TNF and acute respiratory distress syndrome: The observed therapeutic effect of MSCs alone in ALI was not entirely unexpected, since previous reports have suggested that MSCs can inhibit the activation of dendritic cells, T lymphocytes, and natural killer cells, reducing the secretion of inflammatory cytokines (i.e., TNF-α, IFN-γ), increasing the release of anti-inflammatory cytokines (i.e., IL10, IL4), and inducing a tolerant phenotype [66,67].