Myelo-monocytic differentiation potential of the CALLA-positive Nalm 6M1 cell line.

Nalm 6M1 cells, derived from an acute lymphoblastic leukemia of the non-T, non-B type, are known to possess characteristics of early B-lymphocytes. In order to determine whether these cells are able to differentiate along the granulocyte-monocyte pathway, they were cultured in diffusion chambers, and classified according to morphological, cytochemical and immunological criteria. On the basis of this characterization, Nalm 6M1 cells positively labeling with monoclonal anti-human granulocyte or monocyte-specific antibodies were observed in all cases. These immunological changes were accompanied by the appearance of cells positive for the naphthyl-AS-D-chloroacetate esterase reaction. However, no changes in the blast-like appearance of the cultured cells were seen. From these data, we conclude that Nalm 6M1 cells already committed to the B-cell lineage retain their capacity to develop cellular markers of the granulocyte-monocyte series.