Effects of the in vivo depletion of IL-12 or IFN-γ on leukemia growth. (A) SJL mice (10 mice/group) were injected IP on days −1, 0, 2, 4, and 6 with 200 μg of either anti–IL-12 MoAb or rat IgG as an isotype control. On day 0 the mice were immunized IV with irradiated 105 IL12-AML cells, and on day 7, they were challenged with live wt 105 AML cells. In vivo depletion of IL-12 during the immunization with irradiated IL12-AML cells leads to abrogation of protective immunity, and all of the mice developed lethal leukemia. Control mice were resistant to AML challenge. (B) SJL mice were injected IV with live 105IL12-AML cells on day 0 and then injected IP on days 0, 1, 2, and 7 with purified preparations (320 μg/injection) of hybridoma XGM1.2 (•). Control mice were injected with IL12-AML cells and received either no therapy (□) or the same amount of IgG1 as an isotype control (▴). Mice depleted of IFN-γ develop lethal leukemia, and both groups of control mice reject the live IL12-AML cells.
