Figure 5  hMSCs inhibit the pathological course of GvHD through several mechanisms. hMSC-produced IL-4, IL-10, HGF, PGE2, PDL-1, and TGF-β inhibit the proliferation and activation of T and B cells and stimulate the generation of Breg, Treg, and Th2 lymphocytes. hMSCs inhibit the activation of dendritic cells and stimulate the generation of regulatory dendritic cells. hMSC-produced IL-6, IDO, PGE2, and TGF-β suppresses neutrophil respiratory burst, NK cell activation and macrophage polarization to M1, though favors M2 polarization.