IFN-γ promotes GVL effects against GRKO leukemia. (A-C) Lethally-irradiated B6 mice received T cell–depleted (TCD) B6 BMCs (5 × 106) plus allogeneic TCD BMCs (7.5 × 106) and CD4-dep splenocytes (8.5 × 106) from WT (WT allo-HCT; n = 8) or GKO (GKO allo-HCT; n = 8) BALB/c donors. Three groups of leukemic recipients, including those receiving TCD B6 BMCs alone (Syn-HCT+Leukemia; n = 5), TCD B6 BMCs plus WT BALB/c TCD BMCs and CD4-dep splenocytes (WT allo-HCT+Leukemia; n = 7), or TCD B6 BMCs plus GKO BALB/c TCD BMCs and CD4-dep splenocytes (GKO allo-HCT+Leukemia; n = 7), were injected with 3 × 105 GRKO leukemia cells at the time of HCT. (A) Survival. (B) Flow cytometric analysis of GFP+ cells in WBCs, spleen and BM from representative leukemic (WT allo-HCT+Leukemia; open histogram) and nonleukemic (WT allo-HCT; filled histogram) mice receiving WT CD4-dep allo-HCT. (C) WBC (left) and RBC (right) counts of leukemic (WT allo-HCT+Leukemia) versus nonleukemic (WT allo-HCT) mice receiving WT CD4-dep allo-HCT. (D-E) Lethally-irradiated CBF1 mice were reconstituted with a mixture of TCD CBF1 plus WT or GKO BALB/c mouse BMCs. Eight weeks later, these BM chimeras were administered either GRKO leukemia cells (1 × 106 or 1.5 × 106 cells per mouse for Exp I and Exp II, respectively) alone or along with DLI. DLI was performed by injection of 3.5 × 107 (Exp I) or 4.5 × 107 (Exp II) splenocytes from WT or GKO B6 mice into the WT and GKO BM chimeras, respectively. (D) Survival of WT mixed chimeras that received leukemia cells alone (WT MC/NonDLI+L; ○) or along with WT DLI (WT MC/WT DLI+L; ●), and GKO mixed chimeras that received leukemia cells alone (GKO MC/NonDLI+L; □) or along with GKO DLI (GKO MC/GKO DLI+L; ■). The survival curves of the nonleukemic chimeras (with or without DLI), which all survived long-term (see panel E and supplemental Figure 2), are not shown in the figure for the sake of clarity. (E) Gross evidence for tumor at autopsy. Results from Exp I and Exp II are combined.
