Question 1

The main immune response in a case of chronic rejection of a transplanted organ is:&#10;A) B cell activation&#10;B) Both B and T cell activation&#10;C) Allospecific T cell activation&#10;D) Attack of organ by pre-existing antibodies

Accepted Answer

Hyperacute rejection is mediated by pre-existing antibodies to donor antigens, such as HLA or ABO antigens, and begins immediately after the graft is attached to the recipient. Acute rejection is mediated by allospecific T cells. Passenger leukocytes, which are donor dendritic cells, travel to the lymph nodes and activate recipient T cells, leading to an immune response that damages the grafted organ. Chronic rejection occurs after months or years and involves both B and T cell responses. Thickening of the vascular intima, along with smooth muscle proliferation, can lead to blockage of vessels and ischemia of the transplanted organ.

Question 2

Direct antigen presentation occurring during allogeneic graft rejection occurs when:&#10;A) Donor APCs present antigen to the donor T cells&#10;B) A recipient's T cells recognize donor cells as foreign&#10;C) Donor antibodies bind to recipient cell surface molecules&#10;D) A recipient's T cells recognize foreign antigen processed on the recipient's APCs

Accepted Answer

Direct antigen presentation occurs when the recipient directly recognizes foreign antigen on the cell surface of donor APC and endothelial cells of the donor organ or tissue. Indirect antigen presentation occurs when the donor antigens are processed by the recipient's APCs and presented to recipient T cells.

Question 3

Which of the following are advantages of peripheral blood stem cell transplant over traditional bone marrow transplant?
I. Rapid engraftment
II. Sample collection is easy
III. Higher graft survival rates

A) I only
B) III only
C) I and II
D) II and III
E) I, II, and III

I, II, and III

Accepted Answer

With peripheral blood stem cell transplant, sample collection is easier and less invasive than traditional bone marrow aspiration, and often with a greater number of stem cells harvested. The engraftment to the recipient bone marrow is rapid, and, therefore, recovery to normal cell numbers is quicker. In the end, patients have higher graft survival rates than with tradition bone marrow transplant as well.

Question 4

A patient may have pre-existing antibodies to a major or minor HLA antigen caused by:
I- Medication
II- Pregnancy
III- Previous transplant

A) I only
B) III only
C) I and II
D) II and III
E) I, II, and III

Accepted Answer

A patient may be exposed to major and minor HLA antigens that are not self through pregnancy or previous transplants, which increases the difficulty of finding a compatible organ. Medication is not likely to cause the production of antibodies to HLA antigens.

Question 5

How is the T cell response during transplant rejection different from the response during an infection?&#10;A) Few T cells are responding during rejection&#10;B) No T cells respond during rejection, only B cells&#10;C) The number of T cells responding is much higher during rejection&#10;D) The same amount of cells respond, but the response is stronger during rejection

Accepted Answer

During a transplant, the number of T cells that responds is much higher than during an infection. The exact mechanism is not completely understood, but many T cells recognize the graft as foreign and are activated, whereas in an infection, once a few T cells are activated, the immune response continues without the further activation of new naïve T cells.

Question 6

The main immune response in a case of acute rejection of a transplanted organ is:&#10;A) B cell activation&#10;B) Both B and T cell activation&#10;C) Allospecific T cell activation&#10;D) Attack of organ by pre-existing antibodies

Accepted Answer

Hyperacute rejection is mediated by pre-existing antibodies to donor antigens, such as HLA or ABO antigens, and begins immediately after the graft is attached to the recipient. Acute rejection is mediated by allospecific T cells. Passenger leukocytes, which are donor dendritic cells, travel to the lymph nodes and activate recipient T cells, leading to an immune response that damages the grafted organ. Chronic rejection occurs after months or years and involves both B and T cell responses. Thickening of the vascular intima, along with smooth muscle proliferation, can lead to blockage of vessels and ischemia of the transplanted organ.

Question 7

Without genetic modification, what is the main cause of rejection in xenotransplants?&#10;A) Transfer of infection&#10;B) Organs are the wrong size&#10;C) The minor HLA antigens do not match&#10;D) Pre-existing antibodies to alpha-galactosyl

Accepted Answer

Organs of most species other than humans have alpha-galactosyl on their cell surfaces, and humans have pre-existing antibodies to the antigen, leading to hyperacute rejection. The organs are the correct size for transplantation, and the risk of transfer of infection is unknown at this point, since hyperacute rejection occurs before determination of transfer of infection could be made. HLA antigens are specific to humans, so an HLA match cannot be made. Genetic modification of the donor species can eliminate expression of alpha-galactosyl on the surface of the xenograft to reduce the chance of rejection.

Question 8

RD was involved in a car accident and had burns on his right forearm. Doctors removed skin from his leg and grafted it onto his arm. What type of transplant is this?&#10;A) Isograft&#10;B) Allograft&#10;C) Autograft&#10;D) Xenograft

Accepted Answer

When a graft of tissue or marrow is taken from an individual and returned to the same individual, this process is an autograft. An organ, tissue, or marrow transplant from one individual to a genetically identical individual is known as an isograft. A graft between two genetically different individuals of the same species is an allograft. A graft between individuals from two different species, such as a pig heart transplanted into a human, is a xenograft.

Question 9

One of the steps taken to avoid graft-versus-host disease (GVHD) is:&#10;A) Immunostimulation&#10;B) Matching minor histocompatibility&#10;C) Removing all T cells from the graft&#10;D) Removing all B cells from the graft

Accepted Answer

The damage from graft-versus-host disease occurs because functioning donor T cells are transplanted into the recipient as part of the graft. Those donor T cells recognize the recipient as foreign, which leads to the release of proinflammatory cytokines and activates the recipient's immune cells. The response leads to damage of the recipient's tissue. Some of this response may be due to minor HLA antigens, but there are hundreds of minor HLA antigens, which are too many to test for. Immunostimulation would make the problem worse, and the damage is not mediated by B cells, so removing them from the graft would not improve the outcome.

Question 10

Which immunosuppressive agent causes redistribution of CD4 T cells from the peripheral blood to the spleen and bone marrow?&#10;A) Corticosteroids&#10;B) Monomurab-CD3&#10;C) Calcineurin inhibitors&#10;D) Antiproliferative agents

Accepted Answer

Corticosteroids have a variety of effects on the immune system, one of which is to cause CD4 T cells to move out of the peripheral blood and into the spleen and bone marrow. T cell proliferation and B cell maturation are also reduced by corticosteroids. The calcineurin inhibitors block interleukin-2 (IL-2) synthesis, which blocks T cell stimulation. The antiproliferative agents block proliferation of T and B cells. Monomurab-CD3 is a monoclonal antibody that inhibits T cell activation.

Deck 17: Transplantation