Methodological approach and diagnostic usefulness of a new assay for anti-thyroid peroxidase autoantibodies

Although thyroid microsomal antibodies (anti-MAb) have been recently proven to be directly to thyroid peroxidase (TPO), current methods for MAb detection still employ unpurified microsomal fractions. The authors have therefore developed and evaluated a specific radioimmunoassay (RIA) for autoantibodies to TPO (anti-TPO Ab) based on competitive inhibition of 125I-TPO to an anti-TPO monoclonal antibody coated on plastic microtiter wells (RIA-1) or tubes (RIA-2). Preliminary experiments showed that both assays were able to specifically detect anti-TPO Ab, while negative results were obtained with normal sera and with sera containing other organ- and non-organ-specific autoantibodies including anti-thyroglobulin antibodies (anti-TgAb). No significant difference in sensitivity, specificity and reproducibility was found between RIA-1 and RIA-2, and the results obtained with the two techniques were therefore pooled together. Anti-TPO Ab were then assayed in 110 normal controls and in 441 patients with different autoimmune (AITD) or non-autoimmune (N-AITD) thyroid diseases and compared to anti-M Ab as assessed by passive hemagglutination (PH). Positive anti-TPO Ab were observed in 4/110 (3.6 p. cent) normal controls, 88/117 (80 p. cent) patients with Graves' disease, 122/123 with Hashimoto's thyroiditis or idiopathic myxedema and 21/201 (10.4 p. cent) with miscellaneous N-AITD. A highly significant positive correlation (r = 0.91, p less than 0.0001) was found between anti-MAb by PH and anti-TPO Ab by RIA ;discrepant results were limited to sera with negative or low (1/100-1/400) anti-M Ab titers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assays of TSH-receptor antibodies in 576 patients with various thyroid disorders: their incidence, significance and clinical usefulness

The incidence and the significance of TSH-receptor antibodies in Graves' disease and in various thyroid disorders have been evaluated. TSH-binding inhibiting antibodies (TBIAb) and thyroid stimulating antibodies (TSAb) were detected in a large proportion of Graves' disease patients (TBIAb in 68.8% and TSAb in 77.8%), in a small number of patients with idiopathic myxoedema or Hashimoto's thyroiditis, and were not detected in patients with endemic euthyroid goitre, differentiated thyroid carcinoma and toxic adenoma. Furthermore, TSH-receptor antibodies were present in some patients with toxic multinodular goitre (TBIAb in 12.7% and TSAb in 15.9%). When TSH-receptor and other thyroid autoantibodies were compared, it was found that 13 of the 15 Graves' patients with negative tests for thyroglobulin and thyroid microsomal antibodies were positive for TSH-receptor antibodies. On the other hand, 9 of the 11 patients with toxic multinodular goitre who had positive TSH-receptor antibody tests, also had serum thyroglobulin and/or thyroid microsomal antibodies. No significant differences in the prevalence of TSH-receptor antibodies were found in Graves' patients irrespective of the presence of ophthalmopathy or pretibial myxoedema. Elevated TBIAb activity at the end of anti-thyroid drug treatment was found in 52.9% of Graves' patients who subsequently relapsed, while in Graves' patients in remission TBIAb was always negative. TSH-receptor antibody results were not predictive of the outcome of radioiodine treatment in Graves' disease. Finally no correlation could be found between TBIAb and TSAb in Graves' disease and Hashimoto's thyroiditis. In conclusion: the high incidence of TSH-receptor antibodies in Graves' disease confirms their pathogenetic role in the development of hyperthyroidism; TSH-receptor antibodies in Graves' disease are not significantly associated with the presence of ophthalmopathy or pretibial myxoedema; TSH-receptor antibody assays may be useful for the diagnosis of Graves' disease in the absence of other signs of autoimmunity. TBIAb seems to be a good predictor of relapse in Graves' patients treated with anti-thyroid drugs; a fraction of toxic multinodular goitre could be a nodular variant of Graves' disease.     

Characterization of monoclonal antibodies directed towards the microsomal/microvillar thyroid autoantigen recognized by Hashimoto autoantibodies.

Monoclonal antibodies reacting with thyroid microsomes have been described. In this report, we present evidence that some of these monoclonal antibodies (MoAb) MAH C3 and perhaps MAH C6 are directed towards the thyroid microsomal antigen towards which microsomal autoantibodies from Hashimoto patients are directed. Immunofluorescence on cryostat sections with MAH C3 and MAH C6 on thyroid gland gave cytoplasmic staining patterns that were comparable to those obtained with autoantibodies. By western blotting, reactivity of MAH C3 was shown to be directed towards a 105,000 mol. wt component, comparable to that recognized by autoantibodies by immunoprecipitation. Double immunofluorescence with MAH C3 and autoantibodies on cultured, viable thyroid monolayers revealed a large number of comparable binding sites; in contrast, binding sites for asioloagalactothyroglobulin were different of binding of MAH C3 by the autoantibodies suggesting that the epitopes recognized were different. This was confirmed with the use of a rat thyroid cell line FRTL-5 and fluorescence activated cell sorter analysis which showed binding to the rat microsomal component with autoantibodies but negligible binding with MAH C3 and MAH C6. It therefore appears that the monoclonal antibodies recognize species specific determinants while the autoantibodies recognize species cross reactive determinants. These monoclonal antibodies will be useful for purification and immunochemical analysis of this autoantigen in human thyroid disease.     

Thyroid peroxidase antibodies in children with autoimmune thyroiditis.

AIMS: To compare the prevalence of thyroid peroxidase antibodies in 25 children with autoimmune thyroid disorders and in 41 children and young adults with type 1 diabetes, and to test the prevalence of thyrotropin receptor antibodies. METHODS: Two commercially available radioimmunoassays for antibodies to thyroid peroxidase, a commercially available agglutination test of particles coated with thyroid microsomal antigens, and a radioimmunoassay for thyrotropin receptor antibodies were used. Patients and controls were studied. RESULTS: One of the radioimmunoassays detected thyroid peroxidase antibodies not only in all children with autoimmune thyroid disorders and children and young adults with type 1 diabetes and thyroid microsomal antibodies, but also in 20% of healthy control children without microsomal antibodies. With this thyroid peroxidase assay and with microsomal agglutination, 94% of the children with autoimmune thyroiditis, 71% of those with Graves' disease, and over 90% of those with type 1 diabetes and thyroid dysfunction tested positive. In the other radioimmunoassay for thyroid peroxidase antibodies thyroid peroxidase antibody titres in half or more of the children with microsomal antibodies failed to reach the level of positivity given by the producers. Eighty five percent of children with Graves' disease and 71% of those with autoimmune thyroiditis had thyrotropin receptor antibodies but so did 35% of children studied for other endocrinological disorders such as delayed growth or puberty. CONCLUSIONS: Testing patients with well characterised disorders of thyroid function and with other endocrine disorders is important in evaluating the efficacy of new diagnostic tests for thyroid autoantibodies.     

Comparison of radioassay and haemagglutination methods for anti-thyroid microsomal antibodies.

Parallel measurements of circulating anti-thyroid microsomal (anti-M) antibodies by radioassay and haemagglutination were performed on subjects with or without thyroid disorders. Three-quarters (75.4%) of control subjects had undetectable antibody levels (less than 10 u/ml) by radioassay and only 3.1% had concentrations of greater than or equal to 75 u/ml. Abnormally elevated levels (greater than or equal to 75 u/ml) were found in most of the patients with Hashimoto's thyroiditis (94.1%) or idiopathic myxoedema (86.7%), in the majority (75.0%) of those with Graves' disease and only in a minority of those with other thyroid disorders. The percentage of positive sera by haemagglutination was very similar in all groups to that of abnormal values observed in the radioassay. Direct comparison of parallel tests on a total of 631 sera revealed a highly significant correlation (r = 0.91, P less than 0.001) between the two methods, but elevated antibody titres by haemagglutination were found in some sera with negative radioassays. All these sera were from a single patient with thyroid carcinoma associated with Hashimoto's thyroiditis and had elevated levels of anti-thyroglobulin (anti-Tg) antibodies. Evidence that such discrepancies were due to anti-Tg antibodies reacting with microsomal-bound Tg was provided by the demonstration that the haemagglutination produced by these sera could be completely inhibited by the addition of Tg. A similar inhibition was observed with two rabbit antisera to human Tg, but not with sera from patients with thyroid autoimmune disorders containing high levels of anti-microsomal anti-bodies.     

甲状腺激素自身抗体的检测及其临床意义

为探讨患者血清甲状腺激素水平假性升高的原因及检测甲状腺激素自身抗体的方法，为临床正确判断甲状腺激素水平提供帮助，本研究进行了甲状腺激素自身抗体结合实验、自身抗体稀释度实验、自身抗体抑制曲线实验及自身抗体检定实验。结果显示：患者血清与^125I-T2或^125I-T4呈特异性结合，结合率分别为58．77％和49．05％，是正常人或三蒸水对照的8－13倍；得到满意的T3和T4自身抗体稀释度曲线和抑制曲线，并确定甲状腺自身抗体为IgG，与兔抗人T3和T4抗体出现在电泳同一位置。甲状腺激素水平假或高的主要原因是患者体内存在着内源性抗甲状腺激素抗体，检测甲状腺激素自身抗体有利于正确判断甲状腺激素水平，为临床诊断和治疗甲状腺疾病提供帮助。     

Binding of thyroid microsomes by lymphocytes from patients with thyroid disease and normal subjects.

Lymphocytes that could bind 125I-labelled thyroid microsomal membranes (ABL) were present in the peripheral blood of patients with various types of thyroid disease as well as in normal healthy subjects. In patients with anti-thyroid cytoplasmic antibodies the number of ABL was about three times normal (11-21 +/- 0-60 compared with 3-26 +/- 0-18 per 10(4) lymphocytes). In contrast, in patients with thyroid disease without anti-thyroid cytoplasmic antibodies, the number of antigen-binding lymphocytes was not significantly greater than in the normal controls (3-94 +/- 0.14 per 10(4) lymphocytes). The binding of thyroid microsomes by antigen-binding lymphocytes could be blocked by thyroid microsomes but not by thyroid mitochondrial membranes, thyroglobulin or liver microsomes.     

Juvenile onset systemic lupus erythematosus thyroid dysfunction: A subgroup with mild disease?

The aim of this study was to evaluate the frequency of thyroid dysfunction and thyroid antibodies in patients with juvenile onset Systemic Lupus Erythematosus (JOSLE) and its association with clinical and immunological features. Seventy-seven patients with JOSLE, 64 females, median age 19 years, were consecutively enrolled from March to December 2007. Clinical data related to thyroid dysfunction and lupus were obtained by chart review and patient interview. Serum levels of TSH, free T4, anti-thyroglobulin (TgAb), anti-thyroperoxidase (TPOAb), TRAb and lupus related autoantibodies were analyzed by standard techniques. Nine patients were diagnosed as hypothyroidism and 4 hyperthyroidism. 28% JOSLE patients had moderate/high titer of thyroid antibodies: 23% TgAb, 2.6% TPOAb and 3.9% TRAb. JOSLE patients with positive thyroid autoantibodies had higher frequency of anti-U1RNP antibodies than patients without these antibodies (40.9 vs. 14.5%, OR:0.25, CI:0.08–0.76, p = 0.017). Furthermore, renal/neurological/hematological involvement was less frequently observed in patients with hypothyroidism (55.6 vs. 87.5%, OR:0.18, CI:0.04–0.81, p = 0.035) and with thyroid antibodies (68.4 vs. 90.9%, OR:0.22, CI:0.06–0.82, p = 0.027) than in patients without these alterations. No association with PTPN22 polymorphism was found. In conclusion, JOSLE patients have high prevalence of subclinical hypothyroidism. The novel association of anti-thyroid antibodies with anti-U1RNP antibodies in JOSLE seems to identify a subgroup of patients with less life-threatening organ involvement.     

Thyroid antoantibodies and the response to thyrotropin releasing hormone in patients with subclinical hypothyroidism.

AIM--To evaluate the clinical usefulness of the thyrotropin releasing hormone (TRH) test and estimation of thyroid autoantibody concentrations in patients with borderline raised thyroid stimulating hormone (TSH). METHODS--The records of 34 consecutive patients with persistent borderline increased TSH (4.4-9.9 mU/l) referred to the Medical Investigation Unit were reviewed. The response of patients with thyroid autoantibodies to the TRH test was compared with that of patients with a negative antibody screen. RESULTS--Eleven (44%) of 25 patients with positive anti-thyroid microsomal and/or thyroglobulin antibody tests and three (33%) of nine patients with a negative antibody screen had hypothyroid responses to TRH. Neither age nor sex affected the response to TRH. Basal TSH alone was poorly correlated with these indices. Twelve (35%) patients who had elevated basal TSH had a normal response to the TRH test. CONCLUSION--Patients with positive or negative thyroid autoantibodies and an exaggerated response to the TRH test should be regarded as hypothyroid and treated with thyroxine. Patients with positive thyroid autoantibodies and normal TSH response may subsequently develop hypothyroidism and should be given long term follow up.     

The association between anti-thyroid antibodies and pregnancy loss

The incidence of thyroid autoantibodies in women with recurrent fetal loss, infertility or women who miscarried appears to be increased compared with controls of reproductive age without previous abortions. There are few working hypotheses concerning the asociation between anti-thyroid antibodies and the increased risk for pregnancy loss. The first hypothesis suggests that women with high titers of anti-thyroid antibodies have underlying very mild thyroid "under function". Another theory views the anti-thyroid antibodies as simply secondary markers of a predisposition of autoimmune disease rather than the actual cause of pregnancy loss. An evolutionary explanation suggests that reproductive problems in women with high titers of autoantibodies exist in order to prevent the transmission of autoimmune genes to the next generation. The reason for the association between pregnancy loss and thyroid immunity is still not clear. The working hypotheses above supply multi-factorial explanations, which could act together, may even be in synergy, as the propulsion for the pregnancy loss. Until today the mechanism by which anti Tg are responsible for pregnancy loss is not clear. Induced animal models with high titier of anti Tg could provide direct evidence for the pathogenic role of anti-thyroid antibodies and the mechanism that is responsible for the pregnancy loss in autoimmune thyroiditis. In the current presentation we describe data concerning the association between anti-thyroid antibodies and pregnancy loss, and hypothesis which explains this association.     

Antitissue antibodies in interstitial cystitis

Sera from thirty-three female patients with interstitial cystitis were studied for the presence of antitissue antibodies and a positive result was obtained in thirty-one cases (94%). Antinuclear antibodies detected by the immunofluorescence method were found in 85% of the sera in titres of 1:10 or higher. However, the LE-cell phenomenon was not seen in a single patient. complement-fixing antibodies to crude kidney homogenate occurred in 48% of the sera. Antibodies, with an incidence not exceeding that expected in control groups, were against smooth muscle, thyroglobulin and gastric parietal cells. None of the patients had mitochondrial or thyroid cytoplasmic antibodies, rheumatoid factors or biologic false-positive reactions for syphilis.

Bladder specific antibodies could not be demonstrated by the double layer immunofluorescence method.

The results indicate that interstitial cystitis belongs to that group of autoimmune diseases in which the disease is restricted to one organ, whereas the autoantibodies are non-organ specific.

     

Liver cell surface expression of the antigen reacting with liver-kidney microsomal antibody (LKM)

To test the hypothesis that liver membrane antibodies, found in all liver-kidney microsomal antibody (LKM) positive sera from patients with chronic active hepatitis, were directed against antigens shared by both hepatocellular endoplasmic reticulum and plasma membranes, absorption experiments have been performed using viable isolated hepatocytes and liver microsomes as antigens. Results are in agreement with the above hypothesis, LKM, which displays a restricted organ specificity, is thus able to react with antigenic determinants expressed on the liver cell surface, as it has been demonstrated for strictly organ specific antibodies directed against thyroid, adrenal and gastric parietal cell microsomes.     

Studies on thyroid cell surface antigens using cultured human thyroid cells.

Human thyroid cells in primary culture were used for studies of thyroid cell surface antibodies in patients with thyroid autoimmune disorders. Radioiodinated IgG preparations containing thyroid microsomal antibody (TMAb), thyroid stimulating antibody (TSAb) and/or thyroglobulin antibody (TgAb) were tested for binding to thyroid cells. Binding was observed with radioiodinated IgG from patients with Graves' disease, Hashimoto's thyroiditis and idiopathic myxoedema containing TMAb, irrespective of the presence of TSAb and TgAb, while negative results were obtained with normal IgG. A dose-dependent inhibition of binding to thyroid cells was produced by the addition of the corresponding unlabelled IgG preparations. Evidence for tissue specificity was provided by the absence of binding to human skin fibroblasts used as controls. Preabsorption with human thyroid microsomes completely abolished the binding to thyroid cells of a radioiodinated TMAb positive IgG preparation, while only incomplete removal of the reactivity to thyroid microsomes was produced by preabsorption with thyroid cells. These data suggest that some but not all microsomal antigenic determinants are expressed on the thyroid cell surface. Binding to thyroid cells was also observed with purified TgAb, indicating that thyroglobulin antigenic determinants are present on the surface of thyroid cells. No evidence of binding was obtained with a TSAb positive Graves' IgG preparation with undetectable TMAb and TgAb. Unlabelled IgG preparations containing TMAb from patients with either Hashimoto's thyroiditis or idiopathic myxoedema were shown to inhibit the binding to thyroid cells of radioiodinated TMAb positive Graves' IgG and vice versa. These data indicate that antibodies present in these thyroid autoimmune disorders share common thyroid cell surface antigens. However, the binding of radioiodinated IgG from a patient with idiopathic myxoedema was only partially inhibited by Graves' or Hashimoto's IgG, suggesting that some of the thyroid cell surface antibodies of idiopathic myxoedema may not be detectable in other thyroid autoimmune disorders.     

Relation of parietal cell and thyroid antibodies to the state of gastric mucosa and basal serum gastrin levels during a 6-year follow up.

Two groups of volunteers (199 in total, 149 of whom were a random sample of an urban population) were examined twice, with a 6-year interval, for the occurrence of parietal cell antibody (PCA) and thyroid microsomal antibodies (TMA). The antibody findings were compared with the antral and fundal gastric mucosal state, and with the fasting serum gastrin-17 level. During the study period, two new PCA and four new TMA cases appeared. There were no significant changes in the state of gastric antral/fundal mucosa in relation to PCA and/or TMA persistence or appearance, as compared with the gastric mucosa changes in the whole random population sample. However, a good correlation was observed between PCA and basal serum gastrin elevation.     

In vitro production of interferon-gamma by peripheral blood from patients with Graves'' disease, Hashimoto''s thyroiditis and rheumatoid arthritis.

The production of interferon-gamma (IFN-gamma) by peripheral blood mononuclear cells (PBMC), CD4 cells, or CD8 cells in response to interleukin-2 (IL-2) stimulation has been studied; the samples were obtained from 12 healthy control subjects, 19 patients with Graves' disease (10 hyperthyroid and nine euthyroid), 13 patients with Hashimoto's thyroiditis (four hypothyroid and nine euthyroid), and 15 patients with rheumatoid arthritis (11 active and four inactive). A dose of IL-2 (25 U/ml) was utilized to induce IFN-gamma by PBMC from all four groups. The incremental increase in IFN-gamma values (with IL-2 stimulation minus without stimulation) was significantly less in PBMC from patients with Graves' disease, Hashimoto's thyroiditis, and rheumatoid arthritis than that in PBMC from control subjects. The values from PBMC in patients with Graves' disease in a euthyroid state were below normal but greater than those from patients with Graves' disease in a hyperthyroid state. The incremental increase in IFN-gamma values from Graves' disease PBMC correlated with the serum TSH values (r = 0.622, P less than 0.01), but not with thyroid autoantibodies (anti-thyroid microsomal antibodies, anti-thyroid microsomal antibodies, nor TSH-binding inhibitory immunoglobulin activities). The incremental increase in IFN-gamma from PBMC from both control subjects and Graves' disease was correlated with that from CD4 cells (r = 0.711, P less than 0.01), but not with that from CD8 cells. The production of IFN-gamma in response to IL-2 from PBMC in Graves' disease correlated inversely with thyroid function, appearing to reflect the very effect of hyperthyroidism in this process. The precise explanation of these phenomena remains unclear. The decreased response of IFN-gamma to IL-2 stimulation by PBMC from patients with Graves' disease, Hashimoto's thyroiditis, and rheumatoid arthritis seems to be a non-specific phenomenon occurring in both organ specific autoimmune disease and systemic autoimmune disease. It may be due to a down-regulation in autoimmune disease of CD4 cells in response to IL-2, a decreased level of IL-2 cellular receptors or a decreased receptor affinity, associated increased soluble IL-2 receptors, or a defect of the intra-CD4 cellular IL-2 signal to produce or release IFN-gamma in the conditions studied.     

Pancreatic islet and other autoantibodies in juvenile and adult onset diabetics in Australia

The prevalence of serum antibodies to the cytoplasm of the pancreatic islet cell (PICA), and of thyroid microsomal (TMA), gastric parietal cell (GPCA) and anti-nuclear (ANA) antibodies was studied in 135 newly diagnosed diabetics presenting to a hospital for adults and 83 children with recent onset diabetes presenting to a children's hospital. The study also included another 144 diabetic children whose disease had been present longer, and 200 control children. There was a high prevalence (87%) of PICA in the children whose diabetes had just been diagnosed in comparison with control children (1%):(P less than .0001). Diabetic children also had a high prevalence (21%) of one or more of the other autoantibodies in comparison with the control children (9%):(P less than .001). Only 26% of the 58 insulin dependent adults had PICA but 33% had other autoantibodies. Two (3%) of the 77 adult diabetics who did not require insulin had PICA; 8% had other autoantibodies.     

Genetic Control of the Production of Anti-Thyroid Hormone Antibodies in Mice Immunized with Human Thyroglobulin

Various strains of mice with different H-2 and Igh-I allotypes were immunized with human thyroglobulin (HTg) and genetic control of the production of anti-thyroid hormone antibodies was examined. Anti-HTg antisera obtained from different strains of mice were examined for the presence of antithyroid hormone antibodies. At least one Ir-gene which controls the production of anti-T4 antibodies by immunization with HTg was identified in the I-A subregion. The presence of Ir-genes outside the H-2 was also suspected. Concerning the production of anti-T3 antibodies, only three strains (B10.A, C3H.SW, BALB/cJ) were high responders and therefore we were unable to identify the Ir-gene for them. These results indicate the presence of Ir-gene which controls the immune response in mice against thyroid hormone and suggest that the anti-thyroid hormone antibodies observed in various thyroidal and non-thyroidal disorders could be anti-HTg antibodies. The significance of genetic control of the production of anti-thyroid hormone antibodies in mice immunized with HTg is discussed.     

Autoantibodies and immunoglobulin allotypes in healthy North American Blacks of different age groups

A population of 291 healthy North American Black subjects of different ages was studied for immunoglobulin (Ig) allotypes and the prevalence of autoantibodies, to determine possible associations between Ig allotypes and age, autoantibodies and age, and Ig allotypes and autoantibodies. Indirect immunofluorescence was used to detect anti-gastric parietal cell, anti-smooth muscle, anti-thyroid microsomal, anti-nuclear, and anti-mitochondrial antibodies. The sera were typed for the Ig allotypes Gm(1, 2, 3, 5, 6, 13, 14, 17, and 21) and Km(1) with a hemagglutination-inhibition assay. A significant association between advanced age and an increased prevalence of anti-nuclear antibodies was observed in females. There was no significant association between Ig allotypes and the autoantibodies tested. The results suggest that Ig allotypes are not involved in the development of autoantibodies in healthy Blacks.     

Characterization of the human gastric parietal cell auto-antigen

The gastric parietal cell auto-antigen is localized essentially in the microsomal fraction of mucosal homogenates obtained by centrifugation over a sucrose density gradient. The fractionation is facilitated by digestion of gastric mucus with ficin before disruption of the tissue. The antigen was assayed by a quantitative complement-fixation method. The effect of a number of enzymes and chemical treatments upon the serological reactivity of a gastric microsomal preparation was studied. The properties of the gastric antigen suggest an intimate association with insoluble lipoprotein elements of the microsomal membranes. Although immunologically distinct and strictly organ specific, the cytoplasmic auto-antigens of the stomach, and of the thyroid gland, show a remarkable resemblance in their biochemical characteristics. This similarity has a parallel not only in the embryo-logical origin and the iodide trapping mechanisms which the two organs share in common but also in the close serological and clinical associations that have been demonstrated between auto-immune atrophic gastritis and thyroiditis.     

High frequencies of human T-lymphotropic virus type I (HTLV-I) infection and presence of HTLV-II proviral DNA in blood donors with anti-thyroid antibodies

To investigate the relationship between human T-lymphotropic virus (HTLV) types I and II and the pathogenesis of autoimmune thyroid diseases, we examined serum anti-thyroid antibodies in 1019 blood donors with or without serum anti-HTLV-I antibody as well as proviral DNA for HTLV-II in leukocyte DNA by the polymerase chain reaction in 395 blood donors with or without anti-thyroid antibodies. The frequency of donors with anti-HTLV-I antibody who also showed anti-thyroid antibodies (7.9%) tended to be higher than that (6.3%) among donors who did not have the anti-HTLV-I antibody. The frequency of anti-thyroid antibodies in 125 young male donors aged 16–39 years with anti-HTLV-I antibody (4.8%) was significantly higher (P<0.05) than that (0.6%) in 164 control donors without the antibody. In blood donors with anti-thyroid antibody, 25.0% of those with anti-HTLV-I antibody and 14.3% of those without the antibody had HTLV-II proviral DNA. In contrast, in donors without anti-thyroid antibody HTLV-II proviral DNA was detected in 2.3% of those with anti-HTLV-I antibody and in 0.6% of those without the anti body. Thus the detection rates in donors with anti-thyroid antibody were significantly higher (P<0.001) than those in donors without the antibody, regardless of HTLV-I infection. These results suggest that HTLV-I infection and the presence of HTLV-II proviral DNA may be independently related to the pathogenesis of autoimmune thyroid diseases.Abbreviations HTLV Human T-lymphotropic virus - PCR Polymerase chain reaction