CCL2 and acute respiratory distress syndrome: As previously reported, intratracheal LPS-induced ARDS is characterized by initial increase of polymorphonuclear (PMN) cells, albumin, and cytokines (including TNF, IL-1β, IL-6, IL-8, MCP-1, MIP-1) in the BALF, and then (between 24 and 48 h after instillation) there is an additional increase in PMN, monocytes, macrophages, and lymphocytes (Matute-Bello et al., 2008).