Blood transfusion graft-vs.-host disease affects mostly the blood.

The only transplanted tissues that house enough immune cells to cause graft vs. host disease are the blood and the bone marrow.

Bone marrow graft-vs.-host disease comes in an acute and a chronic form. The acute form appears within two months of the transplant; the chronic form usually appears within three months.

The tissues most affected by bone marrow graft-vs.-host disease are the skin, the liver, and the intestines. One form or the other occurs in close to half of the patients

Graft vs Host disease is reaction to a bone or stem cell transplant. This is when the body rejects the new bone or cells. This can result in system failure and lead to death in extreme cases.