Caspaselike activation is required for DC survival. (A) DCs were left untreated, pretreated with zVAD (1 hour, 40 μM), exposed to LPS (100 ng/mL), or pretreated with zVAD and exposed to LPS. After 16 hours cells were visualized by microscopy (Olympus IX50; Olympus Optical, Tokyo, Japan). Original magnification, × 40. Six independent experiments gave similar results. (B) DCs were left untreated, treated with zVAD (40 μM), exposed to LPS (100 ng/mL), or pretreated with zVAD and exposed to LPS. After 16 hours the cells were analyzed for propidium iodide (PI) uptake by flow cytometry. Five independent experiments gave similar results. Horizontal bars indicate necrotic cells.