Circulating pluripotent haemopoietic cells in patients with myeloproliferative disorders

Summary. Peripheral blood cells of 17 patients with myeloproliferative disorders were grown in vitro to form mixed colonies (CFU-mix). CFU-mix were found in four of nine patients with chronic phase chronic myelocytic leukaemia (CML) at levels 28- to 132-fold higher than the upper limits of normal subjects. These patients also had higher than normal levels of circulating granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) progenitors. Development of blastic crisis was associated with disappearance of CFU-mix from the blood. CFU-mix was detected in the blood of three of five patients with polycythaemia vera (PV) and two patients with myelofibrosis with myeloid metaplasia (MMM) at levels slightly higher than those of normal subjects. Our results are consistent with a clonal expansion of multipotent haematopoietic precursor cells in CML and abnormal kinetics of this cell in CML, PV and MMM.