Anti-thyroglobulin Autoantibodies Research Articles

Thyroid involvement in patients with overt HCV-related mixed cryoglobulinaemia.

Mixed cryoglobulinaemia (MC), a systemic vasculitis associated with hepatitis C virus (HCV) infection in >90% of cases, is frequently complicated by multiple organ involvement. The prevalence of thyroid disorders in MC has not yet been studied. To investigate the prevalence and clinical features of thyroid involvement in patients with HCV-associated MC (HCV + MC). Case-control study. HCV + MC patients (n = 93, 17 men and 76 women, mean +/- SD age 63 +/- 10 years, mean disease duration 14 +/- 7 years) consecutively referred to the Rheumatology Unit were matched by sex and age (+/- 2 years) to (i) 93 patients with chronic C hepatitis (CH) without MC and (ii) 93 healthy (HCV-negative) controls from the local population. Measurements included prevalence of hypo- or hyperthyroidism, thyroid autoantibodies, thyroid nodules and thyroid cancer. By McNemar's chi(2) test, the following thyroid abnormalities were significantly more frequent in HCV + MC patients than in HCV-negative controls: serum anti-thyroperoxidase autoantibody (AbTPO) (28% vs. 9%, p = 0.001); serum AbTPO and/or anti-thyroglobulin autoantibody (31% vs. 12%, p = 0.004); subclinical hypothyroidism (11% vs. 2%, p = 0.038); thyroid autoimmunity (35% vs. 16%, p = 0.006). Serum AbTPO were also significantly more frequent in HCV + MC patients than in CH controls (28% vs. 14%, p = 0.035). The prevalence of thyroid disorders is increased in patients with HCV-related mixed cryoglobulinaemia. We suggest careful monitoring of thyroid function in these patients.

Frequency and Levels of Autoantibodies in Healthy Adult Omanis

A previous pilot study showed a high frequency of anti-smooth muscle autoantibody in Omani blood donors and pregnant women. We conducted this larger-scale study to investigate the frequency and significance of several autoantibodies in healthy individuals from different regions of Oman. Sera obtained from 1537 healthy Omanis (1153 males and 384 females), ranging in age from 18 to 57 years, were tested for the presence of ten different autoantibodies using indirect immunofluorescence, haemagglutination and latex agglutination techniques. Low levels of autoantibodies were detected in 33.5%, whereas a few individuals (1.8%) showed high autoantibody titres. Anti-smooth muscle autoantibodies (ASMA) were the most prevalent (11%). Anti-nuclear autoantibodies (ANA) were the second most prevalent (7.6%). Anti-thyroid microsomal autoantibodies (ATMA) and anti-thyroglobulin autoantibodies (ATA) were present in 6.5% and 4.4% of individuals, respectively. The other autoantibodies were detected much less frequently: anti-parietal cells autoantibodies (APCA) were found in 1.6%, anti-brush border antibodies (ABBA) in 1.3%, anti-reticulin autoantibodies (ARA) in 1%, antimitochondrial antibodies (AMA) in 0.8%, antiglomerular basement membrane antibodies (AGBMA) in 0.7% and rheumatoid factor (RF) in 0.4%. The data indicate that autoantibodies are present in healthy Omani individuals, and therefore caution should be taken when interpreting laboratory results of patients suspected of having autoimmune disease.

Increase in Serum Levels of Autoantibodies after Attack of Seasonal Allergic Rhinitis in Patients with Graves’ Disease

Background: The prevalence of allergic disease is increasing worldwide, but its influence on the clinical course of autoimmune diseases is unknown. Objective: The purpose of this study was to assess the effect of seasonal allergic rhinitis on the clinical course of Graves’ disease, which has been considered a Th2-dominant autoimmune disease. Methods: Ten patients with Graves’ disease, who were considered to be in a state of remission or near remission, were serially examined for 18 months starting from August. Five of them had seasonal allergic rhinitis due to Japanese cedar pollen, and the remaining patients had no such allergic disorders. Peripheral eosinophil counts, serum concentrations of cedar-pollen-specific IgE, anti-TSH-receptor antibody, anti-thyroid-peroxidase antibody and antithyroglobulin antibody were assessed at 2- to 4-month intervals. Serum thyroid hormones and TSH levels were also measured to evaluate disease activity. Results: All patients with pollinosis had attacks of allergic rhinitis caused by cedar pollen in early March. Subsequently, peripheral eosinophil counts, pollen-specific IgE activity and serum levels of anti-thyroid-peroxidase and antithyroglobulin autoantibodies markedly increased. Serum levels of anti-TSH-receptor antibody increased in 3 patients in association with an increase in serum thyroid hormones but were always negative in 2 patients. The control patients without pollinosis showed no consistent change of these parameters. Conclusions: Seasonal allergic rhinitis aggravated the clinical course of Graves’ disease and induced an increase in serum antithyroid autoantibody concentrations as well as an increase in pollen-specific IgE concentration. These data suggest that environmental antigens induce not only local allergic reactions, but also stimulate thyroid immune reactions toward Th2 proliferation, and finally aggravate Th2-dependent autoimmune thyroid disease.

Frequency and clinical importance of anti-Tg auto-antibodies (ATG).

To note the frequency of anti thyroglobulin autoantibodies (ATG) and its clinical importance in 25 follow-up cases of differentiated thyroid cancer (DTC). A case control study. The total duration of study was one year (September 2000 to August 2001). Majority of the patients included were the routine follow-up cases at IRNUM, Peshawar. However, few of the cases were also included from NORI, Islamabad and AFIP, Rawalpindi. All the patients who had undergone sub-total or total thyroidectomy followed by I-131 ablation therapy were selected for this study. Thyroglobulin (Tg) and ATG were measured using immunometric assay technique with reference range of non-detectable to 40 IU/L. Patients with serum Tg level 10 ng/mL were included in group-1 (n=15) and all the remaining (n=10) in group-2. Overall, 11 patients showed ATG titer above the pre-defined threshold level. In group-1 patients, 8 had positive anti-Tg antibodies in their sera while in group-2, it was positive in only 3 cases. Risk of relapsing metastatic/recurrent disease in association with ATG was calculated which showed that patients with positive ATG have almost seven-fold increased risk of having recurrent/metastatic disease than those who do not. Samples for s-Tg measurements must also be evaluated for ATG status because more than one-third of these patients have positive ATG titer in their sera. Although in the presence of positive ATG, the risk of concurrent metastatic/recurrent thyroid disease is increased but still more studies are required to support its significance.

Autoimmunity as the Most Frequent Cause of Idiopathic Secondary Adrenal Insufficiency: Report of 111 Cases

The origin of the isolated secondary adrenal insufficiency is unknown in most cases. An observation of a group of over 100 patients with secondary adrenal insufficiency and coexisting autoimmune abnormalities suggests that autoimmunity could be a frequent cause of idiopathic secondary failure, similarly as in Addison's disease. We studied 176 patients with idiopathic isolated secondary adrenal insufficiency. The methods included clinical examination and measurements of pituitary, adrenal, thyroid and gonadal hormones in all the cases. Since thyroid autoimmunity has been the most frequent finding in Addison's disease we have also chosen thyroid autoantibodies as markers of an autoimmune process in our material. Anti-peroxidase, anti-microsomal and anti-thyroglobulin autoantibodies were determined in 151 patients. In 111 out of 151 patients (73%) coexisting autoimmune diseases and/or presence of thyroid autoantibodies were detected. The most frequent autoimmune diseases associated with secondary adrenal insufficiency were primary hypothyroidism, hyperthyroidism (mainly in the past) and premature ovarian failure. Thyroid autoantibodies, especially antiperoxidase autoantibodies, were present in 106 patients. Thus, coexistence of isolated secondary adrenal insufficiency with some autoimmune disorders in 73% of the patients under study suggests that autoimmunity is the most frequent cause of the idiopathic form of this disease.

Diffuse sclerosing variant of papillary thyroid carcinoma—clinical features and outcome

Aim: Diffuse sclerosing variant of papillary thyroid carcinoma (DSPC) is rare and occurs in young patients. This is a single institute retrospective analysis to report the clinical features and outcome of DSPC. Method: DSPC constituted 8 (0.74%) of 1086 papillary thyroid carcinomas (PTC) referred to the department of Clinical Oncology, Queen Elizabeth Hospital Hong Kong from 1960 to 2000. Results: The mean follow-up was 8 years (range: 1.4 to 15.2 years). Six were females and two were males, with age ranging from 11 to 48 years. All were ethnic Chinese. Compared with the whole cohort of PTC followed in the same period, these patients showed younger age at presentation (mean 27.4 vs 45.3 years), larger tumor size (mean 6.9 cm vs 2.4 cm), higher incidence of lymph node metastasis (100% vs 32.4%), and more frequent presence of serum anti-thyroglobulin autoantibody (75% vs 11.3%). The patients were managed as for differentiated thyroid carcinoma according to the institute's protocol, including total thyroidectomy followed by radioiodine (RAI) treatment. External radiotherapy was given to two patients as primary treatment and one patient after regional relapse. One patient had distant metastases at presentation and she was successfully treated by surgery followed by RAI, remaining in complete remission at 12.1 years. One patient had lymph node recurrence after primary total thyroidectomy and RAI treatment and was successfully salvaged by surgery and external radiotherapy. At last follow-up, all eight patients were alive with no evidence of disease. Conclusions: Although DSPC is associated with some unfavourable features at presentation (such as large tumor size, extensive lymph node metastasis), the prognosis appears to be as good as classical PTC. After aggressive treatment by radical surgery, RAI ablation and/or external radiotherapy, the outcome and survival was excellent.

Characteristics of Inflammatory Cells in Spontaneous Autoimmune Thyroiditis of NOD.H-2h4 Mice

Thyroid lesions develop in most NOD.H-2h4 mice 6 weeks after they are given 0.05% NaI in drinking water. B cells are required for spontaneous autoimmune thyroiditis (SAT) development, and anti-thyroglobulin autoantibody levels correlate with SAT severity. Immunohistochemical staining of thyroids obtained 2–10 weeks after administration of NaI water suggested that CD4+ T cells initially infiltrated the thryoid, followed by CD8+ T cells and B cells. Intrathyroidal CD4+ T cells are more numerous than CD8+ T cells. CD4+ T cells and B cells form aggregates in the thyroid, while CD8+ T cells are scattered throughout the thyroid. Intrathyroidal germinal centre-like structures could be observed in thyroid lesions with 2–3+ SAT and intrathyroidal B cells co-expressed OX40L. By RT–PCR, intrathyroidal expression of OX40L, OX40, CD40L, IL-2R, CTLA-4 and Igβ mRNA correlated closely with the SAT severity score. These molecules were not expressed in normal thyroids. In the spleen, OX40L-positive cells were detected at 2 weeks and increased 4–6 weeks after NaI water. OX40, OX40L, CD40L, IL-2R and B7-1 as well as IFN-γ and IL-4 mRNA were minimally expressed in normal spleens, usually began to be expressed at 2 weeks and increased to maximal level 4–8 weeks after NaI water. These results suggest that in NOD.H-2h4 mice, the OX40L, OX40, CD40L and B7 molecules, which increase in the spleen and thyroid of these mice after receiving NaI water, may play a role in SAT development, implying that one or more of these molecules might be good targets for the prevention or treatment of SAT.

Level of Serum Neopterin and Interleukin-6 In Patients with Thyroid Diseases

Summary The purpose of the study was to characterize the immune status in 88 patients (64 women and 24 men) with thyroid diseases and in 36 healthy blood donors as control group. The clinical material consisted of 37 patients with nontoxic nodular goitre, 10 patients with thyroiditis, 27 patients with thyroid adenoma and 14 patients with thyroid carcinoma. The studied parameters included serum neopterin,interleukin-6 (IL-6), also anti-thyroglobulin autoantibodies (ATG) and anti-thyroid microsomal autoantibodies (MAB). The aim of the study was to investigate whether serum neopterin, IL-6, ATG and MAE have any value in distinction between non-toxic nodular goitre, thyroiditis, thyroid adenoma and thyroid carcinoma. 36.4% patients with thyroid carcinoma, 16.7% patients with nontoxic nodular goitre and 9.1 % patients with thyroid adenoma had neopterin levels higher than 10 nmol/1. In patients and in the control group the mean serum levels of neopterin were in normal range. The highest mean level of neopterin was found in patients with thyroid carcinoma (7.14± 5.95 nmol/1). The difference was statistically significant in comparison to the control (p < 0.001) and patients with thyroiditis and thyroid adenoma (p < 0.05). The significantly higher levels of IL-6 were in all patients in comparison to the control (p < 0.0001). Autoantibodies ATG were detected in serum of 45 patients (51.1 %) and autoantibodies MAE were in serum of 34 patients (38.6 % ). Mean levels of these autoantibodies in patients were statistically significantly higher than in the control ' p < 0.05). In patients with ATG and/or MAE mean level of neopterin was significantly higher than in patients without these autoantibodies (p < 0.05). This study has shown that neopterin represents an additional parameter with potential interest in clinical diagnosis of thyroid diseases.

Cloning and analysis of IgG kappa and IgG lambda anti-thyroglobulin autoantibodies from a patient with Hashimoto's thyroiditis: evidence for in vivo antigen-driven repertoire selection.

Antibodies to thyroglobulin (Tg) are commonly found in patients with the autoimmune thyroid diseases Graves' disease and Hashimoto's thyroiditis as well as in individuals with apparently normal thyroid function. Although it is not clear how Tg Abs are involved in the pathology of the diseases, the study and analysis of these Abs may nevertheless be instructive in allowing the development of an Ab response to an autoimmune disease-associated self Ag to be followed. We have prepared IgG kappa and lambda phage display combinatorial libraries from the cervical lymph node of a single Hashimoto's thyroiditis patient with a high anti-Tg titer. These were selected with purified human Tg, and 10 IgG kappa and 9 IgG lambda clones were analyzed further. Sequence analysis of the clones showed a very highly restricted heavy chain usage and a less restricted light chain usage. There was a variable degree of divergence from germ-line sequence in the light chain sequences, with a clear relationship between relatively higher affinity of the Fab for human Tg and an increased degree of somatic hypermutation. The Tg-selected Fab did not bind to Tg from other species, to reduced denatured Tg, or to thyroid peroxidase. The Fab inhibited patient serum binding to human Tg by between 39 and 79%. In summary, we have isolated 19 high affinity, human Tg-specific Fab and shown that the relative affinity of the Fab is directly related to the pattern of somatic hypermutation.

Increased risk of autoimmune hypothyroidism in patients affected by retinitis pigmentosa.

Patients with Retinitis Pigmentosa (RP) show hemeralopia, restricted field of vision and reduced visual acuity, owing to the degeneration and proliferation of photoreceptors and a retinal pigment epithelium. The prevalence in Italy is 1:4,000. A certain number of "syndromic" associations have been described, and, in particular, also that with hypothyroidism, but very few cases have been studied. We describe a family of 40 people, spanning four generations, in which we have recorded the presence of autosomic dominant RP, associated with autoimmune hypothyroidism or with circulating antithyroid autoantibodies (ATA), currently considered as the expression of active autoimmune thyroiditis or a risk factor for this complaint. We measured, in all members, TSH, FT3, FT4, antithyroglobulin and antithyroperoxidase autoantibodies. A fundus oculi examination was performed in every subject, as well as a careful examine of the anterior region on the neck. A control population of 100 healthy people was also studied. Our data show a higher prevalence of ATA, statistically significant, in the patients with RP and in their relatives, compared with the control population and the data from the literature (13 cases over 40 = 32.5%; p < 0.01). 3 patients with RP and ATA were affected by clinically evident hypothyroidism. 10 patients with ATA were clinically euthyroid; 8 patients affected by RP did not show circulating ATA at the time of the study. The interest for the physician in this "syndromic" retinal distrophy reflects the need, emerging from our data, to test the thyroid function in the subjects with RP and in members of their families, since circulating ATA are considered a risk factor for the development of autoimmune hypothyroidism.

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.

Serological markers of autoimmunity in renal transplant patients before and after alpha-interferon therapy for chronic hepatitis C.

Chronic hepatitis C is the major cause of chronic liver disease after successful cadaveric renal transplantation. The aims of this prospective, open study were to assess in such a population, firstly the prevalence of different organ-specific and nonspecific antibodies and related disorders, and secondly their outcome after inteferon-alpha therapy as well as the incidence of new immunologic disorders under and after this therapy. In 15 cadaveric renal transplant patients (10 men, 5 women, ages 29-65 years) with chronic hepatitis C and histological features of chronic active hepatitis, undergoing chronic immunosuppression (ciclosporine A with or without steroid and azathioprine) and treated with recombinant alpha 2b-interferon (IFN alpha) (mean duration 142 +/- 35 days), we assessed before and after this therapy the serum levels of cryoglobulinemia, rheumatoid factors (RF), thyroid-stimulating hormone (TSH), free thyroxine (fT4), and antinuclear (ANA), antismooth muscle (ASMA), antimitochondrial (AMA), anti-LKM1, antimicrosomal thyroid (MCA), antithyroglobulin (TGA) autoantibodies. At the start of IFN alpha therapy, 14 of 15 patients had detectable autoantibodies (RF: 9; ANA > 1/50: 8; ASMA > 1/50: 4; other autoantibodies: 0); 1 had cryoglobulinemia. At the end of therapy the cryoglobulinemia had disappeared, the preexisting autoantibodies remained present in all patients but 2; 3 patients had developed MCA without evidence of clinical or biological thyroid abnormalities and 3 others had developed either RF (1) or ANA (1) or ASMA (1), without any related symptoms. One patient developed transient type II diabetes mellitus without anti-Langerhans beta-cell antibodies. Finally, the occurrence of autoantibodies in our patients was associated either with HLA DR3 or DR4 or DR7 phenotypes. We found that the prevalence of extrahepatic immunologic abnormalities was high in renal transplant patients with chronic hepatitis C and no exacerbation was observed during of after IFN alpha therapy. The most frequent autoantibody appearing after IFN alpha therapy was MCA although without thyroid abnormalities.

Purification of antithyroglobulin autoantibodies (ab-tg) for application in immunodetection- and immunotherapy of thyroid cancer.

The incidence of non-Hodgkin lymphoma (NHL) in persons over the age of 65 years has increased dramatically since the 1950s in western countries. The strongest known risk factors for NHL are primary or acquired immunosuppression, but these severe deficiencies are relatively rare and cannot explain the rapid increase observed in the elderly. Recent work suggests that common exposures which influence immunocompetence, albeit at a much weaker level, may also be risk factors for NHL. Two such risk factors recently associated with NHL are prior history of blood transfusion and certain aspects of diet. In four out of four studies, prior history of blood transfusion was associated with approximately a doubling in NHL risk, even for a transfusion first received a decade or more before diagnosis. Other studies suggest that diets high in animal proteins and fats may increase the risk of NHL while fruit and vegetable consumption may decrease risk. Allogeneic blood transfusion is known to suppress the immune system, and diets high in protein and fat may also lead to altered immunocompetence, although other mechanisms such as viral transmission or the effects of heterocyclic amines and N-nitroso compounds may also play a role. Follow-up of these observations may lead to a better understanding of the NHL epidemic and new approaches to the prevention of NHL.

Thyroid disorders in Korean patients with systemic lupus erythematosus.

Although autoimmune thyroid diseases have been associated with systemic lupus erythematosus (SLE), the prevalence of thyroid disorder is controversial. To clarify the prevalence of thyroid disorder in Korean patients with SLE, thyroid functions and diseases were evaluated in 63 SLE patients. Of these patients, Hashimoto's thyroiditis (9.5%) as well as euthyroid sick syndrome (14.3%) were more common than Graves' disease (4.8%). The prevalence of antithyroid autoantibodies (antimicrosomal and/or antithyroglobulin autoantibodies) in SLE was 27.0%. High titers of these autoantibodies were mainly detected in Hashimoto's thyroiditis. These results suggested that thyroid diseases are not uncommon in SLE and autoimmune thyroid diseases are possible manifestations in some patients with SLE. Antithyroid autoantibodies may be good predictors for the detection of Hashimoto's thyroiditis developing in SLE.

Cloning and analysis of IgM anti-thyroglobulin autoantibodies from patients with Hashimoto's thyroiditis

Hashimoto's thyroiditis is an autoimmune disease in which autoanitbodies reactive to a number of thyroid antigens are made. In order to investigate the autoantibody repertoire in this disease, B cells from four patients with Hashimoto's thyroiditis were immortalised and, after limiting dilution, screened for reactivity to thyroid antigens. After a second limiting dilution, one anti-thyroglobulin IgM-secreting clone from three patients, and four clones from one patient, were analysed. The Ig heavy and light chain genes from each clone were amplified using the polymerase chain reaction and sequenced. The resulting heavy and light chain sequences were heterogeneous, although the four clones from one patient and the clone from a second patient shared a germline V H sequence. All antibodies had similar functional affinity, comparable to serum IgC from Hashimoto's patients. The cross-reactivity of the antibodies was analysed against bovine and rat thyroglobulin, histones, cardiolipin and human skeletal muscle. The antibodies were polyreactive, indicating that they are probably natural autoantibodies of unknown pathogenic significance.

Effect of growth hormone and thyroid hormone on autoimmune thyroiditis in obese chickens

The effect of thyroxine (T 4) and recombinant (rcGH) or purified pituitary-derived (pcGH) chicken growth hormone on the development of spontaneous autoimmune thyroiditis (SAT) was examined in the Obese strain (OS) chicken. Day-old OS chicks were randomly assigned to a control or 1.0 ppm T 4 supplemented diet and a vehicle or 500 μg rcGH/kg BW daily injection, using a 2×2 factorial design. At 4 weeks, sera were analyzed for anti-thyroglobulin autoantibody (TgAAb) using a kinetics-based ELISA. Leucocytic infiltration of the thyroid was assessed using computer-based video imaging techniques. A close correlation between TgAAb and thyroid infiltration was seen with both being decreased ( p<0.05) by the T 4/rcGH treatment. Neither the T 4 or rcGH alone produced this effect and the rcGH treatment significantly elevated TgAAb. In a second experiment, all but the control group received 1.0 ppm T 4 supplementation and two of the T 4-treated groups received either 50 or 200 μg pcGH/kg BW by daily injection. As before, T 4/pcGH significantly reduced TgAAb and thyroid infiltration. T 4 alone produced no significant effects. These data support the conclusion that the combined treatment of T 4 and cGH exert an immunomodulatory effect within a strain that is predisposed to autoimmune thyroiditis while GH treatment alone exacerbated the condition. These results also show that video imaging techniques can be used to evaluate the extent of histopathology present within the OS thyroid.

Significance of antithyroglobulin autoantibodies in differentiated thyroid carcinoma.

The incidence of antithyroglobulin autoantibodies (ATA) was 17.7% in 963 patients (who attended the clinic from 1981 to 1990) with differentiated thyroid carcinoma (DTC). Another 12 patients developed ATA for a transient period after the treatment with radioiodine. The prevalence of ATA in females (21.5%, 123/572) was significantly higher (p < 0.001) than that seen in males (12.0%, 47/391). Age-dependent occurrence of ATA was not seen for the various age decades. The ATA was more prevalent (p < 0.01) with the papillary type of tumor (118/564) as compared to the follicular variety (51/398). ATA did not influence the metastatic spread of the tumor at the initial presentation (105/170 for the ATA-positive group and 445/793 for the ATA-negative group). However, within the group with metastases, 82.9% (87/105) of patients had local spread into the neck in the presence of ATA, which was significantly higher (p < 0.01) than that seen for patients without ATA (63.8%, 284/445). For assessment of the influence of ATA on the outcome of the disease, the data from 222 patients (46 positive and 176 negative for ATA), with a minimum follow-up of 5 years (mean follow-up of 7.4 years), was considered suitable for analysis. The outcome of the disease was comparable in the presence and the absence of ATA (38/46 and 137/176 patients became disease-free in ATA-positive and -negative groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal Anti-idiotypic Antibodies against Human Anti-thyroglobulin Autoantibodies Recognize Idiotopes Shared by Disease-Associated and Natural Anti-thyroglobulin Autoantibodies

Monoclonal murine anti-idiotypic antibodies generated against purified human anti-thyroglobulin (TG) antibodies from a patient with Hashimoto's thyroidiris recognized two major clusters of idiotopes (1C2 and 1B1) on human anti-thyroglobulin antibodies which were framework and paratope-related. A survey of affinity-purified autoantibodies from Hashimoto's patients indicated that the 1C2 and 1B1 idiotopes are expressed on the disease-associated anti-TG antibodies from several patients. 1C2 and 1B1 idiotopes are also detected on affinity-purified anti-TG antibodies isolated from serum of healthy donors and with therapeutic preparations of immunoglobulins obtained from plasma pools of healthy individuals. The observation that both framework and paratope-related idiotopes are shared by natural and patients' autoantibodies suggests that the anti-TG autoantibodies found in sera of patients with Hashimoto's disease represent an abnormal expansion of normal autoreactive B cell clones rather than the emergency of an antigen-driven, disease-specific B cell response.

Expression and control of the natural autoreactive IgG repertoire in normal human serum.

We have investigated the autoreactive repertoire expressed by serum IgG of healthy individuals of various age groups using a large panel of self antigens. Natural IgG autoantibodies against all self antigens of the panel were found in the purified IgG fraction of the serum of all donors that were tested. The mean binding activity to self antigens of IgG of pregnant women was higher than that of IgG purified from the serum of infants, young adults and aged individuals. No increase in IgG autoreactivity was observed with aging neither in the purified IgG fraction of serum nor in whole serum. Whereas autoantibody activity was easily detectable in purified IgG, it was low in serum. No difference was observed, however, between the binding activity of purified IgG and of IgG in serum in the case of foreign antigens nor in the case of anti-thyroglobulin autoantibodies of patients with hashimoto's thyroiditis. Purified IgM from normal serum bound to F(ab')2 fragments of autologous IgG in a dose-dependent fashion and inhibited the binding of autologous IgG to self antigens. Our results thus indicate that autologous IgM contributes to regulate expression of the natural IgG autoreactive repertoire through V region-dependent interactions, resulting in low levels of IgG autoreactivity in serum under physiological conditions.

Immunization with Thyroglobulin-Specific Cytotoxic T Cell Hybridoma Induces Anti-thyroglobulin Antibodies: Characteristics of Monoclonal Anti-thyroglobulin Auto-antibody

We have produced five monoclonal autoantibodies (mA-Abs) to thyroglobulin (Tg) and more precisely to one epitope located within the <10-kDa pTg tryptic fragment suspension capable of inducing experimental autoimmune thyroiditis (EAT). They were selected from spleen cells from CBA/J mouse immunized with the syngeneic cytotoxic T cell hybridoma HTC2. HTC2 cells are specific for one Tg epitope located within the EAT inducer pTg tryptic fragments and are able to prevent EAT induction by pTg. The restricted specificity of the humoral response previously observed in vivo was further demonstrated and defined in vitro at the single cell level. Competitive studies for binding to pTg or to the <10-kDa pTg tryptic fragments demonstrated that HTC2-induced anti-Tg mA-Abs recognized an epitope(s) located in the <10-kDa pTg tryptic fragment (as did 3B8G9, one conventional anti-Tg mA-Ab we selected). We ruled out the possibility that HTC2-induced anti-Tg A-Abs belong to the group of the natural A-Abs due to the lack of recognition of actin, dsDNA, TNP-ovalbumin, tubulin, their isotypes (IgG1 or Ig2a), and their affinities (in the 10-7M order of magnitude). The results strengthen the hypothesis that T and B cells sharing the same specificity can express similar idiotopes on their respective receptors for antigen. They also demonstrate the existence of a regulatory idiotypic network that could explain the protection from EAT after injection of inactivated HTC2 cells or its anti-clonotypic mAb.