AMφ account for approximately 95% of airspace leukocytes (88) . Tissue damage induced by LPS is mediated mainly by inflammatory products released from AMφ (89, 90) , thus activated AMφ play a critical role in the development of ALI (91) . LPS inhalation induces AMφ to produce and release inflammatory mediators TNF-α, IL-1β and MIP-2 in a TLR4dependent manner (92) , which further result in the recruitment of PMN into the lower respiratory tract and activate other cell types, including epithelia and endothelia (93) .