title: T cell responses to type 1 diabetes related peptides sharing homologous regions.
abstract: Glutamic acid decarboxylase (GAD) 65 is a major autoantigen in type 1 diabetes. Regions of homology exist between GAD65 (residues 250-273) and the Coxsackie P2-C protein (residues 28-50) and between GAD65 (residues 506-518) and proinsulin (residues 24-36), and each of these has been reported to be a diabetes-associated T cell target. The aim of this study was to determine whether the homologous regions are shared targets of T lymphocyte reactivity in individual patients with type 1 diabetes. T cell proliferation against the corresponding peptide pairs, GAD254-276 and Coxsackie P2-C32-54 and GAD506-518 and proinsulin24-36, were measured in peripheral blood mononuclear cells from 26 patients with newly diagnosed type 1 diabetes and 24 control subjects. Responses with stimulation indices higher than 3 were found against each of the antigens tested in both patients and control subjects, and no differences were observed between groups. A strong positive correlation was found between responses to the corresponding peptide pairs GAD254-276 and Coxsackie P2-C32-54 (r=0.77, P<0.0001), and between responses to the corresponding peptide pairs GAD506-518 and proinsulin24-36 (r=0.66, P<0.0001). However, a similar correlation was also observed between responses to the noncorresponding pairs Coxsackie P2-C32-54 and proinsulin24-36 (r=0.82, P<0.0001), Coxsackie P2-C32-54 and GAD506-518 (r=0.82, P<0.0001), and GAD254-276 and proinsulin24-36 (r=0.83, P<0.0001). Strikingly, increased responses to peptides were found almost exclusively in subjects with high stimulation indices against the recall antigen tetanus toxoid, further suggesting that peripheral blood T cell responses are related to a general subject hyperreactivity. These data suggest that proliferative T cell responses to peptides containing putative autoreactive epitopes of GAD65 and proinsulin are not specific for type 1 diabetes, that correlation between T cell reactivity to peptides is not restricted to those containing homologous regions, and that non-antigen-specific factors are important determinants of in vitro measurements of T cell reactivity.
authors.affiliation: Department of Internal Medicine, Istituto Scientifico San Raffaele, Milan, Italy. Elena.Sarugeri@hsr.it
authors.forename: E
authors.initials: E
authors.lastname: Sarugeri
authors.forename: N
authors.initials: N
authors.lastname: Dozio
authors.forename: F
authors.initials: F
authors.lastname: Meschi
authors.forename: M R
authors.initials: MR
authors.lastname: Pastore
authors.forename: E
authors.initials: E
authors.lastname: Bonifacio
mesh_terms: D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D029822:Enterovirus B, Human / Q000235:genetics / Q000276:immunology*; D005968:Glutamate Decarboxylase / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011384:Proinsulin / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D016415:Sequence Alignment; D013223:Statistics as Topic; D013601:T-Lymphocytes / Q000276:immunology*; D014764:Viral Proteins / Q000737:chemistry / Q000276:immunology
chemical_list: D007527:Isoenzymes; D010455:Peptides; D014764:Viral Proteins; D011384:Proinsulin; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2