Transplant rejection
Overview
Transplant rejection is a process in which a transplant recipient's immune system attacks the transplanted organ or tissue. This can lead to transplant failure and serious complications. Transplant rejection can be classified as hyperacute, acute, chronic and graft-versus-host disease (GVHD). Each type of rejection has different causes, symptoms, and treatments.
Types of Transplant Rejection
There are four main types of transplant rejection: hyperacute, acute, chronic, and graft-versus-host disease (GVHD).
Hyperacute Rejection
Hyperacute rejection is a rapid and severe response that occurs within minutes to hours after the transplant. It is caused by pre-existing antibodies in the recipient's blood that react with the transplanted organ or tissue.
Acute Rejection
Acute rejection typically occurs within days to weeks after the transplant. It is caused by the recipient's immune system recognizing the transplanted organ or tissue as foreign and attacking it.
Chronic Rejection
Chronic rejection is a slow and progressive process that can occur over months to years after the transplant. It is caused by the long-term damage inflicted by the recipient's immune system on the transplanted organ or tissue.
Graft-versus-Host Disease (GVHD)
Graft-versus-host disease (GVHD) is a unique type of transplant rejection that occurs in bone marrow and stem cell transplants. In GVHD, the transplanted cells (the graft) recognize the recipient's body (the host) as foreign and attack it.
Causes
Transplant rejection is primarily caused by the recipient's immune system recognizing the transplanted organ or tissue as foreign. This recognition triggers an immune response, leading to the attack and potential destruction of the transplant.
Mismatched HLA Antigens
The major cause of transplant rejection is a mismatch between the human leukocyte antigens (HLA) of the donor and recipient. HLA antigens are proteins found on the surface of most cells in the body. They play a crucial role in the immune system's recognition of self and non-self.
Pre-existing Antibodies
In hyperacute rejection, pre-existing antibodies in the recipient's blood react with the transplanted organ or tissue. These antibodies may have been formed in response to previous exposure to foreign antigens, such as through blood transfusions, previous transplants, or pregnancies.
Immune Response
In acute and chronic rejection, the recipient's immune system mounts a response against the transplanted organ or tissue. This involves both the innate and adaptive immune systems, including cells such as T cells, B cells, and natural killer cells.
Symptoms
The symptoms of transplant rejection vary depending on the type of rejection and the organ or tissue transplanted.
Hyperacute Rejection Symptoms
Symptoms of hyperacute rejection can include pain at the transplant site, fever, and organ failure. In kidney transplants, this may also include decreased urine output and swelling.
Acute Rejection Symptoms
Symptoms of acute rejection can include pain at the transplant site, fever, and a decrease in the function of the transplanted organ. For example, in kidney transplants, this may include decreased urine output, swelling, and high blood pressure.
Chronic Rejection Symptoms
Symptoms of chronic rejection are often subtle and may include a slow decline in the function of the transplanted organ. In lung transplants, this may include shortness of breath and decreased exercise tolerance.
GVHD Symptoms
Symptoms of GVHD can vary widely and may affect many parts of the body. They can include skin rashes, diarrhea, nausea, vomiting, and liver problems.
Diagnosis
The diagnosis of transplant rejection involves a combination of clinical assessment, laboratory tests, and often a biopsy of the transplanted organ or tissue.
Clinical Assessment
The first step in diagnosing transplant rejection is a clinical assessment. This involves a thorough medical history and physical examination, focusing on symptoms that may suggest rejection.
Laboratory Tests
Laboratory tests can help confirm the diagnosis of transplant rejection. These may include blood tests to measure levels of certain substances that can indicate organ damage, such as creatinine in kidney transplants or bilirubin in liver transplants.
Biopsy
A biopsy of the transplanted organ or tissue is often required to confirm the diagnosis of transplant rejection. This involves taking a small sample of tissue and examining it under a microscope for signs of rejection.
Treatment
The treatment of transplant rejection involves medications to suppress the immune response and, in some cases, additional surgery.
Immunosuppressive Medications
The mainstay of treatment for transplant rejection is immunosuppressive medications. These drugs work by suppressing the immune system's response against the transplanted organ or tissue. They include corticosteroids, calcineurin inhibitors, mTOR inhibitors, and antimetabolites.
Additional Surgery
In some cases, if the transplanted organ or tissue is severely damaged, additional surgery may be required. This could involve repairing the damaged organ or, in severe cases, performing another transplant.
Prevention
The prevention of transplant rejection involves careful donor-recipient matching, the use of immunosuppressive medications, and regular monitoring.
Donor-Recipient Matching
The best way to prevent transplant rejection is to ensure a good match between the donor and recipient. This involves testing for compatibility of HLA antigens and, in some cases, blood type.
Immunosuppressive Medications
The use of immunosuppressive medications before and after the transplant can help prevent rejection. These drugs suppress the immune system's response against the transplanted organ or tissue.
Regular Monitoring
Regular monitoring after the transplant is crucial to detect early signs of rejection. This involves regular check-ups, laboratory tests, and sometimes biopsies.