EFFECTS OF CD34(-CELL IMMUNODEPLETION ON CORD-BLOOD HEMATOPOIETIC PROGENITORS - RELEVANCE TO STEM-CELL TRANSPLANTATION() SELECTION AND T)

Cord blood (CB) has been used recently for stem cell transplantation. We have investigated two different approaches to deplete CB samples of T cells capable of mounting graft-vs.-host disease (GVHD). The method s used were selection of CD34(+) cells using avidin-biotin columns (Ce llPro) and T cell immunodepletion with T10B9 monoclonal antibody (mAb) plus complement. Using the avidin-biotin columns, 10.3% of the origin al CD34(+) cells were recovered. Although this technique yielded a pop ulation containing 60 +/- 5.5% CD34(+) cells, about 1 log of CFU-GM pr ogenitors were lost. In contrast, after the T10B9 mAb and complement i mmunodepletion, 75 +/- 19% and 62 +/- 7% of the CD34(+) cells and CFU- GM were recovered, respectively. T cell depletion was 3.6 logs using t he CellPro columns and 2.2 logs after immunodepletion. To investigate whether cell losses following T cell depletion could be overcome by ex vivo expansion, cells were cultured in the presence of recombinant hu man interleukin-3 (rhIL-3) and recombinant human c-kit ligand (stem ce ll factor [rhSCF]) for 7 days. There were 14- and six-fold expansions in the number of progenitors recovered after CellPro and immunodepleti on, respectively. To assess the engraftment potential of expanded cell s, we used a murine transplantation model in which the presence of hum an cells was identified by the anti-CD45 mAb. Cells expanded in vitro engrafted in irradiated BNXid mice as efficiently as nonexpanded cells , suggesting that expansion did not affect their transplantability. Th is study shows that both techniques resulted in significant T cell dep letion of CB. Furthermore, in vitro expansion could overcome cell loss es sustained during the separation techniques without impairing the en graftment potential of the expanded cells.