Philadelphia chromosome-positive (Ph + ) hemopoietic cells precan be mobilized, presumably from the bone marrow, into the dominate in patients with chronic myeloid leukemia (CML) in blood of CML patients following chemotherapy. 9 The blood of chronic phase, but some Ph − presumably normal stem cells CML patients has also been used for autologous rescue followpersist in most patients. Ph − cells are relatively frequent, coming high-dose therapy and in some cases Ph chromosomepared to mature cell populations, in primitive hemopoietic cell negative recovery has been observed. 10 IntroductionThe results show that primitive BCR/ABL − cells circulate in the blood of chronic phase CML patients. They are enriched Chronic myeloid leukemia (CML) is characterized by a in the fraction of CD34 + cells that adhere to tissue culture reciprocal translocation between chromosomes 9 and 22 plastic and are predominantly CD33, CD38 and HLA-DR anti-(t[9;22][q34;q11]) which results in the formation of the Philagen-negative. These findings support the view that adhesion delphia (Ph) chromosome. 1 At the molecular level, the Ph to plastic is a property of very primitive normal hemopoietic chromosome involves the fusion of the BCR and ABL genes cells, [18][19][20][21][22] and have implications for the use of peripheral and the production of a p210 protein tyrosine kinase. 2,3 It is blood cells for autografting patients with CML. likely that the rearrangement of BCR and ABL is responsible for the expansion of pluripotent leukemic stem cells and the production of large numbers of committed myeloid, erythroid and megakaryocytic progeny in CML. 4 It may also be responMaterials and methods sible for the adhesive defect that characterizes primitive progenitor cells in CML. 5,6 Cells Good evidence for the persistence of normal hemopoietic stem cells in the marrow of patients with CML has been provided by the Ph chromosome-negative recovery of patients Peripheral blood cells were obtained from patients with treated with ␣-interferon 7 and Ph − hemopoiesis seen after chronic phase (CP) CML in the outpatient clinic ( Norway) according to the manufacturer's instructions.