[Fractionation of normal human bone marrow on albumin gradients].

Bone marrow from 52 healthy donors has been fractionated on two discontinuous albumin gradients with different osmolarities in an effort to eliminate immunocompetent cells and to isolate hemopoietic stem cells. The nutrient agar system of Robinson was utilised as an assay procedure for the detection of colony-forming cells (CFU-c) in the resulting fractions. CFU-c, early granulocytic progenitors, are consistently present in the lighter fractions. On cytochemical staining, they showed a positive reaction for enzymes bound to lysosomes. The concentration of CFU-c was in an average 7 times that of the original marrow. At best, 1 X 10(5) CFU-c could be isolated from 10 ml marrow corresponding to 2 X 10(8) buffy-coat cells. The presence of immunocompetent cells was monitored by Phytohemagglutinin (PHA)-stimulation and T-cell rosette formation. In a human marrow transplant situation it appears that a better yield of CFU-c is necessary than is afforded by albumin gradient technique.