title: Class III alleles at the insulin VNTR polymorphism are associated with regulatory T-cell responses to proinsulin epitopes in HLA-DR4, DQ8 individuals.
abstract: A variable number of tandem repeats (VNTR) polymorphism upstream of the insulin promoter is strongly associated with type 1 diabetes. The short class I alleles are predisposing and the long class III alleles are protective. As a possible mechanism for this effect, we previously reported a two- to threefold higher insulin transcription from class III than from class I chromosomes in thymus where insulin is expressed at low levels, presumably for the purpose of self-tolerance. In this article, we confirm this finding with independent methodology and report studies testing the hypothesis that class III alleles are associated with T-cell tolerance to (pro)insulin. Cytokine release in vitro after stimulation with 21 overlapping preproinsulin epitopes was assessed in blood mononuclear cells as well as naive and memory CD4+ T-cell subsets from 33 individuals with the high-risk DRB1*04, DQ8 haplotype (12 type 1 diabetic patients, 11 healthy control subjects, and 10 autoantibody-positive subjects). No significant differences between genotypes (24 I/I subjects versus 10 I/III or III/III subjects) were observed for gamma-interferon, tumor necrosis factor-alpha, or interleukin (IL)-4. By contrast, the I/III + III/III group showed a significant threefold higher IL-10 release in memory T-cells for whole proinsulin and the immunodominant region. Given that IL-10 is a marker of regulatory function, our data are consistent with the hypothesis that higher insulin levels in the thymus promote the formation of regulatory T-cells, a proposed explanation for the protective effect of the class III alleles.
authors.affiliation: Department of Internal Medicine I, Division of Endocrinology, University of Ulm, Germany.
authors.forename: Ivana
authors.initials: I
authors.lastname: Durinovic-Belló
authors.forename: Eva
authors.initials: E
authors.lastname: Jelinek
authors.forename: Michael
authors.initials: M
authors.lastname: Schlosser
authors.forename: Thomas
authors.initials: T
authors.lastname: Eiermann
authors.forename: Bernhard O
authors.initials: BO
authors.lastname: Boehm
authors.forename: Wolfram
authors.initials: W
authors.lastname: Karges
authors.forename: Luc
authors.initials: L
authors.lastname: Marchand
authors.forename: Constantin
authors.initials: C
authors.lastname: Polychronakos
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics; D005838:Genotype; D006683:HLA-DQ Antigens / Q000235:genetics*; D015804:HLA-DR4 Antigen / Q000235:genetics*; D006801:Humans; D007328:Insulin / Q000235:genetics*; D016753:Interleukin-10 / Q000235:genetics; D017493:Leukocyte Common Antigens / Q000276:immunology; D018598:Minisatellite Repeats / Q000235:genetics*; D011110:Polymorphism, Genetic; D011384:Proinsulin / Q000235:genetics / Q000276:immunology*; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D012016:Reference Values; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D006683:HLA-DQ Antigens; C109756:HLA-DQ8 antigen; D015804:HLA-DR4 Antigen; D007328:Insulin; D016753:Interleukin-10; D011384:Proinsulin; D017493:Leukocyte Common Antigens; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1