Granulocytic progenitor cells in the adherent layer of human long-term bone marrow cultures.

The importance of the adherent layer in long-term mouse bone marrow cultures as a reservoir of the most primitive stem cells is known. The role of the adherent cell layer in long-term human cultures (LTC) is examined from this point of view. Confluent adherent layers developed after about 3 weeks of culture. At that time and weekly thereafter the cellularity and granulocytic-macrophage progenitor (CFU-GM) content of the adherent fraction were determined after tripsinisation. We have documented that CFU-GM were present in the adherent layer of human cultures for at least 8 weeks. These findings emphasize the importance of assessing the progenitor cell content of the adherent layer in long-term human cultures.