title: Gluten-specific antibodies of celiac disease gut plasma cells recognize long proteolytic fragments that typically harbor T-cell epitopes.
abstract: This study aimed to identify proteolytic fragments of gluten proteins recognized by recombinant IgG1 monoclonal antibodies generated from single IgA plasma cells of celiac disease lesions. Peptides bound by monoclonal antibodies in complex gut-enzyme digests of gluten treated with the deamidating enzyme transglutaminase 2, were identified by mass spectrometry after antibody pull-down with protein G beads. The antibody bound peptides were long deamidated peptide fragments that contained the substrate recognition sequence of transglutaminase 2. Characteristically, the fragments contained epitopes with the sequence QPEQPFP and variants thereof in multiple copies, and they typically also harbored many different gluten T-cell epitopes. In the pull-down setting where antibodies were immobilized on a solid phase, peptide fragments with multivalent display of epitopes were targeted. This scenario resembles the situation of the B-cell receptor on the surface of B cells. Conceivably, B cells of celiac disease patients select gluten epitopes that are repeated multiple times in long peptide fragments generated by gut digestive enzymes. As the fragments also contain many different T-cell epitopes, this will lead to generation of strong antibody responses by effective presentation of several distinct T-cell epitopes and establishment of T-cell help to B cells.
authors.affiliation: Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital - Rikshospitalet, 0424 Oslo, Norway.
authors.forename: Siri
authors.initials: S
authors.lastname: Dørum
authors.affiliation: Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital - Rikshospitalet, 0424 Oslo, Norway.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Steinsbø
authors.affiliation: Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital - Rikshospitalet, 0424 Oslo, Norway.
authors.forename: Elin
authors.initials: E
authors.lastname: Bergseng
authors.affiliation: Norwegian University of Life Sciences, NMBU, Department of Chemistry, Biotechnology and Food Science, 1432 Aas, Norway.
authors.forename: Magnus Ø
authors.initials: MØ
authors.lastname: Arntzen
authors.affiliation: Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital - Rikshospitalet, 0424 Oslo, Norway.|Proteomics Core Facility, Oslo University Hospital-Rikshospitalet, 0424 Oslo, Norway.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: de Souza
authors.affiliation: Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital - Rikshospitalet, 0424 Oslo, Norway.
authors.forename: Ludvig M
authors.initials: LM
authors.lastname: Sollid
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D002446:Celiac Disease / Q000276:immunology* / Q000378:metabolism; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D019204:GTP-Binding Proteins / Q000276:immunology; D005903:Gliadin / Q000276:immunology; D005983:Glutens / Q000737:chemistry / Q000276:immunology*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000276:immunology; D013058:Mass Spectrometry; D010446:Peptide Fragments / Q000276:immunology; D010950:Plasma Cells / Q000276:immunology* / Q000378:metabolism; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D059748:Proteolysis; D011503:Transglutaminases / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D018984:Epitopes, T-Lymphocyte; D010446:Peptide Fragments; D005983:Glutens; D005903:Gliadin; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins