Assessment of CD4+ T cell responses to glutamic acid decarboxylase 65 using DQ8 tetramers reveals a pathogenic role of GAD65 121-140 and GAD65 250-266 in T1D development.

I-Ting Chow,Theresa J Gates,Duy T Mai,Eddie A James,William W Kwok,Carla Greenbaum,Junbao Yang,Matthias G Von Herrath

doi:10.1371/journal.pone.0112882

I-Ting Chow, Theresa J Gates + Show 6 more

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https://doi.org/10.1371/journal.pone.0112882

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Journal: PloS one	Publication Date: Nov 18, 2014
Citations: 56	License type: CC BY 4.0

Affiliation: Virginia Mason Medical Center, University of Washington

Abstract

Susceptibility to type 1 diabetes (T1D) is strongly associated with MHC class II molecules, particularly HLA-DQ8 (DQ8: DQA1*03:01/DQB1*03:02). Monitoring T1D-specific T cell responses to DQ8-restricted epitopes may be key to understanding the immunopathology of the disease. In this study, we examined DQ8-restricted T cell responses to glutamic acid decarboxylase 65 (GAD65) using DQ8 tetramers. We demonstrated that GAD65121–140 and GAD65250–266 elicited responses from DQ8+ subjects. Circulating CD4+ T cells specific for these epitopes were detected significantly more often in T1D patients than in healthy individuals after in vitro expansion. T cell clones specific for GAD65121–140 and GAD65250–266 carried a Th1-dominant phenotype, with some of the GAD65121–140-specific T cell clones producing IL-17. GAD65250–266-specific CD4+ T cells could also be detected by direct ex vivo staining. Analysis of unmanipulated peripheral blood mononuclear cells (PBMCs) revealed that GAD65250–266-specific T cells could be found in both healthy and diabetic individuals but the frequencies of specific T cells were higher in subjects with type 1 diabetes. Taken together, our results suggest a proinflammatory role for T cells specific for DQ8-restricted GAD65121–140 and GAD65250–266 epitopes and implicate their possible contribution to the progression of T1D.

Highlights

Type 1 diabetes (T1D) results from destruction of the insulinproducing beta cells of the pancreas
A number of genes have been implicated in T1D development, but genes within the HLA class II region confer most of the disease risk [1]; in particular, it is estimated that 90% of T1D subjects have either an HLA-DQ8 or DQ2 allele [2]
CD4+ T cell responses to GAD65121–140 and GAD65250–266 are detected more often in subjects with type 1 diabetes after in vitro expansion Seven peptides derived from glutamic acid decarboxylase 65 (GAD65) were selected in this study to evaluate their relevance to the progression of autoimmune diabetes

Summary

Introduction

Type 1 diabetes (T1D) results from destruction of the insulinproducing beta cells of the pancreas. In accordance with the importance of MHC class II molecules in antigen presentation, DQ8-restricted CD4+ T cells are likely to have an essential and pathogenic role in the progression of T1D. A special feature of DQ8 is the absence of an aspartic acid residue at position 57 of the beta chain [5]. Lack of this Asp residue at beta 57 leads to reduced affinity for antigenic peptides, giving rise to diabetic pathology as a result of ineffective tolerance induction in the thymus [6,7]. Identification and characterization of DQ8-restricted self-epitopes may be key to comprehending

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