Transplantation and Alloimmunity Quiz
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Questions and Answers

What is the primary reason for transplant rejection in organ transplantation?

  • The presence of pre-existing antibodies in the recipient
  • Recognition of foreign cells due to alloantigens (correct)
  • Incompatibility of blood types
  • The inability to find suitable donors

    • Which of the following best describes an allograft?

  • Transplantation from one site to another in the same individual
  • Transplantation between genetically identical individuals
  • Transplantation from a donor with the same blood type
  • Transplantation between genetically different individuals (correct)

    • What is the role of memory T cells in transplantation?

  • They help produce antibodies against the donor tissue
  • They facilitate chronic rejection responses (correct)
  • They prevent the immune response from occurring
  • They enhance tissue compatibility post-transplant

    • What type of reaction does hyperacute rejection represent?

    <p>Immediate response due to pre-existing antibodies</p> Signup and view all the answers

    What is an important characteristic of the mixed lymphocyte reaction (MLR)?

    <p>It detects HLA differences between individuals</p> Signup and view all the answers

    Which of the following is NOT a type of graft?

    <p>Xenograft</p> Signup and view all the answers

    What makes transplantation more complex compared to blood transfusion?

    <p>The need for MHC matching</p> Signup and view all the answers

    What is a graft-versus-host reaction (GVHR)?

    <p>A reaction where the donor's immune cells attack the recipient's cells</p> Signup and view all the answers

    What is the primary mechanism by which acute rejection occurs?

    <p>Recipient T cells attack allogeneic molecules presented by donor dendritic cells.</p> Signup and view all the answers

    Which type of rejection develops slowly over a longer period of time?

    <p>Chronic rejection</p> Signup and view all the answers

    What role do corticosteroids play in transplant rejection prevention?

    <p>They suppress immune responses by modulating gene expression.</p> Signup and view all the answers

    Which cells are primarily involved in chronic rejection?

    <p>Antibodies damaging the vascular system of the graft.</p> Signup and view all the answers

    What is the primary consequence of the immune response in chronic rejection?

    <p>Gradual thickening of graft vasculature leading to ischemia.</p> Signup and view all the answers

    Which statement is true regarding minor histocompatibility antigens?

    <p>Polymorphisms lead to differences recognized as foreign by the immune system.</p> Signup and view all the answers

    What does NFAT stand for in the context of T cell responses?

    <p>Nuclear Factor of Activated T cells</p> Signup and view all the answers

    Which of the following is a drawback of using corticosteroids as immunosuppressive drugs?

    <p>They can lead to toxic effects on recipient organs.</p> Signup and view all the answers

    What is the primary reason the fetus is tolerated during pregnancy?

    <p>It occupies a site protected by nonimmunogenic tissue barrier.</p> Signup and view all the answers

    Which drug is known to block the activation of NFAT in T cells?

    <p>Cyclosporin A</p> Signup and view all the answers

    How does the placenta protect the fetus from the maternal immune system?

    <p>By being fetal-derived and not targeted by NK cells.</p> Signup and view all the answers

    What is the role of suppressive cytokines like IL-4 and IL-10 in maternal-fetal tolerance?

    <p>They contribute to the non-recognition of the fetus.</p> Signup and view all the answers

    What is a critical requirement for effective bone marrow transplantation?

    <p>Donor and recipient must share HLA class I and II.</p> Signup and view all the answers

    What happens if the recipient's HLA allotypes differ completely from the donor's?

    <p>The recipient will develop severe combined immunodeficiency.</p> Signup and view all the answers

    How can the placenta affect the responsiveness of maternal T cells?

    <p>By starving T cells of nutrients like tryptophan.</p> Signup and view all the answers

    What characterizes the donor-derived thymocytes after bone marrow transplantation?

    <p>They are positively selected on recipient's thymic epithelium.</p> Signup and view all the answers

    Study Notes

    Transplantation and Alloimmunity

    • Organ transplantation significantly extends lifespans, but a key challenge is the rejection of transplanted tissue.
    • Tissue/cell transfer between individuals often triggers a rejection response due to recognition as foreign.
    • This process is known as alloreaction against alloantigens.
    • A key factor in rejection is the highly polymorphic nature of MHC
    • Finding suitable donor tissue is also a major hurdle, often relying on recently deceased donors.

    Immune Responses

    • Blood transfusions are a form of transplantation but simpler, lacking MHC class I or II complexities.
    • Blood groups (O, A, B, AB) are determined by glycosylation of proteins and lipids on red blood cells (RBCs).
    • Natural IgM antibodies are directed against some blood group antigens.

    Skin Grafts in Mice

    • Skin transplant complexity increases, as matching MHC is more difficult.
    • Skin graft experiments in mice illustrate allorejection involves memory T-cells.
    • These memory T-cells are a primary driver of chronic rejection after transplant.

    Allograft Rejection Types

    • Two main types of rejection are:
      • Transplant rejection
      • Graft-versus-host reaction (GVHR)

    Additional Key Terms

    • Autograft: Tissue transferred within the same individual.
    • Syngeneic/Isograft: Transplant between genetically identical/similar individuals (e.g., twins).
    • Allograft/Allogeneic Transplant: Transplant between genetically different individuals.

    Hyperacute Rejection

    • Occurs when pre-existing antibodies against donor antigens exist.
    • Rapid rejection due to antibody binding, complement activation, and tissue destruction.
    • Usually in the context of pre-existing antibodies to blood group antigens.

    Acute Rejection

    • More common type of rejection.
    • Involves T-cell responses to HLA antigens.
    • Takes several days to develop as an allogeneic response.
    • Prevented by massive doses of immunosuppressive drugs.

    Chronic Rejection

    • Takes years to develop.
    • Characterized by reactions within the graft vasculature which result in thickening and lack of blood supply (ischemia).
    • Antibodies (particularly to class I antigens) are significant in this type of rejection.
    • Damage of tissue vasculature by alloreactive antibodies leads to reduced blood flow.

    Minor Histocompatibility Antigens

    • Even with identical MHC, other genetic differences (minor histocompatibility antigens) can cause rejection.

    Immune Suppression

    • Corticosteroids are potent immunosuppressive drugs, but come with toxic effects on other organs/tissues.
    • Drugs like cyclosporin A and FK506 inhibit T cell activation.

    Maternal Fetal Tolerance

    • Fetus has paternal MHC but is not rejected by the mother's immune system.
    • Placenta, a fetal-derived tissue, is crucial in the prevention of maternal immune response against the fetus.
    • Placenta doesn't express certain MHC class molecules, nor is it targeted by NK cells.
    • Placenta may utilize cytokines and alternative mechanisms to regulate the maternal immune response.

    Transplantation of Hematopoietic Stem Cells

    • Used to correct genetic defects.
    • Involves destroying diseased hematopoietic system. An infusion of healthy donor bone marrow is administered.
    • Stem cells in the graft reconstitute a healthy immune system in the recipient.

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    Related Documents

    Transplantation And Alloimmunity Lecture Notes PDF

    Description

    Test your knowledge on organ transplantation and the immune responses involved, particularly in relation to alloreaction and alloantigens. This quiz also covers blood transfusions and the complexities of skin grafts in experimental models. Explore the challenges of donor matching and the role of MHC in rejection processes.

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