Impaired monocyte differentiation in children with acute lymphoblastic leukaemia: its evaluation by peroxidase activity and ultrastructure

The ability of monocyte differentiation in childhood acute lymphoblastic leukaemia (ALL) was evaluated on the basis of the ultrastructure and peroxidase (PO) activity which could show the differentiation of cultured monocytes. In the control, PO activity limited to the granules decreased time-dependently during culture for 4 d, and was closely associated with the morphological development to macrophages. In childhood ALL, monocytes showed poor changes in both PO activity and morphological features during culture for 4 d compared to the control. Therefore, we conclude that monocyte to macrophage differentiation is impaired in childhood ALL.