How much can a T-cell antigen receptor adapt to structurally distinct antigenic peptides?

Archive ouverte

Mazza, Catherine | Auphan-Anezin, Nathalie | Gregoire, Claude | Guimezanes, Annick | Kellenberger, Christine | Roussel, Alain | Kearney, Alice | van Der Merwe, P Anton | Schmitt-Verhulst, Anne-Marie | Malissen, Bernard

Edité par CCSD ; EMBO Press -

Binding degeneracy is thought to constitute a fundamental property of the T-cell antigen receptor (TCR), yet its structural basis is poorly understood. We determined the crystal structure of a complex involving the BM3.3 TCR and a peptide (pBM8) bound to the H-2K(bm8) major histocompatibility complex (MHC) molecule, and compared it with the structures of the BM3.3 TCR bound to H-2K(b) molecules loaded with two peptides that had a minimal level of primary sequence identity with pBM8. Our findings provide a refined structural view of the basis of BM3.3 TCR cross-reactivity and a structural explanation for the long-standing paradox that a TCR antigen-binding site can be both specific and degenerate. We also measured the thermodynamic features and biological penalties that incurred during cross-recognition. Our data illustrate the difficulty for a given TCR in adapting to distinct peptide-MHC surfaces while still maintaining affinities that result in functional in vivo responses. Therefore, when induction of protective effector T cells is used as the ultimate criteria for adaptive immunity, TCRs are probably much less degenerate than initially assumed.

• Description
• Sujet/Public
• Outil
• Outil d'anticipation
• Mémoire et thèse
• Gestion