CD34 positive selection as prophylaxis against graft versus host disease in allogeneic peripheral blood stem cell transplantation.

We report our experience of CD34 positive selection as a means of graft T-cell depletion (TCD) in 14 consecutive HLA-identical Peripheral blood stem cells (PBSC) allografts as prophylaxis against graft versus host disease (GVHDp). CD34 positive selection was performed by immunomagnetic separation achieving a median CD34 and T-cell dose of 4.17 (range 1.4-8.50) x 10(6)/kg and 1.89 (range 0.92-13.18) x 10(4)/kg, respectively, in the graft. This represents 4-log depletion of T-cells. The median time to achieve a neutrophil count of 0.5 x 10(9)/l was 15 days and to achieve a platelet count of 50 x 10(9)/l was 20 days. Only four patients developed acute GVHD at a median of 41 days but this was exclusively mild grade I cutaneous disease and settled with oral steroids. Four patients, all of whom had AML, relapsed or progressed after transplant at a median of 161 (range 109-311) days. One of these had been transplanted in early relapse (9% blasts) whilst another was in second remission. The remaining 10 patients are alive and well. The median progression free survival for the whole population is 69% at 686 days. We conclude that CD34 positive selection by immunomagnetic separation in HLA-identical PBSC allografting achieves significant TCD with clinically trivial acute GVHD, prompt engraftment and an acceptable disease relapse risk.