CD8 T-cells recognize peptide fragments in complex with Major Histocompatibility Complex Class I (MHCI) molecules. Recognition of peptide-MHCI (pMHCI) involves the simultaneous binding of two receptors (T-cell receptor; TCR and CD8). CD8 T-cells can be engineered to express TCRs that recognize cancer antigens and administered in vivo to achieve tumour regression. However, barriers to the widespread use of this approach still exist. One issue is that "natural" anti-cancer TCRs are often characterized by weak affinities. A strategy that could be used to overcome this is to co-express weak anti-cancer TCRs with a high affinity variant of CD8. In addition, our data suggests that the optimal pMHCI/CD8 interaction strength varies between different anti-cancer TCRs. As such, we will: 1) design and biophysically characterize a range of novel high affinity human CD8 molecules; then define their functional profile when expressed at the human T-cell surface; 2) identify the optimal high affinity CD8 pairing for a range of different anti-cancer TCRs ; 3) use combinatorial peptide libraries to examine the consequences of high affinity CD8 on T-cell crossreactivity; 4) gain a mechanistic understanding of the beneficial effects of high affinity CD8 using FRET analysis.