4.1.2 Isolation of CD34+ cells for the protocol The CD34+ cells to be used for research will be selected on a positive immunomagnetic selection column using an Isolex® system. A minimum of 45x106 CD34+ cells is necessary for good functioning of the system. These limiting factors oblige us to use as starting material stem cells mobilized with G-CSF. After removal of this sample for the study, the graft will have to contain a minimum of 7x106 CD34+ cells/kg body weight of the patient.