Overview of Transplantation

The immune system White blood cells normally attacks foreign tissue, including transplants. This reaction is called rejection. Rejection is triggered when the immune system recognizes certain molecules on the surface of a cell as foreign. These cell-surface molecules are called antigens.

For blood transfusions, rejection is relatively easily avoided because red blood cells have only three main antigens on their surface. These antigens determine the blood type and are called A, B, and Rh. Doctors test to make sure that antigens in the donor blood and the recipient blood are a complete match.

For organ transplantation, however, many antigens are involved. These antigens are called human leukocyte antigens (HLA), or the major compatibility complex (MHC). They occur on the surface of every cell in the body. Each person has unique HLA, which determine the tissue type. Ideally, the donor’s tissue type exactly matches the recipient’s tissue type. However, a perfect HLA match is extremely rare, and some people are too ill to wait for a highly compatible donor. In these cases, doctors sometimes use donor tissue that is not an exact match but that is a close match. A close HLA match between the donor and recipient reduces the likelihood and severity of rejection and improves the long-term outcome. However, because immunosuppressant therapy Suppression of the Immune System Transplantation is the removal of living, functioning cells, tissues, or organs from the body and then their transfer back into the same body or into a different body. The most common type of... read more has become more effective, the success of transplantation is less affected by the degree of matching.

Before transplantation, the recipient’s blood is screened for antibodies against the tissues of the donor. The body may have produced such antibodies in response to a blood transfusion, a previous transplant, or a pregnancy. If these antibodies are present, transplantation may not be possible because immediate, severe rejection will occur. Plasma exchange Plasma exchange In apheresis, blood is removed from a person and then returned after substances are removed from it. Apheresis can be used to Obtain healthy blood components from a donor to transfuse to a person... read more and intravenous immune globulin (IVIG) have been used to remove or suppress the antibodies and thus make transplantation possible when a close match is not available. (IVIG is antibodies obtained from blood that is collected from people with a normal immune system.)

Donors are screened for cancer and infections, which can be transmitted during transplantation. Doctors screen donors for cancer by thoroughly reviewing their medical history and carefully inspecting the organ in the operating room at the time of organ recovery. Organs containing cancers are obviously not used for transplantation. Whether or not to use organs from donors who previously had cancer in another organ is based on the likelihood that cancer cells are still present or have spread to the organ being transplanted.

Most bacterial infections are evident to doctors based on the donor’s overall health and have often been diagnosed and treated even before the decision to donate. If treatment has been adequate, organ transplantation is safe, although the recipient may be given additional antibiotic treatment.

To prevent transmission of viral infections, which are often not so obvious, doctors usually test the donor’s blood for certain viral infections. These infections include those due to cytomegalovirus (CMV), Epstein-Barr virus (EBV), hepatitis B and C viruses, human immunodeficiency virus (HIV), and human T-cell lymphotropic virus (HTLV). Some viral infections in the donor, such as HIV infection, mean that transplantation cannot be done unless the infection can be controlled. Other viral infections, such as CMV and EBV, and more recently hepatitis C infections, do not prevent transplantation, but the recipient must take antiviral drugs afterward.

In addition to a complete evaluation of physical health, living donors also undergo comprehensive psychosocial evaluation for mental health problems; past and present smoking. alcohol use, or substance abuse; ability to understand the risks of donation and provide informed consent without coercion; and sufficient resources and support during recovery.

Recipients are also screened for cancer and infections, and their general health is evaluated. Because organ transplant recipients are given immunosuppressants in high doses at the time of transplantation, recipients who have active infections or cancers cannot undergo transplantation until these conditions are controlled or cured. Taking immunosuppressants could make an infection or cancer worse.

People with poor overall health, certain viral infections, or other medical problems in addition to malfunction of the organ requiring transplantation are less likely to do well with a transplant. The decision to transplant is based on the person’s specific circumstances, including age.

Psychosocial screening is done because the lifelong regimen of drugs, treatments, and follow-up visits required to keep a transplanted organ functioning is quite demanding, and not all people are willing or able to comply. In addition to nurses and doctors, psychiatrists and social workers are involved to help people and their families understand the long-term commitment and difficulties involved in accepting a transplant. Everybody’s input is important in determining whether organ transplantation is right for a person.

Rejection, if it occurs, often begins soon after transplantation but can occur after weeks, months, or even years.

Symptoms of rejection vary depending on which organ was transplanted and when rejection occurs. Acute rejection occurs soon after transplantation and causes symptoms that may include fever, chills, nausea, fatigue, and sudden changes in blood pressure. Chronic rejection usually occurs later and can cause ongoing low-level damage to the donated organ.

Several factors increase the risk of infections for transplant recipients:

Infections that may develop in transplant recipients include the same ones that might develop in any person recovering from surgery. Such infections include infection of the surgical site or the transplanted organ, pneumonia, and urinary tract infections.

Transplant recipients are also at risk of unusual (opportunistic) infections that affect mainly people with a weakened immune system. Opportunistic infections may be caused by

After transplantation, most people are given antimicrobial drugs to help prevent infections. After 6 months, the risk of infections goes back to what it was before transplantation in about 80% of people.

Certain cancers are more likely to develop when immunosuppressants are taken a long time, as occurs after transplantation. Such cancers include certain skin cancers, lymphoma Overview of Lymphoma Lymphomas are cancers of lymphocytes, which reside in the lymphatic system and in blood-forming organs. Lymphomas are cancers of a specific type of white blood cells known as lymphocytes. These... read more , cervical cancer Cervical Cancer Cervical cancer develops in the cervix (the lower part of the uterus). Most cervical cancers are caused by human papillomavirus (HPV) infection. Cervical cancer usually results from infection... read more , and Kaposi sarcoma Kaposi Sarcoma Kaposi sarcoma is a skin cancer that causes multiple flat pink, red, or purple patches or bumps on the skin. It is caused by human herpesvirus type 8 infection. One or a few spots may appear... read more .

Treatment is similar to that for people who do not have transplants. But sometimes during treatment for cancer, immunosuppressants are stopped or the doses are decreased.

Atherosclerosis Atherosclerosis Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more (deposits of fatty material in arteries) may develop because some immunosuppressants cause levels of cholesterol and other fats (lipids) to increase. These fats may accumulate in the walls of arteries and reduce or block blood flow, causing a heart attack or stroke.

Atherosclerosis typically develops about 15 years after kidney transplantation.

Kidney problems develop in about 15 to 20% of people with a transplanted organ, particularly the small intestine. The kidneys become less able to remove waste products, which then build up in the blood.

Factors that may contribute to the development of kidney problems include

Gout Gout Gout is a disorder in which deposits of uric acid crystals accumulate in the joints because of high blood levels of uric acid (hyperuricemia). The accumulations of crystals cause flares (attacks)... read more is common, particularly after heart or kidney transplantation. It can be severe and progress rapidly, particularly if people have had gout before transplantation or if they take cyclosporine or tacrolimus.

Graft-versus-host disease occurs when white blood cells (the graft) from the donor attack the recipient's (the host) tissues. This disorder most commonly occurs in recipients of stem cell transplants but can occur in recipients of liver or small intestine transplants.

Symptoms may include fever, rash, jaundice Jaundice in Adults In jaundice, the skin and whites of the eyes look yellow. Jaundice occurs when there is too much bilirubin (a yellow pigment) in the blood—a condition called hyperbilirubinemia. (See also Overview... read more , vomiting, diarrhea, abdominal pain, weight loss, and increased risk of infections. These reactions can be fatal. However, certain drugs such as methylprednisolone can eliminate or reduce the severity of graft-versus-host disease in the recipient.

Use of immunosuppressants (especially corticosteroids) can result in osteoporosis Osteoporosis in people who are at risk of developing osteoporosis before transplantation. These people include those who have a sedentary lifestyle, who use tobacco and alcohol, or who have kidney disease.

In children, use of immunosuppressants can result in stunted growth.

Doctors test most people for osteoporosis before transplantation is done. Sometimes doctors give transplant recipients vitamin D or drugs that prevent bone loss (such as bisphosphonates Drugs ) to help prevent bone loss.

Living donors are also at risk of complications. Some of these complications are those that may occur after any surgery, such as infection and bleeding. Some additional complications depend on which organ has been removed. Donors may also be at risk of emotional and mental complications, so transplant teams carefully evaluate potential donors before a person is selected as a donor.