culture. These results indicate that thyroid lesions with granulomatous histopathology can be induced by both IL-12-dependent and IL-12-independent mechanisms, and TGF-beta can exert both positive and negative effects on the effector cells for G-EAT.

Induction of experimental autoimmune thyroiditis in IL-12-/- mice

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by transfer of mouse thyroglobulin (MTg)-sensitized spleen cells activated in vitro with MTg and anti-IL-2R or MTg and IL-12. Previous work suggested that IL-12 was required in vitro for development of G-EAT. To determine whether IL-12 was also required during the induction and/or effector phases, DBA/1 mice with a disrupted IL-12-P40 gene (IL-12(-/-)) were used for EAT induction. Cells from MTg-sensitized IL12(-/-) donors activated in vitro by MTg or MTg and anti-IL2R induced severe EAT in recipient mice. Compared with effector cells from IL-12(+/+) donors, effector cells from IL-12(-/-) donors induced thyroid lesions dominated by lymphocytes with minimal granulomatous changes. Thyroids of recipients of IL-12(-/-) cells expressed less IFN-gamma mRNA and more TGF-beta, IL-4, and IL-10 compared with recipients of IL-12(+/+) cells. When IL-12 was added during in vitro activation, cells from both IL-12(-/-) and IL-12(+/+) donors induced severe G-EAT, and expression of all cytokines except IL-12 was comparable in thyroids of both IL-12(+/+) and IL-12(-/-) recipients. Transfer of cells from IL-12(+/+) or IL-12(-/-) donors into IL-12(+/+) or IL-12(-/-) recipients indicated that IL-12 expressed in thyroids was derived from recipients. Thus, endogenous IL-12 is not absolutely essential for the sensitization and activation of EAT effector cells to induce severe EAT, although it is required in vitro to promote activation of cells to induce severe granulomatous histopathology.

Adoptive transfer murine model of granulomatous experimental autoimmune thyroiditis

Experimental autoimmune thyroiditis (EAT) is a chronic inflammatory autoimmune disease that can be induced in genetically susceptible animals by immunization with mouse thyroglobulin (MTg) in an appropriate adjuvant or by the adoptive transfer of MTg-sensitized donor spleen cells, activated in vitro with MTg, into naive recipients. In the adoptive transfer model used in our laboratory, donor cells activated with MTg alone induce a relatively mild chronic lymphocytic form of EAT (L-EAT), in which the thyroid infiltrate consists primarily of mononuclear cells, and the thyroid inflammation persists for several months. When the same donor cells are activated with MTg together with anti-IL-2R and/or IL-12, a more severe and histologically distinct granulomatous form of EAT is induced in recipient mice. In addition to having distinct histopathologic features, granulomatous EAT (G-EAT) differs from L-EAT in that granulomatous thyroid lesions are not chronic. After reaching maximal severity 21 days after cell transfer, G-EAT thyroid lesions either resolve or the thyroids become atrophic and fibrotic by day 35. In this review, the histopathologic features of G-EAT and L-EAT are described, and our studies with the adoptive transfer G-EAT model which have focused on the mechanisms involved in induction of G-EAT in mice, and the evolution of G-EAT lesions to resolution of inflammation or fibrosis, are reviewed.

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.

Spontaneous autoimmune thyroiditis in NOD.H-2h4 mice

NOD.H-2h4 mice, which express I-Ak on the NOD genetic background, spontaneously develop autoimmune thyroiditis (SAT) and anti-mouse thyroglobulin (MTg) autoantibodies. The incidence of SAT is nearly 100% in mice of both sexes 6-8 weeks after administration of 0.05% NaI in the drinking water. After reaching maximum severity, inflammation is chronic over the next 3-4 months. All mice that develop thyroid lesions also produce MTg-specific IgG1 and IgG2b autoantibodies. Thyroid lesions and anti-MTg autoantibodies did not develop in CBA/J (H-2(k)) or NOD.SWR(H-2(q)) mice after administration of NaI water. Both CD4(+)and CD8(+)T cells are involved in the initial development of SAT. Depletion of CD4(+), but not CD8(+), T cells after thyroid lesions have developed also markedly reduced SAT severity, indicating that CD4(+)T cells are required for both developing and maintaining SAT. Analysis of cytokine gene expression indicated that both Th1 and Th2 cytokines were expressed in thyroids of NOD.H-2h4 mice with SAT. Th1 and proinflammatory cytokines were maximally expressed 4-6 weeks after mice began receiving NaI water, while Th2 cytokine gene expression was greatest at 8-15 weeks, when lesions had reached maximal severity and were in the chronic phase. TGF-beta was highly expressed in NOD.H-2h4 thyroids, irrespective of whether the mice had received NaI water or had thyroid lesions.

B7.2 Has Opposing Roles During the Activation Versus Effector Stages of Experimental Autoimmune Thyroiditis

APCs provide costimulatory and down-regulatory signals to Ag-activated T cells through interactions between B7.1 and B7.2 on APCs with either CD28 or CTL Ag-4 expressed on T cells. Recipients of mouse thyroglobulin (MTg)-primed spleen cells activated in the presence of anti-B7.2 had decreased experimental autoimmune thyroiditis (EAT) severity compared with recipients of cells cultured with control rat Ig or anti-B7.1. Blocking B7.2 during in vivo priming also suppressed the ability of MTg-primed spleen cells to transfer EAT, implicating a role for B7.2 for priming and in vitro activation of EAT effector cells. In contrast, administration of anti-B7.2 or anti-B7.2 Fab to recipients of MTg-activated spleen cells increased the severity of EAT compared with recipients receiving control Ig. Thyroids from anti-B7.2-treated recipients had increased expression of IL-4 mRNA compared with thyroids from rat Ig-treated controls. Both B7.1 and B7.2 molecules were expressed in the thyroids of mice with EAT, although B7.2 was more prevalent than B7.1. Administration of both anti-B7.1 and anti-B7.2 to recipient mice suppressed the development of EAT, while anti-B7.1 treatment alone had no effect on EAT severity. The suppression of EAT was not observed when anti-B7.1 and anti-B7.2 treatment was delayed until 7 days after cell transfer, suggesting a requirement for B7 in the initiation of EAT in recipient mice. These results suggest that costimulation is required during the effector phase of EAT and that B7.2 may have opposing roles in the activation versus effector stages of autoreactive T cells.

The kinetics of cytokine gene expression in the thyroids of mice developing granulomatous experimental autoimmune thyroiditis

To study the potential roles of cytokines in development and resolution of granulomatous experimental autoimmune thyroiditis (EAT), the kinetics of in vivo expression of cytokine genes in thyroid infiltrates was analysed using reverse transcriptase-PCR (RT-PCR). Both Th1 (IL-2 and IFN-gamma) and Th2 (IL-4 and IL-10) cytokines as well as TGF-betaTNF-alphaIL-12 and IL-1beta were detected in thyroids during both the initial phase and peak of granulomatous EAT. Maximal expression of cytokine genes generally occurred 11-14 days after cell transfer, prior to maximal EAT severity, which occurred 19-21 days after cell transfer. The relative ratios of Th1:Th2 cytokines and mouse thyroglobulin-(MTg)-specific IgG1 and IgG2a autoantibody levels were similar during both the initial phase and peak of EAT. Depletion of CD8(+) T cells did not decrease the severity of EAT but delayed resolution of lesions. Cytokine gene expression in thyroids was not decreased by anti-CD8 treatment. Together, these data indicate that both Th1 and Th2 cytokines produced by CD4(+) T cells are involved in induction and development of granulomatous EAT, and CD8-dependent resolution of granulomatous EAT is apparently not mediated by these cytokines.

IFN-γ-Deficient Mice Develop Severe Granulomatous Experimental Autoimmune Thyroiditis with Eosinophil Infiltration in Thyroids

To study the role of IFN-γ in the development of granulomatous experimental autoimmune thyroiditis (EAT), DBA1 mice with a disrupted IFN-γ gene were used for adoptive EAT induction. Effector cells from either IFN-γ+/+ or IFN-γ−/− donor mice activated with mouse thyroglobulin and anti-IL-2R mAb induced severe granulomatous EAT. A predominant infiltration of the thyroid by eosinophils was observed in recipients of IFN-γ−/− effector cells but not in recipients of IFN-γ+/+ cells. Compared with wild-type mice, thyroids of recipients of IFN-γ−/− effector cells had decreased expression of mRNA for Th1 cytokines and inducible nitric oxide synthetase. Expression of Th2 cytokine mRNA was comparable to that of IFN-γ+/+ mice, and expression of eotaxin was increased in the thyroids of recipients of IFN-γ−/− effector cells. Activation of cells from either IFN-γ+/+ or IFN-γ−/− donors in the presence of IL-12 also induced severe granulomatous EAT. Eosinophil infiltration in recipients of IFN-γ−/− cells was unaffected when effector cells were activated with IL-12, and thyroids expressed predominantly Th2 cytokines. The extent of fibrosis of recipient thyroids was generally greater when donor IFN-γ+/+ and IFN-γ−/− cells were activated with IL-12. Compared with IFN-γ+/+ mice, IFN-γ−/− mice produced lower levels of mouse thyroglobulin-specific autoantibodies after immunization with MTg and LPS. These results indicate that cells from both IFN-γ+/+ and IFN-γ−/− donors can induce severe granulomatous EAT. However, damage of thyroid follicles by IFN-γ−/− and that by IFN-γ+/+ cells appear to involve different mediators of inflammation.

Interleukin-12 promotes activation of effector cells that induce a severe destructive granulomatous form of murine experimental autoimmune thyroiditis

Granulomatous inflammatory lesions are a major histopathological feature of a wide spectrum of human infectious and autoimmune diseases. Experimental autoimmune thyroiditis (EAT) with granulomatous histopathological features can be induced by mouse thyroglobulin (MTg)-sensitized spleen cells activated in vitro with MTg and anti-interleukin-2 receptor (anti-IL-2R), anti-IL-2, or anti-interferon-gamma (anti-IFN-gamma) monoclonal antibody (MAb). These studies suggested that IFN-gamma-producing T cells requiring IL-2 for growth may negatively regulate activation of granulomatous EAT effector cells. As IL-12 promotes activation of IFN-gamma-producing Th1 cells, the present study was undertaken to determine the role of IL-12 in activation of effector cells for granulomatous EAT. MTg-sensitized cells activated in vitro with MTg, anti-IL2R MAb, and IL-12 induced severe, destructive granulomatous thyroiditis with neutrophil inflammation, fibrin deposition, and necrosis. Many glands ultimately underwent atrophy and became fibrotic; some also showed fibrinoid necrosis and a mixed inflammatory cell infiltration of blood vessel walls indicative of a necrotizing vasculitis. Induction of severe granulomatous EAT by IL-12 required MTg in vitro and was unrelated to the IL-12-induced increase in IFN-gamma production. IL-12 markedly increased IFN-gamma production but did not induce a shift to a Th1-dominant phenotype, as other Th1 and Th2 cytokines were generally unaffected and both Th1 and Th2 cytokines were expressed in recipient thyroids. Addition of IL-12 or neutralization by anti-IL-12 at various times indicated that IL-12 exerted its primary effects in the final 24 hours of the 72-hour culture and was not required in recipient mice. Cells cultured with anti-IL-12, MTg, and anti-IL2R MAb transferred mild lymphocytic EAT but little or no granulomatous EAT. Thus, IL-12 profoundly regulates the in vitro activation of effector cells that induce histologically distinct autoimmune inflammatory lesions in the thyroid.

Induction of Granulomatous Experimental Autoimmune Thyroiditis in IL-4 Gene-Disrupted Mice

To study the role of IL-4 in development of granulomatous experimental autoimmune thyroiditis (EAT), IL-4 gene-disrupted mice expressing the EAT-susceptible H-2k haplotype were generated and used for EAT induction. Spleen cells from mouse thyroglobulin (MTg) and LPS-primed IL-4+/+ and IL-4−/− donors could induce severe granulomatous EAT when spleen cells were activated with MTg and anti-IL-2R mAb in the presence of IL-12. Thyroid lesions had extensive follicular cell proliferation, large numbers of histiocytes, polymorphonuclear leukocytes, and multinucleated giant cells, in addition to lymphocytes and other mononuclear cells. Expression of IFN-γ gene mRNA and production of IFN-γ by effector spleen cells stimulated with MTg and IL-12 were similar for both IL-4+/+ and IL-4−/− mice. Although IL-4 was undetectable in IL-4−/− mice, expression of mRNA for IL-5, IL-10, and IL-13 and production of IL-5 by both MTg-activated spleen cells and anti-CD3-activated CD4+ T cells were comparable for cells from IL-4+/+ and IL-4−/− mice, indicating that the absence of IL-4 did not prevent production of other Th2 cytokines. Production of MTg-specific IgG1 was very low or undetectable in IL-4−/− mice. IL-4 gene mRNA and MTg-specific IgG1 could be detected in IL-4+/+ or IL-4−/− recipients only when they received effector cells from IL-4+/+ donor mice, indicating that IL-4- and IgG1-secreting cells are of donor origin. These results demonstrate that IL-4 is not essential for development of granulomatous EAT.

A thyroxine-containing thyroglobulin peptide induces both lymphocytic and granulomatous forms of experimental autoimmune thyroiditis

Mouse thyroglobulin (MTg)-sensitized spleen cells activated in vitro with MTg can induce two histologically distinct forms of experimental autoimmune thyroiditis (EAT). MTg-sensitized cells activated with MTg alone induce a mild chronic form of EAT in which the thyroid infiltrate consists primarily of lymphocytes and other mononuclear cells (lymphocytic EAT). The same donor cells activated with MTg and anti-IL2R mAb induce a more severe and acute form of EAT with a thyroid inflammatory lesion having granulomatous histopathological features. A thyroxine-containing (T4) peptide, corresponding to positions 2549-2560 of human Tg, was shown by others to activate spleen cells of mouse thyroglobulin (MTg)-sensitized CBA/J mice to induce lymphocytic EAT. To determine if the CD4+ effector T cells that induce granulomatous EAT can respond to the same T-cell epitope, the present study was undertaken to determine if both forms of EAT could be induced by the 2549-2560 thyroxine (T4)-containing peptide. This peptide was very effective for activation of T cells from MTg-primed CBA/J donors to induce granulomatous EAT but, in contrast to MTg, did not activate T cells from AKR/J or DBA/1 mice to induce granulomatous EAT. The T4 peptide did not apparently activate peptide-specific B cells in vivo but did activate MTg-primed B cells in vitro to produce anti-MTg autoantibody in recipient mice. These results demonstrate that a single 12-amino-acid thyroxine-containing peptide can activate T cells from CBA/J mice to induce both lymphocytic and granulomatous EAT. However, this peptide does not activate T cells from some other EAT-susceptible strains of mice, suggesting that MTg contains multiple epitopes able to activate T cells to induce granulomatous EAT.

The role of alpha 4 integrin and intercellular adhesion molecule-1 (ICAM-1) in murine experimental autoimmune thyroiditis

Mouse-thyroglobulin (MTg)-sensitized spleen cells activated in vitro with MTg induce a lymphocytic form of experimental autoimmune thyroiditis (EAT) whereas activation of the same cell population with MTg in the presence of anti-interleukin 2 receptor antibody (M7/20) induces a granulomatous form of EAT. The thyroid infiltrate in both lymphocytic and granulomatous EAT includes both CD4+ and CD8+ T cells and CD4+ T cells are the primary effector cells for both forms of EAT. This investigation was undertaken to begin to define the roles of alpha 4 integrin, and intercellular adhesion molecule-1 (ICAM-1) in the migration of CD4+ and CD8+ T cells to the thyroid in EAT. The studies presented here demonstrate the expression of alpha 4 integrin and ICAM-1 on CD4+ and CD8+ T cells infiltrating the thyroid and the expression of vascular cell adhesion molecule (VCAM) and ICAM-1 on thyroid cells of mice with EAT. The effects of anti-alpha 4 and anti-ICAM mAb administration on EAT severity in recipient mice was also determined. Anti-alpha 4 administration reduced or abolished lymphocyte infiltration in the thyroid resulting in reduced severity of both lymphocytic and granulomatous EAT. In contrast, anti-ICAM mAb had little effect on EAT severity. These results suggest that these two adhesion molecules exhibit differential functional roles in the modulation of EAT disease severity and that alpha 4-VCAM interactions may be of particular importance in trafficking of effector cells to the thyroid.

Proliferation and autoantibody production by mouse thyroglobulin (MTg)-specific B cells activated in vitro by MTg and MTg-specific T cells

Immunization of genetically susceptible strains of mice with mouse thyroglobulin (MTg) and adjuvant results in sensitization of MTg-specific CD4+ T cells that can induce experimental autoimmune thyroiditis (EAT) after in vitro activation with MTg. These MTg specific CD4+ T cells also provide help to MTg-specific B cells which produce anti-MTg autoantibodies in vivo. This study was undertaken to develop a system with which to measure MTg-specific helper function in vitro. MTg-activated T cells were shown to provide help to MTg-primed B cells in vitro as assessed by B-cell proliferation and anti-MTg autoantibody production. These responses were MTg-specific and required MTg priming of both the T- and B-cell populations. An MTg-specific CD4+ T-cell line also induced MTg-specific B-cell proliferation and was capable of inducing IgG1, IgG2a and IgG2b synthesis in MTg- primed B cells.

Lymphocytic traffic and homing into target tissue and the generation of endocrine autoimmunity

Endocrine autoimmunity is known to be characterized by the presence of specific autoantibodies and from the histopathological point of view by lymphocytic infiltration in the target tissue. The presence of mononuclear cell infiltrates is the pathological hallmark of most endocrine diseases characterized by an autoimmune process directed against antigens expressed on endocrine cells. Infiltrating cells can usually be detected by biopsy or by using other, non-invasive, techniques. However, in endocrine tissue such as the islets of Langerhans and the adrenal glands it is difficult to perform biopsies and diagnosis of the autoimmune process is dependent mainly upon detection of specific autoantibodies. A crucial aspect of endocrine autoimmunity and of all processes of organ specific autoimmunity is why and how lymphocytes migrate from primary lymphoid tissue to their specific targets. This occurs mainly through contact with specific adhesion molecules which enable lymphocytes to adhere to the endothelial vessels in close proximity to the target tissue. In this review we discuss the homing of peripheral mononuclear cells into target endocrine tissues and the mediating role of adhesion molecules.

Intrathyroidal cell phenotype in murine lymphocytic and granulomatous experimental autoimmune thyroiditis

In-vitro mouse thyroglobulin (MTg) activated spleen cells from immunized donor mice can induce experimental autoimmune thyroiditis (EAT) after transfer to recipient mice. The intrathyroidal cellular infiltrate consists primarily of mononuclear cells (lymphocytic EAT). Cells cultured with MTg together with anti-IL2R antibody induce EAT with a granulomatous histopathology in which the thyroid infiltrate contains mononuclear cells (MNC) in addition to PMN's histiocytes, and multinucleated giant cells. Flow cytometric analysis of intrathyroidal MNC infiltrates demonstrated that both CD4+ and CD8+ T cells infiltrate the thyroid in both lymphocytic and granulomatous EAT and that CD8+ T cells outnumber CD4+ T cells. There were usually increased numbers of PMN's in the granulomatous thyroids, but low number of Ig+ and F4/80+ cells (macrophages) in the intrathyroidal infiltrate of both disease types. IL2R and Pgp-1 were expressed on both CD4+ and CD8+ intrathyroidal T cells. The majority of CD8+ cells were ICAM+, LFA-1+, and CD45RB+ whereas only a small percentage of CD4+ intrathyroidal T cells expressed these markers. There were no major differences in intrathyroidal MNC phenotype between lymphocytic and granulomatous EAT. Depletion of CD8+ T cells in recipient mice did not reduce EAT severity and resulted in an increased percentage of intrathyroidal CD4+ T cells expressing IL2R. These results suggest that CD8+ T cells are not functioning as effector cells in lymphocytic or granulomatous EAT.

Anti-interleukin-2 receptor monoclonal antibody therapy supports a role for Th1-like cells in HgCl2-induced autoimmunity in rats

Brown-Norway (BN) rats injected with HgCl2 develop an autoimmune disease characterized by a T-dependent polyclonal B-cell activation. Increase in major histocompatibility complex class II molecule expression on B cells concomitant with enhancement of serum IgE concentration supports the involvement of the T helper 2 (Th2)-like subset in the induction of the disease. The mercury disease is autoregulated and does not develop in Lewis (LEW) rats. Considering the reciprocal regulation, well defined in mice, between the Th1 and Th2 subsets, we addressed the role of the Th1-like subset in this disease. Brown-Norway and LEW rats injected with HgCl2 were treated with NDS61, a mouse anti-rat-IL-2R MoAb that blocks mainly Th1 cells. Data reported herein show that: (1) HgCl2 treatment does not modify either the percentage of IL-2R+ cells or IL-2R expression in both BN and LEW rats; (2) treatment of BN rats with NDS61 MoAb does not modify the induction phase of the mercury disease but delays in part the regulation phase; (3) such a treatment leads to some immune abnormalities in LEW rats; (4) HgCl2 markedly potentiates the anti-mouse Ig antibody response in BN rats which probably limits the effect of this treatment. This study supports a role for the Th1-like subset in HgCl2-induced autoimmunity in the rat.

Autoreactive T cells from a type I diabetic recognize multiple class II products

Mononuclear cells obtained from a child at the acute presentation of type I diabetes were stimulated in vitro with human insulin followed by IL-2 and IL-4. All of the T-cell clones isolated from this stimulation were autoreactive, recognizing autologous B cells in the absence of insulin or other exogenous antigens. Eleven CD4+ clones were studied in detail to identify the class II MHC antigens stimulating these autoreactive cells. The donor was heterozygous for DR3DQw2 and DR4DQw3.2 haplotypes, a combination of alleles with a greatly increased risk for type I diabetes. The clones demonstrated skewed recognition of class II antigens. Three clones appeared to recognize a peptide derived from one class II beta chain (DR beta 1, DR4Dw4) presented by another class II beta chain (DR beta 4, DRw53). Three clones were stimulated by cells expressing DPw4 molecules. Only one clone recognized a product derived from the DR3 haplotype. In contrast to both antigen-specific and autoreactive T-cell clones derived from normal individuals, many of the autoreactive T cells isolated from this subject were stimulated by class II molecules other than DR beta 1. The results support the hypothesis that autoreactive T cells recognize autologous peptides in association with MHC and some of these peptides are derived from self MHC molecules.

CD3+ and CD4+ cells adoptively transfer experimental hypersensitivity pneumonitis

To characterize the cells responsible for transfer of adoptive murine experimental hypersensitivity pneumonitis (EHP), we depleted Micropolyspora faeni (M. faeni)-sensitized C3H/HeJ spleen cell (SC) cultures of CD3+, CD4+, or CD8+ cells before administration to recipients. We determined the length of time sensitization persists, the ability of cultured lung-associated lymph node (LALN) cells to transfer EHP, and the ability of cultured SC from animals subjected to two, four, or eight weekly intratracheal challenges of M. faeni to transfer EHP. The extent of pulmonary inflammatory response after challenge with intratracheal M. faeni was used to determine adoptive transfer. Depletion reduced the proportion of CD3+ cells from 21 to 1%, CD4+ cells from 15 to 3%, and CD8+ cells from 7 to 1% in the cultured SC population. The proportion of B cells exhibited reciprocal changes. Cultured SC could transfer EHP. Depletion of CD3+ and CD4+, but not CD8+ cells, ablated or diminished the capacity to transfer EHP. Sensitized cells persisted in recipients for at least 8 wk. Cultured LALN cells could transfer EHP. Recipients of cultured SC from 4- and 8-wk donors exhibited less extensive pulmonary abnormalities than recipients of cultured SC from 2-wk donors. The proportion of CD3+, CD4+, CD8+, B cells, and macrophages was the same in cultured cells from 2-, 4-, and 8-wk donors. We conclude that the active cells in SC cultures are CD3+, CD4+, and CD8- T cells, and there are differences in the ability of cultured cells to adoptively transfer EHP that are dependent on the nature of the donor but not on the phenotype of the cell population.

Thyroid autoimmunity

Antigenic structure remains a major focus in thyroid immunology. The genes for three major thyroid antigens--thyroglobulin, thyroid peroxidase and the thyrotropin receptor--were sequenced in the late 1980's, and epitopes for antibody and T cells have been reported within the last year. In addition, new evidence for selective use of T-cell receptor V gene segments in human thyroid infiltrates may point the way to specific immunotherapy.

Factors associated with reactive and reparative fibrosis of the myocardium

Myocardial fibrosis can be defined as an abnormal increase in collagen concentration of either ventricle. This accumulation of collagen, represented predominantly by fibrillar type I collagen, can occur a) on a reactive basis in the interstitial space and adventitia of intramyocardial coronary arteries and does not require myocyte necrosis, or b) as a replacement for necrotic myocytes, where it is considered a scar. Both forms can be found in the same ventricle. Various factors have been found to contribute to the reactive and reparative fibrosis that appears in both ventricles in acquired hypertension. In the case of microscopic scarring, myocyte necrosis is related to catecholamine or angiotensin II- mediated toxicity, reduced potassium stores that accompany chronic mineralocorticoid excess, and coronary vascular remodeling. Reactive fibrosis is associated with elevations in plasma aldosterone concentrations that are inappropriate relative to dietary sodium intake. These findings set the stage for additional in vivo and in vitro studies that may shed more light on our understanding of the factors that regulate the accumulation of fibrous tissue in the myocardium--a major determinant of pathologic structural remodeling which enhances its susceptibility to reentrant arrhythmias and ventricular dysfunction.