FRESH PERIPHERAL-BLOOD MONONUCLEAR CELL PREPARATIONS ARE A BETTER STARTING MATERIAL THAN BONE-MARROW AFTER CRYOPRESERVATION FOR IMMUNOMAGNETIC HARVESTING OF CD34(-CELLS() HEMATOPOIETIC)

Immunomagnetic separation using anti-CD34 monoclonal antibodies and pa ramagnetic microspheres has been used to enrich hematopoietic stem cel ls from human bone marrow, whole cord blood, or mobilized peripheral b lood mononuclear cell collections. This method has been reported to ac hieve high separation purity of CD34+ cells in small scale experiments with fresh material. The aim of the present study was to compare the efficacy of the CD34+ cell selection technique, when thawed bone marro w or fresh peripheral blood mononuclear cells were enriched. Starting with thawed bone marrow containing 2.9% CD34+ cells the final product purity was 67.7% with a 6% CD34+ cell yield (enrichment factor 25.7), and a 85-fold CFU-GM enrichment. Using fresh mobilized peripheral bloo d mononuclear cells the released cells contained 77.6% CD34+ cells wit h a 47% yield (enrichment 86.5-fold), and a 46-fold CFU-GM enrichment. These results indicate that CD34+ cells can be selected from cryopres erved bone marrow using immunomagnetic procedures. However, fresh leuk apheresis products seem to be a much better material for a positive im munomagnetic stem cell selection technique in terms of purity, yield a nd enrichment.