A recent study by Andonegui and colleagues has shown that endothelial cells (ECs) are the key sentinel cells for detecting infection by Gram-negative bacteria and recruiting PMN to peripheral tissues (53, 59) . Indeed, previous studies have shown that direct activation of circulating PMN with LPS is not sufficient to induce their sequestration within the lung (53) . Interactions of PMN with ECs seems important for the process of PMN sequestration into the lung (53, 60) . LPS stimulates the CD14 and TLR4 complex, which in turn activates NF-κB (61) and increases the expression of adhesion molecule E-selection, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule 1 (62, 63) . The TLR4 signaling also leads to production and release of various bioactive molecules, including IL-1β, IL-6, TNF-α, chemokines and nitric oxide (64) , all of which are actively involved in the development of ALI.