Crucial role of TCR gamma chain junctional region in prenyl pyrophosphate antigen recognition by gamma delta T cells.

Human gamma delta T cells recognize prenyl pyrophosphate Ags and their analogues in a V gamma 2V delta 2 TCR-dependent manner. Few data are available regarding the TCR structural requirements for recognition of such prenyl pyrophosphate Ags by gamma delta T cells. Presently, we made chain pair switch, chimeric, and site mutant gamma delta TCRs and transfected them into TCR- mutant Jurkat T cells to examine the effects of changing the TCR gamma junctional region sequences on reactivity to prenyl pyrophosphate Ags. Substitution of the TCR gamma junctional region (N and J) sequences from an Ag-reactive TCR with TCR gamma junctional region sequences from an Ag-nonreactive TCR abrogated reactivity to the prenyl pyrophosphate Ag isopentenyl pyrophosphate and to its synthetic analogue ethyl pyrophosphate but not to a mycobacterial supernatant containing a mixture of prenyl pyrophosphate Ags. Substitution of only the TCR gamma N nucleotide region with that from this Ag-nonreactive TCR destroyed reactivity to isopentenyl pyrophosphate and to the mycobacterial supernatant. Substitution of the entire V delta 2 chain from the Ag-reactive TCR with a V delta 1 chain from an Ag-nonreactive TCR yielded a prenyl pyrophosphate Ag-nonreactive TCR. Thus, using TCR mutagenesis and TCR transfectants, we show that gamma delta TCR reactivity to prenyl pyrophosphate Ags is dependent upon the junctional region of the TCR gamma chain and upon pairing of V gamma 2 and V delta 2 TCR chains. These structural requirements of TCR gamma delta recognition of prenyl pyrophosphates distinguish this reactivity from that of protein superantigens and emphasize the importance of the TCR gamma CDR3 loop and adjacent residues.