Thyroid-specific expression of IFN-gamma limits experimental autoimmune thyroiditis by suppressing lymphocyte activation in cervical lymph nodes

The role of IFN-gamma in the pathogenesis of autoimmune disease is controversial, being described as immunostimulatory in some studies and immunosuppressive in others. To determine the contribution of local expression of IFN-gamma, we derived NOD.H-2(h4) transgenic mice overexpressing IFN-gamma in a thyroid-restricted manner. Transgenic mice, which had serum IFN-gamma levels similar to wild-type littermates, showed up-regulation of MHC class II on thyrocytes, but did not develop spontaneous thyroiditis. Upon immunization with murine thyroglobulin, transgenic mice developed milder disease and reduced IgG1 responses compared with wild type. The milder disease was associated with decreased frequency of activated CD44(+) lymphocytes in the cervical lymph nodes. This suppressive effect was confirmed by showing that blockade of systemic IFN-gamma with mAb enhanced disease and increased IgG1 responses. The study supports a disease-limiting role of IFN-gamma in autoimmune thyroiditis. Furthermore, it provides the first evidence that local IFN-gamma activity in the thyroid is sufficient for disease suppression.

Kinetics of mononuclear cell infiltration and cytokine expression in iodine-induced thyroiditis in the NOD-H2h4 mouse

Mononuclear cell infiltration of the thyroid gland is a common histologic feature of chronic lymphocytic thyroiditis. Although the infiltrating mononuclear cells have been implicated in the destruction of the thyroid, information concerning the progression of infiltration into the thyroid is limited. In this report, we examine the composition and kinetics of mononuclear cell infiltration in the thyroid and the expression of major histocompatibility complex class II (I-Ak), IL-12, and IFN-gamma in the thyroid of the NOD-H2h4 mouse, a model of spontaneous autoimmune thyroiditis accelerated by the administration of excess dietary iodine. Mice were given a low dose of 0.015% NaI in their drinking water for 2, 4, 6, 8, and 16 weeks, and thyroids were removed, serially sectioned, and stained in an avidin-biotin peroxidase assay. The thyroid infiltrate included CD4+ and CD8+ T cells, F4/80+ macrophages, and B220+ B cells. After 2 weeks of iodine treatment, CD4+ T cells were the first seen in the thyroid, followed by CD8+ T cells and F4/80+ macrophages. B220+ B cells entered the thyroid after 4 weeks of iodine treatment. IL-12 and IFN-gamma positive cells were located in the thyroid early in disease and were up-regulated in the focal accumulations of infiltrating cells. Thyrocytes clearly expressed I-Ak after 4 weeks of iodine treatment near the location of mononuclear cell infiltration.

Heterogeneity of the thyroglobulin epitopes associated with circulating thyroid hormone autoantibodies in hashimoto's thyroiditis and non-autoimmune thyroid diseases

We previously implicated TG leakage from fine-needle aspiration biopsy (FNAB) as responsible for circulating thyroid hormone autoantibodies (THAb). However, THAb were not always associated with TGAb. In the literature these negative findings have been interpreted against a role of TG as the antigen for THAb. To evaluate the TGAb status more fully and to gain information on TG epitopes involved in THAb development, we measured: 1) TGAb with an independent hemagglutination assay (HA), and 2) epitope specificity in a competitive ELISA using 2 monoclonal Abs (mAb) against TG: mAb 42C3 and mAb 134C2. MAb 42C3 recognizes a cross-reactive iodinated epitope, whereas 134C2 is specific for human TG. We tested 12 Hashimoto's thyroiditis (HT) and 35 non-HT patients sampled prior to, 1 and 3 months after FNAB. We found that, irrespective of thyroid disease or post-FNAB THAb status, certain patients previously classified as TGAb negative by IRMA tested TGAb positive by HA or by competition ELISA and vice versa. A post FNAB positive response to the 42C3 iodinated epitope in only one THAb IgM-T4+ve HT and a few THAb negative non-HT patients was observed. Furthermore, we observed that the 3 non-HT patients who expressed IgM-T3 THAb failed to bind either TG-mAb epitope. We conclude that a single TGAb assay is not sufficient to define the TGAb status, which can be achieved reliably only by using multiple TGAb assays. In addition, the TG-iodinated epitope recognized by 42C3 is not a major epitope in post-FNAB THAb, and the T3-epitope involved in THAb remains distinct from the mAb epitopes. In light of recent data in the literature, we further suggest that the responsible epitopes are more likely to be expressed in leaked TG fragments, rather than leaked intact TG.

Adhesion molecules as susceptibility factors in spontaneous autoimmune thyroiditis in the NOD-H2h4 mouse

Mononuclear cell infiltration of the thyroid is a prominent feature of chronic lymphocytic thyroiditis. Adhesion molecules play a major role in determining the localization of inflammatory mononuclear cells in the thyroid. Previous reports from animal models and human studies have described the thyroidal expression of adhesion molecules only late in clinical disease. In this study, we examined the distribution and kinetics of expression of E-selectin, VCAM-1, LFA-1, and ICAM-1 in the NOD-H2h4 mouse, a model of spontaneous autoimmune thyroiditis accelerated by dietary iodine. Mice were fed 0.015% NaI in their drinking water for 2, 4, 6, 8, and 16 weeks, and thyroids were removed, serially sectioned, and stained in an avidin-biotin-peroxidase assay. We found a dramatic increase in E-selectin and VCAM-1 expression on intrathyroidal endothelial cells after 16 weeks of iodine treatment. In addition, we describe for the first time that thyrocytes from the NOD-H2h4 mouse, and the parental NOD, constitutively express ICAM-1 independent of iodine treatment and prior to mononuclear cell infiltration of the thyroid gland. ICAM-1 was not detected on the thyrocytes of other untreated strains of mice, implicating expression of this adhesion molecule as a critical event in the recruitment of inflammatory mononuclear cells to the thyroid.

Iodine: an environmental trigger of thyroiditis

Like most autoimmune diseases of humans, chronic lymphocytic (Hashimoto's) thyroiditis results from the combination of a genetic predisposition and an environmental trigger. A body of clinical and epidemiologic evidence points to excessive ingestion of iodine as an environmental agent. In genetically determined thyroiditis in animals, iodine enrichment has been shown to increase the incidence and severity of disease. Its mechanism of action is still uncertain. Using a new animal model of autoimmune thyroiditis, the NOD.H2(h4) mouse, we have been able to show that iodine enhances disease in a dose-dependent manner. Immunochemical studies suggest that iodine incorporation in the thyroglobulin may augment the antigenicity of this molecule by increasing the affinity of its determinants for the T-cell receptor or the MHC-presenting molecule either altering antigen processing or by affecting antigen presentation.

Whole-blood proliferation assay for autoimmune thyroid disease: comparison to density-gradient separated-peripheral blood lymphocytes

Autoimmune thyroid diseases feature prominent cellular infiltration of the thyroid gland as well as autoantibody production to thyroid antigens. The most common assay to evaluate cell-mediated immunity is based on incorporation of tritiated thymidine into proliferating T cells after stimulation by the test antigens. In the past, cell proliferation assays of thyroglobulin (Tg) using peripheral blood mononuclear cells (PBMC) of individuals with autoimmune thyroid diseases required large quantities of blood and specialized separation techniques, and have not yielded high counts or high stimulation indices. We therefore developed a proliferation assay using less than 5 mL of whole blood and compared proliferation of cells in whole blood to that using PBMCs separated by density gradient centrifugation. We also determined if responses could be enhanced by addition of interleukin-2 (IL-2) to the cultures. We found that an IL-2-stimulated proliferation assay to Tg using diluted whole blood is superior to the separated cell assay in detecting Tg-specific T-cell proliferation in autoimmune thyroid disease patients. Further refinement of this technique and larger trials may confirm its value for clinical investigation and special diagnostic applications.

Autoantibodies to thyroglobulin in health and disease

Thyroglobulin (Tg)--a heavily glycosylated, iodinated protein--is a major autoantigen in autoimmune thyroiditis. Tg also induces thyroiditis by immunization of experimental animals. Humans with chronic lymphocytic thyroiditis characteristically produce autoantibodies to thyroglobulin, but similar autoantibodies are also found in some clinically normal, euthyroid individuals. A comparison of the fine specificity of autoantibodies in humans and in experimentally immunized mice was carried out, based on their ability to inhibit a panel of monoclonal antibodies (MAbs). Patients with autoimmune thyroid disease, as well as normal individuals, produced autoantibodies mainly to the conserved, cross-reactive determinants of thyroglobulin. Patients developed additional autoantibodies to species-restricted epitopes. The determinants recognized by patients with Graves' disease differed in some respects from epitopes recognized by thyroiditis patients or patients with differentiated thyroid carcinoma. Similarly, mice that are genetically susceptible to thyroiditis produced autoantibodies that reacted with the mouse-specific antigenic determinants. Using an autoantibody that reacts with one of the epitopes associated with thyroiditis, a reactive 15-kDa fragment of human Tg--localized at the carboxy end of the molecule--was isolated and sequenced. Iodine plays an important role in the precise specificity of the disease-associated epitope, since T cells from patients with thyroiditis react with iodinated but not noniodinated human thyroglobulin. Addition of iodine to Tg generates new or exposes cryptic epitopes. Use of a selected MAb as a surrogate for the T-cell receptor suggests that a specific iodine-containing epitope is sometimes involved in recognition. Finally, thyroglobulin-reactive autoantibodies exhibit proteolytic activity on thyroglobulin.

Peptides of human thyroglobulin reactive with sera of patients with autoimmune thyroid disease

Autoantibodies to thyroglobulin (Tg) are a prominent feature of the two autoimmune thyroid diseases, chronic lymphocytic (Hashimoto's) thyroiditis and Graves' disease. Similar autoantibodies are found in the serum of many normal individuals without evidence of thyroid disease. Previous studies have indicated that patients with autoimmune thyroid disease recognize epitopes of Tg which are not usually recognized by normal individuals. The goal of this investigation was to identify peptide fragments of Tg bearing these disease-associated epitopes. For this purpose, we utilized a panel of mAbs that bind to different epitopes of the Tg molecule. One of these mAbs (137C1) reacted with an epitope that was also recognized by the sera of patients with autoimmune thyroiditis. In the present study, we show that two peptides (15 and 23 kDa) that reacted with mAb 137C1 are located in different parts of the Tg molecule. Each peptide inhibited the binding of mAb 137C1 to the other peptide and to the intact Tg, indicating that the same epitope was represented on the two peptides. Loops and helices of the secondary structure of the two peptides might be involved in the conformational epitope recognized by mAb 137C1. A striking finding of this study is that two apparently unrelated fragments of the Tg molecule bind to the same mAb. These findings may have important ramifications with regard to epitope spread and the progression of the autoimmune response to disease.

Peptides of Human Thyroglobulin Reactive with Sera of Patients with Autoimmune Thyroid Disease

Autoantibodies to thyroglobulin (Tg) are a prominent feature of the two autoimmune thyroid diseases, chronic lymphocytic (Hashimoto’s) thyroiditis and Graves’ disease. Similar autoantibodies are found in the serum of many normal individuals without evidence of thyroid disease. Previous studies have indicated that patients with autoimmune thyroid disease recognize epitopes of Tg which are not usually recognized by normal individuals. The goal of this investigation was to identify peptide fragments of Tg bearing these disease-associated epitopes. For this purpose, we utilized a panel of mAbs that bind to different epitopes of the Tg molecule. One of these mAbs (137C1) reacted with an epitope that was also recognized by the sera of patients with autoimmune thyroiditis. In the present study, we show that two peptides (15 and 23 kDa) that reacted with mAb 137C1 are located in different parts of the Tg molecule. Each peptide inhibited the binding of mAb 137C1 to the other peptide and to the intact Tg, indicating that the same epitope was represented on the two peptides. Loops and helices of the secondary structure of the two peptides might be involved in the conformational epitope recognized by mAb 137C1. A striking finding of this study is that two apparently unrelated fragments of the Tg molecule bind to the same mAb. These findings may have important ramifications with regard to epitope spread and the progression of the autoimmune response to disease.

Linking iodine with autoimmune thyroiditis

A great deal of circumstantial evidence has linked iodine with the rising incidence of autoimmune thyroiditis in the United States. In our investigations, we have shown directly that T cells from humans with chronic lymphocytic thyroiditis proliferate in the presence of iodinated but not in the presence of noniodinated human thyroglobulin. Moreover, the proliferative response is restored when the thyroglobulin is iodinated artificially in vitro. Using a panel of monoclonal antibodies, we found evidence that the presence of iodine induces a number of stereochemical changes in the conformation of the molecule, resulting in the loss of some antigenic determinants and the appearance of others. One prominent determinant was associated with the iodine-containing amino acid thyroxine. Both the number and position of the iodine substituents determine the precise specificity of this epitope. A new model for the study of the role of iodine in inducing thyroid autoimmunity has become available in the form of the nonobese diabetic (NOD)-H2(h4) mouse. This animal develops autoimmune thyroiditis spontaneously but in relatively low prevalence. However, if iodine is added to the drinking water, the prevalence and severity of the thyroid lesions increase markedly. The immune response is specific for thyroglobulin, both in terms of the antibody response and T-cell proliferation. In fact, the appearance of lesions can be predicted by the presence of thyroglobulin-specific IgG2b antibody. The disease, moreover, can be transferred adoptively, using spleen cells from iodine-fed donors treated in vitro with iodinated thyroglobulin. The effects of iodine feeding are greater in conventional animals compared with those maintained under specific pathogen-free conditions. Based on T-cell proliferation, it appears that the NOD-H2(h4) strain of mice has innately a greater response to murine thyroglobulin than do other mouse strains and that the proliferation is increased even more by feeding iodine. We suggest, therefore, that the presence of iodine increases the autoantigenic potency of thyroglobulin, a major pathogenic antigen in the induction of autoimmune thyroiditis. This animal model provides a unique opportunity for investigating in detail the mechanisms by which an environmental agent can trigger a pathogenic autoimmune response in a susceptible host.

Mouse thyroid primary culture

Technological advances have drastically decreased the number of cells required to analyze expression of the genes and functions of the encoded proteins, making even a small organ like a mouse thyroid amenable to study in vitro. We have established primary cultures of mouse thyroids that showed, for up to 14 days after seeding, strong cytoplasmic staining for thyroglobulin. The staining then gradually decreased and was present in only 5-10% of thyrocytes at day 28. Furthermore, cultured thyrocytes expressed the thyroperoxidase and thyrotropin-receptor genes, and, although at lower levels, the sodium-iodide symporter gene. Finally, cultured thyrocytes could be transiently transfected by lipofection, using FuGENE 6. Thus, we report that it is possible to cultivate functional primary mouse thyrocytes that can be used for a variety of biological studies. This system is appealing because it permits the use of the ever-increasing number of transgenic, knock-out and knock-in mouse strains in studying thyroid pathophysiology.

Evidence for genetic transmission of thyroid peroxidase autoantibody epitopic "fingerprints"

Autoimmune thyroid disease is characterized by the tendency to cluster in families and by IgG class autoantibodies to antigens such as thyroid peroxidase (TPO). The epitopes recognized by polyclonal serum autoantibodies can be quantitatively fingerprinted using four recombinant human TPO autoantibodies (expressed as Fab) that define A and B domain epitopes in an immunodominant region. To determine whether these fingerprints are genetically transmitted, we analyzed fingerprints of 63 members of 7 multiplex Old Order Amish families and 17 individuals from 4 Hashimoto thyroiditis families. Inhibition of serum autoantibody binding to [125I]TPO by the recombinant Fab was used to assess recognition of the TPO immunodominant region (4 Fab combined) and recognition of domain A or B (individual Fab). Complex segregation analysis was performed using a unified model (POINTER). For the 4 Fab combined inhibition phenotype, the no transmission model was rejected (chi2(4) = 20.67; P < 0.0032), and the most parsimonious model includes a major gene effect. More importantly, evidence for genetic transmission was obtained for the phenotype defined by the ratio of inhibition by subdomain Fab B1:B2. Thus, for this ratio (reflecting recognition of the B domain), the no transmission model was rejected chi2(4) = 63.59; P < 0.000008). Moreover, the polygenic hypothesis could be rejected, but not the major locus hypothesis, suggesting that major genes might be involved in familial transmission of this trait. In conclusion, our findings suggest that autoantibody recognition of the TPO immunodominant region and the TPO B domain is genetically transmitted. These data may open the way to the identification by candidate analysis or positional cloning of at least one gene responsible for the development of Hashimoto's thyroiditis.

Iodination of human thyroglobulin (Tg) alters its immunoreactivity. II. Fine specificity of a monoclonal antibody that recognizes iodinated Tg

In a previous investigation, we found that murine MoAb 42C3, raised against human Tg, recognized Tg differently depending upon its level of iodination of Tg. A possible explanation for this finding is that iodine is directly involved with the specific epitope recognized by MoAb 42C3. In the present study, we report that the binding of MoAb 42C3 to iodinated Tg is inhibited by T4, T3, reverse T3 (rT3), triiodothyroacetic acid (triac), diiodothyronine (T2), diiodotyrosine (DIT), but not by thyronine (TO) or tyrosine. The order of inhibition of these iodinated compounds is T4 > T3 > rT3 > triac > T2 > DIT. The MoAb 42C3 does not have the same specificity as the T3, T4-receptor since the order of binding of these iodinated compounds on the receptor differed from the order of their inhibition of this MoAb. Monoclonal antibody 42C3 also recognized non-iodinated Tg that was subsequently iodinated in vitro. It failed to recognize another protein, bovine serum albumin, that was iodinated in vitro by the same method. These results suggest that iodinated tyrosines and thyronines determine the binding specificity of MoAb 42C3. The inhibitory effects of these compounds on MoAb 42C3 depend on their iodine content as well as location of iodine in the aromatic ring.

Iodination of human thyroglobulin (Tg) alters its immunoreactivity. I. Iodination alters multiple epitopes of human Tg

Human Tg, the site of synthesis of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), is one of the major autoantigens in autoimmune thyroiditis. The degree of iodination of Tg may have a major impact on its immunological properties by changing its antigenicity with respect to antibody binding. We have previously prepared a panel of MoAbs that bind to different epitopes of the Tg molecule. In the present study, we show that iodination alters the conformation of Tg molecule in such a way that it is recognized differently by different MoAbs. Monoclonal antibody 137C1 recognizes Tg regardless of its iodine content. Monoclonal antibody 42C3 recognizes Tg only if the Tg is iodinated either in vitro or in vivo. Monoclonal antibody 133B1 recognizes both in vivo iodinated Tg and non-iodinated Tg, but this MoAb did not recognize Tg following in vitro iodination. Monoclonal antibody 41A5 recognizes intact Tg and tryptic peptides of normal (in vivo) iodinated and non-iodinated Tg, but did not bind the tryptic peptides of artificially (in vitro) iodinated Tg. From the results of these experiments, we conclude that iodination of Tg by either in vivo or in vitro methods changes its conformation in such a way that some natural epitopes are 'lost' and some 'new' epitopes are generated. The generation of new epitopes may be important in the generation of autoimmune responses leading to autoimmune disease.

Iodine is essential for human T cell recognition of human thyroglobulin

Here we describe for the first time that recognition by human T cells of human thyroglobulin depends upon its iodine content. We have examined the proliferation of lymphocytes from blood of autoimmune thyroiditis patients and normal individuals to thyroglobulin preparations containing different amounts of iodine. A minimal degree of iodination was required to elicit the proliferative response of both patients and normal individuals since thyroglobulin preparations containing no detectable iodine did not induce proliferation. A non-iodinated thyroglobulin preparation that was iodinated in vitro produced significant proliferation of both patient and normal lymphocytes. Addition of IL-2 to the culture medium enhanced proliferation but did not change the pattern of response.

The role of iodine in autoimmune thyroiditis

Like most cancers, autoimmune diseases generally are due to the interaction of a number of genetic traits with an environmental trigger. Autoimmune thyroiditis, a model of organ-specific autoimmune disease, is associated with iodine as a precipitating environmental factor. T cells from patients with chronic thyroiditis proliferate in response to normal human thyroglobulin, but fail to react with non-iodinated thyroglobulin. Using a selected monoclonal antibody, we were able to identify a binding site on thyroglobulin containing iodinated thyronine. The greatest affinity was for tetraiodothyronine and binding depended upon the number as well as the positions of iodines. We have also studied an inbred strain of mice, NOD-H2h4, that developed thyroiditis spontaneously. The onset of disease was hastened in a dose-dependent manner by adding iodine to the drinking water. The occurrence of disease was greater in conventional than in specific pathogen-free mice and correlated with T-cell proliferation and IgG2b antibody to thyroglobulin.

Iodine-induced autoimmune thyroiditis in NOD-H-2h4 mice

Excess iodine ingestion has been implicated in induction and exacerbation of autoimmune thyroiditis in human populations and animal models. We studied the time course and sex-related differences in iodine-induced autoimmune thyroiditis in NOD-H-2h4 mice. This strain, derived from a cross of NOD with B10.A(4R), spontaneously develops autoimmune thyroiditis but not diabetes. NOD-H-2h4 mice were given either plain water or water with 0.05% iodine for 8 weeks. Approximately 54% of female and 70% of male iodine-treated mice developed thyroid lesions, whereas only 1 of 20 control animals had thyroiditis at this time. Levels of serum thyroxin (T4) were similar in the treatment and control groups. Thyroglobulin-specific antibodies were present in the iodine-treated group after 8 weeks of treatment but antibodies to thyroid peroxidase were not apparent in the serum of any of the animals. Levels of thyroglobulin antibodies increased throughout the 8-week iodine ingestion period; however, no correlation was seen between the levels of total thyroglobulin antibodies and the degree of thyroid infiltration at the time of autopsy. The thyroglobulin antibodies consisted primarily of IgG2a, IgG2b, and IgM antibodies with no detectable IgA, IgG1, or IgG3 thyroglobulin-specific antibodies. The presence of IgG2b thyroglobulin-specific antibodies correlated well with the presence of thyroid lesions.

Thyroid peroxidase autoantibody epitopic 'fingerprints' in juvenile Hashimoto's thyroiditis: evidence for conservation over time and in families

In Hashimoto's thyroiditis, the humoral component is manifest by autoantibodies to thyroid peroxidase (TPO). Epitopic 'fingerprinting' of polyclonal serum TPO autoantibodies has been facilitated by the molecular cloning and expression as Fab of a repertoire of human TPO autoantibody genes. To investigate whether TPO autoantibody fingerprints are (i) stable over long periods of time (approximately 15 years), and (ii) inherited, we studied a cohort of nine patients with juvenile Hashimoto's thyroiditis and 21 first degree relatives of four of these patients. Fingerprints were determined by competition between four selected FAB and serum autoantibodies for binding to 125I-TPO. Regardless of titre, the TPO epitopic profile was stable in 10/12 individuals whose TPO autoantibody levels were sufficient for analysis on two or three occasions over 12-15 years. Although the TPO epitopic fingerprint profiles in two families raised the possibility of inheritance, overall the data from all four families did not reveal an obvious pattern of genetic control. In no family was the TPO epitopic fingerprint associated with HLA A, B or DR. In conclusion, TPO autoantibody epitopic fingerprints are frequently conserved over many years. Studies on additional families are necessary to establish whether or not the epitopic profiles of TPO autoantibodies are inherited.

Cyclosporine therapy suppresses ocular and lacrimal gland disease in MRL/Mp-lpr/lpr mice

PURPOSE

MRL/Mp-lpr/lpr (MRL/lpr) mice spontaneously develop an autoimmune disease characterized by lymphoproliferation, vasculitis, glomerulonephritis, autoantibody production, and ocular and lacrimal gland inflammation. Lacrimal gland lesions in MRL/lpr mice are a model for the human disorder Sjögren's syndrome. The target organ lesions in MRL/lpr mice, including those in the eye and lacrimal gland, are composed largely of CD4+ T cells, with lesser numbers of CD8+ T cells and B cells. Cyclosporine therapy was evaluated for its effect on the autoimmune disease, particularly in the eye and lacrimal gland.

METHODS

MRL/lpr mice were administered cyclosporine intraperitoneally at a dosage of 2 mg daily from age 1 to 5 months. Animals were killed at 5 months and evaluated for the presence of autoimmune disease. Control groups consisted of animals given daily injections with either saline or the cyclosporine diluent.

RESULTS

Cyclosporine therapy was effective in reducing the ocular and lacrimal gland disease. Intraocular inflammation was present in 73% of control animals but in only 15% of cyclosporine-treated animals (P < 0.003). Multifocal lacrimal gland inflammatory infiltrates were present in 100% of controls but in only 23% of cyclosporine-treated animals (P < 0.0001). Mean percent area involved by lacrimal gland inflammation was reduced from 19.7% to 4.7% by cyclosporine therapy (P = 0.0003). Systemic autoimmune disease manifestations, including lymphoproliferation, vasculitis, glomerulonephritis, and serologic abnormalities, also were improved.

CONCLUSIONS

Chronic cyclosporine therapy, started at an early age, is effective in controlling the autoimmune disease in MRL/lpr mice, including the ocular and lacrimal gland lesions.

Induction of thyroid autoantibodies in naive mice by idiotypic manipulation

Previously, we have shown that it is possible to induce, in naive mice, systemic autoimmune diseases (e.g., antiphospholipid syndrome and systemic lupus erythematosus) by idiotypic manipulation. In the present study we expanded our experience to examine whether idiotypic manipulation could be utilized to induce organ-specific autoantibodies and a disease mediated by cellular mechanisms, namely, experimental autoimmune thyroiditis. Fifteen BALB/c mice were immunized with a monoclonal mouse anti-human thyroglobulin (hTg) antibody; controls were immunized with an irrelevant mouse IgG. The mice immunized with anti-hTg antibody developed, 6 weeks after immunization, autoantibodies to human thyroglobulin, but not to dsDNA, cardiolipin, or myeloperoxidase. The presence of specific autoantibodies was associated with low production of thyroid hormones, and during a follow-up of 20 weeks the mice did not develop characteristic histological signs of thyroiditis. We conclude that idiotypic manipulation can induce anti-thyroglobulin autoantibodies.

Amino acid sequence of a tryptic peptide of human thyroglobulin reactive with sera of patients with thyroid diseases

Autoantibodies to human thyroglobulin (hTg) are found in the sera of many patients with thyroid diseases. To localize epitopes recognized by these autoantibodies, hTg was incubated with tryspin for 4 hours at 37 degrees C under non-reducing conditions. Releasing peptides from hTg in their natural conformation. These peptides were then analyzed by western immunoblot using either autoantibodies from patients with autoimmune thyroiditis or murine monoclonal antibodies (mAb) produced against hTg. The autoantibodies reacted primarily with two low molecular weight peptides with apparent molecular weights (MWap) of 15 and 20 kDa. The pattern of tryptic peptides recognized by these autoantibodies resembled that of one of the mAbs (137C1), as shown by immunoblots in either one or two dimensional SDS-PAGE. To characterize these peptides further, they were separated by a high performance liquid chromatography (HPLC). The column separated the 4-hour tryptic digest of hTg into multiple peptide peaks. Further analysis by SDS-PAGE showed that one of these peaks contained the 15 kDa peptide. The 15 amino acid sequence at the amino-terminus of this peptide was determined. This amino acid sequence (KVPTFATPWPDFVPR) corresponds to a unique sequence near the carboxyl-terminal end of hTg, starting with amino acid 2657. The size of the peptide indicates that it extends to the carboxyl-terminal end of hTg. This fragment contains one of the antigenic sites of hTg that binds autoantibodies from patients with autoimmune thyroid disease.

IgG subclass distribution of thyroglobulin antibodies in patients with thyroid disease

The IgG subclass distribution of thyroglobulin antibodies (TgAb) has been studied in Hashimoto and Graves' patients by several investigators with conflicting results, in part explainable by methodological problems. We have recently developed a quantitative ELISA to measure in absolute terms the serum concentration of TgAb subclasses. The aim of the present study was to apply this method in a large series of patients with autoimmune as well as, for the first time, non-autoimmune thyroid diseases. We examined 28 patients with Hashimoto's thyroiditis, 30 with Graves' disease, 21 with thyroid carcinoma and 18 with non-toxic goitre, all selected for the presence of TgAbs. The results indicated that TgAbs in thyroid diseases were not restricted to any particular isotype, but comprised all four IgG subclasses. IgG1 was represented similarly in the four groups. The same was true for IgG3, even though its contribution to the total antibody content was very small. IgG4 was the dominant subclass in patients with Graves' disease, thyroid carcinoma and non-toxic goitre, probably reflecting a prolonged antigenic challenge. In Hashimoto's thyroiditis IgG2 was dominant, possibly because T helper lymphocytes infiltrating the thyroid are typically Th1 type.

Tryptic peptides of human thyroglobulin: I. Immunoreactivity with murine monoclonal antibodies

Human thyroglobulin (Tg) was treated with trypsin at different concentrations of trypsin/Tg for various incubation times at 37 degrees C using non-reducing conditions. A ratio of trypsin to Tg of 1:100 (w/w) was optimal to release small peptides that were reactive to murine MoAbs to human Tg. Most peptides were released after only 1 h incubation with trypsin, but these peptides were further degraded at longer incubation times. However, a few small peptides, the largest of which with an apparent molecular weight (MWap) of 40 kD, resisted tryptic digestion up to at least 12 h of incubation. These resistant peptides were further degraded by trypsin at 18-24 h of incubation. Tryptic peptides of Tg, released at 1 h and 4 h of incubation, were analysed for their immunoreactivity to 16 well characterized anti-Tg MoAbs by Western immunoblot. Patterns of peptide recognition of these MoAbs were generally unique. Eight MoAbs reacted with peptides of MWap of 10-25 kD and above. Four other MoAbs reacted with peptides of MWap of 25-43 kD and above, and the remaining four reacted with peptides of MWap > 43 kD. Nine of these MoAbs failed to recognize peptides after reduction, suggesting that the MoAbs bind conformation-dependent epitopes. The above information will promote the development of models relating the structure of Tg to the autoimmune process, and may provide an understanding of those regions of Tg responsible for the induction of autoimmune thyroiditis.

Tryptic peptides of human thyroglobulin: II. Immunoreactivity with sera from patients with thyroid diseases

Tryptic peptides of human thyroglobulin (Tg) were analysed by Western immunoblot for their reactivity to circulating autoantibodies from patients with Hashimoto's thyroiditis (HT), Graves' disease (GD) and thyroid carcinoma, and from normal human controls. Low molecular weight peptides were released after 4 h incubation of Tg with trypsin. The sera of thyroid disease patients reacted with several peptides, but predominantly bound three peptides with apparent molecular weights (MWap) of 25 kD, 20 kD, and 15 kD; the sera of normal individuals did not bind these fragments of Tg. The pattern of tryptic peptides recognized by the majority of sera from GD patients differed from that recognized by sera from most patients with HT. Autoantibodies from both groups of patients recognized a 15-kD peptide with a high frequency, but the sera from 26/43 (60%) GD patients also recognized a peptide with MWap of 25 kD, whereas the sera from 22/35 (63%) of HT patients recognized a 20-kD peptide. A few sera from patients with thyroid carcinoma reacted with peptides with MWap of 15 and 20-kD, and none bound the 25-kD peptide. The immunoreactivity of autoantibodies in HT sera to the 20-kD peptide paralleled the competitive inhibition of the MoAb 137C1 by these sera. In addition, MoAb 137C1 and Hashimoto's sera showed the same Western immunoblot-binding pattern to Tg tryptic peptides, suggesting that a Hashimoto-associated epitope and the 137C1-binding site are found on the same peptide. These findings suggest that distinct peptides are recognized by Tg autoantibodies from patients with different thyroid diseases.