Mobilized Human CD34+ Cells (Plerixafor only). CD34+ stem cells are multipotent and can give rise to all cell types in blood. CD34+ cells are most known for its expression on hematopoietic progenitor cells found in bone marrow and cord blood. Donors are injected with Plerixafor, which stimulates the bone marrow to produce a large number of hematopoietic and progenitor stem cells and mobilizes them into the peripheral blood stream. CD34+ cells are isolated using positive immunomagnetic cell separation procedures from a mobilized leukapheresis collection.