Graft-versus-leukemia effect and graft-versus-host disease can be differentiated by cytotoxic mechanisms in a murine model of allogeneic bone marrow transplantation.

Allogeneic bone marrow transplantation (allo-BMT) is associated with both graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effect. In the present study, we examined the contribution of cytotoxic effector mechanisms, which are mediated by tumor necrosis factor-alpha (TNF-alpha), Fas ligand (FasL), or perforin, to GVHD and GVL effect in a murine BMT model. Bone marrow cells plus spleen cells (BMS) from wild-type, FasL-defective, or perforin-deficient donors were transferred into lethally irradiated recipients in the parent (C57BL/6) to F1 (C57BL/6 x DBA/2) BMT model with or without prior inoculation of DBA/2 leukemia L1210 or P815 mast cytoma cells. The effect of anti-TNF-alpha antibody administration was also examined. Whereas the defect or blockade of each cytotoxic pathway could ameliorate lethal acute GVHD, the GVL effect was differentially affected. The wild-type BMS recipients died of acute GVHD within 50 days without residual leukemia cells. The FasL-defective BMS recipients showed 60%< survival over 80 days without acute GVHD or residual leukemia cells. Administration of anti-TNF-alpha antibody resulted in early leukemia relapse and the recipients died within 25 days with massive leukemia infiltration in the liver. The perforin-deficient BMS recipients died within 60 days with residual leukemia cells. These results suggest that blockade of the Fas/FasL pathway could be used for ameliorating GVHD without impairing GVL effect in allo-BMT.