A comparative study of CD34(+) cells, CD34(+) subsets, colony forming cells and cobblestone area forming cells in cord blood and bone marrow allografts

hematopoietic progenitor cells (HPCs) for allogeneic transplantation. We ha ve developed a new efficient protocol for CB collection. Using this method an average of 17.7 x 10(8) [range (6.8-29.6) x 10(8), n = 13] total nucleat ed cells (TNCs) were harvested. Based on recent Eurocord data, which have s hown safe engraftment using a threshold dose of 0.37 x 10(8) CB TNCs/kg bod y weight (BW), we calculated that six out of thirteen CB grafts collected b y this method were sufficient to engraft adults. The CB derived CD34(+) pop ulation contained two-fold higher numbers of committed HPCs (CFU-GM, BFU-E) and six-fold higher numbers of pluripotent HPCs [CD34(+)/CD38(-) cells, wk 5 and wk 8 cobblestone area forming cells (CAFCs)] than the CD34(+) popula tion of BM. Extrapolation revealed that BM grafts providing the threshold d ose for allogeneic transplantation of 2 x 10(8) TNCs/kg BW contained nearly 3 times more pluripotent HPCs than CB grafts providing the Eurocord thresh old dose. The assessment of CD34(+)/CD38(-) cell numbers in CB grafts was h ighly reproducible and correlated well with the in vitro performance of plu ripotent HPCs, i.e. numbers of CAFCs. We conclude that CB grafts providing high numbers of TNCs have the potential to engraft adults and that the enum eration of pluripotent HPCs by flow cytometry may be a useful tool to defin e the ultimate threshold dose for CB transplantation.