Growth of mixed erythroid-granulocytic colonies in culture derived from bone marrow of patients with paroxysmal nocturnal hemoglobinuria without addition of exogenous stimulator.

Hematopoietic progenitor cell cultures were studied in 16 patients with paroxysmal nocturnal hemoglobinuria (PNH). Both erythroid and granulocyte-macrophage progenitors in the blood and bone marrow decreased despite hypercellular marrow. In eight out of 16 patients, mixed erythroid-granulocytic colonies were observed in the bone marrow cultures without erythropoietin and colony-stimulating factor. Removal of monocytes and T-lymphocytes before culture failed to abrogate spontaneous mixed-colony formation. Conditioned media prepared from blood and bone marrow of PNH patients could not promote the growth of mixed colonies in normal individuals. The autonomous, spontaneous mixed-colony formation in patients with PNH is an abnormality of PNH stem cells not described previously.