Abstract
Bone marrow cells from 62 children with acute leukemia were cultured by the double‐layer agar technique. In this system, granulocytic progenitor cells will form colonies (colony forming units or CFU) of mature granulocytes in the overlayer when stimulated by factors (colony stimulating activity or CSA) produced by peripheral blood cells of normal individuals in the underlayer. It was observed that marrow cell cultures from children with acute lymphoblastic leukemia (ALL) in relapse had substantially decreased numbers of CFU when compared to normal marrow cells. Marrow cell cultures from three children with acute myelogenous leukemia (AML) had normal numbers of CFU at the time of diagnosis. After inducing a remission with chemotherapy in children with ALL, an increase in the number of CFU in their marrow cultures was observed. When peripheral blood cells from children with acute leukemia in relapse were used in the underlayer they did not adequately support the growth of normal CFU. It may be concluded that the defect in granulopoiesis observed in ALL may be due to a decrease in CFU as well as decreased production of CSA by their marrow cells.