EXPANSION OF BLOOD CD34 POSITIVE CELLS - COMMITTED PRECURSORS EXPANSION DOES NOT AFFECT IMMATURE HEMATOPOIETIC PROGENITORS

CD34 positive (CD34(+)) cells contain all hematopoietic progenitors fr om stem cells to committed precursors, Therefore the transplantation o f purified bone marrow or blood CD34(+) cells is sufficient for hemato poietic recovery after a myeloablative radiochemotherapy. Using differ ent techniques, CD34(+) progenitors can be induced to undergo terminal differentiation in a stroma-free liquid culture system in the presenc e of cytokines, In the present study, we have evaluated the functional potential of CD34(+) blood progenitors after ex-vivo expansion cultur es, CD34(+) cells were isolated from 16 samples (PBSC n = 8 and Cord B lood (CB)n = 8) using either ISOLEX(TM) 50 (n = 6), CEPRATE(TM) LC CD3 4 kit (n = 6) or MICROCELLECTOR(TM) T-25 Stem Cell kit (n = 4). CD34() cells were cultured for seven days in the presence of 500 UI/ml of I L-1, 10 ng/ml of IL-3 and 10 ng/ml of SCF. We obtained an 8-fold expan sion of nucleated cells. We observed a 59-fold expansion of GMCSF resp onsive committed precursors, a 4.4-fold expansion of IL-1+IL-3+SCF+Epo responsive multilineage progenitors and a 2.2-fold expansion of the 5 -FU resistant quiescent progenitors. We did not observe any significan t difference in the amplification/expansion parameters between culture s initiated with CD34(+) cells from PBSC or CB. Our data show that cyt okine mediated ex-vivo expansion of blood CD34(+) cells can produce a large number of committed precursors without affecting the compartment of the most immature progenitors. These results suggest that cytokine -mediated amplification technology could be of great interest in the a utologous transplantation setting.