G-CSF-MOBILIZED PERIPHERAL-BLOOD PROGENITOR CELLS FOR ALLOGENEIC TRANSPLANTATION - COMPARISON OF T-CELL DEPLETION STRATEGIES USING DIFFERENT CD34(-1() SELECTION SYSTEMS OR CAMPATH)

Allogeneic transplantation of granulocyte colony-stimulating factor (G -CSF)-mobilized peripheral blood progenitor cells (PBPC) appears to be an attractive alternative to allogeneic bone marrow transplantation ( BMT). However, because vast amounts of potentially graft-vs.-host-reac tive T cells are transfused with PBPC grafts, the use of PBPC in the a llogeneic setting may be associated with an increased incidence or sev erity of graft-vs.-host disease (GVHD). To evaluate strategies for pre vention of GVHD after PBPC allografting, we have studied T cell deplet ion (TCD) of G-CSF-mobilized PBPC samples harvested from six healthy d onors and from five patients scheduled for autologous PBPC transplanta tion. Three approaches (CAMPATH-1 plus autologous complement [C], immu nomagnetic CD34(+) cell selection, and biotin-avidin-mediated CD34(+) cell selection) were compared. TCD of PBPC samples with the monoclonal antibody (MAb) CAMPATH-1 plus autologous C resulted in a median elimi nation of 2.16 log CD3(+) T cells, whereas 39% of CD56(+) natural kill er (NK) cells and 56% of CD34(+) progenitor cells were recovered. TCD by CD34(+) cell selection with the Isolex (Baxter, Munich, Germany) or Ceprate (CellPro, Bothell, WA) devices achieved median depletions (Is olex vs. Ceprate) of 4.04 vs. 3.12 log T cells and >5 vs. 3.27 log NK cells while allowing the recovery of 36 vs. 27% CD34(+) cells. The med ian purity of CD34(+) cells in the final product was 1.7 (CAMPtlTH-1), 94 (Isolex), and 65% (Ceprate). We conclude that all methods tested e ffectively deplete T cells from PBPC preparations harvested from healt hy donors. Whereas immunomagnetic CD34(+) selection is most effective in terms of elimination of T cells, the less intensive T and NK cell d epletions achieved with CAMPATH-1 might be advantageous with regard to retaining engraftment potential and graft-vs.-leukemia (GVL) activity of PBPC allografts.