An immune system disorder that occurs after allogeneic hematopoietic stem cell transplant and is a reaction of donor immune cells against host tissues. Activated donor T cells damage host epithelial cells after an inflammatory cascade that begins with the preparative regimen. The disease is Monarch Disease Ontology identifier MONDO_0013730 (graft versus host disease). Also known as: GVH, GVHD, GvHD, disease, graft-versus-host, disease, graft-vs-host, diseases, graft-versus-host, diseases, graft-vs-host, graft vs host disease.