Transplantation Biology and Histocompatibility

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Questions and Answers

What services are available for telemedicine at the MWU Multispecialty Clinic?

Chiropractic services and occupational therapy

Dental services and audiology

Physical therapy and massage therapy

Nutrition and Counseling (correct)

What is the cost for student acute care visits at the MWU Acute Care Clinic?

$20 copay for every visit

Free, excluding labs and x-rays (correct)

Only covered by insurance

$50 for a consultation

When can students schedule a telehealth appointment?

By appointment only, with no specific hours mentioned

On weekends at any time

Only during weekdays after 5pm

Only during business hours from Monday to Friday (correct)

What should students do to access the free counseling service mentioned?

Text 'hello' to the specified number Signup and view all the answers

What is the coupon code for student appointments starting August 1st?

ALCMWUAZ23 Signup and view all the answers

Which type of graft involves transplantation between genetically identical individuals?

Isograft Signup and view all the answers

Which of the following is correctly ordered according to the degree of immune response elicited during transplantation?

Autograft < Isograft < Allograft < Xenograft Signup and view all the answers

What mechanism is primarily responsible for hyperacute graft rejection?

Pre-existing antibodies against donor antigens Signup and view all the answers

Which type of graft rejection typically occurs days to weeks after transplantation?

Acute rejection Signup and view all the answers

In direct recognition of allogeneic MHC, which cells are directly involved in presenting peptides to activate T cells?

Donor cDCs Signup and view all the answers

What is the primary function of HLA typing in transplantation?

To match histocompatibility antigens between donor and recipient Signup and view all the answers

Which statement accurately describes the role of MHC molecules in transplantation?

MHC molecules are critical for T cell activation and strong rejection reactions. Signup and view all the answers

What distinguishes an autologous graft from an allogeneic graft?

Autologous grafts come from the same individual, while allogeneic grafts come from different individuals of the same species. Signup and view all the answers

What is the primary reason for the significance of crossmatching in transplants?

To identify pre-existing antibodies against donor antigens Signup and view all the answers

What is one characteristic of chronic inflammation following a transplant?

It is mediated by Th1 cells. Signup and view all the answers

What is the time frame for chronic inflammation to develop after a transplant?

Months to years. Signup and view all the answers

Which of the following best describes the approach to managing acute and chronic graft-versus-host disease (GvHD)?

Match MHCs as best as possible. Signup and view all the answers

What role do growth factors play in chronic inflammation post-transplant?

They increase proliferation of vascular smooth muscle. Signup and view all the answers

What is a potential method for preventing acute GvHD?

Implementing partial T cell depletion. Signup and view all the answers

How does the immune response in chronic inflammation compare to acute inflammation?

Chronic inflammation involves a longer-term response. Signup and view all the answers

Why is it essential to only focus on covered figures and tables in the material provided?

The scope of knowledge is limited to what was discussed in class. Signup and view all the answers

What is a key difference between the induction and maintenance phases in transplant scenarios?

Induction involves shorter term strategies. Signup and view all the answers

What resource can a student access for immediate mental health crises?

EMPACT Mobile Crisis Intervention. Signup and view all the answers

Which method is not advised for improving transplant outcomes?

Reducing immunosuppressive therapy. Signup and view all the answers

What is primarily responsible for acute rejection in transplant recipients?

Activation of T cells Signup and view all the answers

What mechanism characterizes hyperacute rejection?

Response to pre-existing antibodies Signup and view all the answers

Which of the following statements about chronic rejection is true?

It is primarily mediated by the immune response from T cells. Signup and view all the answers

Which type of graft has the highest likelihood of experiencing immune rejection?

Allograft Signup and view all the answers

What is the role of alloantibodies in transplant rejection?

They can activate complement and mediate tissue injury. Signup and view all the answers

What is the principal purpose of HLA typing prior to transplantation?

To reduce the risk of acute rejection Signup and view all the answers

Which immune response mechanism is associated with graft vs host disease (GvHD)?

Donor T cells attacking recipient tissues Signup and view all the answers

What outcome follows the activation of preexisting antibodies in hyperacute rejection?

Rapid graft failure Signup and view all the answers

Which immunosuppressive drug inhibits IL-2 synthesis?

Tacrolimus Signup and view all the answers

What is associated with acute antibody-mediated rejection?

B cell activation against graft antigens Signup and view all the answers

What is the major factor in determining graft survival in transplant recipients?

Number of HLA mismatches Signup and view all the answers

What is one consequence of chronic rejection in transplanted tissues?

Fibrosis and loss of graft function over time Signup and view all the answers

In which type of rejection do antibodies play a significant role shortly after transplantation?

Hyperacute rejection Signup and view all the answers

How is smooth muscle cell proliferation related to chronic rejection?

It contributes to vascular intima changes and decreased blood flow. Signup and view all the answers

Study Notes

Graft Types

Autograft: Transplant from one individual to the same individual.
Isograft: Transplant between two genetically identical individuals.
Allograft: Transplant between two genetically different individuals of the same species.
Xenograft: Transplant between individuals of different species.

Alloantigens

Alloantigens are foreign antigens found on the surface of transplanted cells/tissues.
They are usually protein antigens encoded by polymorphic genes, which differ among individuals.
Alloreactive T and B cells are lymphocytes that react against alloantigens.

Histocompatibility Antigens

MHC (Major Histocompatibility Complex) molecules: These are responsible for strong immune responses and mismatches in MHC lead to allograft rejection.
Minor histocompatibility antigens: Various molecules that induce weaker or slower rejection reactions.

Histocompatibility and HLA Typing

Histocompatibility type: An individual's unique set of MHC glycoproteins.
Haplotype: A set of MHC alleles on a chromosome. Each person inherits two haplotypes.
- Identical twins are haploidentical (100% HLA-matched).
- Parents have a 50% HLA match with their children (if they are heterozygous).
HLA (Human Leukocyte Antigen) typing is a vital part of transplant assessment to minimize rejection.

Recognition of Allogeneic MHC

Direct Recognition: Donor dendritic cells (cDCs) present alloantigens to recipient T cells, activating them and leading to graft cell destruction by CTLs (Cytotoxic T Lymphocytes).
Indirect Recognition: Recipient cDCs phagocytose graft cells and present peptides derived from donor MHC molecules in class II MHC, activating Th cells, and leading to antibody-mediated injury and inflammation.

Host vs. Graft Rejection

Types of Host vs. Graft Rejection:
- Hyperacute rejection: Occurs within minutes to hours post-transplant. Mediated by pre-existing antibodies against alloantigens on endothelial cells of the graft.
- Acute rejection: Usually occurs within the first two months post-transplantation. Primarily mediated by T cells responding to alloantigens on endothelial and parenchymal cells.
- Chronic rejection: Develops months to years post-transplantation. Characterized by increased fibrosis due to chronic inflammation and vascular smooth muscle cell proliferation.

Preventing Rejection

ABO Blood Typing and Crossmatching: Essential to prevent hyperacute rejection.
HLA Typing: Important for minimizing acute rejection; the fewer mismatches, the better the chance for graft survival.

Graft vs. Host Disease (GvHD)

A serious complication of HSC transplantation (and occasionally other transplants). Occurs when donor T cells from the graft recognize alloantigens on recipient tissues and attack host tissues.
Can be acute or chronic, commonly affecting the skin, liver, and gastrointestinal tract.

Immunosuppressive Therapies

General Immunosuppressive Agents:
- Corticosteroids: Inhibit inflammation, decrease IL-1 and IL-2 production, and reduce MHC expression on APCs.
- Mitotic inhibitors: Inhibit nucleic acid synthesis.
- Examples: Azathioprine (Aza), Mycophenolate mofetil (MMF)
T Cell Specific Immunosuppressive Agents:
- Tacrolimus: Inhibits IL-2 synthesis.
- Basiliximab: Anti-CD25 antibody that blocks IL-2 binding to IL-2R.
- Sirolimus: Inhibits IL-2R signaling (mTOR inhibitor).

Summary Table of Rejection

Type: Hyperacute, Acute, Chronic
Mechanism: Pre-existing antibodies, T cell activation, Th1-mediated inflammation, vascular smooth muscle proliferation
Time Frame: Minutes to hours, 7-10 days to 2-3 months, Months to years
Prevention: ABO typing, Crossmatching, HLA typing
Therapy: Varies, General and specific immunosuppressive therapy

Resources

MWU Student Support: Counseling, Academic Support, Multispecialty Clinic
Teletherapy: Academic Live Care (ALC), 24/7 In the Moment Counseling

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the different types of grafts, alloantigens, and histocompatibility antigens. This quiz covers key concepts relevant to transplantation biology, including MHC molecules and HLA typing. Perfect for students in immunology or medical fields.