Immunosuppressive properties of mesenchymal stromal cells

The main interest in mesenchymal stromal cells (MSCs) is correlated with their ability to suppress the proliferation of T lymphocytes induced by mitogenic agents and alloantigens which regulate the transplantation rejection. Moreover, MSCs are resistant to the CD8+ T lymphocyte cytotoxicity, they are able to inhibit the differentiation of dendritic cells responsible for the antigen presentation, the proliferation, and antibody production of B lymphocytes and they stimulate the formation of regulatory T cells. The mechanisms at the basis of MSCs activity need cell-cell interaction and the secretion of soluble molecules induced by the micro-environment. The inhibitory functions of MSCs involve several soluble molecules as hepatocyte growth factor, transforming growth factor-beta, interleukin-10 and -2, tumor necrosis factor-alpha, prostaglandin E2, indoleamine 2,3-dioxygenase (IDO), and soluble HLA-G antigens. A large consensus has been obtained on the immuno-modulatory role of IDO and HLA-G molecules.