Phenotype and Function of Hematopoietic Stem Cells

: Using an in vivo selection technique, we can isolate individual cells that can repopulate the hematopoietic system of a lethally irradiated murine recipient. These cells rapidly acquire a CD34 phenotype in the animal. Progenitors in our long‐term chimeras are of donor type. We also have evidence that transplantation of limiting numbers (as low as a single cell) that have this long‐term repopulating ability (LTRA) can self‐renew. This is demonstrated by serial transplantation of marrow from engrafted recipients 11 months post transplant into new hosts for four additional months.