Further evidence for a γ/δ T cell receptor-mediated TCT.1/CD48recognition

We have demonstrated recently that a molecule, termed TCT.1 (Blast-1/CD48), is recognized on the surface of target cells by a series of alloreactive γ/δ T cell clones generated from PBL of one healthy individual (designated E). Southern blot analyses suggested that these clones express a TCR associating a V3-JP2-C2 γ-chain and V1-D-J1-C δ-chain. In the present study, we have developed from PBL of a second normal donor (designated G) a novel series of γ/δ cloned T cell lines with similar functional activity (i.e., specific recognition of TCT.1 protein). The TCR γ- and δ-chain nucleotide sequences of both the E and G clones were determined. Results show that 1) sequences from all the clones are identical in each individual donor, 2) the δ-chains expressed by the E and the G clones are encoded by distinct gene rearrangements including V1-D-Jδ1 and V1-D-Jδ2, respectively, 3) the γ-chains expressed by the E and the G clones are encoded by the same genomic variable elements, namely Vγ3 and JP2, whereas the junctional regions are distinct. Because the latter rearrangement is very infrequent in human peripheral blood, these data support the view that TCT.1/CD48 recognition is likely to be TCR dependent.