High proliferation rates but low functionality of antigen-specific T cells in lymphopenic Rag1^−/− hosts versus low proliferation but high functionality after Treg depletion plus or minus rhIL-7. (A) Representative CFSE profiles of pmel-1 T cells transferred into hosts with B16 melanoma treated as shown and gated using CD8/Thy1.1/Vβ13.1 on day 20 in schema shown in Figure 2A. Pmel-1 T cell transferred into Rag1^−/− hosts show substantially increased numbers of cells with CFSE dilution compared with those transferred into lymphoreplete hosts. rhIL-7 increased pmel-1 proliferation in all groups. (B top panel) Absolute numbers of adoptively transferred pmel-1 T cells recovered from the TDLNs on day 20 of B16-bearing hosts treated as shown. Pmel-1 T cells were identified as per panel A. (Middle panel) Net number of cells producing IFN-γ in response to gp100 peptide, control Db126 peptide in groups, and at time points shown. (Bottom panel) Percentage of pmel-1 T cells producing IFN-γ in response to gp100 on day 20 calculated by dividing the number shown in the middle panel/total pmel-1 cells determined as per top panel. Thy-B (days 16, 20, and 27) and TXY (days 16 and 27) groups receiving αCD25 plus rhIL-7 show significantly higher IFN-γ production than Rag1^−/− groups at the same time points. Results shown represent the mean ± SEM of the groups (n = 3-8/group), and consistent results were seen in 2 separate experiments. *P < .05. **P < .005.