Antigenic analysis of hematopoiesis. VI. Flow cytometric characterization of My-10-positive progenitor cells in normal human bone marrow.

We have previously shown [1] that the anti-My-10 murine monoclonal antibody detected an epitope of a 115-kDa glycoprotein expressed specifically on KG-1a leukemia cells and a small subset of normal human bone marrow cells. This My-10+ marrow cell subset was shown to contain a highly enriched population of morphologic blast cells and hematopoietic colony-forming cells [1]. In this report, My-10+ cells were characterized, by flow cytometry, as an approximately 1% subpopulation of normal human bone marrow cells. My-10+ cells were slightly larger than lymphocytes and agranular, as determined by their fluorescence-activating cell sorting (-er) (FACS) light-scattering properties. In two-color immunofluorescence experiments, My-10+ cells coexpressed the HLA-DR antigen. However, there was no detectable cellular coexpression of My-10 with either the Leu 1-5, 7, 9, 11, 15, M3, or My-18 antigens. There was an average of approximately 50,000 My-10 molecules per My-10+ marrow cell. This provides further evidence that the My-10 molecule is expressed, at relatively low levels, selectively on early human marrow cells but not on mature lymphohematopoietic cells.