BCR/ABL-negative clonogenic hematopoietic cells do not accumulate in the plastic-adherent fraction of peripheral blood mononuclear cells from patients with chronic myeloid leukemia in stable chronic phase

PBMNC from patients with CML and healthy control persons were separated int o plastic-adherent and nonadherent cell fractions. A colony assay in semiso lid medium was used to estimate the number and lineage commitment of CFC in each of the fractions. The (CML blood-derived colonies were isolated and a nalyzed by FISH for BCR/ABL sequences. Thus, we were able to test the hypot hesis whether a selective enrichment is possible of normal progenitor cells in the blood of CML patients in stable chronic phase after HU and/or IFN, Although the number of leukocytes differed considerably between patients at diagnosis and in stable chronic phase, the proportion of adherent and nona dherent cells was about the same in all preparations tested. There were als o only minor differences of adherence between MNC of CML and normal origin. Furthermore, BCR/ABL-positive and negative colonies were equally distribut ed among unseparated, adherent, and nonadherent PBMNC fractions. In conclus ion, an accumulation of BCR/ABL-negative CFC was not found in any of the PB MNC fractions. CFC from PBMNC of the same lineage commitment were simultane ously present in plastic-adherent and nonadherent cell fractions, indicatin g that their surface charges might be different and, on the other hand, tha t different lineage commitment precursors can be present in either of the f ractions irrespective of CML or blood origin.