IDO1 and Sepsis: These findings are consistent with previous studies, which demonstrated the capacity of bmMSCs to drive macrophage polarisation towards the M2 phenotype by producing soluble factors, including PGE2, TSG6, IL-6, IL-8, IDO and TGF-β1, following ischaemia reperfusion injury, sepsis and other disease models in which inflammation was the underlying mechanism [28, 38].