FLT-3 ligand mobilizes hematopoietic primitive and committed progenitor cells into blood in mice

We investigated the effects of the administration of FLT-3 ligand (FL) on mobilization of primitive and committed progenitor cells in mice. C57bl/6J mice were injected subcutaneously with FL once a day for 5 d at doses of 20, 100 and 200 microg/kg. After the collection of peripheral blood, we determined the number of white blood cells (WBCs) with the differential counts. The formation of colony-forming cells (CFCs) in peripheral blood, bone marrow and spleen was evaluated. Although the administration of FL, 20 microg/kg, did not stimulate leukocytosis, its administration at doses of 100 and 200 microg/kg increased the number of WBC up to 1.7- and 2.4-fold, respectively. Committed progenitor cells were mobilized into the peripheral blood dose-dependently and the number of CFCs was increased up to 5.5-fold by the administration of FL at 200 microg/kg on d 5. The number of CFCs in the bone marrow increased, but not dose-dependently. The number of CFCs in the spleen also increased up to 32-fold at a dose of 200 microg/kg FL. Mobilized peripheral blood mononuclear cells were transplanted into lethally irradiated mice and the number of CFU-S (d 12) was scored. A dose-dependent mobilization of CFU-S (d 12) into peripheral blood was also observed. These observations suggest that FL can mobilize hematopoietic primitive and committed progenitor cells into the peripheral blood of mice and those cells mobilized by FL may be applicable to peripheral blood stem cell transplantation.