What is "graft-versus-host disease"

Graft-versus-host disease (GvHD) is a medical complication following the receipt of transplanted tissue from a genetically different person. GvHD is commonly associated with stem cell or bone marrow transplant but the term also applies to other forms of tissue graft. Immune cells (white blood cells) in the donated tissue (the graft) recognize the recipient (the host) as "foreign." The transplanted immune cells then attack the host's body cells. GvHD can also occur after a blood transfusion if the blood products used have not been irradiated or treated with an approved pathogen reduction system.