Participants who undergo the PBSC procedure will be required to receive injections of G-CSF, a protein found normally in the body, twice a day for 4 to 8 days prior to the procedure; G-CSF has been found to help increase the amount of CD34+ cells in the blood. Once the CD34+ level is within a certain range, the PBSC procedure will begin through an IV placed in the arm or a temporary collection catheter placed under the participants' collarbone. Blood cells will be collected, with some cells separated out and the remainder of the cells infused back into the participant. The length of this procedure will vary for each participant; it will take 3 to 6 hours a day, for 1 to 4 days. Participants may require blood and/or platelet transfusions prior to and during the procedure.