To determine the molecular mechanisms of inflammatory monocyte-mediated lung damage, we investigated the role of TRAIL (TNF-related apoptosis-inducing ligand), as TRAIL is a soluble or cell-surface molecule that is upregulated on inflammatory monocytes during severe influenza infection and can induce apoptosis of target cells expressing the TRAIL receptor DR5 25, 44. This evidence concerns the gene TNFSF10 and influenza.