Abstract
The studies described compare the subpopulations of granulocyte- macrophage progenitor cells present in normal marrow with those derived from the marrow of patients with Ph1-positive chronic myelogenous leukemia (CML). The subpopulations were separated on the basis of size by velocity sedimentation and measured for their proliferative capacity by the colony formation technique. A pattern of development of colonies in the individual fractions was obtained by assaying the absolute number of colonies present at time intervals from 3 to 21 days. The number of colonies present at 3 days was taken as 100%, and the percentage of increase or decrease from this value was determined on subsequent days. In the fractions containing the most rapidly sedimenting large cells, the pattern of development of colonies derived from normal and CML marrow was similar. The CML colony-forming units in culture (CFU-C) began to show a deviation from the normal CFU-C pattern of development in the fractions containing CFU-C intermediate in size, and this deviation became progressively more pronounced in the slowest sedimenting small cell fractions. In these latter fractions, the CFU-C derived from CML marrow decreased in number at a rate similar to those arising from the more rapidly sedimenting fractions. This is in contrast to CFU-C derived from normal marrow, which increased in number in the more slowly sedimenting fractions and in the intermediate fractions, remained constant in number, or decreased at a rate slower than those arising from the more rapidly sedimenting fractions. The most likely explanation for these findings is accelerated maturation of the early small granulocyte-macrophage progenitor cells in CML so that these cells show the same limited proliferative capacity as do the later larger progenitor cells.
