Colony formation by primitive haemopoietic progenitors in cocultures of bone marrow cells and stromal cells.

Human bone marrow contains a class of human haemopoietic progenitor cells that adhere to cultured marrow stromal cells and form colonies of blast cells. These progenitor cells are found in the non-adherent mononuclear fraction of normal human bone marrow. They are not in active cell cycle and do not express Ia-like (HLA-DR) antigens but appear to be capable of self-renewal in vitro. These properties indicate that they should be classified as members of the primitive haemopoietic progenitor cell compartment.