Thymidine-suicide of human granulocytic progenitor cells (CFU-C).

The quantitative and qualitative changes of human granulopoietic stem cells (CFU-C) after perturbation give a comprehensive view of their reaction pattern. The proliferative state of CFU-C may be assessed using the 3H-Thymidine (3H-TdR) technique. This technique is well established in experimental animals. In order to utilize it for the study of human CFU-C, the kinetics and the variables affecting the suicide of human CFU-C were analysed in detail. From the results, it appears that under optimal conditions considerable higher 3H-TdR concentrations (greater than or equal to 100/muCi/ml) have to be utilized than have been reported to be satisfactory in the murine system. Colony growth inhibition is S-phase-specific; if reutilization of the label occurs in vitro, it does not detectably affect colony growth. Minimum exposure of CFU-C to 3H-TdR is 20 minutes. Using these optimal suicide conditions, human marrow CFU-C can be shown to be a highly proliferating cell population.