Human UC-MSC-derived EVs were found to reduce the production of inflammatory cytokines (IL-2, TNF-α, and IFN-γ) and promote anti-inflammatory cytokine IL-10 production in Concanavalin A-activated splenocytes and in graft-versus-host disease (GVHD) in a mouse model of allogeneic hematopoietic stem cell transplantation. This evidence concerns the gene IL2 and graft versus host disease.