Pluripotent hemopoietic precursors in vitro (CFUMIX) in aplastic anemia.

When human marrow cells were cultured in a medium containing alpha-medium, methylcellulose, fetal calf serum, bovine serum albumin, erythropoietin, and leucocyte-conditioned medium, mixed colonies composed of erythrocytic cells and granulocytes were formed. The clonal nature of the mixed colonies was confirmed by the linear relationship between the numbers of cells plated and the number of colonies, and the absence or presence of Y-chromatin in the mixed colonies in a co-culture experiment with male and female cells. Using the methylcellulose cell culture techniques, the pluripotent hemopoietic precursors (CFUMIX) in marrow cells from 15 patients with aplastic anemia were assayed. In the control subjects of patients with iron-deficiency anemia, lymphoadenitis, reactive leucocytosis or Hodgkin's disease, 8 X 10(5) marrow cells in 4 dishes produced 12.7 +/- 6.9 (mean +/- SD) mixed colonies. On the other hand, 8 X 10(5) marrow cells from patients with aplastic anemia formed only 2.1 +/- 5.5 (mean +/- SD) mixed colonies. Furthermore, the marrow cells from 5 patients who were repeatedly receiving transfusions contained no CFUMIX which give rise to mixed colonies. The present results provided the first direct evidence that pancytopenia in most patients with aplastic anemia results from a reduced influx into the compartment of maturing hemopoietic cells from the compartment of pluripotent hemopoietic precursors.