Primitive progenitor cells in the blood of patients with chronic granulocytic leukemia.

We measured the number of blast colony-forming cells (Bl-CFC) in the blood of 11 patients with untreated chronic granulocytic leukemia (CGL). The culture system used detects three types of Bl-CFC (Types I, II and III) in normal marrow, of which Bl-CFC (I) are the most primitive and might represent the putative hemopoietic stem cell. The mean numbers of Bl-CFC (I) in CGL blood, normal bone marrow and normal blood were 134 +/- 29 (+/- SEM), 127 +/- 21 and 1.5 +/- 0 respectively per 1 X 10(6) mononuclear cells. These findings are consistent with the concept that CGL is due to a primary increase in stem cell numbers with secondary increases in committed progenitor and leukocyte numbers.