Transplant rejection

Definition

Transplant rejection is the immune system's response to foreign tissues that have been introduced into the body through organ or tissue transplantation. This reaction occurs because the immune system recognizes the transplanted tissue as non-self, leading to an attack on the foreign cells. The degree of rejection can vary, ranging from acute to chronic, and is influenced by factors such as the compatibility of Major Histocompatibility Complex (MHC) molecules between the donor and recipient.

5 Must Know Facts For Your Next Test

1. Transplant rejection can occur in different forms: hyperacute, acute, and chronic rejection, each with distinct mechanisms and timelines.
2. Hyperacute rejection happens immediately after transplantation and is often due to pre-existing antibodies against donor antigens.
3. Acute rejection usually occurs days to weeks after surgery and is mediated by T cells recognizing foreign MHC molecules.
4. Chronic rejection develops over months or years and involves a slow and progressive deterioration of graft function, often due to ongoing immune responses.
5. Matching donor and recipient MHC molecules improves the chances of graft acceptance and reduces the risk of rejection.

Review Questions

• How do MHC molecules influence the process of transplant rejection?
  • MHC molecules are critical in determining how the immune system recognizes self from non-self. When a transplant occurs, if the MHC molecules on the donor tissue differ significantly from those of the recipient, the recipient's immune system identifies these cells as foreign. This recognition triggers an immune response leading to transplant rejection. Therefore, closely matching MHC molecules between donor and recipient is essential to minimize this risk.
• Discuss the role of immunosuppression in managing transplant rejection.
  • Immunosuppression plays a crucial role in managing transplant rejection by dampening the recipient's immune response. Medications that suppress T-cell activation and proliferation help prevent acute rejection episodes by reducing the likelihood that the immune system will recognize and attack the transplanted organ. While effective, these treatments carry risks of increased vulnerability to infections and other complications due to their impact on overall immune function.
• Evaluate the long-term implications of chronic transplant rejection on patient health and organ function.
  • Chronic transplant rejection poses significant long-term challenges for patient health and organ function. It leads to a gradual loss of graft viability over time due to persistent low-level immune activity against the transplanted organ. This can result in chronic inflammation and fibrosis within the graft, ultimately leading to organ failure. Managing chronic rejection often requires adjustments in immunosuppressive therapy, ongoing monitoring, and sometimes re-evaluation for a second transplant, emphasizing the importance of long-term care strategies in transplant patients.

Related terms

Major Histocompatibility Complex (MHC): A set of molecules displayed on cell surfaces that are crucial for the immune system to recognize foreign substances, playing a significant role in transplant compatibility.

Immunosuppression: The reduction of the immune response, often achieved through medication, to prevent transplant rejection and allow for successful acceptance of the transplanted organ.

Graft-versus-host disease (GVHD): A condition that occurs when donor immune cells attack the recipient's tissues, which can happen after certain types of transplants, particularly bone marrow transplants.