Résumé : In this Special Issue, directed and supervised by Dr. Mehdi Najar, a collection of basic research articles and reviews, on the state of the art of Mesenchymal Stem/Stromal Cells (MSCs) immune biology, is presented. Among the major goals of this Special Issue is the presentation of an update about the immunomodulatory properties of MSCs and their capacity to respond to tissue microenvironment changes. MSCs hold great promise in the field of immunotherapy and regenerative medicine. Accordingly, a better understanding of MSC immune biology will improve their therapeutic value and use.