Juvenile chronic myelogenous leukemia: surface antigen phenotyping by monoclonal antibodies and cytogenetic studies.

Cells from three children with juvenile chronic myelogenous leukemia were studied using culture in semisolid media, cytogenetic analysis, and surface staining with the monocyte-specific monoclonal antibodies 61D3 and 63D3. The percentage of bone marrow mononuclear cells that were 61D3- and 63D3-positive was markedly increased in all three patients. Bone marrow and peripheral blood mononuclear cells exhibited exceptionally bright immunofluorescence with these antibodies. The presence of monocyte-specific antigens on the surface of juvenile chronic myelogenous leukemia cells suggests that they are derived from a precursor with monocytic characteristics. A specific chromosomal abnormality (47,XY+21) was present in fresh bone marrow cells from one patient; in contrast, 50 metaphases from phytohemagglutinin-stimulated peripheral blood contained a normal karyotype. The chromosomal abnormality was also identified in myeloid colonies grown in vitro from this patient. Granulocytic elements were demonstrated in tissue sections and in cultured myeloid colonies from this child. Our data suggest that malignant transformation in juvenile chronic myelogenous leukemia involves a myeloid progenitor population capable of differentiation in vitro to cells with monocytic or granulocytic characteristics.