CD8 T cell autoreactivity to preproinsulin epitopes with very low human leucocyte antigen class I binding affinity

Authors

  • J. R. F. Abreu,

    1. Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
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  • S. Martina,

    1. Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
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  • A. A. Verrijn Stuart,

    1. Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
    2. Department of Pediatric Endocrinology and Centre Cellular and Molecular Intervention, UMC Utrecht, Utrecht, the Netherlands
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  • Y. E. Fillié,

    1. Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
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  • K. L. M. C. Franken,

    1. Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
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  • J. W. Drijfhout,

    1. Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
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  • B. O. Roep

    Corresponding author
    1. Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
    2. JDRF Center for Beta Cell Therapy in Diabetes in Europe, Leiden, the Netherlands
      B. O. Roep, Leiden University Medical Center, Dept of Immunohematology and Blood Transfusion, E3-Q, PO Box 9600, 2300 RC Leiden, the Netherlands. E-mail: boroep@lumc.nl
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B. O. Roep, Leiden University Medical Center, Dept of Immunohematology and Blood Transfusion, E3-Q, PO Box 9600, 2300 RC Leiden, the Netherlands. E-mail: boroep@lumc.nl

Summary

Beta cells presenting islet epitopes are recognized and destroyed by autoreactive CD8 T cells in type 1 diabetes. These islet-specific T cells are believed to react with epitopes binding with high affinity to human leucocyte antigen (HLA) expressed on beta cells. However, this assumption might be flawed in case of islet autoimmunity. We evaluated T cell recognition of the complete array of preproinsulin (PPI) peptides with regard to HLA binding affinity and T cell recognition. In a comprehensive approach, 203 overlapping 9–10mer PPI peptides were tested for HLA-A2 binding and subjected to binding algorithms. Subsequently, a high-throughput assay was employed to detect PPI-specific T cells in patient blood, in which conditional HLA ligands were destabilized by ultraviolet irradiation and HLA molecules refolded with arrays of PPI peptides, followed by quantum-dot labelling and T cell staining. Analysis of patient blood revealed high frequencies of CD8 T cells recognizing very low HLA binding peptides. Of 28 peptides binding to HLA-A2, a majority was predicted not to bind. Unpredicted peptides bound mainly with low affinities. HLA binding affinity and immunogenicity may not correlate in autoimmunity. Algorithms used to predict high-affinity HLA peptide binders discount the majority of low-affinity HLA binding epitopes. Appreciation that peptides binding HLA with very low affinity can act as targets of autoreactive T cells may help to understand loss of tolerance and disease pathogenesis and possibly point to tissue-specific immune intervention targets.

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