Graves' disease--the thyroid stimulating antibody and immunological networks

Anti-Idiotypic Agonistic Antibodies: Candidates for the Role of Universal Remedy

Anti-idiotypic antibodies (anti-IDs) were discovered at the very beginning of the 20th century and have attracted attention of researchers for many years. Nowadays, there are five known types of anti-IDs: α, β, γ, ε, and δ. Due to the ability of internal-image anti-IDs to compete with an antigen for binding to antibody and to alter the biologic activity of an antigen, anti-IDs have become a target in the search for new treatments of autoimmune illnesses, cancer, and some other diseases. In this review, we summarize the data about anti-IDs that mimic the structural and functional properties of some bioregulators (autacoids, neurotransmitters, hormones, xenobiotics, and drugs) and evaluate their possible medical applications. The immune system is potentially able to reproduce or at least alter the effects of any biologically active endogenous or exogenous immunogenic agent via the anti-idiotypic principle, and probably regulates a broad spectrum of cell functions in the body, being a kind of universal remedy or immunacea, by analogy to the legendary ancient goddess of universal healing Panacea (Πανάκεια, Panakeia in Greek) in the treatment and prevention of diseases, possibly including non-infectious somatic and even hereditary ones.

Immunocytochemical localization of bovine thyrotropin and thyroid auto-antibodies in porcine thyrocytes

Interactions of receptor-bound bovine thyrotropin (bTSH) and immunoglobulins G from sera of patients with Graves' (G-IgG) or Hashimoto's (H-IgG) disease with porcine thyrocytes were studied by immunocytochemistry. Porcine thyroid fragments were fixed and prepared for immunoreaction or enzymatically dissociated with collagenase and dispase II. The dispersed cells were cultured in primary monolayer in a hormone-free medium or in a medium with bTSH (150 micrograms/ml) for 7 days. After immunostaining the thyrocytes in fragments and monolayers were stained with periodic acid Schiff (PAS) or with PAS and haemalum. Cultivation of the isolated thyrocytes in bTSH-enriched medium leads to a monolayer with globular aggregates, i.e., reconstructed three-dimensional follicles. Follicular cells in these monolayers and in fragments give a weak to moderate immunoreaction to anti-bTSH and a strong reaction to G-IgG and H-IgG (vs. control IgG). Precipitate is found particularly in the perinuclear area and to a lesser degree throughout the cytoplasm. Cells cultured in the absence of bTSH show minimal immunoreaction to anti-bTSH, but moderate reaction to G-IgG and H-IgG. Preincubation with bTSH leads to a strong reduction of immunoreaction to G-IgG but does not affect reaction to H-IgG. Morphological results indicate that G-IgG and H-IgG interact with the same cellular sites as bTSH. Hashimoto's disease antibodies bind to a determinant on the TSH receptor separate from the one on which TSH and Graves' IgG bind.

Use of anti-idiotypic antibodies as probes for the interaction of TSH subunits with its receptor

TSH is a heterodimeric glycoprotein hormone, whose dissociated subunits are without biological activity. This has precluded the assessment of the relative contribution of each subunit to hormone action. We have raised anti-idiotypes to monoclonal antibodies specific, respectively, for the alpha and beta hTSH subunits. The anti-beta anti-idiotype inhibited 125I-hTSH binding to the beta subunit-specific monoclonal quantitatively, whereas 125I-hTSH binding to the alpha subunit-specific monoclonal was not inhibited by anti-alpha anti-idiotypes, suggesting that only the former is an "internal image" anti-idiotype. Neither of the two anti-idiotypes nor equimolar mixtures thereof inhibited 125I-bTSH binding to thyroid membranes, even though radiolabelled anti-idiotypes showed saturable binding to thyroid plasma membrane which was inhibited 41-65% by bTSH. Each anti-idiotype alone caused 9% inhibition (compared to 50% by NRIgG) of thyroid plasma membrane adenylate cyclase. Equimolar mixtures (125 micrograms/ml IgG of each anti-idiotype) induced enzyme activity equivalent to 85% of that of 250 mU/ml of TSH. The TSH-like action of the two anti-idiotypes was also reflected in their capacity to increase (450% by 250 micrograms/ml IgG compared to normal rabbit IgG) the uptake of 131I into isolated thyrocytes and to promote the organization of such cells into follicular structures. At 250 micrograms/ml, anti-beta anti-idiotype promoted the organization of small follicles and only at a concentration of 500 micrograms/ml did it enhance 131I uptake.

An anti-idiotypic antibody against Graves' IgG

Rabbit antibodies were raised against Graves' IgG adsorbed onto a TSH-receptor affinity and eluted thereof by [3H]NaCl. The rabbit serum absorbed against normal human IgG (ARI) still bound to Graves', control and Hashimoto's IgG preparations but in the latter two, binding was inhibited by bTSH (10 mU/ml). In addition, ARI stimulated thyroid cell cyclic AMP accumulation in both human and rat thyroid cells. The ARI preparation may, therefore, contain an "internal image" anti-idiotype causing thyroid (Ab2) stimulation, a Graves' disease specific anti-idiotype whose binding with Ab2 inhibits its ability to bind TSH and anti-anti-idiotype (Ab3) to "internal image" Ab2. In further studies, Graves' specific cross-reactive idiotype was found in 10/11 IgGs from patients with active Graves' disease. This study emphasizes the workings of Jerne's immunologic network and the complexity of polyclonal "anti-idiotypic" antibodies.

Genetic factors in Graves' ophthalmopathy

We investigated the distribution of HLA and immunoglobulin G heavy chain markers (Gm) in 117 patients with Graves' disease, 62 with ophthalmopathy and 55 without. With Graves' disease per se, there is a closer association with HLA-DR3 than with B8. The opposite was true for Graves' patients with ophthalmopathy (odds ratio for ophthalmopathy associated with B8 was 12.4 and with DR3 was 7.7, both with P less than 0.0005). HLA-DR7 interacts with B8 in modifying the risk for eye disease; using the phenotype B8- DR7- as reference, the odds ratios were 16.7 for B8+ DR7+, 8.7 for B8+ DR7- and 0.26 for B8- DR7+. Thus, DR7 enhanced the risk for ophthalmopathy in the presence of B8+ but had a protective influence in its absence. Although Gm showed no association with eye disease, it modified the risk for ophthalmopathy associated with HLA-B8; the odds ratios were 20.9 for B8+ Gmfb homozygozity (fb+), 15.3 for B8+ fb- and 1.7 for B8- fb+ (B8- fb- = 1.00). We conclude that the genetic factors contributing to Graves' ophthalmopathy are different from those related to liability for Graves' hyperthyroidism.

Interaction of IgG heavy-chain allotypes (Gm) and HLA in conferring susceptibility to thyroid carcinoma

We have recently reported an increase in HLA-DR1 in 52 patients with thyroid epithelial cancer from Eastern Hungary (Juhasz et al., 1986). We have now investigated the association of IgG heavy chain markers (Gm) in 50 patients with this disease and explored possible interaction between Gm and HLA in modifying the risk for thyroid cancer. No Gm phenotype showed significant increases in the patients compared to 168 local controls. When both Gm and HLA, however, were considered, a marked heterogeneity in risk was noted. The odds ratio for DR1+fb+ homozygotes was 37.5, for DR1+fb- individuals 6.0 and for DR1-fb+ individuals 2.6 (DR1-fb- = 1.0). Thus Gm and HLA interact to enhance greatly the risk of thyroid cancer.

Further characterization of the low and high affinity binding components of the thyrotropin receptor

Following cross-linking with disuccinimidyl suberate and analysis by SDS-PAGE and autoradiography, both the high- and low-affinity TSH binding components exhibited two similar 125I-TSH-labeled bands, with Mr values of 80,000 and 68,000. IgG fractions from patients with Graves' disease inhibited 125I-TSH binding to both components, while normal IgG had no effect. Although not entirely conclusive, these results suggest that the high- and low-affinity components share similar subunit composition and antigenic determinants.

Covalent crosslinking of thyrotropin to thyroid plasma membrane receptors: subunit composition of the thyrotropin receptor

The subunit composition of the thyrotropin (TSH) receptor has been characterized using the bifunctional crosslinking agent, disuccinimidyl suberate (DSS), to covalently link [125I]TSH to its receptor. Purified thyroid membranes were labeled with [125I]TSH, and the hormone-receptor complex was crosslinked by incubation with 0.1 mM DSS. Analysis of this crosslinked complex by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions indicated the presence of a specifically labeled hormone-receptor complex, corresponding to a Mr of 68,000 +/- 3000 before correction for the relative molecular mass of TSH. When reducing agents were absent during SDS solubilization, the mobility of the band increased slightly, suggesting the presence of intramolecular disulfide bonds. The labeling of the 68,000 band was specifically inhibited by TSH, but not by other glycoprotein hormones. Specific labeling occurred only in thyroid, and not in liver or muscle plasma membranes. Protease-free immunoglobulin G, isolated from sera of patients with Graves' disease and capable of competing with TSH for binding to its receptor, inhibited the labeling of the 68,000 complex. When the hormone-receptor complex was crosslinked with higher concentrations of DSS (greater than 0.3 mM), a second specifically labeled band was observed, with a Mr of 80,000 +/- 5000. This complex exhibited hormone, tissue, and immunologic specificities similar to those of the 68,000 band. Continuous sucrose density gradient analysis indicated that the intact solubilized receptor possessed a sedimentation coefficient of 10.5 S prior to correction for detergent binding. However, this value increased to 16 S when determined under conditions which took into account the change in hydrodynamic properties attributable to bound Triton X-100. These data suggest that the 80,000 and 68,000 bands represent binding components of the TSH receptor and that the receptor molecule most likely contains multiple subunits, linked by noncovalent forces.

Interplay of immunoglobulin G heavy chain markers (Gm) and HLA in predisposing to systemic lupus nephritis

We have studied the distribution of IgG heavy chain markers (Gm) among 90 Hungarian patients with systemic lupus erythematosus (SLE) (55 of whom were also typed for HLA). This study confirms previously described increases in HLA-B8 and DR3 in this condition. No difference in the distribution of Gm phenotypes was found between patients and 168 controls from the same geographical area. HLA-B8/Gm homozygous individuals were, however, at greater risk for SLE (relative risk = 5.13) compared to B8 + Gm heterozygotes or B8- individuals, irrespective of Gm phenotype. When patients with renal manifestation (n = 40) were compared to those without, the Gm phenotype 3; 5, 13 was found to be significantly increased (chi 2 = 10.36, P less than 0.0001, relative risk (RR) = 4.69). HLA and Gm increased additively the risk for renal manifestations in that for those patients who were both Gm3;5,13+ and HLA-B8+, PR was 110, while it was 21.2 for Gm3;5, 13-/B8+, 7.9 for Gm3;5, 13+/B8- and 1.0 for Gm3;5, 13-/B8- patients. The study suggests that combined HLA and Gm typing can be used to identify SLE patients at high risk for manifesting renal abnormalities.

The thyroid "microsomal" antigen is an epitope on the thyrotropin receptor

Antimicrosomal antibodies are present in the sera of most patients with autoimmune thyroiditis, and Graves' disease. It has, in general, been difficult to separate antimicrosomal activity from that directed against the thyrotropin (TSH) receptor in Graves' IgG preparations. The "microsomal" antigen has been localized to the endoplasmic reticulum and microfollicular aspect of thyrocytes; its structure is however unknown. In an attempt to identify the thyroid microsomal antigen, we studied the interaction of Hashimoto's IgG with high microsomal antibody titre and negative for thyroglobulin with purified thyroid plasma and light microsomal membranes. We allowed Hashimoto's, Graves', and control IgGs to bind to protein blots of thyroid plasma membranes resolved on SDS-PAGE under non-reducing conditions. All seven Hashimoto's IgG at a concentration of 2 mg/ml interacted with an M approximately 197,000 polypeptide corresponding to the TSH holoreceptor. By contrast to Graves' IgG (which were positive at 1 mg/ml), however, this binding was not blocked by pretreatment of the protein blots with TSH. Normal IgGs showed no binding at concentrations of up to 2 mg/ml. Both Hashimoto's and Graves' IgG interacted with TSH-affinity column-purified receptor preparations. Two of the Hashimoto's IgGs induced adenylate cyclase activation in thyroid plasma membranes, three inhibited TSH-stimulated enzyme activation, and two were without effect. Two classes of autoantibodies, other than TSH receptor directed, were encountered; one class raised to antigens common to all seven patients and another class unique to individual patients, eg, Mr 210,000 and Mr 20,000 polypeptides. We propose that the TSH receptor has multiple epitopes (functional domains), and the one to which antimicrosomal antibody bind is likely to be spatially separated from that with which Graves' IgG and TSH interact. Differences in affinity or number of sites allows for the demonstration of Graves' IgG against a background of antimicrosomal antibody.

A prognostic score for Graves' disease

We have reanalysed the clinical and laboratory data on 196 individuals with Graves' disease. The consensus of two clustering techniques and a new method of allocating patients to a cluster resulted in two groups of patients, those with a severe and others with a mild disease. The severe disorder is characterized by a high frequency of HLA-B8 and -Al, a low complement level, high titres of circulating immune complex and anti-thyroglobulin antibody, a high lymphocyte transformation index and serum T3 level, a low level of active E-rosettes, large goitres and a high value for the Crooks test. The mild disorder shows a higher frequency of HLA-B12 and an abnormally low absolute lymphocyte number. A weight was calculated for each character according to the relative frequency in the two clusters. A total score could then be calculated for each patient based on their clinical and laboratory findings. There were two distinct distributions of scores corresponding to the two subgroups. This suggests different aetiological factors which may be more easily studied in these more homogeneous groups. Prognostic predictions can be made using the score. The risk of recurrence and the frequency and severity of ophthalmopathy increases dramatically as the score increases. The use of the score in making therapeutic decisions needs to be tested.

Humoral autoimmune manifestation in subacute thyroiditis

To study the autoimmune manifestations in subacute thyroiditis (SAT), the patterns of thyroid antibodies, thyroglobulin and circulating immune complexes were investigated in 10 patients during the course of the disease. Eight patients were thyrotoxic at diagnosis, and became euthyroid during recovery with a median observation of 8 months (4-30 months). Thyroid stimulating immunoglobulins were measured as TSH binding inhibiting immunoglobulins (TBII) and as thyroid stimulating antibodies (TSAb). TBII were present in all patients at least once during the observation period and remained detectable in six patients after recovery. TSAb were detected in three patients without relation to the hyperthyroid state. Thyroglobulin antibodies (TgAb) were present in four patients and persisted in three, while microsomal antibodies (MAb) were negative. Thyroglobulin (Tg) in the TgAb negative patients (n = 6) was high at diagnosis (median 229 micrograms/l, range 55-375) and fell rapidly during the course of SAT. Circulating immune complexes (CIC), which were found in all patients, reached maximal levels shortly after the onset of the disease and persisted after recovery. No correlation could be demonstrated between the different thyroid antibodies, and there was no clear relation between the levels of CIC and presence of the autoantibodies. However, the changes in CIC paralleled the changes in TBII, and it is suggested that immune complex formation is a major feature of the regulatory mechanisms controlling the immune responses in SAT.

Structure of the porcine thyrotropin receptor: a 200 kilodalton glycoprotein heterocomplex

We have determined that the porcine thyroidal TSH receptor is a glycoprotein heterotetramer composed of two Mr approximately 35,000 (epsilon) covalently linked subunits which interact noncovalently with two copies of delta (Mr 66,000) chains.

Specific suppressor T cell function in a patient with Graves' disease and her healthy identical twin

Immunoregulatory defects have been suggested in autoimmune disorders including Graves' disease. The finding that Concanavalin A-induced suppressor T cell function was sub-optimal in Graves' disease has been disputed; a restricted defect in TSH-receptor antigen-specific suppressor cells has instead been proposed by Okita et al. (1980). To explore this further, we studied both specific and non-specific suppressor cell function in a pair of HLA identical twins, one of whom had Graves' disease. By contrast to the euthyroid healthy twin and 10 healthy controls (612 cpm/10(6) cells) the patient's mononuclear cells (MNCs) incorporated more (3H)-thymidine (7365 cpm/10(6) cells) in response to thyroid membrane antigen (TMA). Removal of glass-adherent cells before addition of antigen increased (3H)-uptake by cells from the healthy twin to 1808 cpm but reduced those from the Graves' twin to 3411 cpm. The influence of MNCs cultured with Con A or TMA for 24 h upon (3H)-thymidine uptake by 2 X 10(6) indicator cells triggered by Con A for 72 h or TMA for 96 h was taken as a measure of non-specific and specific suppressor cell function respectively. Both Con A and TMA induced suppressor cells were reduced, the latter to a more marked degree, in the patient compared to the healthy twin; mixing of MNCs from patient and healthy twin in a 1:1 ratio improved the patient suppressor cell function. When the patient's MNCs triggered for 24 h with Con A were mixed in a 1:1 ratio with her fresh MNCs and TMA, less blast transformation was found compared to an equal number of fresh cells (3H-thymidine uptake 3250 vs 7365 cpm/10(6). Similarly, preincubated cells from the healthy twin had greater suppressive effect (1820 cpm/10(6) cells). We conclude that (1) the HLA identical healthy twin has TMA autoreactive lymphocytes regulated by adherent regulatory cells; (2) the increased ratio of helper/suppressor cells in the adherent cell population in the patient leads to a decrease of (3H) incorporation upon their removal; (3) in the patient, the specific suppressor cell defect is more severe than the non-specific defect; (4) lack of specific TMA induced triggering may be the critical immunoregulatory defect in Graves' disease.