Which clinical phenomenon involves donor white blood cells attacking the recipient?

Graft-versus-host disease (GVHD) occurs when donor white blood cells (usually found in a transplant) recognize the recipient's body tissues as foreign and initiate an immune response against them. This phenomenon is particularly observed in allogeneic stem cell or organ transplants where the donor and recipient are not genetically identical. The donor immune cells contain T lymphocytes that can react against the recipient's major histocompatibility complex (MHC) and other tissue antigens, leading to inflammation and tissue damage.

In contrast, transplant rejection typically involves the recipient's immune system mounting a response against the donor organ, not the other way around, which distinguishes it from GVHD. Hemolytic disease of the newborn concerns maternal antibodies attacking fetal red blood cells, whereas autoimmune hemolytic anemia involves the body's own immune system attacking its red blood cells, neither of which involves donor white blood cells attacking the recipient.