BOTH EARLY AND COMMITTED HEMATOPOIETIC PROGENITORS ARE MORE FREQUENT IN PERIPHERAL-BLOOD THAN IN BONE-MARROW DURING MOBILIZATION INDUCED BYHIGH-DOSE CHEMOTHERAPY PLUS G-CSF

Haemopoietic growth factor administration following high-dose chemothe rapy markedly amplifies progenitor cell pool in the peripheral blood ( PB). Collection and reinfusion of these cells enable rapid haemopoieti c reconstitution following autograft. Less is known on engraftment pot entiality of bone marrow (BM) cells taken under analogous conditions, To investigate this tissue, PB and BM were evaluated simultaneously du ring maximal mobilization in a series of 14 patients undergoing the HD S chemotherapy programme. A significantly higher growth of committed p rogenitors was found from PB rather than from BM (663 +/- 123 v 267 +/ - 40 CFU-GM/10(5) MNC, respectively). Also, significantly more CFU-GM could be collected by a median of three leukaphereses, compared to tho se harvested from BM (158 +/- 31 v 16 +/- 4 x 10(4) CFU-GM/kg, respect ively). Most mobilized CFU-GM were phenotypically immature (CD15(-)); in addition, circulating cells included primitive progenitors, as asse ssed by LTC-IC assay, or by evaluation of non-proliferating pre-CFU-GM , selected by an anti-CD71 immunotoxin. The amount of pre-CFU-GM deter mined by both techniques was consistently higher in PB than in BM. Mor eover, a direct correlation could be established between circulating C FU-GM and primitive precursors. Thus, during optimally induced mobiliz ation, PB contains many more haemopoietic progenitors, of both committ ed and primitive stages, than does BM. Under such conditions, PB is pr obably the best source of material for graft purposes.