Fortunately, recent data suggested that MSCs antagonized the activation of mast cells by secreting PGE2 and TGF-β1, leading to decreased degranulation, reduced ability of chemotaxis and reduced release of TNF-α by mast cells (Figure 5).98, 99 Moreover, accumulative evidence suggest that human MSCs are powerful in protecting against Gram-negative bacteria-induced sepsis, relying on their secretions of LL-37, IDO and heme oxygenase-1 (HO-1), and strengthening the phagocytosis by neutrophils and macrophages as well (Figure 5).100, 101, 102, 103. Here, HMOX1 is linked to Sepsis.