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W Richter

Publications and source records attributed to W Richter.

At least 91 records · Page 5Linked to original sources
PubMed1996

Immune reactivity of diabetes-associated human monoclonal autoantibodies defines multiple epitopes and detects two domain boundaries in glutamate decarboxylase.

Autoreactive islet cell Abs (ICA) accompany the pathogenic destruction of pancreatic beta cells in insulin-dependent diabetes mellitus (IDDM). Human monoclonal ICA (MICA 1-6), previously derived from a DR1/DR7-positive newly diagnosed diabetic patient, recognized the islet cell autoantigen glutamate decarboxylase 65 (GAD65) and defined two distinct conformational (MICA 1/3 and MICA 4/6) and one linear (MICA 2) autoimmune epitopes in this molecule. We have isolated 4 new ICA-reactive B cell lines, one from a DR4/DR11-positive newly diagnosed IDDM patient (MICA 7) and three from a DR3 homozygous patient with both IDDM and Graves' disease (MICA 8-10). Like MICA 1-6, MICA 7-10 are specific for GAD65, suggesting that GAD65-reactive B cells dominate the ICA response in IDDM. Comparative analysis of MICA 1-6 and MICA 7-10, using GAD65 mutants and blocking experiments, showed that MICA 7-10 define three novel conformational autoimmune epitopes in GAD65. Further structural analysis of the MICA 1-10 epitopes revealed two distinct and one overlapping region of epitope clusters. Thus, the C-terminal region, defined by amino acids 450 to 570, harbors the conformational MICA1/3 and MICA 7 epitopes as well as the linear epitope of MICA 2 (amino acids 506-531). The MICA 4/6 and MICA 10 epitopes are located in the middle region of the molecule defined by amino acids 245 to 449, whereas the N-terminal region contributes only to the MICA 8/9 epitopes (encompassed in amino acids 39-585). MICA 1-6, 7, and 8-10, derived from three IDDM patients of different HLA haplotypes, define six different epitopes in GAD65 and represent tools to determine the spectrum, possible HLA association, and temporal order of epitope recognition in IDDM.

Antibodies, Blocking↗
PubMed1996

Evidence for somatic mutation and affinity maturation of diabetes associated human autoantibodies to glutamate decarboxylase.

The processes that lead to the production of islet cell autoantibodies in insulin-dependent (type 1) diabetes mellitus (IDDM) are largely unknown. Humoral autoimmunity may be the result of an antigen-independent polyclonal B cell activation, or a consequence of an antigen driven B cell activation and selection for the antigen. We have analysed the gene elements encoding the immunoglobulin variable regions of seven human monoclonal islet cell antibodies (MICA) 1-7 directed to the major islet autoantigen glutamate decarboxylase (GAD65). These autoantibodies were derived from two patients with newly diagnosed IDDM. The variable gene regions of the MICA revealed different sequences, and no relation between V gene usage and shared epitope recognition of the MICA was evident. An elevated usage of VH 1, VH 4 and Vlambda 2 gene segments was observed. The underrepresentation of VH 3 family members in the MICA discriminated them from most autoantibodies. The high relative avidities for GAD65 of MICA 1, 3, 4 and 6 and their high, nonrandom ratio of replacement versus silent mutations in the antigen binding regions indicated that the humoral response to GAD65 is driven by the antigen. MICA 2, 5 and 7 showed as well an excess of replacement mutations in the antigen binding regions, but revealed lower relative avidities for their antigen. Since these clones accumulated many somatic mutations in their variable gene regions, they may be characteristic for later stages of the autoimmune disease. The results suggest that, in humans, an antigen driven B cell activation and affinity maturation process may contribute to the production of GAD65-autoantibodies found in patients with IDDM.

Antibodies, Monoclonal↗
PubMed1996

[Principles and results of systematic lymph node dissection in surgically treated bronchial carcinoma].

Lymphatic spread of bronchial carcinoma can reach any part of the mediastinum, irrespective of the localisation of the primary tumor. Metastatic spread may not affect all topographical lymph node positions, but this is unpredictable. The number of lymph nodes in each position varies. Therefore, systematic mediastinal lymph node dissection includes all ipsilateral compartments of the mediastinum. It is also possible to reach contralateral sites. In right-sided thoracotomies the lymph node dissection is standardized. Mobilizing the aortic arch and the large vessels also allows complete mediastinal dissection by a left-sided approach. The surgical technique is described. Perioperative morbidity does not increase. Systematic mediastinal lymph node dissection is the gold standard for evaluation of an exact pN stage. The stage-related survival rate is significantly improved. Therefore, it should be required that systematic mediastinal lymph node dissection be standard in the surgical treatment of bronchial carcinoma.

Carcinoma, Bronchogenic↗
PubMed1996

Mapping of an autoreactive epitope within glutamate decarboxylase using a diabetes-associated human monoclonal autoantibody and an epitope cDNA library.

Glutamate decarboxylase (GAD65) is a major autoantigen in insulin-dependent diabetes (IDDM) and the neurological disorder Stiff-Man-Syndrome (SMS). We derived a human monoclonal autoantibody (MICA 2) from peripheral blood of a patient newly diagnosed with IDDM, which reacted with GAD65 in Western blots. This indicated that a linear epitope is recognized by MICA 2. Using an epitope cDNA library we mapped the MICA 2 epitope to a contiguous stretch of 26 amino acids (506-531) in the C-terminus of GAD65. Neither blocking experiments with synthetic peptides nor analysis of overlapping decapeptides expressed as fusion proteins allowed us to further narrow down the epitope to the typical size of linear epitopes of 6-8 amino acids. We suggest that a miniconformational epitope provided by amino acids 506-531 is recognized by MICA 2, which withstands SDS gel electrophoresis without destruction or partially refolds during the Western blot procedure. A sequence homology with human heat shock protein 60 (HSP60) maps to this region of GAD65 but no cross-reactivity of MICA 2 with HSP60 occurred. Our data demonstrate that reactivity of an antibody in Western blots does not necessarily define a classic linear epitope of 6-8 amino acids and describe a new autoreactive epitope in GAD65 different from those reported for sera from patients with SMS.

Amino Acid Sequence↗
PubMed1996

Human immunoglobulin G autoantibodies to the thyrotropin receptor from Epstein-Barr virus-transformed B lymphocytes: characterization by immunoprecipitation with recombinant antigen and biological activity.

The TSH receptor (TSH-R) is the target antigen for disease-related autoantibodies in Graves' disease and primary myxoedema, but the repertoire of the antibodies or the nature of the precise antigenic epitopes is not known. We have immortalized peripheral blood B cells from six different autoimmune thyroid disease patients with Epstein-Barr virus and selected IgG-producing B cells by magnetic selection on anti-IgG-coated beads. Purified recombinant insect cell-derived extracellular region of TSH-R was used to identify the positive wells for expansion in culture. Stable B cell lines (n = 11) were obtained, which after limiting dilution led to two stable B cell clones. B cell lines and clones secreted IgG antibody that were shown to react biochemically with metabolically labeled or in vitro translated, nascent extracellular region of TSH-R, giving strong, confirmatory evidence of the presence of anti-TSH-R antibody. Supernatants from lines contained thyroid-stimulating activity, thyroid-blocking activity (as assessed by inhibition of TSH-mediated cAMP stimulation), or both of these activities. Interestingly, antibodies with stimulating activity were generated from a primary myxoedema patient, and antibodies of blocking specificities were obtained from newly diagnosed thyrotoxic Graves' disease patients. Our results favor a fine balance between stimulating and blocking autoantibody activities in determining the clinical presentation observed in patients with autoimmune thyroid disease patients who have these antibodies present in their serum.

Antigens↗
PubMed1996

[Contrast medium behavior of epithelial skin tumors and tumor-like changes in high resolution magnetic resonance tomography].

To evaluate the use of Gd-DTPA in imaging epithelial skin tumors and tumor-like lesions, 29 benign, 8 malignant and 4 semimalignant skin tumors were prospectively examined by high-resolution MRI at 1.5 Tesla using a 2.5-cm surface coil. For tumor assessment, transverse plain and contrast-enhanced scans (0.1 mmol Gd-DTPA/kg body mass) were performed (TR 500 ms, TE 25 ms, 3 acquisitions, 256 x 256 matrix, FOV 2.5 cm). Contrast enhancement was quantitively determined as the percent enhancement of signal intensity. Histologic findings were correlated using the Mann-Whitney-test (p < 0.05). Quality of contrast enhancement was independently assessed by three investigators, who mostly described inhomogeneous enhancement, regardless of histologic findings. Malignant tumors could not be differentiated from benign lesions by contrast enhancement. MRI using Gd-DTPA does not provide differentiation of skin tumor types.

Adolescent↗
PubMed1996

[Radical surgery and lymph node dissection in bronchial carcinoma].

Lymphatic spread of bronchial carcinoma can involve each position in the mediastinum. Localisation of the primary tumor has no influence. Metastatic skipping of topographical lymph node positions is not calculable. Therefore, systematic mediastinal lymph node dissection includes all ipsilateral compartments of the mediastinum. It is also possible to reach contralateral sides. In right-sided thoracotomies, the lymph node dissection is standardised. Mobilising the aortic arch and the large vessels also allows from a left-sided approach a complete mediastinal dissection. The surgical technique is described. Perioperative morbidity does not increase. Systematic mediastinal lymph node dissection is the golden standard for the evaluation of an exact pN stage. The stage-related survival rate is significantly improved. Therefore, the systematic mediastinal lymph node dissection should be a standard in the surgical therapy of bronchial carcinoma.

Carcinoma, Bronchogenic↗
PubMed1995

The appearance of cytoplasmic membranes of Escherichia coli cells in freeze-fracture electron microscopy after stringent and relaxed response.

Guanosine-5'-diphosphate-3'-diphosphate (ppGpp), an effector for many metabolic pathways, is synthesized by the relA gene product after amino acid limitation. Studies of stringent controlled Escherichia coli CP78 (relA+) and relaxed controlled E. coli CP79 (relA-) were carried out to test whether these strains differ in the appearance of their cytoplasmic membranes after induction of stringent and relaxed response. Cytoplasmic membrane structures of the cells were investigated by freeze-fracture electron microscopy after cooling the cells. The obtained micrographs showed a net-like distribution of the particles in the cytoplasmic membranes of relaxed controlled cells whereas such a pattern was not detectable in the stringent controlled counterparts.

Amino Acids↗