The host response to type I IFN after Cy conditioning is required for enhancing adoptive immunotherapy. Following the same experimental protocol as shown in Figure 2, we treated tumor-bearing wild-type mice or IFN-α/βRKO mice with or without Cy 1 day before adoptive transfer of Tg CD4⁺ T cells. At 7 days after T-cell transfer, donor cell division status was examined by FACS (A). Numbers in each plot represent the percentage of each individual subset in the donor population. (B) Enumerated number of divided donor cells in spleen (total splenocyte count × percent CFSE_low donor cells in spleen). Data are shown as mean ± SD. Data shown are pooled from 2 independent experiments with 5 mice per group.