Heat-killed BCG stimulates TRAIL/Apo-2L release from neutrophils to the same degree as viable BCG and protease activity is needed for maximum TRAIL/Apo-2L release. TRAIL/Apo-2L levels in neutrophil lysates (A,C) and the culture medium (B,D) were determined over a period of 24 hours from unstimulated (•, ○), BCG-stimulated (▪, □), or heat-killed (HK; ▾, ▿) BCG-stimulated neutrophils (3 × 10⁶ neutrophils/mL; 1 CFU/cell). Heat-killed BCG was incubated at 70°C for 1 hour before adding to neutrophils. In addition, some neutrophils were treated with DFP (1 mM) for 20 minutes at room temperature (C-D) before placing into culture. Results are representative of 3 independent experiments.