The use of hydroxyurea to study the proliferative state of T-cell precursors (CFUT) in murine bone marrow

The cycle specific drug, hydroxyurea (HU), has previously been used to study the proliferative kinetics of various hemopoietic precursor cells such as granulocyte-macrophage precursors (CFUc) and multipotential stem cells (CFUs). We have investigated the kinetics of another hemopoietic precursor, a T-cell colony (CFUT). When mice are exposed to two doses of HU, separated by 7 h, CFUT are reduced to approximately 30% of the control value. Surviving cells in the bone marrow quickly replenish the population and return it to normal values 2 days after HU treatment. When fresh bone marrow cells or bone marrow cells harvested from mice exposed 24 h earlier to HU are treated in vitro with HU, CFUT activity is reduced by approximately 70%. These data indicate that CFUT is a rapidly proliferating population with a large proportion of the cells always in cell cycle.