TR lymphocytes display higher alloreactivity than SE and CE T cells. TR, SE, CE T cells, and control mock-transduced (mock-trd) cells were separately plated in mixed lymphocyte reactions with irradiated allogeneic PBMCs. After 2 cycles of stimulation (S1, 10 days; S2, 7 days), effector cells were tested against a PHA cell line obtained from the same allogeneic targets and against the autologous cells in a IFN-γ Elispot (A) and in a ⁵¹Cr release (B) assay (shown is the E/T ratio of 50:1). No responses were observed against the autologous cells (not shown). Simultaneously, NY-ESO-1–redirected and mock-transduced T cells, stimulated as described previously, were tested against the HLA-A2^pos T2 cell line pulsed with the NY-ESO-1_157-165 peptide (C-D). Mean and SEM are shown. **P < .01; *P < .05, by 1-way ANOVA and Bonferroni’s multiple comparison test.