Immune System

Question 0

Mr Ayers, had surgery on his dissected aorta.  As a result, a clot formed that caused a massive stroke. Unfortunately, this left him with severe and permanent brain damage, and he was declared brain dead.
A discussion of Mr. Ayers's situation with his family confirmed his statis as an organ donor. The organ recovery coordinator evaluated Mr.Ayers suitability as a candidate for organ donation.
Tissue typing (histocompatibility) tests were conducted, and the results were entered into UNOS database. Two potential recipients were identified. Mr.Ayers's right kidney was given in transplantation to a 35 year old man, and his left kidney was given to a 27 year old woman. Following surgery, both recipients were placed on immunosuppressive drug therapy.

Answer 0

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Question 1

Tissue typing characterizes the class I and II MHC proteins. What is an MHC protein?

Answer 1

A major histocompatibility complex MHC protein is a type of cell surface protein that the human body uses to recognize self and to help coordinate the recognition of nonself, or foreign, antigens. These proteins are involved in the display of antigens to T cells.

Question 2

In organ transplants, the transplanted organ is referred to as a graft? What type of graft is represented by the two kidneys that Mr. Ayers had donated?

Answer 2

The two kidneys transplanted in this case represent allografts.

Question 3

What is the difference between class I and class II MHC proteins?

Answer 3

Class I MHC proteins are found on virtually all of the body’s cell, while class II MHCs are found only on antigen-presenting cells (APCs). Class I MHCs display antigens for recognition by CD8 T cells ( including cytotoxic T cells). Class II MHCs display antigens for recognition by CD4 T cells (including helper T cells).

Question 4

Why is the matching of MHC molecules and tissue compatibility so important in this case?

Answer 4

A foreign MHC protein will provoke an immune response, so the donor’s and recipient’s MHCs must match as closely as possible to minimize attack. Tissue typing dramatically reduces the risk of organ rejection due to attack by the recipient’s immune system.

Question 5

Why were the recipients of the two kidneys put on immunosuppressive drug therapy?

Answer 5

In this case, the donor and recipient were not genetically identical. Even with very careful tissue typing and compatibility testing, there will still be some differences that the recipients’ immune systems will recognize as foreign. To reduce the risk of organ rejection, the recipients are given drugs to suppress their immune system.