Antigen-driven T cell expansion: affinity rules

Abstract

TCR affinity and ligand off-rate have both been found to influence the degree of T cell activation by peptide-MHC. A report in this issue of Immunity finds that ligand off-rate does not correlate with antigen-specific peripheral T cell expansion. Moreover, the data point to the surprising notion that there exist TCR affinity thresholds and, once attained, T cells with higher affinity receptors have no competitive advantage.