Fig. 1

The immunosuppressive mechanisms of MSC MSCs activated by IFN-γ and other inflammatory factors regulate a variety of immune cells through secreting IDO, TGF-b, NO, PGE2 and other molecules, exosomes, and cell–cell connection, including T, B, NK and Macrophages. Among which T cells are the main target cells of MSC immunosuppression, can inhibit the polarization of naive T cells to pro-inflammatory cells Th1 or Th17, Tfh, and promote the differentiation of naive T cells to regulatory immune cells Treg, and indirectly through T cells Inhibit the proliferation and differentiation of B cells. In addition, MSC can directly inhibit the differentiation of B cells into plasma cells, promote the differentiation of B cells into Breg cells. MSCs promote the polarization of macrophages to the inflammation-suppressing phenotype M2, and inhibit maturation of DC