Phenotypic and functional characterization of the hematopoietic stem cell.

The purpose of this report is to demonstrate the phenotypic and functional characteristics of a primitive hematopoietic stem cell (HSC). We present evidence that an isolated murine HSC can repopulate the hematopoietic tissues of lethally irradiated recipient animals long term. By limiting dilution, as few as ten isolated stem cells can reconstitute mice for their lifetime. The stem cell which we have isolated does not copurify with colony forming unit-spleen or radioprotect recipients from lethal radiation. The phenotypic characterization of this rare cell, which represents 0.005% of total bone marrow, includes either the absence or very low expression of markers associated with long-term repopulating cells described by other groups. We believe this stem cell represents a very early self-renewing stem cell in the mouse.