Vγ2Vδ2 T Cell Receptor Recognition of Prenyl Pyrophosphates Is Dependent on All CDRs

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Abstract
γδ T cells differ from αβ T cells in the Ags they recognize and their functions in immunity. Although most αβ TCRs recognize peptides presented by MHC class I or II, human γδ T cells expressing Vγ2Vδ2 TCRs recognize nonpeptide prenyl pyrophosphates. To define the molecular basis for this recognition, the effect of mutations in the TCR CDR was assessed. Mutations in all CDR loops altered recognition and cover a large footprint. Unlike murine γδ TCR recognition of the MHC class Ib T22 protein, there was no CDR3δ motif required for recognition because only one residue is required. Instead, the length and sequence of CDR3γ was key. Although a prenyl pyrophosphate-binding site was defined by Lys109 in Jγ1.2 and Arg51 in CDR2δ, the area outlined by critical mutations is much larger. These results show that prenyl pyrophosphate recognition is primarily by germline-encoded regions of the γδ TCR, allowing a high proportion of Vγ2Vδ2 TCRs to respond. This underscores its parallels to innate immune receptors. Our results also provide strong evidence for the existence of an Ag-presenting molecule for prenyl pyrophosphates.

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