Immunomodulatory Behavior of Mesenchymal Stem Cells

The use of Mesenchymal Stem Cells (MSCs) in the treatment of diseases where immunomodulation impacts therapy is increasing steadily. Recent studies aim to achieve effective use of MSCs in treatment of Graft versus Host Disease (GvHD), Crohn's disease and organ transplantations. The molecular mechanisms governing immunomodulatory properties of MSCs have not been fully understood, although current studies are indicating progress. Especially, in vitro studies and animal models provide a major contribution to our knowledge in clinical use of MSCs. The immunosuppressive and immune-enhancer properties of MSCs are -typically- determined with respect to type and concentrations of soluble molecules found in their physiological environment. In mammals the immune system protects the organism -not only- from certain microorganisms, but also from any entity that it recognizes as foreign, including its own cells when it is received as a threat. This protection can sometimes occur by increasing the number of immune cells and sometimes by suppressing a pathologically hyper-induced immunological response. In particular, realization of the bi-directional effect of MSCs on immune cells has placed substantial emphasis on this area of research. This chapter focuses on the interaction of MSCs with the immune cells, the bilateral role of these interactions, and whether studies that aim to understand these interactions can yield promising results in terms of developing improved use of MSCs in treatment.