HUMAN HEMATOPOIETIC PRECURSORS IN LONG-TERM CULTURE - SINGLE CD34+ CELLS THAT LACK DETECTABLE T-CELL, B-CELL, AND MYELOID CELL ANTIGENS PRODUCE MULTIPLE COLONY-FORMING CELLS WHEN CULTURED WITH MARROW STROMAL CELLS

CD34+ human marrow cells not expressing T cell-, B cell-, and myeloid cell-associated antigens (TBM−) were cloned by two-color cell sorting into culture wells containing irradiated marrow stromal cells. After 4 wk of culture, 3.7 t 2.1% of these cells generated colony-forming cells (CFC), with each of these cells generating 6.3 ± 5.3 CFC. This was not due to the 0.5 ± 0.5% CFC present in the purified CD34+ TBM- cells, as <1% of CFC persist in these cultures. This is the first demonstration that single immature precursor cells in human long-term cultures generate multiple CFC progeny. The immature nature of these clonable CD34+ TBMprecursors suggests their candidate status as human hematopoietic stem cells. © 1990, Rockefeller University Press., All rights reserved.