Characterization of a new functional TCR J delta segment in humans. Evidence for a marked conservation of J delta sequences between humans, mice, and sheep.

Through analysis of TCR delta-chain cDNA derived from human gamma delta T cell clones and polyclonal gamma delta T cell lines, we isolated a novel functional J delta gene segment (termed J delta 4) whose genomic fragment has been mapped within the TCR-delta locus between J delta 2 and J delta 1. Frequency of J delta 4 use was estimated among adult gamma delta PBL by using V delta 1, V delta 2, and V delta 5 genes. In all cases, this new J element was used at a low, albeit significant frequency, close to that of J delta 2. Finally, like human J delta 1 and J delta 2, which show a high degree of homology with their counterparts in the mouse and sheep, but unlike other J gamma, J beta, or J alpha elements, J delta 4 turned out to be highly homologous to a recently described ovine J delta. These results suggest the existence of strong selective pressures, possibly linked to an Ag-driven process, leading to specific conservation of J delta sequences among these three species.