Figure 1. MSC administration and aGVHD response to MSC therapy.

SR/SD-aGVHD, steroid refractory/dependent acute graft-versus-host disease; CR, complete response of aGVHD; CR≥ 1m, complete response lasting more than 1 month; MSC, mesenchymal stromal cell; No R, no response of aGVHD; PR, partial response of aGVHD; <90d, within 90 days after first MSC infusion. ¹One patient died of diffuse alveolar damage within 24 hours after MSC infusion. ²Among the 5 patients who achieved PR<90d with MSC therapy, 1 maintained PR for at least 1 month whereas 3 experienced aGVHD worsening and 1 died of TTP within the month after achieving PR. ³ Among the 17 patients with no response to MSC therapy: 2 died less than 10 days after first MSC infusion (1 of infection and 1 of aGVHD); 6 did not receive rescue therapy other than a second MSC infusion; and 9 received a median of 1 (range 1–3) additional line (s) of immunosuppressive therapy (including anti-T-cell globulins, mycophenolate mofetil, mTOR inhibitors, anti-TNFα agents) with the first of them initiated after a delay of less than 10 days in 3 patients. Among these 9 patients, 4 were successfully rescued with subsequent salvage therapies. For the two patients who died less than 10 days after first MSC infusion, because the cause of death was directly or indirectly (infection) related to aGVHD, they were considered as non-responders to MSC therapy. ⁴Three patients experienced aGVHD recurrence 16, 23 and 25 days after achieving CR. Two had grade II and one had grade III aGVHD. ⁵Two patients died of infections within the month after achieving CR.