Mesenchymal stem cells for acute graft-versus-host disease/Authors' reply

Besides the immune regulatory role of mesenchymal stem cells, in models of experimental injury, intravenous administration of these cells improves organ healing, mainly through paracrine effects and a shift from the production of proinflammatory to anti-inflammatory cytokines at the site of injury.2,3 Furthermore, we have previously shown that immune reconstitution improves after mesenchymal stem-cell infusion, with resolution of graft-versus-host disease and subsequent tapering of immunosuppressive drugs.4 However, we acknowledge that the present study is insufficiently powered to exclude an effect of mesenchymal stem cells on the rate of infections.