In vitro characteristics of childhood leukemic monoblasts

Leukemic monoblasts obtained from three children were evaluated for their in vitro physiologic characteristics. These monoblasts were alpha naphthyl acetate esterase positive, exhibited glass adherence, had IgG membrane receptors, phagocytized latex particles with subsequent nitroblue tetrazolium (NBT) reduction, and matured to macrophages in vitro, either when adherent to glass slides or in feeder layer suspensions. Employing the double layer in vitro bone marrow culture technique, leukemic marrows from these children failed to produce colonies in culture in the presence or absence of normal feeder layers. Varying the concentration of leukemic cells in the feeder layers failed to augment colony growth from normal bone marrows. Although monoblasts were observed to mature to macrophages in vitro, no increase in colony stimulating factor activity was observed with aging of the feeder layers. These studies suggest that childhood leukemic monoblasts lack the ability to produce colony stimulating activity, differing in this respect from monoblastic leukemia in adults.