Western immunoblot analysis of TRAIL expression from normal mouse osteoblasts co-cultured with S. aureus. Normal mouse osteoblasts were grown in the lower chamber of Transwell plates. S. aureus at a MOI of 25:1, 75:1, or 250:1 was added separately to Transwell® cell culture chamber inserts. As a control, osteoblasts were directly infected with S. aureus at a MOI of 250:1. TRAIL expression was monitored at 45 minutes following the addition of bacteria. Twelve micrograms of total osteoblast protein was loaded for each lane.