Our immune systems tend to mount an immune response to the entry of an antigen from the same species (Eg. renal transplant). Discuss on the factors to be considered to prevent renal transplant rejection. Artificial implants (like pace makers, knee/hip joints...) and corneal transplants are not rejected by our immune system? WHY?


Let's familiarized ourselves with terms like:

Immune System

• The body's innate defense against disease isnatural immunity [reference 2].

Renal Transplant

transplanting kidney to a patient with end-stage renal disease.

Click HERE to view a renal transplant animation!

Transplantation

• The act or process of transplanting a tissue or an organ from one body or body part to another.
  
• The artificial removal of part of an organism and its replacement in the body of the same of a different individual.

***
What is Transplant Rejection?
When the immune system of the recipient of a transplant attacks on the transplanted organ or tissue.

This is because a normal healthy individual human immune system can distinguish foreign tissues and destroy them.

Inactive organisms such as bacteria and viruses are destroyed in this way!

Adaptive immune response is mediated through both T-cell mediated and humoral immune (antibodies) mechanisms.
The T lymphocyte activation pathway. T cells contribute to immune defenses in two major ways: some direct and regulate immune responses; others directly attack infected or cancerous cells. [reference 4]

Renal Rejection is an Acute Rejection..
It occurs to some degree in all transplant excepts between identical twins. It is caused by a mismatch Human Leukocyte Antigens (HLA) present on all cells.

Renal Rejections can be prevented by

• Getting your twin to donate their liver as T-cell mediated response will not be generated to the transplanted organ.
  
• Ensuring donor and recipient are ABO blood group compatible.
  
• Perform cytotoxic crossmatch prior to the transplantation to ensure that antibodies to the donor are not present. Donor and recipient should ideally share as many antigens (molecules that stimulate antibody generation) as possible.
  
• Taking medicines (immuno-suppressants) to suppress the immune system from rejecting the donor's organ.

Acute rejection is normally treated initially with short course of high dose methylprednisolone!

Common drugs used to prevent transplant rejection

• Azathioprine
  
• Prednisolone
  
• Rapamune [reference 1 & 6] combined with cyclosporine and corticosteriods

HOWEVER...
These drugs can cause side effects like weight gain, rapid growth of body hair etc) or weaken your immune system in fighting off other infections.

The drugs make the skin more sensitive to the effects of sunlight (sunburn and even a slightly increased risk of getting skin cancer) hence it is important to protect yourself from the sun.

DO YOU KNOW...
NOT all implants will get rejected...
Noncellular tissues where the donor cells are not important to the graft can usually be successfully transplanted without any signs of rejection.

Bone Marrow Transplant effectively bring their own immune system with them, often rejecting the new host, instead of the other way round, in a reaction known as gaft-versus-host disease[reference 3].

Corneal Transplant have a high success rate largely because there are fewer blood vessels in the cornea that corneal antigens may never enter the host's system to stimulate an immune reaction [reference 5].

Click HERE to view how a corneal transplant is carried out!
Heart Pace-maker, Joints and Bones can be transplanted successfully because such organs (prostheses) do not produce antigenic substances.

***
References

1. U.S. Food and Drug Administration. (2007). Rapumune. Retrieved 10 Feburary, 2007 from http://www.fda.gov/ohrms/dockets/ac/99/slides/3529s1h/sld004.htm



2. The National Pediatric Myoclonus Center. (2007). The immune system. Retrieved 10 Feburary, 2007 from http://www.omsusa.org/index.htm

3. University of Maryland Medical Center. (2004). Bone Marrow Transplant. Retrieved 10 Feburary, 2007 from http://www.umm.edu/surgeries/bonemarrowtransplant_3.html

4. Wikipedia. (2007). T lymphocytes. Retrieved 8 Feburary, 2007 from http://en.wikipedia.org/wiki/Adaptive_immune_response

5.Wikipedia. (2007). Corneal transplantation. Retrieved 10 Feburary, 2007 from http://en.wikipedia.org/wiki/Cornea_transplant

6. Wyeth. (2006). Rapamune. Retrieved 10 Feburary, 2007 from http://www.wyeth.com.tw/products/medicine/rapamune_tablets.html

this blog is managed by

stefenie

trina

xinru

yong ying

supported by our mentor Mdm Kalpana.