Allogeneic peripheral blood stem cell transplantation following CD34⁺ enrichment by density gradient separation

GVHD is a significant cause of morbidity and mortality following allogeneic peripheral blood stem cell transplantation (AlloPBSC). CD34⁺ cell selection could reduce GVHD by negative selection of T cells. In an attempt to reduce the T cell content of alloPBSC we carried out a trial in which 11 patients with hematologic malignancies received alloPBSC from HLA-matched siblings following density gradient separation using an isotonic colloidal silica solution (BDS 60; Dendreon Corporation). Cyclosporine and methylprednisone were used for GVHD prophylaxis. The mean yield of CD34⁺ cells was 69 ± 15.6% with a purity of 2.9 ± 1.7%. The mean number of CD3⁺ cells infused was 1.0 ± 1.2 x 10⁷/kg, representing a 1.3 log depletion. A high risk of acute GVHD was observed: grade II-IV in 7/11 (64%) and grade III-IV GVHD in 5/11 (45%) patients. Nine of the 11 (82%) patients died with a median survival of 68 days. Cytokine expression in PBSC was compared pre and post processing. Interferon-gamma was detected only following density gradient separation while IL-8 expression increased 3- to 6-fold post processing. Therefore, processing with this device may augment production of pro-inflammatory cytokines.