A leukapheresis procedure that collects hematopoietic progenitor cells (HPCs) from peripheral blood following mobilization from the bone marrow. PBSC collection has largely replaced bone marrow harvest as the primary source of stem cells for autologous and allogeneic transplantation.
Granulocyte colony-stimulating factor stimulates the bone marrow to produce and release hematopoietic progenitor cells into the peripheral blood. Standard dosing is 10 µg/kg/day subcutaneously for 4–5 days before collection begins.
Chemotherapy is administered first (typically cyclophosphamide or disease-specific regimens), followed by G-CSF during the recovery phase. The rebound hematopoiesis after chemotherapy-induced myelosuppression produces a surge of CD34+ cells in peripheral blood.
Plerixafor is a CXCR4 antagonist that blocks the interaction between stromal cell-derived factor-1 (SDF-1) and CXCR4 on hematopoietic progenitor cells, rapidly releasing them from the bone marrow niche into the bloodstream. Used for poor mobilizers or as rescue mobilization.
On the day of collection, a peripheral blood CD34+ count is measured to confirm adequate mobilization. A CD34+ count of at least 10–20 cells/µL in peripheral blood is generally required to proceed with collection; lower counts predict poor yield and may prompt plerixafor rescue or delay.
The collection uses a large-volume leukapheresis protocol, typically processing 3–5 times the patient's total blood volume over 4–6 hours. The apheresis instrument separates the mononuclear cell fraction (which contains the CD34+ progenitors) from red blood cells, granulocytes, and platelets. The collected product is enriched with CD34+ cells and may be further processed by the cell therapy laboratory.
The collected cells are tested for CD34+ cell count, viability, and sterility, then either used fresh or cryopreserved in DMSO-containing media for future use. Most autologous collections are cryopreserved until the patient has completed conditioning chemotherapy.
CD34+ Cell Targets: The minimum dose for reliable engraftment in autologous transplantation is 2×10⁶ CD34+ cells/kg. An optimal dose of ≥5×10⁶ CD34+ cells/kg is associated with faster neutrophil and platelet engraftment and better long-term outcomes. For allogeneic transplants, targets vary by conditioning regimen and donor type.
Splenic Rupture Risk (Allogeneic Donors): G-CSF causes splenomegaly in healthy donors. Rare but life-threatening splenic rupture has been reported. Donors should be counseled to report sudden severe left-sided abdominal pain immediately and avoid contact sports during mobilization.