In the present study, we demonstrate that resting and rIL-2-activated NK cells had no inhibitory effects on peripheral blood-derived hematopoietic progenitor (HP) cells. Peripheral blood HP cells were similar to bone marrow progenitors in phenotype and clonogenic colony formation capabilities. Peripheral blood HP cells could be cocultured in vitro with rIL-2-activated autologous NK cells for 3 d without adverse effects on the HP cells. Acute myelogenous leukemia patients in stable remission were shown to have normal percentages of NK cells and elevated percentages of peripheral blood HP cells. NK cells from most of these patients could be activated with rIL-2 to lyse fresh uncultured tumor cells as well as autologous leukemia cells without effecting the peripheral blood HP cells. These results suggest that rIL-2-activated NK cells may be used to purge peripheral blood HP cell preparations of residual tumor cells before hematopoietic reconstitution.

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