title: Dendritic Cells Guide Islet Autoimmunity through a Restricted and Uniquely Processed Peptidome Presented by High-Risk HLA-DR.
abstract: Identifying T cell epitopes of islet autoantigens is important for understanding type 1 diabetes (T1D) immunopathogenesis and to design immune monitoring and intervention strategies in relationship to disease progression. Naturally processed T cell epitopes have been discovered by elution from HLA-DR4 of pulsed B lymphocytes. The designated professional APC directing immune responses is the dendritic cell (DC). To identify naturally processed epitopes, monocyte-derived DC were pulsed with preproinsulin (PPI), glutamic acid decarboxylase (65-kDa isoform; GAD65), and insulinoma-associated Ag-2 (IA-2), and peptides were eluted of HLA-DR3 and -DR4, which are associated with highest risk for T1D development. Proteome analysis confirmed uptake and processing of islet Ags by DC. PPI peptides generated by DC differed from those processed by B lymphocytes; PPI signal-sequence peptides were eluted from HLA-DR4 and -DR3/4 that proved completely identical to a primary target epitope of diabetogenic HLA-A2-restricted CD8 T cells. HLA-DR4 binding was confirmed. GAD65 peptides, eluted from HLA-DR3 and -DR4, encompassed two core regions overlapping the two most immunodominant and frequently studied CD4 T cell targets. GAD65 peptides bound to HLA-DR3. Strikingly, the IA-2 ligandome of HLA-DR was exclusively generated from the extracellular part of IA-2, whereas most previous immune studies have focused on intracellular IA-2 epitopes. The newly identified IA-2 peptides bound to HLA-DR3 and -DR4. Differential T cell responses were detected against the newly identified IA-2 epitopes in blood from T1D patients. The core regions to which DC may draw attention from autoreactive T cells are largely distinct and more restricted than are those of B cells. GAD65 peptides presented by DC focus on highly immunogenic T cell targets, whereas HLA-DR-binding peptides derived from IA-2 are distinct from the target regions of IA-2 autoantibodies.
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Menno
authors.initials: M
authors.lastname: van Lummel
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Peter A
authors.initials: PA
authors.lastname: van Veelen
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Arnoud H
authors.initials: AH
authors.lastname: de Ru
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: George M C
authors.initials: GM
authors.lastname: Janssen
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Jos
authors.initials: J
authors.lastname: Pool
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Sandra
authors.initials: S
authors.lastname: Laban
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Antoinette M
authors.initials: AM
authors.lastname: Joosten
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Tatjana
authors.initials: T
authors.lastname: Nikolic
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: Jan W
authors.initials: JW
authors.lastname: Drijfhout
authors.affiliation: Department of Pediatrics, Leiden University Medical Center, 2300 RC Leiden, the Netherlands;
authors.forename: M Luisa
authors.initials: ML
authors.lastname: Mearin
authors.affiliation: Diabeter, Center for Pediatric and Adolescent Diabetes Care and Research, 3011 TA Rotterdam, the Netherlands;
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Aanstoot
authors.affiliation: Department of Immunobiology, School of Medicine, King's College London, London SE1 9RT, United Kingdom; and.
authors.forename: Mark
authors.initials: M
authors.lastname: Peakman
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2300 RC Leiden, the Netherlands; Department of Diabetes Immunology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA 91010 b.o.roep@lumc.nl.
authors.forename: Bart O
authors.initials: BO
authors.lastname: Roep
mesh_terms: D001324:Autoantigens / Q000276:immunology; D015551:Autoimmunity / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D015803:HLA-DR3 Antigen / Q000276:immunology*; D015804:HLA-DR4 Antigen / Q000276:immunology*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D011498:Protein Precursors / Q000378:metabolism; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8 / Q000378:metabolism
chemical_list: D001324:Autoantigens; D018984:Epitopes, T-Lymphocyte; D015803:HLA-DR3 Antigen; D015804:HLA-DR4 Antigen; D007328:Insulin; D011498:Protein Precursors; C013737:preproinsulin; C516862:PTPRN protein, human; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2