Peripheral Blood Stem Cell Collection Collection and Processing of Blood or Marrow Along with chemotherapy and other forms of treatment, blood and marrow transplantation may help cancer patients to live cancer free. This treatment allows stem cells, which are healthy, immature cells that do not have specific functions in the body, to become mature cells with specific functions. Stem cells can, for example, become red blood cells, platelets, or lymphocytes that fight disease and infection. During PBSC, the apheresis machine removes stem cells from either the patient’s blood or the blood of a relative or other donor and then returns the remaining blood to the body. The stem cells are processed, frozen for later use, and returned to the patient in a blood and marrow transplant. The Blood and Marrow Transplantation Program is a designated National Marrow Donor Program Transplant Center.