Isolation of the germ cell–enriched fraction and the leukemic fraction from leukemic mice. (A and B) Flow cytometric analysis of the G1 fraction of germ cells from C1498-inoculated mice. The H-2K^b/H-2D^b– and CD45^– fraction composes the germ cell–enriched fraction (G2), and the H-2K^b/H-2D^b+ and CD45⁺ fraction composes the leukemic cell fraction (G3). Each fraction (G2 and G3) was isolated by FACS. (C) Survival after intraperitoneal injection of cell fractions sorted by FACS. All mice injected with the germ cell–enriched fraction (G2) survived without onset of leukemia for 300 days (n = 12) whereas all mice injected with the leukemic cell fraction (G3) developed terminal signs of leukemia within 40 days (n = 12).