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 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.     

Cellular immune response to acetylcholine receptors in murine experimental autoimmune myasthenia gravis: inhibition with monoclonal anti-I-A antibodies

Gene(s) at the I-A subregion of the murine major histocompatibility complex influence susceptibility to experimental autoimmune myasthenia gravis. C57Bl/6 mice immunized with acetylcholine receptors (AChR) in complete Freund's adjuvant demonstrated cellular and humoral immune responses to AChR. They developed muscle weakness characteristic of myasthenia gravis and demonstrated a reduction in the muscle AChR content. The kinetics of AChR-specific lymphocyte proliferation generally correlate with anti-AChR antibody response. AChR-specific lymphocyte proliferation was also observed in C57Bl/6 splenocytes after secondary immunization with AChR. The in vitro cellular reactivity to AChR in experimental autoimmune myasthenia gravis (EAMG) mice (C57Bl/6) was suppressed by monoclonal anti-I-Ab antibodies directed against private (Ia20) or public (Ia8) specificities, suggesting a critical role for these Ia determinants in the cellular immune response to AChR in murine EAMG.     

Augmentation of transfer of experimental autoimmune thyroiditis (EAT) in mice by irradiation of recipients

Experimental autoimmune thyroiditis (EAT) can be adoptively transferred to normal syngeneic recipients using spleen cells from susceptible strains of mice primed in vivo with mouse thyroglobulin (MTg) and lipopolysaccharide (LPS) following in vitro activation of spleen cells by culture with MTg. Irradiation of recipient animals markedly augments the severity of thyroiditis induced in this system. Irradiation of recipients does not alter the time course of the development of thyroiditis, nor does it alter the requirement for both in vivo priming and in vitro activation of spleen cells for the development of EAT. Spleen cells from EAT-resistant strains of mice (e.g., Balb/c) do not induce EAT in irradiated recipients. Irradiated recipients develop significant levels of anti-MTg antibodies while unirradiated recipients have little detectable antibody response. The augmenting effect of irradiation can be substantially reversed by transferring naive spleen cells to recipients prior to the transfer of MTg/LPS-primed in vitro-activated spleen cells. In addition athymic CBA/Tufts nude mice develop more severe EAT than CBA/Tufts nude/+ littermates following transfer of activated CBA/J spleen cells. These data suggest that natural suppressor cells may regulate the development of EAT at the effector cell level.     

Induction of experimental autoimmune thyroiditis in mice with in vitro activated splenic T cells

Spleen cells from CBA/J or SJL mice sensitized with mouse thyroglobulin (MTg) and lipopolysaccharide (LPS) could be activated in vitro with MTg to transfer experimental autoimmune thyroiditis (EAT) to normal syngeneic recipients. EAT induced by these transferred cells was similar in incidence and severity to EAT induced by active immunization of mice with MTg and adjuvant and cells from EAT-resistant Balb/c mice could not be activated to induce EAT. The specific antigen MTg was required both for initial sensitization of the mice and for activation of spleen cells in vitro. The cells that were active in transferring EAT to mice were shown to be T cells. Removal of B cells from the cultured spleen cells had no effect on the ability of the cells to induce EAT.     

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.     

The role of cellular proliferation in the induction of experimental autoimmune thyroiditis (EAT) in mice

Experimental autoimmune thyroiditis (EAT) can be induced in susceptible strains of mice by injection of mouse thyroglobulin (MTg) and adjuvant. Lymphocytes from immunized mice develop a proliferative response to MTg which generally correlates with the development of EAT. We utilize a cell transfer system wherein spleen cells from CBA/J mice primed with MTg and lipopolysaccharide (LPS) in vivo are activated by culture with MTg in vitro to transfer EAT to naive recipients. In vivo priming of CBA/J mice is required to develop an antigen specific proliferative response to MTg. This response is optimal between 48 and 90 hr of culture at an MTg concentration of 125-250 micrograms/ml. The correlation between proliferation and transfer of EAT is not absolute as primed Balb/c X CBA/J F1 and AKR lymphocytes do not proliferate detectably in response to MTg but can be activated to transfer EAT; primed Balb/c lymphocytes neither proliferate nor transfer EAT. Proliferation per se is not sufficient to activate cells to transfer EAT as culture with nonspecific mitogens is not effective in activating primed CBA/J spleen cells to transfer EAT. However, lymphoblasts generated during in vitro culture of primed CBA/J spleen cells with MTg are responsible for transfer of EAT; small lymphocytes are ineffective. We conclude that antigen specific proliferation in response to MTg is essential in activating lymphocytes in vitro to transfer EAT.     

Transfer of experimental autoimmune thyroiditis with T cell clones

We have investigated three T lymphocyte clones isolated from CBA/CaJ mice primed with mouse thyroid extract (MTE) in adjuvant. All three clones are L3T4+, Ig-, and Lyt2- and proliferate to MTE, mouse thyroglobulin (MTG) and rat thyroid extract. Clones A7 and B7 transfer thyroiditis to irradiated (475 rad) syngeneic mice, but not to normal recipients. The thyroid lesion induced by the B7 clone is characterized by the infiltration of both mononuclear and polymorphonuclear cells. The thyroiditis is transient in that lesions are apparent 7 and 14 days after transfer, but thyroids return to normal by day 21. Clone B7 showed helper activity for trinitrophenyl-keyhole limpet hemocyanin-primed B cells in vitro when stimulated with trinitrophenyl-MTG and also stimulated the production of anti-MTG antibody in recipient mice. Clone A7 induced thyroid lesions characterized by infiltration of the thyroid with mononuclear cells, with virtually no polymorphonuclear cell infiltration. This clone has shown no helper activity following stimulation with trinitrophenyl-MTG. The third clone (D2) proliferates to and shows helper activity to MTG, but fails to transfer thyroiditis to syngeneic, irradiated mice. On continuous culture, clone B7 lost its surface Thy. The loss of Thy appears unrelated to the ability to transfer thyroiditis since subclones of B7 with markedly different percentages of Thy+ cells transferred disease equally well.     

T-cell subsets in the thyroids of mice developing autoimmune thyroiditis

To examine the role of T-cell subsets in the development of thyroid lesions, female CBA/J mice were immunized with 60 μg mouse thyroglobulin (MTg) in 0.1 ml complete Freund's adjuvant in both hind footpads. The thyroids were removed 12–21 days later, pooled, and dispersed. The cell suspension was examined by membrane immunofluorescence for the distribution of Thy-1⁺, Lyt-1⁺, Lyt-2⁺, and sIg⁺ lymphocytes. For comparison, peripheral blood leukocytes (PBL) from the same animals were similarly examined. Throughout this 10-day interval, B cells in the thyroid were consistently below 5%, whereas B cells represented 19–24% of PBL. Thy-1⁺ cells in PBL ranged from 45 to 59%, whereas Thy-1⁺ cells in the thyroid were 37–50%. However, only thyroidal T cells showed a consistent decline with time and were replaced gradually by cells without T or B cell markers. In particular, there was a clear shift in the Lyt-1⁺:Lyt-2⁺ ratio from about 7 down to 2 in the thyroid as the early predominance of Lyt-1⁺ cells was followed by a relative increase in Lyt-2⁺ cells. Our results show that there is an accumulation of Lyt-1⁺ and Lyt-2⁺ cells in the infiltrated thyroid. These cells may include MTg-reactive, helper, and cytotoxic T cells which localize (or differentiate) in the thyroid and initiate the lesions.     

Effects of the adjuvants SGP and Quil A on the induction of experimental autoimmune thyroiditis in mice

In the present study, two adjuvants, SGP and Quil A, were assessed for their ability to induce experimental autoimmune thyroiditis (EAT) in mice. SGP (a synthetic copolymer of starch, acrylamide, and sodium acrylate) and Quil A (a plant saponin) were compared with lipopolysaccharide (LPS) and complete Freund's adjuvant (CFA) given together with mouse thyroglobulin (MTg) for their ability to induce EAT in CBA/J mice. Immunization with MTg and LPS, MTg and CFA, or MTg with SGP was effective in inducing anti-MTg antibodies and histologic EAT, while MTg with Quil A was ineffective in inducing either anti-MTg antibodies or EAT. MTg with LPS was able to prime mice for the development of an in vitro spleen cell proliferative response to MTg while MTg with SGP or with Quil A was unable to prime spleen cells to proliferate detectably in response to MTg. MTg with LPS given in vivo primes CBA/J spleen cells for further activation by in vitro culture with MTg to transfer EAT to naive CBA/J recipients. MTg with SGP was also effective in priming CBA/J spleen cells for in vitro activation and transfer of EAT while MTg with Quil A was ineffective. The effective adjuvant activity of SGP and its lack of toxicity relative to LPS should make it a useful agent for further studies in murine models of EAT.     

Suppression of experimental autoimmune thyroiditis in guinea pigs by pretreatment with thyroglobulin-coupled spleen cells

Pretreatment of Strain 2 and Strain 13 guinea pigs with guinea pig thyroglobulin (GPTG) coupled to syngeneic spleen cells (GPTG-SC) suppressed the development of experimental autoimmune thyroiditis (EAT) induced by immunization with GPTG in complete Freund's adjuvant (CFA). Antibody titers to GPTG were only minimally suppressed in GPTG-SC pretreated animals. GPTG-SC also suppressed the sensitization of periotneal exudate T lymphocytes which proliferate in vitro in the presence of GPTG.     

Mechanisms of spontaneous resolution versus fibrosis in granulomatous experimental autoimmune thyroiditis

When granulomatous experimental autoimmune thyroiditis (G-EAT) was induced in CBA/J or DBA/1 mice, thyroid lesions resolved in less severe (3+) G-EAT in wild-type mice or severe (5+) G-EAT in IFN-gamma(-/-) mice, but progressed to fibrosis in 5+ G-EAT in wild-type mice. To define the mechanisms leading to these distinct outcomes, the expression of inflammatory and apoptotic molecules and infiltrating cells was evaluated using immunohistochemistry, RT-PCR, and confocal microscopy. The ratio of CD4(+)/CD8(+) T cells in thyroid infiltrates was one factor that predicted G-EAT outcome. CD4(+) T cells outnumbered CD8(+) T cells when lesions progressed to fibrosis, while CD8(+) T cells outnumbered CD4(+) T cells in thyroids that resolved. Fas, Fas ligand, FLIP, TNF-alpha, inducible NO synthase, TGF-beta, and IFN-gamma were highly expressed by infiltrating cells when G-EAT progressed to fibrosis. The expression of active caspase-3 was low, possibly contributing to the persistence of CD4(+) T cells in fibrosis. In contrast, FLIP was mainly expressed by thyrocytes in resolving G-EAT, the expression of active caspase-3 was high, and resolution correlated with apoptosis of infiltrating cells. There was also relatively less expression of TGF-beta, IFN-gamma, TNF-alpha, and inducible NO synthase and higher expression of IL-10 in resolving G-EAT than in G-EAT that progressed to fibrosis. These differences were particularly striking when comparing IFN-gamma(-/-) vs wild-type mice. These results suggest that several opposing biological mechanisms contribute to the outcome of an ongoing autoimmune response. These include differential expression of pro- and antiapoptotic molecules, cytokines, and the ratio of CD4(+) vs CD8(+) T cells.     

Thymosin alpha 1-induced modulation of cellular responses and functional T-cell subsets in mice with experimental autoimmune thyroiditis

The effects of Ta-1, a peptide constituent of thymosin fraction 5, were studied on murine autoimmune thyroiditis using two congenic strains of mice, B10.Br (Br) and B10.D2 (D2), which are sensitive and resistant to experimental autoimmune thyroiditis (EAT) induction, respectively. EAT was induced by either 2 weekly iv injections of mouse thyroglobulin with adjuvant lipopolysaccharide (LPS) or intradermal injection of thyroglobulin mixed with complete Freund's adjuvant (CFA). The criteria for induction and intensity of thyroiditis were the level of lymphoid infiltration in the thyroid gland and the titer of anti-thyroglobulin antibodies. Ta-1 was given in 5 or 10 daily sc injections in doses ranging from 0.0001 to 0.1 microgram/injection. The injections were commenced at varying intervals from the 1st to the 4th week after immunization. T-Cell subsets in the spleens were determined 2 weeks after the first antigen injection and thyroid infiltration was determined 3 weeks later. Treatment with Ta-1 between the two antigen injections increased the level of thyroiditis in resistant mice, but had no effect in sensitive mice. Treatment for the first 2 weeks had similar effects in resistant mice, but also suppressed thyroiditis in the sensitive strain. Later treatments, during the 3rd and 4th weeks after immunization also revealed immunomodulating properties of Ta-1, with a suppressing effect on thyroiditis in sensitive mice and an enhancing effect in the resistant strain. Both effects of Ta-1 were dose dependent. The effects of Ta-1 on the individual phenotypes were also dose dependent. The dose of 0.01 microgram greatly lowered the percentages of Lyt-2+3+ cells in D2 mice and mildly increased the percentages in Br mice, but did not change the Lyt-1+ cell level in either strain. On the other hand, the dose of 0.001 microgram greatly increased the percentage of Lyt-1+ cells in D2 mice and mildly decreased it in the Br strain, but did not alter the Lyt-2+3+ cell subset in either strain. Thus, both doses of Ta-1 modulated Lyt-1+/2+3+ ratios, with each dose affecting a different T-cell subset. The changes in the response to thyroglobulin are apparently exerted through the regulation of the functional T-cell subset balance.     

Prevention of experimental autoimmune thyroiditis through the anti-idiotypic network.

The central goal in the therapy of autoimmune diseases is to develop potent tools able to exert specific control of the immune response to self Ag. Anti-Id may provide such specific immunodulators because the relevance of the idiotypic network in autoimmunity is well documented. We now describe the protective immunity against experimental autoimmune thyroiditis induced exclusively by a thyroglobulin (Tg)-specific cytotoxic T cell clone and show that this down-regulation occurs through the generation of anti-Id antibodies (Ab) (Ab2Beta) which recognize the paratope of a anti-Tg mAb (Ab1) specific to the pathogenic epitope of the Tg molecule. We further analyze the various steps of the Ab responses (Ab1, Ab2, and Ab3) in terms of poly-, mono-, and autospecificities for the pathogenic epitope of the Tg molecule and for the idiotope of the related Ab.     

Sequential analysis of experimental autoimmune thyroiditis induced by neonatal thymectomy in the Buffalo strain rat

We have studied the evolution of thyroiditis induced by neonatal thymectomy in Buffalo strain rats, with particular emphasis on the thyroid lymphocytic infiltrate. The earliest change was increased endothelial Ia expression, and infiltration of the thyroid at 5 weeks by ED1- and ED2-positive macrophages and B and T cells. The T cells comprised equal numbers of Ox 8 (T cytotoxic/suppressor)- and W3/25 (T helper)-positive cells. Ia-positive thyroid follicular cells were seen only in the presence of a T-cell infiltrate. Thyroglobulin antibody levels, thyroid weight, thyroid follicular cell Ia expression, and lymphocytic infiltration of the thyroid were maximal between Weeks 12 and 24, and impairment of macrophage function by injection of silica at this time produced amelioration of disease. The thyroid weight returned to control levels by Week 34 and Ia expression by thyroid cells disappeared. Circulating Ox 8-positive T cells were reduced between Weeks 12 and 24 and by Week 34 had returned to control levels. Our results indicate that the mononuclear infiltrate precedes thyroid follicular cell Ia expression and macrophages play an important role in perpetuating thyroiditis. Recovery from disease is accompanied by a return to normal in circulating suppressor/cytotoxic T cells.     

Induction of granulomatous experimental autoimmune thyroiditis in mice with in vitro activated effector T cells and anti-IFN-gamma antibody.

Experimental autoimmune thyroiditis (EAT) can be induced in mice after the transfer of mouse thyroglobulin (MTg)-sensitized donor spleen cells that have been activated in vitro with MTg. CD4+ T cells are required for the transfer of EAT in this model. Because CD4+ T cells produce various lymphokines, such as IFN-gamma, that may be involved in the activation or regulation of the immune response to MTg and the development of EAT, the present study was undertaken to determine whether a neutralizing mAb to IFN-gamma could modulate the induction or expression of EAT. The anti-IFN-gamma mAb XMG-1.2 had no effect on sensitization of donor cells. However, addition of XMG-1.2 mAb during in vitro activation of MTg-primed spleen cells resulted in more severe EAT in recipient mice. The thyroid lesions in recipients of cells cultured with MTg and XMG-1.2 mAb also exhibited granulomatous changes, which differed qualitatively from the predominantly lymphocytic cell infiltrates in recipients of cells cultured with MTg alone. Recipients of MTg-activated spleen cells also developed severe granulomatous EAT when they were given injections of XMG-1.2 mAb. The effects of XMG-1.2 could be neutralized by IFN-gamma. Recipients of cells cultured in the presence of XMG-1.2 mAb had augmented autoantibody responses, although there were no apparent differences in the IgG subclass distribution of the anti-MTg autoantibody responses. These studies suggest that neutralization of endogenous IFN-gamma results in increased activity of cells capable of inducing granulomatous EAT in mice.     

Effect in neonatal thymectomy on experimental autoimmune thyroiditis in guinea pigs.

These studies examined the effect of neonatal thymectomy on the induction of experimental autoimmune thyroiditis (EAT) in the guinea pigs. Thymectomy was found to result in a consistent and profound inhibition of the development of lesions of EAT in both strain 2 and strain 13 guinea pigs. Thymectomized guinea pigs also had reduced antibody titers to guinea pig thyroglobulin (GPTG), while delayed hypersensitivity reactions to GPTG were less markedly affected by thymectomy. Thymectomized guinea pigs had significant functional peripheral T cells as evidenced by normal responses of lymph node cells to T cell mitogens. These results indicate that a T cell subpopulation which is sensitive to neonatal thymectomy is required for the development of EAT and antithyroglobulin antibody in the guinea pig.     

The effect of aging on the induction of experimental autoimmune thyroiditis

The effect of age on the ability to elicit the various immune functions comprising experimental autoimmune thyroiditis in mice has been examined. Compared with young mice (2 to 3 mo), CBA/CaJ and A/J aged mice (20 to 30 mo) show a drastic reduction in their ability to develop circulating antibody after injection of mouse thyroglobulin (MTg) or mouse thyroid extract (MTE) in complete Freund's adjuvant (CFA). Delayed-type hypersensitivity responses were also depressed, as well as the ability of aged lymph node cells to proliferate in vitro to antigen and the ability of aged splenic T cells to function as helper cells for in vitro antibody production. However, after injection of these thyroid antigens in CFA, aged mice developed thyroid lesions either comparable to or only slightly less intense than those observed in young mice. The disparity between the levels of immune responses and thyroid lesions observed in aged mice can be explained by the greater susceptibility of aged thyroids to tissue damage, since transfer of identical numbers of Con A-activated MTE-primed young splenocytes to young and aged recipients results in a more severe thyroiditis in the aged recipients. Priming mice to MTE in CFA at 9 mo of age, at which time mice are responsive to MTE, did not enhance either T or B cell responsiveness to injection of MTE in CFA at 24 mo of age. Lymphocytes from MTE-injected aged mice also failed to transfer thyroiditis to young recipients after in vitro activation of the lymphocytes with Con A.     

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.