Heterogeneity of human colony-forming cells (CFUc) with respect to their sensitivity to chloramphenicol

Human granulocyte-macrophage progenitor cells (CFUc) fractionated by velocity sedimentation at unit gravity exhibit heterogeneity with respect to inhibition by the drug chloramphenicol (CAP). An inverse correlation is observed between sedimentation velocity and sensitivity to CAP, e.g., increasing sensitivity with decreasing velocity. This heterogeneity is not a result of protection by endogenously produced colony stimulating factor since the same result obtains after removal of adherent cell populations. This heterogeneity in CFUc sensitivity to CAP may be a determining factor in the variability of bone marrow suppression by the drug.