Molecular coordination of αβ T-cell receptors and coreceptors CD8 and CD4 in their recognition of peptide-MHC ligands

The interaction of the αβ T-cell receptor (TCR) with its ligand, peptide-MHC (pMHC), is enhanced by the recognition of the coreceptor CD8 or CD4 to the same pMHC in the immunological synapse. In the past few years, the coordination of these interactions at the molecular level has been revealed by analysis of their complex crystal structures and binding dynamics. Here we discuss the interactions of pMHC with the TCR and coreceptor CD8 or CD4 on the surfaces of αβ T cells and antigen presenting cells, and the implications for TCR signalling and the T-cell repertoire.