Self-reactive T cells must escape thymic negative selection to mediate pathogenic autoimmunity. In the NOD mouse model of autoimmune diabetes, several β cell-cytotoxic CD8 T cell populations are known, with the most aggressive of these represented by ...
Self-reactive T cells must escape thymic negative selection to mediate pathogenic autoimmunity. In the NOD mouse model of autoimmune diabetes, several β cell-cytotoxic CD8 T cell populations are known, with the most aggressive of these represented by AI4, a T cell clone with promiscuous Ag-recognition characteristics. We identified a long-elusive β cell-specific ligand for AI4 as an unusually short H-2D(b)-binding 7-mer peptide lacking a C-terminal anchor residue and derived from the insulin A chain (InsA14-20). Crystallography reveals that compensatory mechanisms permit peptides lacking a C-terminal anchor to bind sufficiently to the MHC to enable destructive T cell responses, yet allow cognate T cells to avoid negative selection. InsA14-20 shares two solvent-exposed residues with previously identified AI4 ligands, providing a structural explanation for AI4's promiscuity. Detection of AI4-like T cells, using mimotopes of InsA14-20 with improved H-2D(b)-binding characteristics, establishes the AI4-like T cell population as a consistent feature of the islet infiltrates of NOD mice. Our work establishes undersized peptides as previously unrecognized targets of autoreactive CD8 T cells and presents a strategy for their further exploration as Ags in autoimmune disease.
Organizational Affiliation:
The Jackson Laboratory, Bar Harbor, ME 04609;,Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461;,Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461;,St. Vincent's Institute, Fitzroy, Victoria 3065, Australia; Department of Medicine, The University of Melbourne, St. Vincent's Hospital, Fitzroy, Victoria 3065, Australia; and.,Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461; Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461 teresa.dilorenzo@einstein.yu.edu dave.serreze@jax.org.,The Jackson Laboratory, Bar Harbor, ME 04609; teresa.dilorenzo@einstein.yu.edu dave.serreze@jax.org.
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