A24 induced apoptosis of HTLV-1⁺ cells. (A) Comparative effect of A24, 30.9, and VP16 on the induction of programmed cell death in selected cells. Cells were activated or not with PHA and IL-2 and incubated in the presence of 30.9, A24, and VP16. Apoptotic and necrotic cells were followed by flow cytometry using an annexin V-FITC/PI kit. The percentage of cells located in right histogram quadrants is indicated: (i) cells from ATL acute form, (ii) normal, nonstimulated PBMCs, (iii) nonstimulated CIB cell line. (Bi) Annexin V staining of activated leukocytes from patients with acute ATL; cells were incubated with 30.9 (grey line), VP16 (discontinuous line), or A24 (continuous line). (Bii) Mitochondrial depolarization revealed by DIOC staining of activated leukocytes from ATL acute patient incubated with 30.9 (grey line), VP16 (discontinuous line), or A24 (continuous line). Data represent one of 3 different experiments.