Inhibition of protein synthesis by cycloheximide induces apoptosis and processing of caspase-8. (A) Jurkat (3 × 10⁴) (⧫) or Jurkat-R cells (◊) were treated with the indicated concentrations of cycloheximide for 24 hours. Assessment of apoptotic nuclei was accomplished by flow cytometry of propidium iodide-stained hypodiploid nuclei. (B) Jurkat or Jurkat-R cells (1 × 10⁶) were incubated with cycloheximide (lanes 4,8: 10 μg/mL; lanes 3,7: 2 μg/mL; lanes 2,6: 0.4 μg/mL; lanes 1,5: diluent control) for 5 hours. Total cell lysates were immunoblotted with anti-caspase-8 antibody as described in Fig 5A. Filled arrowheads (◂) indicate the cleaved intermediate forms of 43 kD and 41 kD of caspase-8a and caspase-8b.