Bone marrow. Container of bone marrow aspirate. Genetically-compatible marrow is sucked up through large bore needles from punctures made into the iliac crests - the ridges of bone at top and back of the pelvis - of the donor. Harvested marrow is filtered and prepared for infusion into the recipient's bloodstream. The recipient is given pretransplant conditioning with chemotherapy or whole body irradiation. Such conditioning aims to destroy active leukaemia cells and disable the recipient immune system, thus preventing rejection of the grafted marrow.