Differential recognition of CD1d-α-galactosyl ceramide by the Vβ8.2 and Vβ7 semi-invariant NKT T-cell receptors

摘要

CD1d presents lipid-based antigens (Ag) that are recognised by the semi-invariant T cell receptor (TCR) expressed on Natural Killer T (NKT) cells. While the TCR α-chain is typically invariant, the TCR β-chain expression is more diverse, particularly in mice where at least three different Vβ chains are commonly expressed. We report the structures of Vα14-Vβ8.2 and Vα14-Vβ7 NKT TCRs in complex with CD1d-α-galactosylceramide (α-GalCer), as well as a 2.5 Å structure of the human NKT TCR-CD1d-α-GalCer complex. Both Vβ8.2 and Vβ7 NKT TCRs, as well as the human NKT TCR, ligated CD1d-α-GalCer in a broadly similar manner, thereby highlighting the evolutionarily-conserved nature of this interaction. However, differences within the Vβ domains of the Vβ8.2 and Vβ7 NKT TCR-CD1d complexes not only resulted in altered TCR-β-CD1d-mediated contacts, but also surprisingly modulated recognition mediated by the invariant α-chain. Mutagenesis studies revealed the differing contributions of Vβ8.2 and Vβ7 residues within the CDR2β loop in mediating contacts with CD1d. Collectively we provide a structural basis for the differential NKT TCR Vβ usage in NKT cells.