CD34 SORTING: CD34 sorting is a means of selecting hematopoietic stem cells among heterogeneous populations of cells. The technique is based on the fact that only hematopoietic stem cells (excepting a few tumoral cells) carry the CD34 antigen. Generally this type of manipulation is performed in case of stem cell grafts or for the treatment of certain malignant hematological diseases or certain solid tumors.For autologous grafts, CD34 sorting reduces the number of tumoral cells contained in the graft and thus limits the risk of induced relapse. For allografts, CD34 sorting reduces the number of reinjected T cells, and thus the risk of severe, often life-threatening, graft-versus-host disease.Five techniques have been developed using anti-CD34 antibodies. Currently, the most widely used techniques rely on immunomagnetic methods where the antibody is bound to a magnetic bead (Baxter, Miltenyi). The Systemix technique (high-flow cytometry) can only be applied in industrial settings. In all cases, there is at least a 2 log reduction in the number of tumoral cells and T cells with a more or less pronounced loss of CD34 cells (maximal loss 50%).No randomized study has been reported for CDR-sorted autografts in comparison with non-sorted grafts, but several authors have published results showing an advantage in terms of overall survival and disease-free survival. For allografts, only a few studies have been reported to date. CD34 sorting appears to lower the rate of graft-versus-host disease if sufficient T-cell depletion is achieved.CD34 sorting is also used in other types of cell manipulations: cell expansion, gene transfer, production of dendritic cells for immunotherapy.