B-ALL cells developed in MLL-AF9-HSC-grafted HIS mice are transplantable in immunodeficient mice and in HIS mice with an established autologous human immune system (i.e., HIS mice made with human Thy/HSC from the same fetus from which CD34+ cells were used to develop the B-ALL) (38). This evidence concerns the gene KMT2A and acute lymphoblastic leukemia.