Graft-versus-host disease (GVHD) is a common side effect of an allogeneic bone marrow or cord blood transplant (also called a BMT). An allogeneic transplant uses blood-forming cells donated by a family member, unrelated donor or cord blood unit. In GVHD, the immune cells from the donated marrow or cord blood (the graft) attack the body of the transplant patient (the host). GVHD can affect many different parts of the body. The skin, eyes, stomach and intestines are affected most often. GVHD can range from mild to life-threatening.
GVHD occurs because some of your donor's immune cells (known as T cells) attack cells in your body. The immune system uses markers called HLA antigens to recognize which cells belong in your body and which do not. When it finds cells with HLA antigens it does not recognize, it attacks those cells. In GVHD, your donor's immune cells do not recognize the HLA antigens on your body's cells, so they attack your cells. That is one reason your donor's HLA antigens need to match yours as closely as possible. Selecting a closely matched donor or cord blood unit can help reduce your risk of getting GVHD.
Blood transfusion graft-vs.-host disease affects mostly the blood. Blood cells perform three functions: carrying oxygen, fighting infections, and clotting. All of these cell types are decreased in a transfusion graft-vs.-host reaction, leading to anemia (lack of red blood cells in the blood), a decrease in resistance to infections, and an increase in bleeding. The reaction occurs between four to 30 days after the transfusion.
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 acute disease produces a skin rash, liver abnormalities, and diarrhea that can be bloody. The skin rash is primarily a patchy thickening of the skin. Chronic disease can produce a similar skin rash, a tightening or an inflammation of the skin, lesions in the mouth, drying of the eyes and mouth, hair loss, liver damage, lung damage, and indigestion. The symptoms are similar to an autoimmune disease called scleroderma. Both forms of graft-vs.-host disease bring with them an increased risk of infections, either because of the process itself or its treatment with cortisone-like drugs and immunosuppressives. Patients can die of liver failure, infection, or other severe disturbances of their system.
For recipients of blood transfusions who are especially likely to have graft-vs.-host reactions, the red blood cells can safely be irradiated (using x rays) to kill all the immune cells. The red blood cells are less sensitive to radiation and are not harmed by this treatment. Much current research is directed towards solving the problem of graft-vs.-host disease. There are efforts to remove the immunogenic cells from the donor tissue, and there are also attempts to extract and purify bone marrow cells from the patient before treating the cancer. These cells are then given back to the patient after treatment has destroyed all that were left behind.