Interplay between TCR affinity and necessity of coreceptor ligation: high-affinity peptide-MHC/TCR interaction overcomes lack of CD8 engagement.

CD8 engagement is believed to be a critical event in the activation of naive T cells. In this communication, we address the effects of peptide-MHC (pMHC)/TCR affinity on the necessity of CD8 engagement in T cell activation of primary naive cells. Using two peptides with different measured avidities for the same pMHC-TCR complex, we compared biochemical affinity of pMHC/TCR and the cell surface binding avidity of pMHC/TCR with and without CD8 engagement.

A correlation between TCR Valpha docking on MHC and CD8 dependence: implications for T cell selection.

T cell receptors (TCR) adopt a similar orientation when binding with major histocompatibility complex (MHC) molecules, yet the biological mechanism that generates this similar TCR orientation remains obscure. We show here the cocrystallographic structure of a mouse TCR bound to a human MHC molecule not seen by the TCR during thymic development. The orientation of this xenoreactive murine TCR atop human MHC deviates from the typical orientation more than any previously determined TCR/MHC structure.

High affinity xenoreactive TCR:MHC interaction recruits CD8 in absence of binding to MHC.

The TCR from a xenoreactive murine cytotoxic T lymphocyte clone, AHIII 12.2, recognizes murine H-2D(b) complexed with peptide p1058 (FAPGFFPYL) as well as human HLA-A2.1 complexed with human self-peptide p1049 (ALWGFFPVL).