COMBINED NEGATIVE AND POSITIVE SELECTION OF MOBILIZED CD34(-CELLS() BLOOD)

We tested four negative and two positive selection methods for separat ion of CD34(+) cells from mobilized blood cells, and analysed fold-enr ichment, purity and recovery of CD34(+) cells after selection procedur es. The elimination of mature CD34(-) cells was achieved by adhesion t o nylon-wool fibre (5 . 9+/-1 . 0 mean fold-enrichment and 65 . 2+/-2 . 3 mean recovery of CD34(+) cells), Standard or modified Ficoll-Hypaq ue and Percoll density gradients, as well as phagocytosis with magneti c beads, were less effective in eliminating CD34(-) cells, both purity and fold-enrichment of CD34(+) cells being lower than those obtained with separation by nylon-wool, Both positive selection methods tested, Ceprate and MiniMacs System, generated highly purified CD34(+) cell p opulations ranging from 80% to 90%, The recovery of CD34(+) cells was optimal with MiniMacs (77 . 9+/-3 . 6) and low with Ceprate (28 . 8+/- 2 . 8). Based on these results, in two large-scale experiments we comb ined nylon-wool fibre and MiniMacs System in a two-step separation pro cedure obtaining a 36 . 9+/-2 . 6 mean fold-enrichment and a 50 . 5+/- 0 . 3 mean recovery of CD34(+) cells, In this way we achieved optimal enrichment and recovery of CD34(+) cells, with a substantial saving of cost compared to either selection method alone.