Detection of CD4 on CD66⁺ cells. Flow cytometric analyses of whole blood from 2 representative HIV-infected (top panels) and 2 uninfected (bottom panels) individuals on dual staining with CD4 and CD66b mAbs. Shown are the fluorescence intensities within morphologic gate R3 (neutrophils). The numbers indicate the percentage of positive cells in each quadrant. Ten percent of neutrophils from one of the uninfected donors were also positive on staining with another directly conjugated anti-CD4 mAb (anti–CD4-PE, clone SK3, mIgG1; BD Biosciences).