IFNG and leukemia: Consistent with the in vitro data, ELISA assays using serum derived from mice engrafted with either MC or KO#7 cells (N = 4) showed a significant increase in IFN-γ levels in the mice engrafted with MC cells compared with mice engrafted with KO#7 cells (Fig. 6D), and IFN-γ produced by the leukemia cells contributes 60–80% of total IFN-γ in the serum.