Force-dependent transition in the T-cell receptor β-subunit allosterically regulates peptide discrimination and pMHC bond lifetime

The αβ T-cell receptor (TCR) on mammalian T lymphocytes recognizes intracellular pathogens to afford protective immunity. Detection of various foreign peptides bound to MHC molecules as TCR ligands occurs during immune surveillance where mechanical forces are generated through cell movement. Using single-molecule optical tweezer assays, we show with isolated and complete receptors on single T cells that both sensitivity and specificity of the biological T-lymphocyte response is dependent upon force-based interactions. Our work demonstrates a catch-and-release αβTCR structural conversion correlating with ligand potency wherein a strongly binding/compact state transitions to a weakly binding/extended state. An allosteric mechanism controls bond strength and lifetime, supporting a model in which quaternary αβTCR subunit associations regulate TCR recognition under load.