Ceramide induces transcription-regulated cell apoptosis. In the absence or presence of actinomycin D (0.15 μg/mL), mouse T-hybridoma 10I cells and human Jurkat T cells were treated with 20 or 40 μM C₂-ceramide for 12 and 24 hours, respectively. Apoptotic cells were detected using PI staining followed by flow cytometric analysis. Representative histograms (A) and the percentages of apoptotic cells (B) are shown (means ± SD of triplicate cultures; *P < .05; **P < .01; ***P < .001 as compared with the groups without actinomycin D treatment).