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Biomedical subjects

N G Morgenthaler

Publications and source records attributed to N G Morgenthaler.

At least 37 records · Page 2Linked to original sources
PubMed2000

Graves' ophthalmopathy in the absence of elevated free thyroxine and triiodothyronine levels: prevalence, natural history, and thyrotropin receptor antibody levels.

The aims of this study were to (a) determine the prevalence of patients without elevated thyroid hormone levels in Graves' ophthalmopathy (GO) using current generation free thyroid hormone assays, (b) measure the prevalence of thyrotropin receptor antibodies (TRAb) in these cases, and (c) identify possible predictors of hyperthyroidism. Over a 30-month period, 1020 cases of thyroid eye disease were evaluated, of which only 19 (1.9%) met the diagnostic criteria. Ten (1%) had subclinical thyrotoxicosis, 7 (0.7%) were euthyroid, and 2 (0.2%) were hypothyroid as determined by a third-generation thyrotropin (TSH) assay. TRAb levels were measured in 16 of these 19 patients. The prevalence of TRAb varied according to the assay used. Polyethylene glycol-extracted thyroid-stimulating immunoglobulin (PEG-TSI), unfractionated thyroid-stimulating immunoglobulin (uTSI), first-generation porcine TSH-binding inhibitory immunoglobulin (pTBII), and second-generation human TSH-binding inhibitory immunoglobulin (hTBII) assays were positive in 93.8%, 50%, 18.8%, and 81.3% of patients, respectively. TRAb was detected by at least one method in all patients. Patients were followed up for 15 to 45 months. Hyperthyroidism developed in 4 patients (25%). Suppressed TSH levels and elevated TBII were predictors of hyperthyroidism. When sensitive assays are used, the prevalence of GO patients without elevated thyroid hormone levels is extremely low. The sensitivities of assays for TRAb detection differ substantially in these cases. PEG extraction improves the detection rate of TSI (p = 0.02), and hTBII assays improve the detection of TBII in these patients (p = 0.002). The high prevalence of TRAb in such cases supports a role for these antibodies in the pathogenesis of thyroid-associated eye disease.

Adolescent↗
PubMed2000

Rarity of anti- Na+/I- symporter (NIS) antibody with iodide uptake inhibiting activity in autoimmune thyroid diseases (AITD).

The search for antibody against the Na+/I- symporter (NIS) has seen conflicting results over the years. Prior to cloning of NIS, Raspe et al found iodide uptake inhibiting sera were rare in autoimmune thyroid diseases (AITD) while post-cloning, others reported the presence of antibody in 12-15% of Hashimoto's thyroiditis (HT) and 30-84% of Graves' disease (GD). To evaluate the role of NIS as a potential antigen in AITD, a stable COS 7 cell line expressing high level of functional hNIS was established which allowed the screening of large number of sera for iodide uptake inhibiting activity in a 96-well plate format. Five hundred and fourteen serum samples taken from normal subjects and patients with AITD, non-autoimmune thyroid diseases, and non-thyroid autoimmune diseases were assayed for presence of iodide uptake inhibiting activity. Under the influence of these sera, iodide uptake showed a normal frequency distribution and diminution of uptake 2 SDs below the mean of controls was observed with 14 sera. Among these, 7 that were available for further study were re-evaluated after dialysis and/or Ig G extraction. All 7 sera lost their iodide uptake inhibiting activity, indicating that the effects were not antibody mediated and unknown serum factors had been responsible. In conclusion, contrary to previous results, the present study indicates that antibodies capable of modulating NIS activity are rare in AITD.

Animals↗
PubMed2000

Low frequency of autoantibodies to the human Na(+)/I(-) symporter in patients with autoimmune thyroid disease.

Several studies suggest that the sodium-iodide symporter (NIS) may represent a major autoantigen in autoimmune diseases of the thyroid. The aim of the present paper was to investigate the importance of autoantibodies to human NIS (hNIS-Ab) in patients suffering from Hashimoto's thyroiditis (HT) and Graves' disease (GD). Full-length human NIS (hNIS) was cloned from thyroid tissue, expressed by in vitro transcription and translation in the presence of [(35)S]methionine, and used to analyze autoantibodies in a direct binding assay. The structurally similar glucose transporter, GLUT-2, was produced in the same system as control protein. Autoradiography revealed that full-length hNIS was expressed, recognized by a NIS monoclonal antibody, and strongly bound by some sera from patients with autoimmune thyroid disease, which did not react with the GLUT-2 control protein. Using the 95.2th percentile of healthy controls as threshold for positivity, 19 of 177 (10.7%) patients with GD and 15 of 72 (20.8%) patients with HT had hNIS-Ab, respectively. Applying more stringent cut-off criteria (99.4th percentile of normal controls), hNIS-Ab were found in only 5.6% of patients with GD and 6. 9% of patients with HT. In HT significantly higher hNIS-Ab levels were observed compared with GD and normal controls (P: < 0.001). There was no correlation between hNIS-Ab and TSH receptor antibodies and only a weak correlation to thyroid peroxidase antibodies (P: < 0. 05). Comparison of hNIS-Ab, thyroid peroxidase, and TSH receptor antibodies in individual sera revealed that the additional detection of hNIS-Ab did not increase the diagnostic power for GD or HT. Our data indicate that hNIS is not a major antigen in autoimmune thyroid disease, as it is the target of humoral autoimmunity in only a few patients with GD and HT. The frequency of hNIS-Ab may be lower than that reported in previous studies.

Adolescent↗
PubMed1999

T cell reactivity to DR*0401- and DQ*0302-binding peptides of the putative autoantigen IA-2 in type 1 diabetes.

Type 1 diabetes is thought to be an autoimmune disease mediated by T lymphocytes recognizing critical islet cell antigens. Recently, the tyrosine phosphatase like protein IA-2 was suggested as a putative autoantigen in type 1 diabetes since autoantibodies are detected in sera of diabetic patients and prediabetic subjects. Similarly, T cell responses of peripheral blood lymphocytes of type 1 diabetic patients to this protein have been described. Only very few data is available about immunodominant epitopes of IA-2 recognized by T cells. We have studied T cell responses in type 1 diabetic patients and age and partly HLA matched controls to IA-2 peptides designed to bind HLA risk alleles of IDDM as DR*0401 and DQ*0302. Both diabetic patients and controls responded to IA-2ic and some of the peptides. Three peptides of the C-terminal region of IA-2 were recognised by T cells of a fraction of diabetic patients but at least two of these peptides triggered also T cell responses in DR*0401/DQ*0302-matched controls. Most peptides bound to different HLA alleles ("promiscous binders"). The identification of autoantigenic epitopes may offer clues to related sequences e.g. of viral origin what relates to models of diabetes pathogenesis ("molecular mimicry"). Secondly, the design of antigen- or even epitope-specific immune intervention strategies aiming at tolerization of disease specific T cells in type 1 diabetes may profit from the knowledge of immunodominant T cell epitopes of a putative autoantigen.

Adolescent↗
PubMed1999

Antibodies to human recombinant tissue transglutaminase measured by radioligand assay: evidence for high diagnostic sensitivity for celiac disease.

Celiac disease is associated with endomysial antibodies (EmA), which have recently been reported to be directed to tissue transglutaminase (tTG). To demonstrate binding of antibodies to recombinant tTG, human tTG was cloned, expressed by in vitro transcription/translation and used to develop novel radioligand assays for combined and single detection of immunoglobulin A (IgA) and G (IgG)-specific antibodies. IgA and IgG-tTGA were found in 43 (95.6%) of 45 patients with newly-diagnosed celiac disease verified by biopsy. In addition, all 30 sera from patients with gastrointestinal symptoms and positive EmA were positive for IgA-tTGA, and all but one serum (96.7%) had antibodies of the IgG class. Receiver-operating characteristic analysis including 574 sera from healthy controls revealed a specificity of 99.5%. By means of these new assays, we identified all patients with endomysial antibodies and achieved, at equal specificity, an even improved sensitivity (95.6%) as compared to EmA (91.1%) detected by the standard immunofluorescence test. Here, we have provided direct evidence that recombinant tTG is a major target of antibodies in celiac disease. Our data suggest that tTGA measured by radioligand assay have the power to overcome the limitations of the EmA-test. This new strategy may considerably facilitate large-scale screening for silent and latent celiac disease.

Adolescent↗
PubMed1999

Detection of autoantibodies to the diabetes-associated antigen IA-2 by a sensitive enzyme-linked immunosorbent assay.

The tyrosine phosphatase like protein IA-2 is an important autoantigen in insulin-dependent diabetes mellitus (type 1 diabetes). Autoantibodies to IA-2 (IA-2A) are present in the serum of patients with type 1 diabetes even before the onset of the disease. Previously, we reported on a radioimmune assay to detect IA-2A, using E. coli-derived 125I-labelled IA-2 as antigen. Although this assay could be shown to be equivalent to the common reference method for IA-2A detection (radioligand assays using in vitro synthesised 35S-methionine labelled antigen), the disadvantages of both assays with respect to synthesis and handling of the radioactive antigen limit their use in routine laboratories. In this study, we have evaluated a non-radioactive enzyme-linked immunosorbent assay (ELISA) for the simple detection of IA-2A. We report on an ELISA where the biotinylated intracytoplasmic part of IA-2 (IA-2ic) is captured on streptavidin-coated plates. The sensitivity of the ELISA was similar to the validated radioligand assay, as it detected 47 of 69 (69%) patients with type 1 diabetes as compared to 46 of 68 (67 %) with the reference method for IA-2A detection (radioligand assays using in vitro synthesised 35S-methionine labelled antigen). Only 2 of 50 (4%) patients with autoimmune thyroid disease and 1 of 114 (1 %) healthy controls were detected in the ELISA, confirming specificity. There was a significant correlation between the ELISA and the radioligand assay (r = 0.64, p<0.001). We conclude that this ELISA is suitable to detect IA-2A in the serum of patients with type 1 diabetes with a similar sensitivity and specificity to the radioligand assay. This ELISA will allow rapid and simple measurement of IA-2A where the radioligand assay is inconvenient or not available.

Antibody Specificity↗
PubMed1999

Second generation assay for thyrotropin receptor antibodies has superior diagnostic sensitivity for Graves' disease.

Detection of autoantibodies to the TSH receptor (TSH-R) in Graves' disease has found widespread use in clinical routine and is performed mostly by commercial RRAs measuring TSH binding inhibitory activity. We report in this study on a second generation TSH binding inhibitory assay using the human recombinant TSH-R with two major improvements: 1) superior diagnostic sensitivity for Graves' disease, and 2) for the first time, nonradioactive and radioactive coated tube (CT) technology. Full-length human recombinant TSH-R was expressed in the K562 leukemia cell line and grown in suspension at a high density. A murine monoclonal antibody was selected for binding to the native TSH-R without interfering with autoantibodies or TSH and was coated to polystyrene tubes. After detergent extraction, TSH-R was affinity immobilized on antibody-coated tubes. The binding of TSH to the TSH-R could be demonstrated by the addition of 125I- or acridinium ester-labeled bovine TSH, and this binding could be inhibited by sera from patients with Graves' disease up to 95%. Subsequently, these novel assays, a CT RRA and a CT luminescence receptor assay, were compared to the conventional RRA based on porcine antigen in a blinded clinical multicenter trial. Sera from 328 patients with Graves' disease (86 untreated, 116 treated, and 126 in remission) and 520 controls (comprised of healthy blood donors and patients with autoimmune diseases or goiter) were tested in all 3 assays. Receiver-operating characteristic plot analysis resulted in a specificity of 99.6% with a sensitivity of 98.8% for both CT assays, compared to 99.6% specificity and 80.2% sensitivity for the conventional RRA (P < 0.001). In all 3 groups of patients with Graves' disease, the 2 CT assays were significantly more sensitive for the disease than the conventional assay, without loss of specificity in the control groups. This increase in sensitivity and the nonradioactive or radioactive CT format constitute a significant improvement over the currently available assays.

Adolescent↗
PubMed1999

Development of a luminescent bioassay for thyroid stimulating antibodies.

The hyperthyroidism of Graves Disease (GD) is due to thyroid stimulating antibodies (TSAb) which are thyrotropin (TSH) agonists. They are detected routinely by measuring their ability to inhibit TSH binding to the receptor (TBII), which does not reflect their true biological activity. Current bioassays which measure cAMP by RIA, are not suitable for routine use. We have developed a luminescent bioassay for TSAb, by introducing a cAMP responsive luciferase construct into CHO cells stably expressing the human TSH receptor (TSHR). Clone lulul displays dose dependent TSH response detectable from 10 microU/ml and maximal at 10 mU/ml when a >25 fold increase in light output is obtained. 34 euthyroid sera were tested to determine a reference range, with values >1.5 relative light units (R.L.U.) being considered positive. An international TSAb standard responded in a dose dependent manner with 10 mIU/ml giving an R.L.U. of >10. The assay was adapted to a 96 well format for automatic readout and 100 treated GD samples (50 TBII negative and 50 TBII positive) were tested, 73% being positive. In contrast only 4% of 79 control sera from individuals with Hashimoto's, non-thyroid autoimmunity or multinodular goitre produced R.L.U. >1.5. When 44 of the GD sera were compared in a traditional salt-free bioassay, 61% were positive compared with 75% in the new luminescent assay. In conclusion, we have developed a luminescent bioassay for TSAb, using unfractionated serum which is capable of high throughput suitable for routine use.

Animals↗
PubMed1999

Direct binding of thyrotropin receptor autoantibody to in vitro translated thyrotropin receptor: a comparison to radioreceptor assay and thyroid stimulating bioassay.

Graves' disease is characterized by the presence of autoantibodies to the thyrotropin receptor (TSHR), which are pathogenic and responsible for disease activity. It is well recognized that the autoantibodies are heterogeneous and recognize a number of different conformational dependent epitopes on the TSHR. In this study, we have extended our previous observations to study the interaction of Graves' disease autoantibodies with TSHR ectodomain produced by in vitro transcription and translation reaction. The specific activity of the translated TSHR ectodomain has been increased by a log fold by adding an efficient ribosome binding Kozak sequence before the translation initiation codon as well as double labelling with 35S-methionine and 35S-cysteine during the translation reaction. Addition of canine pancreatic microsomes to the translation mix showed that the glycosylation of TSHR ectodomain did not occur efficiently for the nascent receptor protein. In order to determine the specificity and sensitivity of the improved assay with nonglycosylated TSHR ectodomain, we have studied 331 sera from Graves' disease patients and as controls 100 sera from patients with nonthyroid autoimmune disorders as well as sera from 200 normal control subjects with no family history of thyroid autoimmunity. With this large cohort of sera from Graves' disease and control individuals, 25% of Graves' disease sera immunoprecipitated the dual labeled, in vitro transcribed and translated TSHR ectodomain, exceeding the 98th percentile of the control sera. There was no correlation between the autoantibodies that immunoprecipitate the in vitro translated TSHR ectodomain and those that inhibit iodinated TSH binding in the radioreceptor assay and those with biological activity in a bioassay. The data are consistent with the finding that a proportion of Graves' disease autoantibodies can interact directly with TSHR ectodomain produced by in vitro transcription and translation. However, in contrast to the wide use of similar translation and immunoprecipitation assays to measure other autoantibodies for the diagnosis of autoimmune disorders, such as type 1 diabetes, the TSHR immunoprecipitation on its own is unsuitable for diagnosis of Graves' disease.

Animals↗
PubMed1998

Immunological heterogeneity in type I diabetes: presence of distinct autoantibody patterns in patients with acute onset and slowly progressive disease.

Type I diabetes mellitus may represent a heterogeneous disorder with a distinct pathogenesis in patients with young and adult onset of the disease. To investigate whether serological markers directed to different autoantigens have the potential to distinguish acute onset from slowly progressive Type I diabetes we analysed antibodies to tyrosine phosphatases IA-2/ICA512 (IA-2A) and IA-2beta/phogrin (IA2betaA), antibodies to GAD65 (GADA) and cytoplasmic islet cell antibodies (ICA) in a non-selected group of diabetic patients clinically classified as having Type I or Type II diabetes at diagnosis. Both IA-2A and IA-2betaBA were found to be positively associated with onset before the age of 20 years and the presentation of classical features of Type I diabetes. In Type I diabetes 56 % (112/200) of patients were positive for IA-2A and 38 % (76/200) for IA-2betaA. In contrast, only 1 of 785 (0.1 %) patients with Type II diabetes had IA-2A and all of them were negative for IA-2betaA (p < 0.001). Among the patients with Type II diabetes 7.6% (n = 60) were ICA positive and 2.8% (n = 22) had GADA suggesting the presence of slowly progressive Type I diabetes. GADA were found in 8 of 60 (13.3 %) ICA positive subjects which was lower than the percentage detected in patients with acute onset of diabetes (115/157 73.2%) (p < 0.001). Blocking of double antibody positive sera showed that only 3 of 8 (37.5 %) patients with slowly progressive diabetes had ICA restricted to GAD or IA-2 whereas ICA were completely inhibited in 12 of 20 (60.0 %) patients with Type I diabetes. Among 193 patients with Type II diabetes available for follow-up, 35 % of ICA positives, 58 % of GADA positives and 60 % of those positive for both markers required insulin by 3 years. However, using strict criteria for the switch to insulin treatment the corresponding sensitivity of each marker was only low (9%, 10% and 5%). We show that clinical subtypes of Type I diabetes are associated with distinct humoral autoimmunity. IA-2A and GADA were associated with classical features of Type I diabetes whereas GADA and an uncharacterized ICA subspecificity indicate slowly progressive disease.

Acute Disease↗
PubMed1998

Application of a bioassay with CHO cells for the routine detection of stimulating and blocking autoantibodies to the TSH-receptor.

The importance of bioassays measuring stimulating and blocking autoantibodies to the TSH-receptor (TSH-R) by their effect on cAMP production in CHO cells transfected with the recombinant TSH-R is increasingly recognized. The standard technique for this bioassay is cumbersome, as it involves purification of serum IgG with polyethylene glycol (PEG) and resuspension in hypotonic buffer. We have therefore established a simpler approach for the detection of stimulating and blocking autoantibodies using JP09 CHO cells and unfractionated human serum. The cAMP concentration was measured by a highly sensitive commercial radioimmuno assay. Thyroid stimulating autoantibodies (TSAb) were present in 107 out of 126 patients with Graves' disease (85%) and in 4 out of 40 patients with Hashimoto's thyroiditis (10%). Specificity was confirmed by the fact that only 1 patient with insulin dependent diabetes mellitus (IDDM) out of 64 patients with different non-thyroid autoimmune disorders (46 with IDDM, 10 with stiff man syndrome and 8 with rheumatoid arthritis) and 2 out of 100 healthy controls (2%) were positive in this assay. In the subgroup of hyperthyroid Graves' disease patients 76 out of 83 (92%) had TSAb and the same number had TSH binding inhibiting immunoglobulin (TBII), as assessed by the commercial TRAK assay. Although both antibody types showed only a weak correlation (r = 0.30), a combination of TSAb and TBII detected 98% of all Graves' patients and 99% of the hyperthyroid subgroup. Thyroid blocking autoantibodies (TBAb) were measured in 4 out of 24 TSAb negative patients with Graves' disease (17%), who were hypothyroid and positive for TBII. A comparison of our bioassay with the standard bioassay using PEG precipitation showed a good correlation (r = 0.76,p < 0.001), demonstrating the feasibility of the simplified assay for the routine detection of TSAb and TBAb in Graves' disease.

Adult↗
PubMed1998

Recombinant IA-2 expressed in E. coli can be used for the routine detection of autoantibodies in Type-I diabetes.

We have investigated the possibility of measuring autoantibodies to IA-2 (IA-2A) using recombinant protein expressed in E. coli in a new radioassay. The intracellular part of IA-2 (IA-2ic) was expressed in E. coli as a biotinylated fusion protein and affinity-purified on a streptavidin column. The average yield of IA-2ic was about 1 mg purified protein from one litre of culture medium with E. coli. We could demonstrate the immunological activity of this material by blocking the autoantibody reactivity to in vitro synthesised IA-2ic. The IA-2ic fusion protein was then radiolabelled with 125I, purified by HPLC, and used in an immunoprecipitation assay for the detection of IA-2A. Sera from 46 of 68 (67%) patients with Type-I diabetes were positive by this radioassay, in contrst to only 2 of 50 (4%) patients with autoimmune thyroid disease and 1 of 114 (1 %) controls. There was a correlation between this radioassay and the previously established radioligand assay using synthesized 35S-methionine-labelled IA-2ic in vitro (r = 0.79, p < 0.001). We conclude that E. coli-derived IA-2 has the correct immunogenic conformation, and can be used for the detection of IA-2A with a similar sensitivity and specificity as the validated radioligand assay. This new assay can facilitate the measurement of IA-2A in routine laboratories where the radioligand assay is inconvenient or not available.

Adolescent↗
PubMed1997

Human B cells secreting immunoglobulin G to glutamic acid decarboxylase-65 from a nondiabetic patient with multiple autoantibodies and Graves' disease: a comparison with those present in type 1 diabetes.

Antibodies to glutamic acid decarboxylase-65 (GAD65) are present in a number of autoimmune disorders, such as insulin-dependent (type 1) diabetes mellitus (IDDM), stiff man syndrome, and polyendocrine autoimmune disease. Antibodies to GAD in IDDM patients usually recognize conformation-dependent regions on GAD65 and rarely bind to the second isoform, glutamic acid decarboxylase-67 (GAD67). In contrast, those present in stiff man syndrome and polyendocrine disease commonly target the second isoform (GAD67) and include antibodies that are less dependent on the conformation of the molecule. By immortalizing peripheral blood B cells with Epstein-Barr virus, we have generated three human IgG autoantibodies, termed b35, b78, and b96, to GAD65 from one patient with multiple autoantibodies to endocrine organs and Graves' disease. All three autoantibodies are of the IgG1 isotype, with islet cell activity, and do not react with GAD67. The regions on GAD65 recognized by the three autoantibodies have been investigated by immunoprecipitation with a series of chimeras, by binding to denatured and reduced antigens, and using protein footprinting techniques. Using chimeric GAD proteins, we have shown that b35 targets the IDDM-E1 region of GAD65 (amino acids 240-435) whereas both b78 and b96 target the IDDM-E2 region of GAD65 (amino acids 451-570). Furthermore, examination of binding to recombinant GAD65 and GAD67 by Western blotting revealed some differences in epitope recognition, where only b78 bound denatured and reduced GAD65. However, b35, b78, and b96 autoantibodies had different footprinting patterns after trypsin treatment of immune complexes with GAD65, again indicating different epitope recognition. Our results indicate that antibodies to GAD65 present in nondiabetic patients with multiple autoantibodies to endocrine organs show similarities to those in IDDM (by targeting IDDM-E1 and IDDM-E2 regions of GAD65) as well as subtle differences in epitope recognition (such as binding to denatured and reduced GAD65 and by protein footprinting). Thus, the GAD65 epitopes recognized by autoantibodies in different autoimmune diseases may overlap and be more heterogeneous than previously recognized.

Adult↗
PubMed1997

Antibodies to the tyrosine phosphatase-like protein IA-2 are highly associated with IDDM, but not with autoimmune endocrine diseases or stiff man syndrome.

Antibodies to the 40 kD antigen (identified as tyrosine phosphatase IA-2) and glutamate decarboxylase (GAD65) are strongly associated with insulin dependent diabetes mellitus (IDDM). However, antibodies to GAD (GADA) can appear in the absence of IDDM, particularly in stiff man syndrome (SMS) and in some individuals with autoimmune polyendocrine syndrome type II (APS II) and organ specific autoimmune diseases. The aim of this study was to compare the specificity of IA-2 antibodies (IA-2A) and GADA for IDDM by determining their frequency in different patient groups. IA-2A were present in 64/114 (56%) IDDM patients and 9/19 (47%) APS II patients with IDDM but in only 4/28 (14%) SMS patients. 1/24 (4%) APS II patients without IDDM and 1/113 (0.9%) patients with organ specific autoimmune disease had low level IA-2A. In contrast GADA were present in 77/114 (68%) IDDM patients and 17/19 (89%) APS II patients with IDDM, but also in 25/28 (89%) SMS patients, 5/24 (21%) APS II patients without IDDM and 22/113 (19%) patients with organ specific autoimmune diseases. Furthermore, within the group of new onset IDDM, IA-2A seemed to be associated with ICA and age: 63% of ICA positive IDDM patients had IA-2A (74% had GADA) increasing to 77% in the group below 20 years of age (69% for GADA). Our results demonstrate that IA-2A may be more specific for IDDM than GADA, as the latter are also present in patients with SMS, APS II without IDDM and organ specific autoimmune diseases. IA-2A were less frequent in older patients with IDDM than GADA or ICA. A combination of IA-2A and GADA detected 84% of total and 93% of ICA positive IDDM patients.

Adolescent↗
PubMed1997

Characterisation of the antibody response to the extracellular region of recombinant thyrotropin receptor.

Autoantibodies to the human thyrotropin receptor (TSH-R) are pathogenic in a number of autoimmune thyroid diseases including Graves' disease. We have characterised polyclonal antisera to TSH-R for antibodies which may mimic those present in autoimmune thyroid disease. For immunisations, recombinant extracellular region of human TSH-R which does not interact with its ligand TSH was used. The induced antibodies react with the full length membrane receptor in transfected mammalian cells by flow cytometry showing the presence of antibody capable of recognising the native functional receptor. The properties of the generated antibodies have been compared after two injections or following a multiple immunisation protocol with the receptor in adjuvant. High titre antisera were readily generated after the short injection protocol and further immunisations did not lead to any change in antibody titers. Analysis of the epitopes recognised using synthetic peptides confirmed previous observations that the immunodominant determinants localise to the amino and the carboxyl terminal part of the extracellular region of the receptor. Antisera from both rabbits contain TSH blocking antibody as assessed by inhibition of TSH mediated cAMP stimulation. There was an increase in TSH binding inhibitory immunoglobulin (TBII) activity with multiple injections. Furthermore, the increase in TBII activity was not related to spreading of the antibody response to new determinants on TSH-R. Our results support previous observations on the difficulties in reproducing, by adjuvant immunisation with recombinant TSH-R preparations, the fine specificity of antibodies to TSH-R present in autoimmune disorders such as Graves' disease or primary myxoedema.

Animals↗
PubMed1996

Combined screening for autoantibodies to IA-2 and antibodies to glutamic acid decarboxylase in first degree relatives of patients with IDDM. The DENIS Study Group. Deutsche Nikotinamid Interventions-Studie.

To determine the value of antibodies to the intracytoplasmic domain of the tyrosine phosphatase IA-2 (anti-IA-2ic) and glutamic acid decarboxylase (GADA) for identification of subjects at risk for insulin-dependent diabetes mellitus (IDDM) we investigated 1238 first degree relatives of patients with IDDM for the presence of anti-IA-2ic and GADA and compared the results with cytoplasmic islet cell antibodies (ICA). Anti-IA-2ic were observed in 54 (4.4%) first degree relatives, in 51 of 86 (59.3%) ICA positive relatives and in 3 of 4 individuals who developed overt IDDM within a follow-up period of 1 to 28 months. GADA were found in 78 of 1238 (6.3%) first degree relatives. They were detected in 22 of 35 (62.9%) sera with ICA alone and in 1 of 3 subjects with anti-IA-2ic in the absence of ICA. Of the 1238 subjects 37 (3.0%) sera were positive for all three antibodies. Both anti-IA-2ic and GADA were positively correlated with high levels of ICA. Anti-IA-2ic and GADA were detected in 39.1 and 47.8% of subjects with ICA of less than 20 Juvenile Diabetes Foundation units (JDF-U) but in 66.7 and 76.2% of individuals with ICA of 20 JDF-U or more, respectively (p < 0.05). The levels of ICA and GADA in first degree relatives with at least one additional marker were significantly higher than in subjects with ICA alone (p < 0.005) or GADA alone (p < 0.03). The combination of anti-IA-2ic and GADA identified 84.9% of all ICA positive subjects and 93.7% of individuals with high level ICA (> or = 20 IDF-U). All 4 individuals who progressed to IDDM had either IA-2ic or GADA. Our data indicate that primary screening for anti-IA-2ic and GADA provides a powerful approach with which to identify subjects at risk for IDDM in large-scale population studies which may represent the basis for the design of new intervention strategies.

Adolescent↗
PubMed1996

In vitro synthesized TSH receptor as a tool for autoantibody detection.

Immunoprecipitation is a reliable method for the detection of many antigens but so far this has not been applied to the TSH receptor. We demonstrate here a novel assay for the detection of antibodies to the TSH receptor using in vitro synthesized protein. The TSH receptor was translated in vitro as a stable protein of 87 kD (full length) and 50 kD (extracellular), respectively. The 50 kD protein reacted by immunoprecipitation analysis with murine and human monoclonal antibodies, polyclonal rabbit sera and with a proportion of unfractionated Graves' disease sera. A limited form of epitope mapping was achieved with the murine monoclonal antibodies. This assay may serve as a new method for the detection of autoantibodies to the TSH receptor from patients' sera.

Animals↗