Dose-dependent introduction of TAT-FITC into PMNs. PMN staining after incubation with free FITC or TAT-FITC was studied by flow cytometry. Cells were treated for 10 minutes with increasing concentrations of free FITC or TAT-FITC as indicated. After washing, the fluorescence intensity was assessed in the FL-1 channel. Thin solid lines represent cell autofluorescence; dotted lines, fluorescence after free FITC incubation; and bold lines, FL-1 staining of cells incubated with TAT-FITC. The data indicate increased staining of PMNs that were incubated with TAT-FITC, but not with free FITC.