CCL2 and acute respiratory distress syndrome: Preconditioning with flagellin enhanced the therapeutic actions of AD-MSCs, resulting in a decrease in lung exudate, cell infiltration, and levels of inflammation-associated mediators (IL-1, IL-6, monocyte chemoattractant protein [MCP]-1 and TNF-α) in experimental LPS-induced ARDS (Li et al., 2020).