Journal
DIABETES
Volume 71, Issue 5, Pages 1012-1022Publisher
AMER DIABETES ASSOC
DOI: 10.2337/db21-0993
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Funding
- National Institutes of Health [AI125301, DK114456]
- Robert and Janice McNair Foundation
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Accumulating evidence suggests that posttranslationally modified islet neoantigens play a critical role in type 1 diabetes. However, our understanding of thymic development and peripheral activation of PTM autoantigen-reactive T cells is limited. This study found that deamidation of GAD65(115-127) generates a more immunogenic epitope, leading to recruitment of T cells with promiscuous recognition of both deamidated and native epitopes and reduced frequency of regulatory T cells.
Accumulating evidence supports a critical role for posttranslationally modified (PTM) islet neoantigens in type 1 diabetes. However, our understanding regarding thymic development and peripheral activation of PTM autoantigen-reactive T cells is still limited. Using HLA-DR4 humanized mice, we observed that deamidation of GAD65(115-127) generates a more immunogenic epitope that recruits T cells with promiscuous recognition of both the deamidated and native epitopes and reduced frequency of regulatory T cells. Using humanized HLA/T-cell receptor (TCR) mice, we observed that TCRs reactive to the native or deamidated GAD65(115-127) led to efficient development of CD4(+) effector T cells; however, regulatory T-cell development was reduced in mice expressing the PTM-reactive TCR, which was partially restored with exogenous PTM peptide. Upon priming, both the native-specific and the deamidated-specific T cells accumulated in pancreatic islets, suggesting that both specificities can recognize endogenous GAD65 and contribute to anti-beta-cell responses. Collectively, our observations in polyclonal and single TCR systems suggest that while effector T-cell responses can exhibit cross-reactivity between native and deamidated GAD65 epitopes, regulatory T-cell development is reduced in response to the deamidated epitope, pointing to regulatory T-cell development as a key mechanism for loss of tolerance to PTM antigenic targets.
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