Figure 6
Flow data on controls of spectral isolation of fluorochrome emission and specificity of TUNEL-labeling of U937 cells. Cells in spontaneous apoptosis (a to c) and after treatment (24 hours) with TNFα (d) were fixed (PFA), FITC-labeled by the TUNEL reaction, stained with DAPI, and analyzed as whole cells. In the TUNEL control (-TDT), the TDT-enzyme was omitted. The cells were analyzed by FCM at unchanged gain settings using single fluorescence excitation at 365 nm and 488 nm, respectively, and dual wavelength excitation. Spectral isolation of DAPI and FITC fluorescence was highly specific (a to c). The negative control was used to determine a decision boundary (line) for counting of TUNEL-positive cells. Fractions of events above the line are indicated.
