Aplastic anemia: presence in human bone marrow of cells that suppress myelopoiesis.

Abstract
Bone marrow from a patient with aplastic anemia had a block in early myeloid differentiation. This block was overcome in vitro by elimination of marrow lymphocytes. This differentiation block was transferred in vitro to normal marrow by coculturing with the patient''s marrow. Some cases of aplastic anemia may be due to an immunologically based suppression of marrow cell differentiation rather than to a defect in stem cells or their necessary inductive environment.