Engineered T-cell receptor tetramers bind MHC-peptide complexes with high affinity

In this study we extend tetramerization technology to T-cell receptors (TCRs). We identified TCR ab pairs in the absence of accessory molecules, ensuring isolation of high-affinity TCRs that maintain stable binding characteristics after tetramerization. Subtle changes in cognate peptide levels bound to the class I molecule were accurately reflected by parallel changes in the mean fluorescence intensity of cells that bound TCR tetramers, allowing us to accurately assess the binding affinity of a panel of peptides to major histocompatibility complex (MHC) class I. Using a TCR tetramer specific for the Mamu-A*01 allele, we identified animals expressing this restricting class I allele from a large cohort of outbred rhesus macaques. TCR tetramers should facilitate analysis of the MHC-peptide interface and, more generally, the design of immunotherapeutics and vaccines. Detailed biochemical studies have established that TCR/MHC-peptide complex interactions are typically weak (KD values E 0.1–90 mM) 1 . Current evidence suggests that fast off-rates and serial engagement of MHC-peptide and TCR complexes may be crucial for T-cell activation 1,2 . Tetramerization of MHC class I molecules was a major milestone in quantifying antigen-specific T cells 3 , as multimerization resulted in higher binding affinity 1 . Tetramerized MHC class I and