Class II-restricted T cell receptor engineered in vitro for higher affinity retains peptide specificity and function

Area of Science:

• Immunology
• Molecular Biology

Background:

• T cell receptor (TCR) affinity is crucial for T cell specificity and function.
• It is hypothesized that low TCR affinities are maintained in vivo to prevent reduced functional capacity or self-reactivity.

Purpose of the Study:

• To investigate the functional consequences of high-affinity TCRs.
• To explore whether increased TCR affinity impacts T cell activation and specificity.

Main Methods:

• Engineering of higher-affinity TCR mutants using a yeast display system.
• Selection and characterization of TCR mutants with defined affinity (K(D) down to 25 nM).
• Functional analysis of T cells transfected with wild-type and mutant TCRs.

Main Results:

• Engineered TCRs exhibited increased affinity due to faster on-rates and slower off-rates.
• High-affinity TCRs did not impair T cell activation or specificity for the cognate peptide.
• An antagonist peptide for wild-type TCR became an agonist with higher-affinity TCRs.

Conclusions:

• T cells expressing high-affinity class II TCRs are functional.
• There exists an affinity threshold beyond which further increases do not significantly enhance T cell activation.
• High-affinity TCRs can alter the agonist/antagonist profile of peptide ligands.