Determinant spreading is evident in T-cell–replete hosts receiving adoptive immunotherapy with Treg depletion and rhIL-7 but is not evident in lymphopenic Rag1^−/− adoptive immunotherapy recipients. Mean net number of splenocytes from treated groups producing IFN-γ in response to Trp1 (top panels) and Trp2 (bottom panels) are shown at time points according to schema in Figure 2A. *P < .05, **P < .005, results in tumor plus pmel-1 plus αCD25 plus IL-7 compared with the same time point in Rag1^−/− recipients of adoptive immunotherapy.