Absence of RORγt/T-bet preserves CTL function after BMT. (A) Splenocytes from recipients given WT, RORγt^−/−, T-bet^−/−, and RORγt^−/−/T-bet^−/− T cells were harvested 2 weeks after BMT. Equal numbers of donor splenocytes were set up in a conventional 4-hour ³H-release assay with p815 cells as a target cell, as described in “Methods.” EL-4 cells were used as a negative control, but no killing activity was observed (data not shown). Data are presented as means ± SEM (from n = 4/group). (B) Granzyme B expression of donor T cells is shown gated in H-2K^b+Ly5.1^-CD8⁺ T cells. (C) Granzyme B expression is shown on gated H-2K^b+Ly5.1⁻CD8⁺ T cells from 3 mice.