Differential expression of CD164 epitopes on CD34⁺ bone marrow and cord blood cells from normal donors. Mononuclear cells were stained with CD164-specific MoAbs 103B2/9E10, 105A5, 67D2, and N6B6 together with CD34 as indicated in Materials and Methods and gated on forward and side scatter (top dot plots) before analysis on a FACSCalibur flow cytometer. In four independent bone marrow and three independent cord blood analyses, 4.6 ± 0.8% and 1.2 ± 0.1% of the scatter gated cells were CD34⁺, respectively. In the representative experiment shown, median fluorescence values for the CD34⁺CD164⁺ subsets of the human bone marrow (BM) gated cells were: N6B6 = 138.24; 103B2/9E10 = 212.88; 105A5 = 45.32; 67D2 = 198.10 and for the CD34⁻CD164⁺ gated subsets were: N6B6 = 294.97; 103B2/9E10 = 184.34; 105A5 = 220.67; 67D2 = 697.83. Median fluorescence values for the CD34⁺CD164⁺ subsets of human cord blood (CB) cells were: N6B6 = 148.55; 103B2/9E10 = 294.27; 105A5 = 37.86; 67D2 = 283.87 and for the CD34⁻CD164⁺ gated subsets were: N6B6 = 119.71; 103B2/9E10 = 69.78; 105A5 = 77.74; 67D2 = 273.84. Cells were also labeled with CD34-FITC or the CD34 MoAb, 43A1, plus an anti–IgG₃-FITC secondary antibody, together with isotype-matched irrelevant control MoAbs for each CD164 MoAb used plus anti-isotype–specific PE-conjugated antibodies. Under these conditions, 0.08% to 0.12% of cells occured in the CD34⁺ Ig Isotype⁻ gates, and 0.08% to 0.38% of cells occured in the CD34⁻ Ig Isotype⁻ gates.