Steroids are still the first line treatment for established severe acute-graft-versus-host-disease (aGVHD), with a response rate of 30-50%, and there is no established and effective therapy for severe steroid-refractory (aGVHD). The outcome for patients is poor and overall survival low, with few patients alive at 2 years.||In the case of failure after corticosteroid treatment, different therapeutic options have been introduced as second or third-line strategies. In this scenario, infusion of ex vivo expanded mesenchymal stromal cells (MSCs) has emerged as an additional tool for treatment of GVHD.||The purpose of this work is conduct a study in patients with refractory and/or resistant GVHD corticosteroids treatment. It will be randomized into two groups: one group that will receive the MSCs and the other group will follow the acute GVHD steroid-resistant and/or refractory treatment according to the routines of the Bone Marrow Transplantation (BMT) service of Hospital de Clinicas de Porto Alegre. It will be evaluated aspects of immune recovery early after MSCs infusion.