Cyclosporine A abolishes activation-induced resistance to apoptosis. (A) HuT78 and (B) CEM cells were either left untreated or stimulated for 16 hours with 20 ng/mL PMA and 1 μM ionomycin (Iono) with or without 1 μM CsA. Cells were then treated for an additional 8 hours with the indicated concentrations of CD95L. Apoptosis was determined by measuring DNA fragmentation and cell nuclei with hypodiploid DNA.