 The Tcra/Tcrd locus undergoes V-D?-J? rearrangement in CD4(-)CD8(-) thymocytes to form the TCR? chain of the ?? TCR and V-J? rearrangement in CD4(+)CD8(+) thymocytes to form the TCR?-chain of the ?? TCR.     ///    "Our results demonstrate that usage of TRAV15/DV6 family V gene segments for Tcrd recombination in double-negative thymocytes is regulated, at least in part, by intrinsic features of TRAV15/DV6 promoters, and argue that Tcra/Tcrd locus V? gene segments are defined by their local chromatin accessibility in CD4(-)CD8(-) thymocytes. "