Vα24-JαQ-independent, CD1d-restricted recognition of α-galactosylceramide by human CD4⁺ and CD8αβ⁺ T lymphocytes

Human CD1d molecules present an unknown ligand, mimicked by the synthetic glycosphingolipid α-galactosylceramide (αGC), to a highly conserved NKT cell subset expressing an invariant TCR Vα24-JαQ paired with Vβ11 chain (Vα24+Vβ11+ invariant NK T cell (NKTinv)). The developmental pathway of Vα24+Vβ11+NKTinv is still unclear, but recent studies in mice were consistent with a TCR instructive, rather than a stochastic, model of differentiation. Using CD1d-αGC-tetramers, we demonstrate that in humans, TCR variable domains other than Vα24 and Vβ11 can mediate specific recognition of CD1d-αGC. In contrast to Vα24+Vβ11+NKTinv Vα24-/CD1d-αGC-specific T cells express either CD8αβ or CD4 molecules, but they are never CD4 CD8 double negative. We show that CD8αβ+Vα24-/CD1d-αGC-specific T cells exhibit CD8-dependent specific cytotoxicity and have lower affinity TCRs than Vα24+/CD1d-αGC-specific T cells. In conclusion, our results demonstrate that, contrary to the currently held view, recognition of CD1d-αGC complex in humans is not uniformly restricted to the Vα24-JαQ/Vβ11 NKT cell subset, but can be mediated by a diverse range of Vα and Vβ domains. The existence of a diverse repertoire of CD1d-αGC-specific T cells in humans strongly supports their Ag-driven selection.