DIFFERENT EXPRESSION OF ADHESION MOLECULES ON MYELOID AND B-LYMPHOID CD34(-MARROW() PROGENITORS IN NORMAL BONE)

The expression of adhesion molecules was studied on B lymphoid and mye loid CD34(+) precursors in normal bone marrow. Bone marrow aspirates w ere labelled in a double fluorescence procedure with the CD34 monoclon al antibody 43A1 and with antibodies directed against maturation and d ifferentiation antigens and adhesion molecules. Three clusters of CD34 (+) cells could be distinguished by their light scatter characteristic s in flow cytometry The population with the lowest forward scatter con tained B-lymphoid precursors while the two others showed phenotypic ch aracteristics of, respectively, early and late myeloid precursors. Nea rly all CD34(+) cells in the 3 subpopulations expressed VLA-4, VLA-5, LFA-3 and H-CAM. B-lymphoid progenitors showed a higher density of VLA -4 and VLA-5 than the myeloid progenitors. Myeloid precursors, and par ticularly the late subset, expressed more HCAM than the B-lymphoid pro genitors. The majority of the CD34(+) cells also expressed LFA-1 and L -selectin. Higher numbers of positive cells were found in the myeloid subset. The early myeloid subset showed the highest positivity for L-s electin. We conclude that B lymphoid and early and late myeloid CD34() precursors in normal bone marrow show a different profile of adhesio n molecules. These profiles could reflect a higher tendency of the mye loid CD34(+) precursors to circulate.