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Clinical Studies |
Department of Laboratory Medicine, Osaka University Medical School, 22 Yamadaoka, Suita, Osaka 565, Japan
Address all correspondence and requests for reprints to: Yoh Hidaka M.D., Department of Laboratory Medicine, Osaka University Medical School, 22 Yamadaoka, Suita, Osaka 565, Japan.
| Abstract |
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| Introduction |
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(IFN-
), and lymphotoxin
and induce cellular responses. Th2 cells secrete IL-4, IL-5, IL-6,
IL-9, IL-10, and IL-13 and promote production of antibodies (1).
Graves thyrotoxicosis is induced by thyroid stimulating
autoantibodies to TSH receptor (2), the production of which is likely
to depend upon Th2 cell function. Th2 response may play an important
role in the pathophysiology of the thyroid destructive process in
Hashimotos thyroiditis because anti-microsomal autoantibodies damage
thyrocytes in vitro (3, 4), although main cytotoxic activity
might be induced by cell-mediated immunity (5, 6). The CD30 molecule, a member of the tumor necrosis factor (TNF)/nerve growth factor (NGF) receptor superfamily (7), is inducible on the membrane of some T cells that secrete Th2-type lymphokines (8). After CD30 appears on the activated T cell surface, the extracellular portion of the CD30 molecule is proteolytically cleaved to produce an 88-kDa soluble form (sCD30), which is released by cells expressing CD30 (9).
In this study, we demonstrated that increased levels of sCD30 are present in patients with Graves disease and Hashimotos thyroiditis, especially in the active stages, and we observed a significant correlation between sCD30 levels and TSH receptor antibody levels.
| Subjects and Methods |
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We studied 71 patients with Graves disease, 37 patients with Hashimotos thyroiditis, and 21 normal controls. Patients with Graves disease were divided into four groups; (1) 21 untreated thyrotoxic patients with positive TSH receptor antibody (TSH-R Ab) (37.2 ± 13.8 yr old, mean ± SD); (2) 8 euthyroid patients under maintenance treatment with antithyroid drugs (methimazole 5 mg or propylthiouracil 50 mg per day) with positive TSH-R Ab (39.4 ± 16.2 yr old); (3) 21 euthyroid patients under maintenance treatment with antithyroid drugs with negative TSH-R Ab (36.1 ± 12.6 yr old); and (4) 21 euthyroid patients in remission (43.1 ± 12.8 yr old). They were not treated with surgery or radioiodine. Patients with Hashimotos thyroiditis were divided into three groups; (1) 8 thyrotoxic patients (30.3 ± 3.8 yr old); (2) 21 untreated euthyroid patients (38.4 ± 10.1 yr old); and (3) 8 hypothyroid patients (43.8 ± 11.2 yr old). The thyrotoxicosis in patients with Hashimotos thyroiditis was caused by destruction of thyrocytes or thyroid follicles and was diagnosed by the increased levels of serum thyroid hormones for less than 3 months, later development of transient hypothyroidism, and/or low radioactive iodine uptake. The mean age in each group was not significantly different from that of normal controls (37.0 ± 12.0 yr old). All were Japanese females. This study was approved by the institutions ethics committee, and all the patients gave informed consent before participation in this study.
sCD30 assay
Detection of sCD30 was performed on serum samples kept frozen at -20 C, using a sandwich enzyme-linked immunosorbent assay (CD30, Ki-1 antigen, ELISA: DAKO, Glostrup, Denmark), which is based on the use of two monoclonal antibodies reacting with two different epitopes on the 88-kDa soluble form of the CD30 molecule, as previously described (10). Briefly, predicted sCD30 calibrators, a curve control, and patient specimens were added to peroxidase-conjugated mouse anti-CD30 in polystyrene microtiter wells precoated with another CD30 monoclonal antibody. After a 2-h incubation and washing to remove unbound material, a chromogenic substrate was added to the wells. The reaction was then stopped, and absorbance at 450 nm was measured. The standard curve was prepared from six sCD30 calibrators (0, 5, 16, 41, 101, 238 U/mL), and the concentration of sCD30 in serum samples was determined by interpolation. The intraassay coefficient of variation was 2.4%, and the interassay coefficient of variation was 3.7%. The detection limit of the assay was 5 U/mL.
Thyroid autoantibodies
Serum levels of TSH-R Ab were measured by a radioreceptor assay with a commercial kit (Cosmic Corp., Tokyo, Japan) (11). The results were expressed as percent inhibition of binding of labeled TSH. The normal value was less than 12%. Serum levels of antibodies to thyroperoxidase (TPO) and thyroglobulin (TG) were measured using commercial enzyme immunoassay kits (Boehringer Mannheim, Mannheim, Germany). Normal values of TPO antibody and TG antibody were less than 16.0 IU/mL and less than 86.4 IU/mL, respectively.
Statistical methods
Five U/mL were assigned to the value less than 5 U/mL in the statistical calculation of sCD30. The Mann-Whitney test was used to compare sCD30 levels between different groups. Linear correlation analysis was used to examine the correlation between sCD30 levels and other immunological parameters.
| Results |
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Serum levels of sCD30 were increased in patients with Graves
disease (n = 71, 29.2 ± 25.2 U/mL, mean ±
SD, P < 0.0001), and Hashimotos
thyroiditis (n = 37, 29.9 ± 26.9 U/mL, P <
0.0001) compared with those in normal controls (n = 21, 7.1
± 4.5 U/mL). In Graves disease, the mean value of sCD30 in 21
thyrotoxic patients was 41.7 ± 31.2 U/mL, that in 8 euthyroid
patients with positive TSH-R Ab was 38.4 ± 26.6 U/mL, that in 21
euthyroid patients with negative TSH-R Ab was 26.6 ± 22.1 U/mL,
and that in 21 remission patients was 15.8 ± 11.0 U/mL (Fig. 1
). Serum levels of sCD30 in thyrotoxic patients
(P < 0.001) and in euthyroid patients with positive
TSH-R (P < 0.05) were significantly higher than those
in remission patients. In Hashimotos thyroiditis, the mean value of
sCD30 in 8 thyrotoxic patients was 48.8 ± 34.4 U/mL, and that in
21 euthyroid patients was 24.2 ± 19.4 U/mL, and that in 8
hypothyroid patients was 25.8 ± 30.5 U/mL (Fig. 1
). Serum levels
of sCD30 in thyrotoxic patients were significantly (P
< 0.05) higher than those in euthyroid patients.
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Significant correlation was observed between individual values of
serum sCD30 and serum activities of TSH receptor antibody (r =
0.444, P < 0.0001) in 71 patients with Graves
disease (Fig. 2
). There was no significant correlation
between individual values of serum sCD30 and serum titers of TPO
antibody nor TG antibody in 37 patients with Hashimotos thyroiditis
(data not shown).
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| Discussion |
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Many autoimmune endocrinopathies appear to be directly mediated by autoreactive CD8+ cytotoxic T lymphocytes with help from Th1 CD4+ cells, while others appear to be mediated by autoantibodies to cellular receptors that arise as part of the Th2 response. Mullins et al. (18) reported that TSH receptor-specific T cell clones, made from the intrathyroidal lymphocytes of a Graves patient, showed Th0/Th2 characteristics. Heuer et al. (19) reported that the thyroid tissue from Graves patients showed a shift to a more Th2-driven cytokine pattern as determined by reverse transcriptase polymerase chain reaction. Recently, we found that allergic rhinitis not only aggravated Graves disease but also induced the clinical onset of Graves thyrotoxicosis, suggesting that Th2-derived cytokines, produced in type I allergy, help to produce TSH-R antibody (20, 21). This study shows that serum levels of sCD30 were increased in Graves disease and that significant correlation was observed between serum levels of sCD30 and TSH receptor antibody. Del Prete et al. (8) showed that CD30 is preferentially expressed on Th cells producing Th2-type cytokines, and that CD30 acts as a costimulatory molecule whose cross-linking is able to promote both expansion and effector function of Th2-like cells (22). These findings therefore suggest the in vivo involvement of Th2 cells in the regulation of immunological processes in Graves disease. The natural ligand for CD30 (CD30L) has been cloned (23), and the blockage of CD30L-CD30 interaction by anti-CD30L favored the development of higher numbers of Ag-specific Th cells showing the opposite (Th1-like) phenotype (22). This kind of molecule might be used to down-regulate undesired Th2 responses in Graves disease, and other autoimmune diseases.
Cytotoxic T lymphocytes specific for thyroid epithelial cells can be cloned from intrathyroidal lymphocytes in Hashimotos thyroiditis (5). The proportion of intrathyroidal CD8+ CD11b- cytotoxic T cells is high in Hashimotos thyroiditis (6). These findings suggest a potential role of cytotoxic T lymphocytes in the thyroid damage caused by Hashimotos thyroiditis. On the contrary, anti-microsomal autoantibodies may damage thyrocytes via activation of the complement system and antibody-dependent cell-mediated cytolysis (ADCC) (3, 4). This study has also shown that serum sCD30 increased in Hashimotos thyroiditis, especially in patients with active Hashimotos thyroiditis who show transient thyrotoxicosis caused by destruction of thyrocytes or thyroid follicles by immunological cytotoxic factors (destructive thyrotoxicosis). These findings suggest that not only Th1 cells but also Th2 cells are involved in the destruction of the thyroid gland in Hashimotos thyroiditis.
| Footnotes |
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Received December 16, 1996.
Revised February 13, 1997.
Accepted February 27, 1997.
| References |
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