Nonautoimmune Thyroid Disorders Research Articles

Association between anti-thyroid antibodies and quality of life in patients with Hashimoto thyroiditis: a systematic review and meta-analysis.

The aim of this review was to evaluate the association between anti-thyroid antibodies and quality of life in people with euthyroid Hashimoto thyroiditis. Patients with Hashimoto thyroiditis report symptom distress more often than those with non-autoimmune thyroid disorders. Therefore, anti-thyroid antibodies may be related to decreased quality of life in persons with Hashimoto thyroiditis. The etiology of lingering symptoms, even in euthyroidism, remains unknown. The relationship between anti-thyroid antibodies and quality of life for people with Hashimoto thyroiditis has not been evaluated in a systematic review. The participants were males and females at least 12 years of age, in any country, with Hashimoto thyroiditis. Participants not in a euthyroid state were excluded from this review. In this review, the exposure was the presence of anti-thyroid antibodies and the primary outcome was quality of life as measured by a validated scale. A three-step search strategy was implemented with an initial search of PubMed and CINAHL. A comprehensive database search using all identified keywords and index terms was undertaken in March 2019 for relevant published literature, gray literature, and clinical trial registries. The final updates to the search strategies were conducted in December 2019. The search was limited to studies published in English after 1956. Two independent reviewers completed screening for inclusion and utilized the recommended JBI approach to critical appraisal, study selection, data extraction, and data synthesis. The findings are presented in a meta-analysis and in a narrative synthesis, which includes tables and figures. All 13 studies had high methodological quality. Four studies found a significant correlation (P < 0.05) between the presence of anti-thyroid antibodies and quality of life. A fifth study found a significant correlation (P < 0.001) between higher antibody levels and quality of life. A meta-analysis was conducted using two cross-sectional studies, which revealed that the summative small effect size was statistically significant and suggested a lower quality of life in antibody-positive patients. Due to the heterogeneity of the studies, a narrative synthesis was conducted for the three secondary outcomes: symptom distress, executive function, and mental health. Three studies found a statistically significant (P < 0.05) correlation between symptom distress and antibodies, two studies found a statistically significant (P < 0.05) association between executive function and antibodies, and all but one study found a statistically significant (P < 0.05) relationship between mental health and antibodies. The findings in this review did not reveal a definitive relationship between antibodies and quality of life. However, our meta-analysis suggested a link between anti-thyroid antibodies and decreased quality of life in euthyroid children and adults. Though not conclusive, poor mental health and symptom distress may be associated with anti-thyroid antibodies. Therefore, it may be beneficial to periodically evaluate the quality of life and mental health in euthyroid patients with positive antibodies. It is unlikely that antibodies and executive functions are related. The studies and our review's limitations require replication of findings to confirm a connection between antibodies, quality of life, and the secondary outcomes. Future research should continue to evaluate the relationship between anti-thyroid antibodies and the quality of life in individuals with euthyroid Hashimoto thyroiditis. PROSPERO CRD42018084663.

Human herpesvirus 6A active infection in patients with autoimmune Hashimoto's thyroiditis

BackgroundHypothyroidism due to Hashimoto's thyroiditis (HT) is the commonest autoimmune endocrine illness in which antibodies against thyroid organ result in inflammation. The disease has a complex etiology that involves genetic and environmental influences. Viral infections may be involved in triggering of the disease as their molecular mimicry enhance autoimmune responses. Human herpesvirus-6 (HHV-6) is recognized for its contribution to some autoimmune diseases. ObjectiveIn the current study, the prevalence of HHV-6 active infection in patients with HT and with non-autoimmune thyroid disorders were compared with patients with euthyroidism. In addition, a correlation between presence of HHV-6 infections and HT was investigated. MethodsA total of 151 patients with clinically and laboratory confirmed HT, 59 patients with non-autoimmune thyroid disorders, and 32 patients with normal thyroid function were included in the study. For further confirmation of HT disease, all the precipitants were tested for anti-thyroid peroxidase (TPO), and anti-thyroglobulin (TG) antibodies. For detection of both HHV-6 types A and B, nested PCR and restriction enzyme digestion were used. HHV-6 DNA positive samples were further investigated by DNA sequencing analysis. ResultsHHV-6A DNA was found in serum sample of 57 out of 151 patients (38%) with HT, which was significantly more often than in patients with non-autoimmune thyroid disorders (p=0.001). However, HHV-6 DNA was not detected in serum samples of euthyroid subjects. ConclusionsThe results support a possible role for active HHV-6A infection, demonstrated by the presence of HHV-6 DNA in sera, in the development of HT.

Peripheral blood natural killer cells and mild thyroid abnormalities in women with reproductive failure.

Abnormalities in peripheral blood natural killer (NK) cells have been reported in women with primary infertility and recurrent spontaneous abortion (RSA) and several studies have been presented to define cutoff values for abnormal peripheral blood NK cell levels in this context. Elevated levels of NK cells were observed in infertile/RSA women in the presence of thyroid autoimmunity (TAI), while no studies have been carried out, to date, on NK cells in infertile/RSA women with non-autoimmune thyroid diseases. The contribution of this study is two-fold: (1) the evaluation of peripheral blood NK cell levels in a cohort of infertile/RSA women, in order to confirm related data from the literature; and (2) the assessment of NK cell levels in the presence of both TAI and subclinical hypothyroidism (SCH) in order to explore the possibility that the association between NK cells and thyroid function is not only restricted to TAI but also to SCH. In a retrospective study, 259 age-matched women (primary infertility [n = 49], primary RSA [n = 145], and secondary RSA [n = 65]) were evaluated for CD56+CD16+NK cells by flow cytometry. Women were stratified according to thyroid status: TAI, SCH, and without thyroid diseases (ET). Fertile women (n = 45) were used as controls. Infertile/RSA women showed higher mean NK cell levels than controls. The cutoff value determining the abnormal NK cell levels resulted ⩾15% in all the groups of women. Among the infertile/RSA women, SCH resulted the most frequently associated thyroid disorder while no difference resulted in the prevalence of TAI and ET women between patients and controls. A higher prevalence of women with NK cell levels ⩾15% was observed in infertile/RSA women with SCH when compared to TAI/ET women. According to our data, NK cell assessment could be used as a diagnostic tool in women with reproductive failure and we suggest that the possible association between NK cell levels and thyroid function can be described not only in the presence of TAI but also in the presence of non-autoimmune thyroid disorders.

Increased prevalence of antibodies to central nervous system tissue and gangliosides in Hashimoto's thyroiditis compared to other thyroid illnesses

Previous studies point to central nervous system (CNS) alterations in euthyroid patients with Hashimoto's thyroiditis (HT). The aim of the present study was to investigate the prevalence and clinical significance of antibodies (Abs) against CNS tissue and gangliosides in female patients with HT compared to patients with other non-autoimmune thyroid disorders, comprising diffuse or nodular goitre and thyroid surgery for goitre. 58 HT patients (mean age: 46+/-17 years) and 89 patients with other thyroid disorders (mean age: 51+/-15 years) were recruited consecutively from our endocrine outpatient clinic. Serum Abs against CNS tissue and gangliosides were determined using an enzyme-linked immunosorbent assay (ELISA). In a subgroup of 23 HT patients, neurocognitive function was studied using established neuropsychological tests. In HT patients, the prevalence of serum anti-ganglioside-Abs and anti-CNS-Abs were significantly higher compared to patients with other thyroid disorders (p<0.05 and p<0.005, respectively). In both cases, the number of Ab-positive HT patients was twice that of Ab-positive controls. Reactivity of IgM-Abs to gangliosides and IgG-Abs to CNS tissue was significantly higher in HT patients than in controls (p<0.05 and p<0.01, respectively). However, prevalence and reactivity of Abs to gangliosides and CNS tissue were associated neither with the prevalence of depression nor with impairment of neurocognitive function in HT patients. Ab reactivity towards CNS tissue and gangliosides is markedly enhanced in patients with HT as compared to patients with other thyroid disorders. Whether these Abs could be of prognostic value to evaluate the risk of future neurocognitive impairment has to be investigated in longitudinal studies.

One-tube-PCR technique for CCL2, CCL3, CCL4 and CCL5 applied to fine needle aspiration biopsies shows different profiles in autoimmune and non-autoimmune thyroid disorders

Autoimmune thyroid diseases are characterized by lymphocytic infiltration of the thyroid gland. Chemokines are crucial in the recruitment of lymphocytes and might play an important role in the pathogenesis of autoimmune thyroid disease. The aim of this study was to test the feasibility of analysing by one-tube reverse-transcriptase polymerase chain reaction (RT-PCR) technique CC chemokine profiles in samples obtained by fine needle aspiration biopsy (FNAB). In 27 out of 35 (77%) samples, the material was sufficient for analysis and in 16 (59%) chemokines were detected, thus demonstrating the potential of this technique. Moreover, even in this small group, a statistically significant increase of CCL3 and CCL4 was found in samples from patients with autoimmune thyroid disease as compared to those with multinodular goiter. Chemokine profile measured by improved multiamplification techniques in FNAB thyroid samples may become a useful complementary tool for the management of thyroid autoimmune disease as it constitutes a source of data for research of their pathogenesis.

Autoimmune and non-autoimmune thyroid diseases have different patterns of cellular HLA class II expression.

Surface HLA-DR antigen is usually only expressed by antigen-presenting cells (APC). In autoimmune thyroid disease, follicle cells function as APC, thus expressing HLA-DR. However, non-autoimmune thyroid diseases may also express surface class II antigens. To evaluate the presence and pattern of HLA class II expression in autoimmune and non-autoimmune thyroid disorders. Retrospective: histopathological and immunohistochemical analysis. Referral center, university hospital. Ten histologically normal thyroids, 11 Graves' disease, 7 Hashimoto's thyroiditis, 10 atoxic multinodular goiter and 3 toxic adenomas were analyzed by immunohistochemistry, using a monoclonal antibody anti-HLA-DR. The presence of these antigens in thyroid follicular cells and their relation to inflammatory infiltrate was evaluated. The pattern of HLA-DR expression in thyroid follicular cells was analyzed: membrane, cytoplasmic or both. Although HLA-DR antigens were sparsely present in one of the 8 normal thyroids, in 6 of the 9 atoxic multinodular goiter and in 2 of the 3 toxic adenomas a net positivity could be seen in large areas. In all 5 Hashimoto's thyroiditis and in 7 of the 10 Graves' disease cases. This expression occurred in follicle cells either in contact with inflammatory cells or not. In non-autoimmune thyroid disease, HLA-DR positivity was essentially cytoplasmic, whereas in Graves' disease and Hashimoto thyroiditis it was mainly in cell membranes. It is suggested that the HLA class II expression on the surface of follicle cells could be related to auto-antigen presentation to the immune system by these cells, leading to inflammation.

Prevalence of anti-thyroid peroxidase antibodies in autoimmune and nonautoimmune thyroid disorders in a relatively low-iodine environment

We evaluated the prevalence of antithyroid peroxidase antibodies (anti-TP0 Ab) in 402 patients with thyroid disease and 30 healthy controls by a commercial radioimmunoassay (RIA) and compared the results with the passive hemagglutination (HA) method. The patients in the study had autoimmune thyroid disorders (AITD) such as Graves' disease and Hashimoto's disease or had nonautoimmune thyroid diseases (NAITD) such as thyroid cancer, congenital goiter, endemic goiter, and nodular goiter. Subjects were recruited from a population with a mild iodine deficiency (Sao Paulo, Brazil). The effect of specific therapy (for either thyrotoxicosis or chronic thyroiditis) on the circulating anti-TPO levels was also investigated. Positive anti-TPO Ab was detected in 89.9% of the patients with AITD as compared with a prevalence of positive tests of only 4.8% in patients with NAITD. Positive microsomal antibody (M Ab) was found in 68.4% of the patients with AITD and in 6.4% of the patients with NAITD. A positive and significant correlation was obtained between M Ab and anti-TPO Ab. A positive anti-TPO test with negative anti-M was found in 14.1% of the patients with AITD but in only 4.3% of the patients with NAITD and normal controls. These results suggest that anti-TPO Ab by RIA is more sensitive and specific than M Ab by HA. In patients with AITD, anti-TPO Ab levels usually decreased after treatment, suggesting that this parameter could be used in the follow-up of these thyroid disorders.

Prevalence of Antibodies Reactive with a 64 kDa Eye Muscle Membrane Antigen in Thyroid-Associated Ophthalmopathy

We have determined the prevalences of antibodies reactive with certain pig eye muscle membrane antigens, as determined from SDS-polyacrylamide gel electrophoresis (PAGE) and western blotting, in patients with autoimmune thyroid disorders with or without associated ophthalmopathy. The most frequently detected antibody was that directed against a protein of 64 kDa. Antibodies against this antigen were detected in 33% of unselected patients with ophthalmopathy and in 75% of those with severe, active, orbital inflammation of less than 12 months duration. Such antibodies were detected also in 33% of patients with Graves' hyperthyroidism with no apparent eye disease and in 17% of patients with Hashimoto's thyroiditis with no eye disease but were not detected in patients with nonautoimmune thyroid disorders in 25 normal subjects tested. In the majority of sera showing reactivity with this protein, reactivity with membrane antigens of 55 and 95 kDa also were observed, suggesting that the three proteins were conformationally associated. Cytotoxic antibodies against human eye muscle cells, measured in antibody-dependent cell-mediated cytotoxicity (ADCC), were demonstrated in 37% of patients with ophthalmopathy. There was no significant correlation, in patients with eye disease, between positive ADCC tests and antibodies to the 64 kDa protein, the 64 kDa reactive antibody being found in 50% of patients with positive ADCC and in 35% of those with negative tests. In this study, a clear association has been shown between thyroid-associated ophthalmopathy and the detection, in immunoblotting, of antibodies reactive with a 64 kDa eye muscle membrane antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Isotype and Immunoglobulin Subclass Distribution of eye Muscle Membrane Reactive Antibodies in the Serum of Patients with Thyroid-Associated Ophthalmopathy as Detected in Western Blotting

We have determined the immunoglobulin (Ig) class (isotype) and IgG subclass of autoantibodies in the serum of patients with thyroid-associated ophthalmopathy (TAO) or autoimmune thyroid disorders without evident ophthalmopathy reactive in Western blotting with antigens of 55, 64, 75 and 95 kDa in pig eye muscle membrane (PEMM). The 22 sera studied were shown, previously, to contain IgG antibodies reactive with one or more of the four antigens. The majority of sera antibodies reactive with PEMM antigens were of two or more IgG subclasses. Of the IgG subclass specificities IgG3 and IgG4 subclass antibodies were, overall, the most common. We were unable to demonstrate IgG subclass restriction for antibodies reactive with the 95 or 55 kDa antigens in PEMM, antibody activity being equally distributed in all four subclasses tested. While most of the sera which recognized a 64 kDa antigen did so with an IgG4 antibody, all other subclasses were also represented. On the other hand all 13 sera reactive with a 75 kDa antigen did so using Ig of the IgG3 subclass and 12 of these used the IgG4 subclass as well, IgG1 and IgG2 subclasses being represented in only 3 and 4 sera, respectively. There were no differences, in respect to Ig class or IgG subclass distribution of eye muscle reactive antibodies between patients with Graves' hyperthyroidism with ophthalmopathy and those with Hashimoto's thyroiditis, and eye disease. Control sera from five normal subjects and three patients with nonautoimmune thyroid disorders did not contain antibodies reactive with these PEMM antigens of any Ig class or IgG subclass.(ABSTRACT TRUNCATED AT 250 WORDS)

CD4+ T‐Cell Clones from Autoimmune Thyroid Tissue Cannot be Classified According to their Lymphokine Production

In order to define whether CD4+ T cells from autoimmune and non-autoimmune thyroid tissue could be classified according to their mediator production, lymphokine production was studied in 63 thyroid-derived CD4+ T-cell clones from four patients with Graves' disease, one with Hashimoto's thyroiditis, and one with non-toxic goitre (9-12 clones per patient). The production of interleukin 2 (IL-2), gamma interferon (IFN-gamma), tumour necrosis factor alpha (TNF-alpha), lymphotoxin (LT), interleukin 6 (IL-6) and transforming growth factor beta (TGF-beta) was assessed at the mRNA level by slot-blot analysis in unstimulated clones as well as after activation with monoclonal anti-CD3 (OKT3) and IL-2. No lymphokine production was found in unstimulated clones, whereas 56% of the clones produced all six lymphokines simultaneously after stimulation. In the remaining 44% usually not more than one lymphokine was missing from the complete panel. Lymphokine mRNA concentrations varied between different clones and different patients, but, in this small sample, not between the diseases from which the clones were originated. There was a significant correlation between IL-6, LT, and IL-2 mRNA levels and T-cell helper function, which was estimated by the stimulation of thyroid microsomal autoantibody production using autologous peripheral B cells. TGF-beta and IFN-gamma mRNA expression was unrelated to T-cell help. The results demonstrate that intrathyroid T cells from autoimmune and non-autoimmune thyroid disorders cannot be classified according to their lymphokine production, unlike some results with in vitro-induced mouse T-cell clones, where two populations, Th1 and Th2, have been described. Single T cells are capable of producing a whole panel of lymphokines and thus are capable of triggering a multitude of different processes.

Decreased lymphocyte function-associated antigen-1 molecule expression on peripheral blood lymphocytes from patients with Graves' disease.

Humoral and cellular abnormalities have been described in autoimmune thyroid diseases, but a deficient cooperation between humoral and cellular systems has been poorly investigated in such diseases. Lymphocyte function-associated antigen-1 (LFA-1), a glycoprotein expressed on T- and B-lymphocytes, plays an important role in cell-cell interaction mechanisms and is involved in the homing phenomenon. The expression of this molecule was investigated on peripheral blood lymphocytes from patients suffering from various thyroid disorders. Decreased numbers of LFA-1-positive cells were observed in 30 patients with Graves' disease, while normal values were present in 8 patients with Hashimoto's thyroiditis and 37 subjects with nonautoimmune thyroid disorders. Treatment-induced improvement of Graves' disease was associated with an increase in LFA-1-positive cell number.

Antibodies to Human Thyroid Peroxidase in Autoimmune Thyroid Disease: Studies with a Cloned Recombinant Complementary Deoxyribonucleic Acid Epitope*

Previous studies carried out by screening a lambda gt11 human thyroid cDNA library with serum samples from selected patients with Hashimoto's thyroiditis and a polyclonal antibody to porcine thyroid peroxidase (TPO) confirmed, at the molecular level, that TPO is a major component of the thyroid microsomal antigen (M). That investigation led to the isolation of a clone (C2) which encodes an 85-amino acid segment of TPO and harbors a major epitope recognized by serum from several patients with autoimmune thyroid disease that contained anti-M autoantibodies (MAb). In this study, C2 antigen that was produced as a beta-galactosidase fusion protein was used to establish an enzyme-linked immunoabsorbent assay for the detection of anti-C2 autoantibodies (C2Ab). C2Ab then were assayed in 191 patients with different autoimmune and nonautoimmune thyroid disorders, and 50 patients with nonthyroidal autoimmune diseases. The results were compared with the titers of anti-TPO antibodies (TPOAb; as detected by monoclonal antibody-assisted RIA) and MAb (as detected by passive hemagglutination). Positive C2Ab was found in the serum of 85 of 136 (63%) patients whose serum contained TPOAb and/or MAb. A significant positive correlation was found between the levels of C2Ab and those of TPOAb (r = 0.76; P less than 0.001) or MAb (r = 0.69; P less than 0.001), which was independent of the type of underlying autoimmune thyroid disorder. Low levels of C2Ab also were found in 10 of 105 (9%) serum samples that did not contain TPOAb. Western blot analysis carried out on the latter samples showed that in 2 samples the apparent C2Ab reactivity was due to the presence of antibodies reacting with beta-galactosidase. In conclusion, we confirmed the validity of screening lambda gt11 cDNA human thyroid libraries to better characterize thyroid autoantigens and demonstrated the feasibility of using recombinant proteins to establish diagnostic assays for autoantibodies.

Affinity purification of orbital membrane antigens for the study of the pathogenesis of Graves' ophthalmopathy.

We characterized 22 human monoclonal antibodies (MCAB) reactive with human orbital antigens. Most of these monoclonal antibodies had variable degrees of reactivity with eye muscle, orbital connective tissue, thyroid, and extra-thyroid tissue preparations when tested in an enzyme-linked immunosorbent assay (ELISA). Eight of the MCABs, selected on the basis of their reactivity with human eye muscle or orbital connective tissue antigens, were used to affinity purify orbital membrane antigens. All purified fractions were tested in the ELISA for reactivity with the MCAB used for their purification. Four of the purified antigens with a high reactivity were not proteins. To increase the specificity of the reactivity of serum autoantibodies with affinity-purified antigens, we developed a competitive binding ELISA in which the MCAB-immunoglobulin was directly labeled with alkaline phosphatase. We tested the serum of 24 patients with Graves' ophthalmopathy, 10 patients with a history of Graves' hyperthyroidism and no eye disease, 14 patients with Hashimoto's thyroiditis without eye disease, 8 patients with other nonautoimmune thyroid disorders, and 20 normal subjects for reactivity with an affinity-purified nonprotein orbital antigen. The levels of serum autoantibodies against this antigen in patients with Graves' ophthalmopathy were significantly higher than those in normal subjects or patients with Graves' hyperthyroidism with no eye disease. Although unlikely to be of primary pathogenetic significance, it is possible that levels of this antibody in patients with Graves' ophthalmopathy may reflect the extent of orbital inflammation and, therefore, be useful as a clinical marker.

The assay for thyroid stimulating immunoglobulins using cultured human thyroid cells.

Recent reports have shown that thyroid-stimulating immunoglobulins (TSI) may be detected by measuring cyclic AMP increases in cultures of isolated thyroid cells in response to added patient immunoglobulins (Ig). We have compared the frequency that TSI may be detected in the Ig fraction of 114 sera from 112 patients with a variety of thyroid disorders, to the presence of thyrotrophin binding inhibitor Ig (TBII). Whereas the sera of 46 out of 48 (95.6%) patients with untreated thyrotoxic Graves' disease had detectable TSI, only 26 out of 48 (54.2%) had detectable TBII. We did not find any significant correlation between TSI and TBII for these patients but there was a significant correlation between TSI and both serum T3 (r = +0.55, P less than 0.01) and T4 (r = +0.50, P less than 0.01). Twelve patients were studied at the time of relapse of thyrotoxicosis due to Graves' disease. All sera contained detectable TSI whereas only one contained detectable TBII. Of the sera from 20 patients in remission after antithyroid drug therapy three were positive for TSI. One of these samples as well as two others had detectable TBII. The two samples with TBII in the absence of TSI came from patients who had developed hypothyroidism. TSI were detected in the serum of one out of nine patients with Hashimoto's thyroiditis but not in the sera of 20 other patients with a variety of non-autoimmune thyroid disorders including five patients with thyrotoxicosis not due to Graves' disease. However TSI was found in the sera of three out of five patients with exophthalmos and no history of hyperthyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)

An improved assay for thyrotropin-binding blocking activity in serum of patients with Graves' disease.

An improved assay for detecting blocking or inhibitory activity on TSH-binding (TBBA) in neat serum of patients with Graves' disease is described. The assay is sensitive, reproducible, simple, and quick. Crude membranes prepared from guinea pig fat (FCM) were used as the source of TSH receptors. One major feature of the assay is the use of small amounts of FCM to increase assay sensitivity. The sensitivity of the assay was found to be inversely proportional to the amount of FCM used. Using a quantity of 10-20 micrograms crude FCM achieved a satisfactory balance between assay sensitivity and accuracy. The assay employs two sequential one-hour incubations at room temperature, first incubating the FCM with the serum sample, followed by removal of excess sample and washing, and then incubating the exposed FCM with 125I-TSH for quantitative determination of specific TSH binding. The assay is recommended as a standard method for measurement of blocking activity in serum of specific TSH binding. Seventy-four percent of the patients with Graves' disease showed positive blocking activity while all normal individuals and patients with Hashimoto's thyroiditis and with nonautoimmune thyroid disorders were negative.

A new solid phase immunoradiometric assay for antithyroid microsomal antibody.

A new sensitive, quantitative, and specific immunoradiometric assay (IRMA) for antithyroid microsomal (anti-M) antibody has been developed. Samples to be tested are incubated within wells of polyvinyl microtiter plates coated with solubilized thyroid microsomal antigen. After removal of unbound material, anti-M antibody is detected by adding purified [125I]antihuman immunoglobulin G (IgG) antibody. Using 1.0 microliter serum, anti-M antibody was found by IRMA in all of the patients with Hashimoto's thyroiditis or idiopathic myxedema (n = 19), in 86% of those with Graves' disease (n = 42), in 10.9% of subjects with other nonautoimmune thyroid disorders (n = 37), and in 8.4% of normal controls (n = 71). A good correlation was found with the results obtained in anti-M antibody tests by passive hemagglutination. Using larger volumes of serum (up to 100 microliters), anti-M antibody detectable by IRMA was found in some patients with Graves' disease and negative passive hemagglutination tests. Quantitative measurements of anti-M antibody by IRMA could be performed using a standard IgG preparation containing high levels of anti-M antibody. The minimal detectable amount ranged between 1-2 ng IgG, corresponding to a sensitivity 15-30 times greater than that of the competitive binding radioassay. We suggest that the present IRMA may be proposed as a general technique for the detection of different organ-specific autoantibodies.