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An alternative approach that is gaining renewed research interest is genetic modification of donor animals, such as pigs, to provide transplantable organs that do not elicit an immune response in the recipient. The approach involves excising the genes in the pig (in the embryo) that are most responsible for the rejection reaction after transplantation. Finding these genes and effectively removing them is a challenge, however. So too is identifying and neutralizing risks from viral sequences that might be embedded in the pig genome, posing a risk for infection in the human recipient.

Resolution

Kerry's tests come back positive, confirming a diagnosis of lupus , a disease that occurs 10 times more frequently in women than men. SLE cannot be cured, but there are various therapies available for reducing and managing its symptoms. Specific therapies are prescribed based on the particular symptoms presenting in the patient. Kerry's rheumatologist starts her therapy with a low dose of corticosteroid s to reduce her rashes. She also prescribes a low dose of hydroxychloroquine, an anti-inflammatory drug that is used to treat inflammation in patients with RA, childhood arthritis, SLE, and other autoimmune diseases. Although the mechanism of action of hydroxychloroquine is not well defined, it appears that this drug interferes with the processes of antigen processing and activation of autoimmunity. Because of its mechanism, the effects of hydroxychloroquine are not as immediate as that of other anti-inflammatory drugs, but it is still considered a good companion therapy for SLE. Kerry’s doctor also advises her to limit her exposure to sunlight, because photosensitivity to sunlight may precipitate rashes.

Over the next 6 months, Kerry follows her treatment plan and her symptoms do not return. However, future flare-ups are likely to occur. She will need to continue her treatment for the rest of her life and seek medical attention whenever new symptoms develop.

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Key concepts and summary

  • Grafts and transplants can be classified as autografts , isografts, allografts , or xenografts based on the genetic differences between the donor’s and recipient’s tissues.
  • Genetic differences, especially among the MHC (HLA) genes, will dictate the likelihood that rejection of the transplanted tissue will occur.
  • Transplant recipients usually require immunosuppressive therapy to avoid rejection, even with good genetic matching. This can create additional problems when immune responses are needed to fight off infectious agents and prevent cancer.
  • Graft-versus-host disease can occur in bone marrow transplants, as the mature T cells in the transplant itself recognize the recipient’s tissues as foreign.
  • Transplantation methods and technology have improved greatly in recent decades and may move into new areas with the use of stem cell technology to avoid the need for genetic matching of MHC molecules.

Matching

Match the graft with its description.

___autograft A. donor is a different species than the recipient
___allograft B. donor and recipient are the same individual
___xenograft C. donor is an identical twin of the recipient
___isograft D. donor is the same species as the recipient, but genetically different

B, D, A, C

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Fill in the blank

For a transplant to have the best chances of avoiding rejection, the genes coding for the ________ molecules should be closely matched between donor and recipient.

MHC

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Because it is a “transplant” that can include APCs and T cells from the donor, a bone marrow transplant may induce a very specific type of rejection known as ________ disease.

graft-versus-host

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Short answer

Why is a parent usually a better match for transplanted tissue to a donor than a random individual of the same species?

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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