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Updated: Jun 15, 2026
12:09
Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation
Published on: February 28, 2019
Constraints within major histocompatibility complex class I restricted peptides: presentation and consequences for
Alex Theodossis1, Carole Guillonneau, Andrew Welland
1The Protein Crystallography Unit, Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Victoria 3800, Australia.
Summary
Constrained peptides, not independent pegs, anchor to MHC-I molecules. Disrupting these peptide constraints alters T-cell receptor interactions and can lead to viral escape.
Area of Science:
- Immunology
- Structural Biology
- Virology
Background:
- Major histocompatibility complex class I (MHC-I) glycoproteins present peptide fragments to T-cell receptors (TCRs).
- Previously, peptide residues were thought to act as independent anchors to MHC-I and TCRs.
Purpose of the Study:
- To investigate the role of inter-residue interactions within peptides bound to MHC-I.
- To explore the concept of "constrained" peptides and their impact on immune responses.
Main Methods:
- Mining of the pMHC-I structural database.
- Mutational analysis of constrained self- and viral peptides.
- Reverse genetics in a murine influenza model.
Main Results:
- Identified extensive direct inter-residue interactions in many self- and viral peptides, termed "constrained" peptides.
- Demonstrated that flanking residues within peptides govern the conformation of key residues like arginine.
- Showed that mutating a constrained residue diminished cytotoxic T lymphocyte (CTL) response and narrowed the TCR repertoire.
Conclusions:
- Peptide-MHC-I (pMHC-I) epitope conformation is finely controlled by internal peptide residue interactions.
- Perturbation of these constraints represents a novel mechanism for viral escape from immune surveillance.
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