A method described to purify pluripotent hemopoietic stem cells ( PHSC ) from adult mouse bone marrow. The method consists of three separation steps. First, bone marrow cells are centrifuged in a discontinuous metrizamide gradient and simultaneously labeled with wheat germ agglutinin-fluorescein isothiocyanate (WGA-FITC). Second, the low density cells are analyzed by a fluorescence-activated cell sorter (FACS) and the WGA-positive cells with medium forward and low perpendicular light scatter intensities are sorted. The WGA-FITC is removed from the cells by incubation with N-acetyl-D-glucosamine. Finally, the sorted cells are incubated with anti-H-2K-biotin and avidin-FITC and sorted a second time to enrich cells with high H-2K density. The sorted cells gave rise to 2 spleen colonies per 100 injected cells at 8 d and 6.6 colonies per 100 cells at 12 d after transplantation into lethally irradiated syngeneic recipients. The average enrichment factor for day 12 CFU-S (colony-forming unit/spleen) was 135 (range, 90--230; n = 15) and was similar to that for the cell type that provides radioprotection (180 +/- 70), indicating that these functional properties were copurified. Indirect evidence suggests that the spleen-seeding efficiency (f factor) of these cells is 0.10 and, therefore, the average purity of the sorted PHSC was 65% (range in 15 experiments, 35--110%). The sorted cells were all in the G1 or G0 phase of the cell cycle. They appeared to be undifferentiated blasts by morphological criteria. Electron microscopy revealed that the sorted cells consisted primarily of two cell types, possibly representing G0 and G1 cells. The FACS was used to deposit single selected cells into individual microwells of Terasaki trays. 32% of the sorted cells could be induced to form myeloid progeny in vitro. This procedure should be useful for direct studies on the regulation of hemopoietic cell differentiation.

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