The present invention relates to methods for treatment and/or prevention of acute as well as chronic graft-versus-host-disease (GVHD), and in particular to methods for decreasing mortality and increasing especially long term survival； acute complications associated with GVHD such as diarrhea, weight loss and sepsis based on normalization of gut, liver, lung and skin microbiota and mucosal defense； rebalance of the immune system with normalization of cytokine production of IFN-γ, TNF-α, 11-4, IL-5, IL-6, IL-8, IL-9, IL-10 and IL-13 and prevention and/or treatment of cytokine storm； chronic complications associated with GVHD such as bronchiolitis obliterans and scleroderma, the method comprising oral, subcutaneous, intrapulmonary and/or dermal/transdermal administration of one or more mammalian defensins selected from the group of α- and β-defensins in a patient that has or is about to receive an allogeneic hematopoietic stem cell transplantation.
