How can DNA Technology Be Used in Organ Transplants?
Posted August 3, 1998
Every year, tens of thousands of people wait for an organ transplant, such as a heart, liver, lung, or kidney. Unfortunately, the supply of organs is limited and not
all transplants are successful. The human immune system identifies the transplanted cells as foreign, just like harmful bacteria or viruses, and tries to destroy them. Identification
of foreign cells by the immune system depends on the proteins found on the cell's surface. How can scientists use DNA technology to provide more organs for transplant and protect them
from the body's immune system?
Research with pigs may provide an answer. Pig organs are very similar in structure to human organs and could be readily available for transplants. However, the surface
proteins of pig cells are quickly recognized as foreign by the human immune system and destroyed. If these proteins could be genetically altered to more closely resemble human proteins,
the immune system would not attack them.
Complement inhibitor is a protein found on human cells that signals the immune system not to attack. This surface protein is not on pig cells. Using DNA technology,
scientists added strands of DNA containing this human gene to fertilized pig eggs. In some cases, the human DNA was incorporated into the pig DNA and the pig cells produced the human
complement inhibitor protein. An organ from one of these pigs was transplanted into an ape. The presence of human complement inhibitor protein gave some protection to the pig organ,
however, the ape's immune system eventually recognized the pig cells and destroyed them.
Scientists realize that even with human surface proteins, the presence of other pig proteins would still leave the cells vulnerable to the immune system following
an organ transplant. To solve this problem, they added a gene to pig DNA. The gene is for an enzyme that would alter one of the pig's proteins to make it more human-like. Scientists
are now trying to breed pigs that contain both the human complement inhibitor protein and the altered pig protein. No one knows how many human proteins will have to be added to pig cells,
or how many pig proteins will have to be altered before pig cells will be accepted by the human immune system.
Using these DNA techniques and others, researchers are hoping to create cells that will be accepted by the human immune system. This may provide more hope for transplant
patients.
Think Critically
What might some of the risks be in transplanting organs from a pig into a human?
References
Poole, Robert. "Saviors." Discover, May 1998, Vol. 19, No. 5, pp. 52-57.
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