THE PROLIFERATIVE STATE OF GRANULOCYTIC PROGENITOR CELLS IN HUMAN BLOOD AND MARROW

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Abstract
A double layer agar technique was used to investigate the proliferative state of granulocytic progenitor cells (colony forming units in culture; CFUc) in human peripheral blood and bone marrow. Sensitivity of the progenitor cells to the S-phase specific agent, hydroxyurea, was used as an index of the proportion of cells engaged in DNA synthesis. In the presence of low concentrations of colony stimulating factor (CSF) the CFUc were virtually insensitive to the drug. When cultured in the presence of increasing concentrations of CSF the proportion of CFUc apparently killed by hydroxyurea increased to a maximum of 23% for those cells in the blood and 39% for those in the marrow. CFUc which were slowly proliferating were apparently sensitive to low concentrations of CSF. CFUc which were proliferating more rapidly required high concentrations of CSF before they formed colonies in culture. A model was devised which suggests that as CFUc mature, their cell cycle time shortens and their sensitivity to CSF decreases.