Structural Mechanism Underpinning Cross-reactivity of a CD8+ T-cell Clone That Recognizes a Peptide Derived from...

Area of Science:

• Immunology
• Structural Biology
• Molecular Medicine

Background:

• T-cell cross-reactivity is vital for immune surveillance but can lead to autoimmunity.
• T-cell receptors (TCRs) typically bind peptides via focused interactions with minimal motifs.
• However, many TCRs interact with broader peptide regions, the structural basis of which is less understood.

Purpose of the Study:

• To investigate the structural basis of T-cell cross-reactivity in a CD8+ T-cell clone (ILA1).
• To understand how TCRs engage multiple peptide-major histocompatibility complexes (pMHCs) with non-focused binding.
• To explore the relationship between TCR-peptide contacts and T-cell degeneracy.

Main Methods:

• Structural analysis of the ILA1 T-cell clone interacting with its cognate peptide-major histocompatibility complex (pMHC).
• Examination of the T-cell receptor (TCR) binding footprint on the peptide.
• Correlation of structural contact sites with observed T-cell cross-reactivity.

Main Results:

• The ILA1 TCR exhibited a broad peptide binding footprint, contacting spatially distant residues.
• Despite non-focused binding, the ILA1 T-cell clone demonstrated significant cross-reactivity.
• TCR-peptide contact sites correlated with peptide degeneracy, indicating intolerance to changes at key positions.

Conclusions:

• Broad TCR-peptide interactions, not just focused binding, can mediate T-cell cross-reactivity.
• Structural insights into TCR binding can explain functional T-cell degeneracy.
• Understanding these mechanisms has implications for pathogen surveillance, autoimmunity, and transplantation.