A friend tells you the following story. "My aunt just received a heart transplant. Her doctors warned us that her body might reject the tissue. I just can't understand how that could happen as human hearts are made of the same tissues, aren't they?" How do you respond?

Question

A.  "Yes, all human hearts are made of cardiac muscles."
B.  "Yes, all human hearts are made of cardiac muscles, except some humans have different tissues inside their hearts and this could lead to a tissue rejection by the recipient."
C.  "Yes, all human hearts are made of cardiac muscles. As far as the rejection of tissues goes, your aunt might have different antibodies than did the donor, which could lead to a rejection."
D.  "Yes, all human hearts are made of cardiac muscles. However, your aunt might have been given some type of drug during the transplant operation that might cause tissue rejection. You can never be too careful in a hospital, you know."
E.  "Yes, all human hearts are made of cardiac muscles. As far as the rejection issue, everyone has different MHC proteins on their tissues. Your aunt's immune system recognizes the ‘self' tissues but can cause tissue rejection because of the ‘nonself' tissue in her body having different MHC proteins."


Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?
 
Gather Content
What do you already know about tissues and transplants? What other information is related to the question?

  Choose Answer
Given what you now know, what information is most likely to produce the correct answer?

Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
 

Answer 1

E.  "Yes, all human hearts are made of cardiac muscles. As far as the rejection issue, everyone has different MHC proteins on their tissues. Your aunt's immune system recognizes the ‘self' tissues but can cause tissue rejection because of the ‘nonself' tissue in her body having different MHC proteins."

Clarify Question
What is the key concept addressed by the question?
        · This question is asking about the underlying cause of transplant rejection.
What type of thinking is required?
        · Apply level:
            o You are being asked to take what you already know and use, or apply, it to understand the cause of transplant rejection.
 
Gather Content
What do you already know about tissues and transplants? What other information is related to the question?
        · In vertebrates, 4 tissue types give rise to all structures in the body. These are the epithelial, muscle tissue, connective tissue, and nervous tissue.
        · Tissues are arranged into organs.
        · An organ in one person is made of the same type of tissue in another person. For instance, heart tissue includes cardiac muscle in all people.
        · In addition to the foundational tissues that do not differ between people, within a species, there are molecular markers that include species, individual and tissue-level identity. These include MHC markers.
        · The immune system of one individual recognizes self-markers and does not attack tissue with those markers.
        · Anything that lack self-markers is attacked by the immune system.

  Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
        · Although organs are made of the same general tissue types, individual MHC markers differ between individuals.
        · Transplant rejection is not caused by pharmaceutical ingestion.
        · If non-self markers are encountered, the immune system attacks the foreign tissue, which causes transplant rejection.

Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        · Apply level:
            o Answering this question correctly depended on your ability to use immune function in a new situation. If you got an incorrect answer, did you remember that tissues have MHC markers on them, or that if the immune system does not recognize the markers, that the tissue is attacked? Did you have trouble extending immune function to determine the correct answer?