Molecular basis for the recognition of two structurally different major histocompatibility complex/peptide complexes...

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• Cytotoxic T lymphocytes (CTLs) play a crucial role in adaptive immunity.
• The 2C T-cell receptor (TCR) is a model system for studying T-cell recognition.
• Alloreactivity, where TCRs recognize non-self Major Histocompatibility Complex (MHC) molecules, is a key phenomenon in transplantation immunology.

Purpose of the Study:

• To investigate the structural basis for the crossreactivity of the 2C TCR with two distinct ligands.
• To determine whether ligand structural similarity or TCR adaptation underlies this crossreactivity.
• To elucidate the differential roles of peptides in self- vs. allo-MHC-restricted T-cell responses.

Main Methods:

• Utilized MHC-binding assays to assess peptide binding affinities.
• Performed T-cell assays to measure T-cell responses to different MHC-peptide complexes.
• Employed molecular modeling studies to analyze the structural and electrostatic properties of the ligands.
• Synthesized modified peptides to probe structure-function relationships.

Main Results:

• The two ligands, differing significantly in molecular surface charge distribution, were recognized by the 2C TCR.
• Modifications increasing peptide similarity to the natural ligand reduced T-cell response capacity.
• Self-MHC-restricted responses were highly sensitive to peptide modifications, unlike allo-MHC-restricted responses.
• Allo-MHC-restricted responses largely disregarded peptide modifications, indicating TCR adaptation.

Conclusions:

• TCR adaptation to diverse ligand structures, rather than molecular mimicry, explains 2C TCR crossreactivity.
• This mechanism has significant implications for T-cell receptor immunology.
• Understanding this crossreactivity is vital for addressing immunological disorders.