Biomedical subjects

Øyvind Molberg

Publications and source records attributed to Øyvind Molberg.

10 recordsLinked to original sources

PubMed2006

A gut feeling for joint inflammation - using coeliac disease to understand rheumatoid arthritis.

Major advances have been made in the molecular understanding of coeliac disease, initiated by the identification of intestinal gluten-reactive T cells. It is now clear that this common intestinal disorder, which is precipitated by the ingestion of wheat gluten, is mediated by DQ2-restricted T cells specific for gluten peptides modified by transglutaminase 2, the same enzyme that is targeted by disease-specific autoantibodies. Interestingly, many of the important features identified in coeliac disease, including HLA association, target organ T-cell infiltration, disease-specific autoantibodies and the distinct targeting of in vivo modified antigens, are also present in rheumatoid arthritis. The experiences from coeliac disease should therefore help identify disease-relevant T-cell epitopes in rheumatoid arthritis.

Arthritis, Rheumatoid↗

PubMed2006

A unique dendritic cell subset accumulates in the celiac lesion and efficiently activates gluten-reactive T cells.

BACKGROUND & AIMS: Celiac disease is a chronic inflammation of the duodenal mucosa driven by gluten-reactive T cells restricted by the disease-associated HLA-DQ2 molecule. The mechanisms that regulate the activation of mucosal T cells are, however, understood poorly. The aim of this study was to identify the antigen-presenting cells that are responsible for the activation of gluten-reactive T cells in the celiac lesion. METHODS: Intestinal biopsy specimens obtained from untreated and treated celiac patients and normal controls were either snap-frozen directly or incubated for 24 hours with or without gluten peptides. Cryosections were subjected to multicolor immunofluorescence applying monoclonal antibodies to a range of antigen-presenting cell markers. Macrophages and dendritic cells were isolated from enzymatically digested small intestinal biopsies of untreated patients and incubated with gluten-reactive T-cell clones to measure their antigen-presenting capacity. RESULTS: HLA-DQ2+ cells in the normal duodenal mucosa consisted of 2 distinct cell populations: about 80% were CD68+ DC-lysosome intercellular adhesion molecule-3-grabbing nonintegrin+ macrophages and 20% were CD11c+ dendritic cells. Importantly, the CD11c+ dendritic cells accumulated in the celiac lesion and revealed an activated phenotype expressing CD86 and DC-specific-associated membrane protein. Moreover, when isolated from challenged biopsy specimens, the CD11c+ dendritic cells efficiently activated gluten-reactive T cells. CONCLUSIONS: Our results suggest that a unique subset of dendritic cells are responsible for local activation of gluten-reactive T cells in the celiac lesion.

Adolescent↗

PubMed2005

[Pathophysiologic aspects of systemic sclerosis].

BACKGROUND: The pathological changes in systemic sclerosis are characterised by severe organ fibrosis, obliteration of arteries and arterioles and disturbance of immunological functions. Recent research has yielded new insight into the complex pathogenesis of systemic sclerosis, with new therapeutic options as a possible consequence. MATERIALS AND METHODS: Relevant medical literature has been reviewed. RESULTS: The pathological deposition of extracellular matrix in systemic sclerosis is most probably caused by changes in the regulation of dermal fibroblasts. The review focuses on three of the many molecules involved in the regulation of fibrosis; Transforming growth factor beta, Connective tissue growth factor and Endothelin-1. INTERPRETATION: Treatment of organ-specific disease complication has for long remained the only therapeutic option in systemic sclerosis. Based on current knowledge of the process of fibrosis, new therapeutic trials employing substances directed towards pro-fibrotic molecules are now in progress.

Connective Tissue Growth Factor↗

PubMed2004

The molecular basis for oat intolerance in patients with celiac disease.

BACKGROUND: Celiac disease is a small intestinal inflammatory disorder characterized by malabsorption, nutrient deficiency, and a range of clinical manifestations. It is caused by an inappropriate immune response to dietary gluten and is treated with a gluten-free diet. Recent feeding studies have indicated oats to be safe for celiac disease patients, and oats are now often included in the celiac disease diet. This study aimed to investigate whether oat intolerance exists in celiac disease and to characterize the cells and processes underlying this intolerance. METHODS AND FINDINGS: We selected for study nine adults with celiac disease who had a history of oats exposure. Four of the patients had clinical symptoms on an oats-containing diet, and three of these four patients had intestinal inflammation typical of celiac disease at the time of oats exposure. We established oats-avenin-specific and -reactive intestinal T-cell lines from these three patients, as well as from two other patients who appeared to tolerate oats. The avenin-reactive T-cell lines recognized avenin peptides in the context of HLA-DQ2. These peptides have sequences rich in proline and glutamine residues closely resembling wheat gluten epitopes. Deamidation (glutamine-->glutamic acid conversion) by tissue transglutaminase was involved in the avenin epitope formation. CONCLUSIONS: We conclude that some celiac disease patients have avenin-reactive mucosal T-cells that can cause mucosal inflammation. Oat intolerance may be a reason for villous atrophy and inflammation in patients with celiac disease who are eating oats but otherwise are adhering to a strict gluten-free diet. Clinical follow-up of celiac disease patients eating oats is advisable.

Atrophy↗

PubMed2004

Antigen presentation to celiac lesion-derived T cells of a 33-mer gliadin peptide naturally formed by gastrointestinal digestion.

Celiac disease is an HLA-DQ2-associated disorder characterized by intestinal T cell responses to ingested wheat gluten proteins. A peptide fragment of 33 residues (alpha(2)-gliadin 56-88) produced by normal gastrointestinal proteolysis contains six partly overlapping copies of three T cell epitopes and is a remarkably potent T cell stimulator after deamidation by tissue transglutaminase (TG2). This 33-mer is rich in proline residues and adopts the type II polyproline helical conformation in solution. In this study we report that after deamidation, the 33-mer bound with higher affinity to DQ2 compared with other monovalent peptides harboring gliadin epitopes. We found that the TG2-treated 33-mer was presented equally effectively by live and glutaraldehyde-fixed, EBV-transformed B cells. The TG2-treated 33-mer was also effectively presented by glutaraldehyde-fixed dendritic cells, albeit live dendritic cells were the most effective APCs. A strikingly increased T cell stimulatory potency of the 33-mer compared with a 12-mer peptide was also seen with fixed APCs. The 33-mer showed binding maximum to DQ2 at pH 6.3, higher than maxima found for other high affinity DQ2 binders. The 33-mer is thus a potent T cell stimulator that does not require further processing within APC for T cell presentation and that binds to DQ2 with a pH profile that promotes extracellular binding.

Amino Acid Sequence↗

PubMed2003

Intestinal T-cell responses to high-molecular-weight glutenins in celiac disease.

BACKGROUND & AIMS: The chronic, small intestinal inflammation that defines celiac disease is initiated by a HLA-DQ2 restricted T-cell response to ingested gluten peptides after their in vivo deamidation by tissue transglutaminase (TG2). To date, celiac disease can only be treated by a lifelong abstinence from foods that contain wheat, rye, or barley; better therapeutic options are hence needed. An attractive target would be to identify nontoxic wheat cultivars or components thereof with intact baking qualities. Because these qualities are mainly determined by the high molecular weight (HMW) glutenin proteins of gluten, it is critical to know if these proteins are toxic or, more specifically, if they will trigger the activation of T cells in the celiac lesion. METHODS: Different, highly purified HMW glutenins were isolated from wheat cultivars or expressed as recombinant proteins. The proteins were first tested for recognition by a large panel of gluten-specific T-cell lines established from celiac lesions and then applied during ex vivo challenges of celiac biopsies to allow for a direct identification of HMW specific T cells. RESULTS: Intestinal T-cell responses to TG2-deamidated HMW glutenins but not the corresponding native proteins were detectable in 9 of the 22 adult and childhood celiac disease patients tested. CONCLUSIONS: T cells within celiac lesions frequently recognize deamidated HMW glutenin proteins. This finding questions the possibility of implementing these proteins in novel food items destined to be nontoxic for celiac disease patients.

Adult↗

PubMed2002

Structural basis for gluten intolerance in celiac sprue.

Celiac Sprue, a widely prevalent autoimmune disease of the small intestine, is induced in genetically susceptible individuals by exposure to dietary gluten. A 33-mer peptide was identified that has several characteristics suggesting it is the primary initiator of the inflammatory response to gluten in Celiac Sprue patients. In vitro and in vivo studies in rats and humans demonstrated that it is stable toward breakdown by all gastric, pancreatic, and intestinal brush-border membrane proteases. The peptide reacted with tissue transglutaminase, the major autoantigen in Celiac Sprue, with substantially greater selectivity than known natural substrates of this extracellular enzyme. It was a potent inducer of gut-derived human T cell lines from 14 of 14 Celiac Sprue patients. Homologs of this peptide were found in all food grains that are toxic to Celiac Sprue patients but are absent from all nontoxic food grains. The peptide could be detoxified in in vitro and in vivo assays by exposure to a bacterial prolyl endopeptidase, suggesting a strategy for oral peptidase supplement therapy for Celiac Sprue.

Amino Acid Sequence↗

PubMed2002

Gliadin T cell epitope selection by tissue transglutaminase in celiac disease. Role of enzyme specificity and pH influence on the transamidation versus deamidation process.

Tissue transglutaminase (TG2) can modify proteins by transamidation or deamidation of specific glutamine residues. TG2 has a major role in the pathogenesis of celiac disease as it is both the target of disease-specific autoantibodies and generates deamidated gliadin peptides that are recognized by CD4(+), DQ2-restricted T cells from the celiac lesions. Capillary electrophoresis with fluorescence-labeled gliadin peptides was used to separate and quantify deamidated and transamidated products. In a competition assay, the affinity of TG2 to a set of overlapping gamma-gliadin peptides was measured and compared with their recognition by celiac lesion T cells. Peptides differed considerably in their competition efficiency. Those peptides recognized by intestinal T cell lines showed marked competition indicating them as excellent substrates for TG2. The enzyme fine specificity of TG2 was characterized by synthetic peptide libraries and mass spectrometry. Residues in positions -1, +1, +2, and +3 relative to the targeted glutamine residue influenced the enzyme activity, and proline in position +2 had a particularly positive effect. The characterized sequence specificity of TG2 explained the variation between peptides as TG2 substrates indicating that the enzyme is involved in the selection of gluten T cell epitopes. The enzyme is mainly localized extracellularly in the small intestine where primary amines as substrates for the competing transamidation reaction are present. The deamidation could possibly take place in this compartment as an excess of primary amines did not completely inhibit deamidation of gluten peptides at pH 7.3. However, lowering of the pH decreased the reaction rate of the TG2-catalyzed transamidation, whereas the rate of the deamidation reaction was considerably increased. This suggests that the deamidation of gluten peptides by TG2 more likely takes place in slightly acidic environments.

Amino Acid Sequence↗

PubMed2002

Celiac lesion T cells recognize epitopes that cluster in regions of gliadins rich in proline residues.

BACKGROUND & AIMS: Celiac disease is a gluten-induced enteropathy that shows a strong association with HLA-DQ2 and -DQ8. Gluten-specific T cells, invariably restricted by DQ2 or DQ8, can be isolated from celiac lesions. Such gut-derived T cells have a preference for recognition of gluten that has been specifically deamidated by tissue transglutaminase. Only a few gliadin T-cell epitopes have been identified by earlier work. The aim of this study was to perform a systematic characterization of DQ2-restricted T-cell epitopes in alpha- and gamma-gliadins. METHODS: Epitopes were identified by mass spectrometry analysis of peptide fragments of recombinant gliadins and by use of synthetic peptides. RESULTS: We identified several new gamma-gliadin epitopes and an additional alpha-gliadin epitope. Interestingly, these and the previously identified epitopes are not randomly scattered across the gliadins but cluster in regions of the proteins with high content of proline residues. CONCLUSIONS: Several DQ2-restricted T-cell epitopes exist in gliadin that are located in regions rich in proline. This likely reflects epitope selection at the levels of digestive and antigen-presenting cell processing, transglutaminase-mediated deamidation, and/or peptide binding to DQ2.

Amino Acid Sequence↗

PubMedDate not supplied

Identification and analysis of multivalent proteolytically resistant peptides from gluten: implications for celiac sprue.

Dietary gluten proteins from wheat, rye, and barley are the primary triggers for the immuno-pathogenesis of Celiac Sprue, a widespread immune disease of the small intestine. Recent molecular and structural analyses of representative gluten proteins, most notably alpha- and gamma-gliadin proteins from wheat, have improved our understanding of these pathogenic mechanisms. In particular, based on the properties of a 33-mer peptide, generated from alpha-gliadin under physiological conditions, a link between digestive resistance and inflammatory character of gluten has been proposed. Here, we report three lines of investigation in support of this hypothesis. First, biochemical and immunological analysis of deletion mutants of alpha-2 gliadin confirmed that the DQ2 restricted T cell response to the alpha-2 gliadin are directed toward the epitopes clustered within the 33-mer. Second, proteolytic analysis of a representative gamma-gliadin led to the identification of another multivalent 26-mer peptide that was also resistant to further gastric, pancreatic and intestinal brush border degradation, and was a good substrate of human transglutaminase 2 (TG2). Analogous to the 33-mer, the synthetic 26-mer peptide displayed markedly enhanced T cell antigenicity compared to monovalent control peptides. Finally, in silico analysis of the gluten proteome led to the identification of at least 60 putative peptides that share the common characteristics of the 33-mer and the 26-mer peptides. Together, these results highlight the pivotal role of physiologically generated, proteolytically stable, TG2-reactive, multivalent peptides in the immune response to dietary gluten in Celiac Sprue patients. Prolyl endopeptidase treatment was shown to abolish the antigenicity of both the 33-mer and the 26-mer peptides, and was also predicted to have comparable effects on other proline-rich putatively immunotoxic peptides identified from other polypeptides within the gluten proteome.

Amino Acid Sequence↗