ATP-induced apoptosis detected by the TdT-mediated dUTP nick end labeling (TUNEL) technique.

DCs were incubated with ATP (5 mmol/L) for 30 minutes at 37°C, washed twice with PBS/BSA, and incubated additionally for 6 hours in complete RPMI medium. Apoptosis was ascertained by the TUNEL technique and flow cytometry. The resulting fluorescence intensity profiles of control DCs (lower left histogram; Ct2) and those treated with 5 mmol/L ATP (lower right histogram; ATP) are shown. As a negative control, DCs were incubated with FITC-conjugated dUTP only (upper left histogram; Ct1) without TdT. Positive control was performed by treating the DCs with DNAse (10 μg/mL) immediately before incubation with TUNEL reaction mixture (upper right histogram; DNAse).