 Study participants will be asked to interview with the research team, undergo physical exams, donate a blood sample, and receive G-CSF by injection, followed by dexamethasone orally about three weeks later. They also will be required to undergo apheresis three times, a procedure in which blood is drawn from a donor and separated into its components. Some components are retained for research analyses, such as granulocytes, and small amount of blood; the remainder is returned by transfusion to the donor. This procedure will be required of participants before they receive G-CSF, the day after they receive G-CSF, and the day after they receive dexamethasone. Gene messages mRNA will be isolated from granulocytes, and analyzed to better understand granulocyte growth and movement. 