Differential Roles of Kinetic On- and Off-Rates in T-Cell Receptor Signal Integration Revealed with a Modified Fab'-DNA Ligand.

T cells read kinetic information from ligands binding to T-cell receptors (TCRs) to make cell fate decisions. Unique kinetic features of a modified Fab'-DNA ligand enable direct visualization multiple TCR signal coordination through a nascent LAT condensation event. We further observed positive feedback through a kinetic on-rate enhancement in the growing LAT condensate. These observations help unify several seemingly disparate aspects of TCR signaling that have been debated in the literature. Furthermore, calibration of the Fab'-DNA ligand against native agonist pMHC establishes a basis for quantitative analysis of TCR signaling in polyclonal T cell populations.