Mesenchymal stem cells immunomodulation: The road to IFN-γ licensing and the path ahead

Mesenchymal Stem Cells (MSCs) have gained prominence as an important tool in cell therapy, especially considering their capacity to control the immune system. Due to this property, the application of MSCs has been investigated for the treatment of several immune disorders, such as diabetes, rheumatoid arthritis, Crohn's disease, systemic lupus erythematosus, and graft-versus-host-disease (GvHD). The application of MSCs to treat inflammatory diseases has led to impressive results. However, individual response to treatment is still heterogeneous, and the number of cells required to treat humans is very high. The possibility of increasing the immunosuppressive potential of MSCs is seen at this point as a promising alternative to overcome such limitations. One of the most exploited strategies for this purpose has been the licensing of MSCs prior to clinical application. In this review, we will discuss the mechanisms by which MSCs modulate the immune response and the main advances in the licensing of these cells, with a special focus on the use of interferon gamma (IFN-γ). Also, we will address the main challenges ahead before licensed MSCs are finally used successfully in clinical practice.