Two-color analysis of immunofluorescent staining of T cells in the unfractionated and density fractionated cells from three different donors (A, B, and C). Cells were stained with PE-conjugated anti-CD4 and anti-CD8 monoclonal antibodies, and counterstained with FITC-conjugated anti-CD3 or anti-TCRαβ MoAbs. The upper boxes in (A) and (B) enclose CD4⁺CD3⁺ and CD8⁺CD3⁺ T cells. The lower boxes enclose CD4⁻CD8⁻CD3⁺ T cells. In (C), the staining with anti-CD3 antibodies was compared to that with anti-TCRαβ antibodies for unfractionated cells and cells in fraction C5.