IL2 and graft versus host disease: We hypothesized that due to much more effective and faster induction of anti-cancer effects inducible by mismatched IL-2 activated killer cells, elimination of malignant cells could be accomplished within a few days by non-engrafting donor lymphocytes, thus avoiding the need for prior SCT to ensure consistent rejection of mismatched donor lymphocytes after induction of cytotoxicity against the malignant cells for prevention of GVHD.