Circulating Granulocytic and Erythroid Progenitor Cells in Chronic Granulocytic Leukaemia

S ummary . We used a standard methyl cellulose method to assay erythroid progenitor cells in the blood of 35 patients with untreated CGL and of 18 normal controls. In 28 patients we simultaneously assayed granulocyte/nionocyte committed progenitor cells (CFU-c) by an agar method. Circulating erythroid burst-forming units (HFU-e) in CGL wcre increased above normal by a factor of about 180; CFU-c were increascd by a factor of about 9000. Both BFU-e and CFU-c numbers were linearly related to the total leucocyte count in individual patients but not to numbers of circulating blast cells. There was a positive correlation in individual patients between CFU-c and BFU-e numbers. Circulating BFU-e and erythroid colony-forming cells (CFU-e) were unable to proliferate in vitro in the absence of erythropoietin. We conclude that erythroid progenitor cells are involved in the'clonal expansion'that characterizes CGL, but apparently to a lesser extent than are granulocyte/monocyte progenitor cells.