Graft versus host disease (GVHD) is a rare disorder that occurs when the immune cells from donated bone marrow stem cells or a blood transfusion attack the recipient. The only transplanted tissues that contain enough immune cells (specifically T-lymphocytes) to cause GVHD are the blood and the bone marrow. This condition typically occurs in patients who have extremely weakened immune systems.
Researchers estimate that about 90% of bone marrow recipients develop GVHD. This is because before the transplant is performed, the recipient's bone marrow, which produces immune cells, is destroyed with chemotherapy or radiation therapy.
Bone marrow transplantation, also called hematopoietic stem-cell transplantation (HSCT), is a curative treatment for bone marrow cancer and inherited blood disorders like sickle-cell anemia.
Blood transfusions, which are used to replace blood-forming cells and immune cells, rarely cause GVHD. This condition is most likely to occur in individuals who have weakened immune systems (like chemotherapy or HIV patients).
Symptoms of GVHD generally include skin rash, liver dysfunction, and intestinal problems such as diarrhea (ranging from mild to severe) and abdominal pain, which may lead to decreased appetite and weight loss.
When the donated blood or organ is from an individual other than the recipient, it is called an allogeneic transplant. GVHD is most likely to occur after an allogeneic transplant or transfusion than an autologous transplant or transfusion.
An autologous transplant or transfusion is when the blood product or organ is removed from the recipient and then later returned to the same patient. This type of transplant is often conducted with stem cells from the bone marrow. For instance, chemotherapy destroys both healthy cells and cancer cells. Therefore, patients may have some of their stem cells removed and stored before chemotherapy. After treatment, the patient receives an infusion with these stem cells to help boost the immune system. Mild episodes of GVHD may occur after an autologous transplant because high doses of chemotherapy may damage the patient's DNA. The transplanted bone marrow may not recognize the cells if the DNA is damaged.
GVHD is treated with corticosteroids like prednisone (Deltasone®, Orasone® or Meticorten®) or immunosuppressants like cyclosporine (Restasis®). These drugs weaken the immune responses of both the transplant recipient and the donated stem cells or blood. The donated cells usually develop a tolerance to the host cells after six to 12 months, and the medications can be gradually withdrawn.
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matching donors to recipients
General: Bone marrow transplant recipients undergo tissue typing and blood typing tests before they are added to the national transplant list. Donated bone marrow also undergoes these tests. Once a donor and recipient have been shown to be close tissue and blood matches, a procedure called crossmatching is performed before surgery to ensure that the organ will not be rejected.
Transfusion recipients must undergo tissue typing to ensure that the donor and recipient have the same type of blood.
Tissue typing: A histocompatibility antigen blood test analyzes inherited proteins on the surface of cells. The results can be used to match donated tissue to organ transplant recipients.
Proteins called human leukocyte antigens (HLA) are found in the membranes (outer coating) of nearly every cell in the body. These antigens are in especially high concentrations on the surface of white blood cells.
HLA molecules are the major determinants used by the body's immune system for recognition and differentiation of self from non-self (foreign substances). There are many different major histocompatibility (HLA) proteins, and each person has only a small, relatively unique set that is inherited from their parents. It is unlikely that two unrelated people will have the same HLA make-up.
To help to prevent serious complications, such as graft-versus-host disease or transplant rejection, the potential donor and recipient must be tested to determine whether their HLA molecules are closely matched, making them compatible. Each person has unique HLA molecules (except for twins, who have identical molecules). Therefore, this test cannot prevent 100% of complications. However, the test can significantly reduce the number of patients who develop complications after transplantations.
Blood typing: Blood typing is performed because the donor and recipient must have the same blood type. Blood typing is a laboratory test that determines a patient's blood type. A potential donor and recipient are both blood typed before they are crossmatched. There are four blood types in the ABO blood group:
A, B, AB, and O. These blood types are determined by agglutinogens (type of protein) that are present on the outside of the patient's red blood cells. Patients who have type AB blood are considered universal recipients because they can receive blood or blood products from any other blood type. However, these patients may only donate their blood to patients who have AB blood. Patients who have O blood are considered the universal donors because they can give blood to patients of any other blood type. However, they can only receive blood from patients who have O blood.
In addition, patients have either positive or negative blood.
Patients who also have a protein called D antigen on their red blood cells are considered Rh-positive. If the D antigen is absent, the patient is Rh-negative. For instance, if a patient has type A agglutinogens but no D antigen, he/she has type A-negative blood.
Cross matching: A crossmatch is performed to determine whether the potential recipient will react to the donated bone marrow. During the procedure, white blood cells from the recipient and red blood cells from the donor are mixed. Clumping of the cells indicates that the patient has developed antibodies to the donor's cells. This means the patient will reject the donated organ if it is transplanted. Therefore, if clumping occurs, the blood is not compatible. If clumping does not occur, the blood is compatible.