Granulopoiesis in childhood aplastic anemia.

The soft agar technique was employed to investigate factors involved in the regulation of granulopoiesis in ten children with aplastic anemia. Children with AA had greatly reduced numbers of granulocytic colony-forming cells in their bone marrow and in their peripheral blood when compared to "control" children. Colony-stimulating activity was decreased in five of the ten children tested. Serum from eight children with AA did not inhibit colony formation when added to normal adult bone marrow cells in culture. The defect in AA residues in the stem cell, with involvement of the CSA-producing cells in some cases. The serum of these patients does not contain an inhibitor of granulopoiesis.