Kidney Transplantation and Rejection Mechanisms

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Questions and Answers

What is sought in kidney transplants to minimize the risk of rejection?

A close match of MHC I and II antigens (correct)

A distant geographic origin of the donor

A perfect match of blood types

A compatible donor age

What is a primary immunosuppressive drug used in preventing transplant rejection?

Adrenaline

Cyclosporine (correct)

Etanercept

Cyclophosphamide

What occurs during the host vs. graft reaction after a kidney transplant?

The donor's body starts to reject its own tissue

There is no immune response from the host

The graft completely fails immediately

The recipient's leukocytes enter the transplant (correct)

What role do dendritic cells from the graft play in transplantation?

Enter the host and cause immune tolerance Signup and view all the answers

What factor becomes less significant in heart and liver transplants compared to kidney transplants?

The exact matching of MHC antigens Signup and view all the answers

What is the main barrier to successful transplantation?

Transplant rejection Signup and view all the answers

What are the two mechanisms involved in T cell-mediated graft rejection?

Destruction of graft cells by CD8+ CTLs and delayed hypersensitivity reactions Signup and view all the answers

Which of the following pathways plays a major role in acute cellular rejection?

Direct pathway via recipient's CD4+ and CD8+ recognition Signup and view all the answers

Which cells are primarily involved in the cellular rejection mechanism?

CD4+ helper cells and CD8+ CTLs Signup and view all the answers

What type of rejection occurs when preformed antidonor antibodies are present?

Hyperacute rejection Signup and view all the answers

What is the role of CD4+ helper cells in transplant rejection?

Triggering delayed hypersensitivity reactions Signup and view all the answers

What primarily causes hyperacute rejection?

Preformed antibodies Signup and view all the answers

How does the indirect pathway of rejection operate?

Involves processing of antigens by the recipient’s APCs Signup and view all the answers

Which of the following is a characteristic of acute rejection?

Can be adequately controlled by chemotherapy Signup and view all the answers

Which type of immune response is characterized by both cell-mediated and humoral rejection processes?

Acute rejection Signup and view all the answers

What is a gross finding associated with hyperacute rejection?

Cyanotic, flaccid kidney Signup and view all the answers

Which sequence of events is characteristic of hyperacute rejection?

Thrombotic occlusion in arterioles Signup and view all the answers

What type of immune responses are involved in acute rejection?

Mixed antibody and T-cell response Signup and view all the answers

Which of the following is NOT a microscopic feature of acute cellular rejection?

Delayed hypersensitivity reaction Signup and view all the answers

What is indicated by the term 'antibody-mediated acute damage' in the context of rejection?

Obstruction of blood vessels by fibroblasts and macrophages Signup and view all the answers

Which type of rejection develops months to years after transplantation?

Chronic rejection Signup and view all the answers

What characterizes chronic rejection in a kidney allograft?

It involves progressive dysfunction over time. Signup and view all the answers

What immune cells primarily mediate graft vs. host (GVH) reactions?

CD4+ and CD8+ T cells Signup and view all the answers

Which organs are most commonly affected in graft vs. host disease?

Skin, liver, and GI tract Signup and view all the answers

What commonly occurs in acute graft vs. host disease?

Jaundice due to bile duct damage Signup and view all the answers

What is a key histological finding in chronic rejection?

Intimal fibrosis in arteries Signup and view all the answers

How can chronic graft vs. host disease manifest over time?

As extensive cutaneous injury and fibrosis Signup and view all the answers

Which of the following is a symptom associated with acute graft vs. host disease?

Desquamating rash Signup and view all the answers

What is the primary cause of graft vs. host disease?

Recognition of host alloantigens by donor T cells Signup and view all the answers

Study Notes

Transplantation Overview

Transplantation is a surgical procedure replacing a tissue or organ with a corresponding part from another part of the body or from another individual.
The donor provides the tissue or organ, while the recipient receives it.

Types of Transplantation

Autograft: Tissue or organ transferred from one part of the body to another part of the same body (e.g., moving tissue from the leg to the arm).
Isograft: Tissue or organ transferred between genetically identical individuals (e.g., identical twins).
Allograft: Tissue or organ transferred between different individuals of the same species (e.g., from one person to another).
Xenograft: Tissue or organ transferred between different species (e.g., from an animal to a human).
Autografts and isografts are typically accepted by the recipient's body because they are already compatible. However, allografts and xenografts are more likely to be rejected.

Transplant Rejection

Rejection is a major hurdle in transplantation, where the recipient's immune system recognizes the graft as foreign and attacks it.
A significant goal of immunologic research is successful transplantation without rejection.
Rejection involves cell-mediated and antibody-mediated responses, with both pathways contributing to the complex process.

T Cell-Mediated Reactions

Cell-mediated rejection is triggered by two mechanisms:
- Destruction of graft cells by CD8+ cytotoxic T lymphocytes (CTLs).
- Delayed hypersensitivity responses initiated by activated CD4+ helper T cells.
The recipient's T cells recognize donor antigens (allogeneic antigens) in the graft via two pathways (direct and indirect).

Transplant Rejection Mechanisms

T-cell mediated rejection includes:
- Direct pathway: Recipient T cells directly recognize donor MHC class I or MHC class II molecules present on donor cells.
- Indirect pathway: Recipient APCs process donor antigens and present them to recipient T cells.
Antibody-mediated rejection involves preformed antibodies against donor antigens leading to hyperacute rejection in situations where the recipient already has antibodies against the donor.

Hyperacute Rejection

Occurs within minutes to hours after transplantation.
Caused by preformed antibodies existing in the recipient against donor antigens.
Leads to rapid endothelial damage, thrombosis, and necrosis in the transplanted organ.

Acute Rejection

Occurs within days after transplantation.
Involves both cellular and humoral immune responses.
Characterized by a cellular infiltrate composed of lymphocytes and other immune cells attacking the graft.
Microscopic visualization shows interstitial mononuclear cell infiltrates.
Antibody-mediated acute damage can also be present.

Chronic Rejection

Develops months or years after transplantation.
Characterized by gradual dysfunction of the graft.
Involves changes like vascular damage, intimal fibrosis (the thickening of the inner layer of blood vessels), and tubule atrophy.
The arteries exhibit intimal fibrosis, containing also plasma cells and eosinophils in the interstitial spaces.

Host vs. Graft Reactions

Reactions between the recipient's immune system and the transplanted tissue.
With kidney transplants, a close match of MHC I and II antigens is crucial for acceptance.

Graft vs. Host Reactions (GVH)

Occurs primarily in bone marrow transplantation.
Transplant's immune cells attack the recipient's tissues.
Affects and damages various organs (skin, GI tract, liver, and lungs).
GVH reactions can be acute or chronic.
Acute GVHDR usually arises within weeks of transplantation.
Chronic GVHDR can occur after acute GVHR.
This has similarities to systemic autoimmune disorders.

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Description

This quiz explores key concepts related to kidney transplantation, including immunosuppressive drugs, mechanisms of rejection, and the roles of various immune cells. Test your understanding of the host vs. graft reaction and factors influencing transplant success.