- Apheresis to donate white blood cells. Participants will undergo two apheresis procedures-once before receiving G-CSF and a second time immediately after finishing the 5-day course of the drug. For this procedure, whole blood is removed using a needle placed in an arm vein. The blood is circulated through a cell separator machine, where the white cells are removed and collected in a plastic bag. The rest of the blood, including the red cells, platelets, and plasma, are returned to the donor through a needle in the other arm. The procedure takes 2 to 3 hours, during which time the donor lies quietly.