In 2000, Cobaleda et al. transplanted Philadelphia chromosome-positive (Ph+) ALL cells into non-obese diabetic/severe combined (NOD/SCID) mice and found that only the CD34+CD38− fraction could give rise to ALL [10]; the CD34+CD38+ and CD34− fractions contained no cells with this capability. The gene discussed is CD38; the disease is acute lymphoblastic leukemia.