ABSTRACT
Mesenchymal stromal cells (MSCs) have shown an exceptional safety profile in a large number of early studies performed worldwide as well as sufficient efficacy to obtain approval by regulatory agencies in Europe, Japan, and the United States as treatment for pediatric graft versus host disease (GvHD). In this review, we sum up the clinical trials that have paved the way to translation. A potency assay for MSC immunosuppressive efficacy has remained elusive. Recent data suggest a mode of action by MSCs through cell graft destruction followed by monocyte-efferocytosis-mediated skewing of the immune repertoire and clarify why neither MSC engraftment nor MHC matching appears important for MSC therapy for GvHD.
