Acute rejection

Definition

Acute rejection is a type of immune response that occurs when the transplanted tissue or organ is recognized as foreign by the recipient's immune system, typically happening within days to weeks after transplantation. This process involves the activation of T cells and the production of antibodies against the transplanted material, leading to inflammation and damage to the graft. Understanding acute rejection is crucial for managing transplant outcomes and emphasizes the importance of histocompatibility and the need for immunosuppression.

5 Must Know Facts For Your Next Test

1. Acute rejection is characterized by a rapid onset, often occurring within the first few weeks post-transplant, and can be either cellular or humoral in nature.
2. In cellular acute rejection, T cells directly attack the donor cells, while in humoral acute rejection, antibodies target the donor's blood vessels, leading to inflammation.
3. The incidence of acute rejection can vary based on the level of histocompatibility between the donor and recipient; better matching reduces risk.
4. Prompt diagnosis and treatment of acute rejection are critical, as it can lead to graft loss if not managed effectively.
5. Immunosuppressive therapy plays a vital role in reducing the likelihood of acute rejection by dampening the recipient's immune response.

Review Questions

• How does allorecognition contribute to acute rejection following transplantation?
  • Allorecognition is essential in acute rejection because it describes how the recipient's immune system identifies donor antigens as foreign. When transplanted tissue is perceived as non-self, T cells are activated, leading to an aggressive immune response. This activation results in inflammation and tissue damage, highlighting why understanding allorecognition is crucial for preventing and managing acute rejection.
• What are the differences between cellular and humoral acute rejection, and how do they affect transplant outcomes?
  • Cellular acute rejection involves T cell-mediated responses that directly damage donor tissues, while humoral acute rejection is driven by antibodies that attack blood vessels in the graft. Both types can severely compromise transplant function, but they may require different therapeutic approaches. Cellular rejection often responds well to corticosteroids, whereas humoral rejection might necessitate more aggressive treatments like plasmapheresis. Knowing these differences helps tailor interventions for better graft survival.
• Evaluate the impact of immunosuppressive therapy on reducing acute rejection rates in organ transplantation.
  • Immunosuppressive therapy significantly lowers acute rejection rates by inhibiting key components of the immune response responsible for identifying and attacking transplanted organs. By targeting T cell activation and antibody production, these therapies help maintain graft acceptance. However, while they reduce rejection risk, they also come with potential side effects, such as increased vulnerability to infections and malignancies. Therefore, striking a balance between adequate immunosuppression and patient safety is crucial for optimal transplant outcomes.

Related terms

Allorecognition: The process by which the immune system identifies and responds to foreign antigens from a donor's tissue.

T-cell activation: The process through which T cells are stimulated to respond to foreign antigens, playing a key role in acute rejection.

Immunosuppressive therapy: Medications used to suppress the immune response to prevent rejection of transplanted organs or tissues.