Collection of Peripheral Blood Stem Cells

Background: - Many treatments for immune system disorders involve the use of stem cells that have been collected from blood marrow. To obtain these stem cells without surgery, individuals receive granulocyte colony-stimulating factor (G-CSF) to encourage the production of stem cells that can be collected through blood donations. However, not all patients or normal donors respond to G-CSF alone. - Plerixafor, recently approved by the Food and Drug Administration, is different from G-CSF but also allows stem cells to be collected from donated blood. However, more research is needed on the quality and viability of the stem cells collected after using both G-CSF and plerixafor. Objectives: - To collect and study the blood cells produced after treatment with G-CSF and plerixafor in healthy volunteers. Eligibility: - Healthy volunteers between 18 and 65 years of age who are eligible to donate blood. Design: - Participants will be screened with a medical history, physical examination, and initial blood tests. - At the start of the study cycle, participants will receive daily morning injections of G-CSF for 5 days. These may be given at the clinical center or by the participant after teaching, depending on the participant s preference. - On the morning of Day 4, participants will visit the clinical center to provide a blood sample after the injection. On the evening of Day 4, participants will receive an injection of plerixafor. - Participants will have the final injection of G-CSF on the morning of Day 5, and will provide another blood sample. - On Day 5, participants will have apheresis to separate the stem cells from the rest of the blood. The apheresis may take up to 5 hours to complete. - The study will end after a follow-up phone call 7 to 14 days after the apheresis procedure.