Tickling the TCR: selective T-cell functions stimulated by altered peptide ligands

Recent observations of T-cell responses following T-cell receptor (TCR) interaction with altered peptide ligands have highlighted the complexity of this signalling system. The indications are that the TCR responds to minor changes in ligand with gradations of T-cell activation and effector functions. Brian Evavold, Joanne Sloan-Lancaster and Paul Allen review these studies and present a model in which partial T-cell activation and TCR antagonism are related events in a continuum of signalling through the TCR.