CRUCIAL ROLE OF TCR-GAMMA CHAIN JUNCTIONAL REGION IN PRENYL PYROPHOSPHATE ANTIGEN RECOGNITION BY GAMMA-DELTA T-CELLS

Human mu delta T cells recognize prenyl pyrophosphate Ags and their an alogues in a V gamma 2V delta 2 TCR-dependent manner. Few data are ava ilable regarding the TCR structural requirements for recognition of su ch prenyl pyrophosphate Ags by gamma delta T cells, Presently, we made chain pair switch, chimeric, and site mutant gamma delta TCRs and tra nsfected them into TCR-mutant Jurkat T cells to examine the effects of changing the TCR gamma junctional region sequences on reactivity to p renyl pyrophosphate Ags. Substitution of the TCR gamma junctional regi on (N and J) sequences from are Ag-reactive TCR with TCR gamma junctio nal region sequences from an Ag-nonreactive TCR abrogated reactivity t o the prenyl pyrophosphate Ag isopentenyl pyrophosphate and to its syn thetic analogue ethyl pyrophosphate hut not to a mycobacterial superna tant containing a mixture of prenyl pyrophosphate Age. Substitution of only the TCR gamma N nucleotide region with that from this Ag-nonreac tive 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 TC R mutagenesis and TCR transfectants, we show that gamma delta TCR reac tivity to prenyl pyrophosphate Ags is dependent upon the junctional re gion of the TCR?I chain and upon pairing of V gamma 2 and V delta 2 TC R chains, These structural requirements of TCR gamma delta recognition of prenyl pyrophosphates distinguish this reactivity from that of pro tein superantigens and emphasize the importance of the TCR gamma CDR3 loop and adjacent residues.