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Hazim, Yong Siang, BooKeong, YuYuan (PBPN)

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Sunday, February 7, 2010
Our immune system tends to mount an immune response to the entry of an antigen from the same species (e.g. renal transplant).Discuss on the factors to be considered to prevent renal transplant rejection. Implants (like pace makers, knee/hip joints) and corneal transplants are not rejected by our immune system? Why?

Antigen - Any substance that, when introduced into the body, it is recognized by our immune system as a foreign macromolecule and elicits an immune response, or even a portion of one of these organisms.

In order for our immune system to mount an immune response, T lymphocytes are produced. T-lymphocytes are cells that belong to the group of white blood cells which helps to build up the immune system for the body against pathogens, toxins, allergens and micro organisms

T-lymphocytes provide the body via cell mediated immunity. When the body senses foreign antigen in the body, the body will activate antigen-specific cytotoxic T lymphocytes “Killer T lymphocytes”, which will be able to kill and destroy the foreign antigen.

After that, T-lymphocytes provide the body via cell mediated immunity. When the body senses foreign antigen in the body, the body will activate antigen-specific cytotoxic T lymphocytes “Killer T lymphocytes”, which will be able to kill and destroy the foreign antigen.

So how does T lymphocyte interfere with kidney transplant?

During kidney transplant, as the transplant kidney possess antigen that is different from the host body, thus after the transplant operation, the body will activate cytotoxic T lymphocytes to cause cells in the transplanted tissue to lyse and cause the death of the transplanted tissue.


Why does rejection takes place?

Rejection is an adaptive immune response and is mediated through both T cell mediated and humoral immune (antibodies) mechanisms. The amount of mismatched alleles determines the speed and magnitude of the rejection response.

Transplant rejection occurs when a transplanted organ or tissue is not accepted by the body of the transplant recipient. Its because the immune system of the recipient attacks the transplanted organ or tissue. This is expected to happen, as the immune system's purpose is to identify foreign material within the body and attempt to destroy it, just as it attempts to destroy infecting organisms such as bacteria and viruses.


Factors to consider to prevent renal transplant rejection

1. blood type and size of the organ(s) needed

2. Free from any disease, infection or injuries that affects the kidney
3. the relativity between donor and recipient
4. the medical urgency of the recipient
5. the degree of immune-system match between donor and recipient
6. whether the recipient is a child or an adult

The use of adult donors for transplantation in children under 1 year of age is impossible.

There is a need of a careful preoperative hydration in order to prevent hypotension and to minimize the chance of a renovascular thrombosis.

Firstly, the suitability of donor is based on two factors this two factors first
  • Blood type. Your blood type (A, B, AB, or O) must be compatible with the donor’s blood type.
  • HLA factors. HLA stands for human leukocyte antigen, a genetic marker located on the surface of your white blood cells. A higher number of matching antigens between the transplanted kidney and the recipient body decrease the chance of transplant rejection and allowing the kidney transplant to last in the body.
If you're selected on the basis of the first two factors, a third is evaluated:
  • Antibodies. Your immune system may produce antibodies that act specifically against something in the donor’s tissues. To see whether this is the case, a small sample of your blood will be mixed with a small sample of the donor’s blood in a tube. If no reaction occurs, you should be able to accept the kidney. Your transplant team might use the term negative cross-match to describe this lack of reaction.

ABO blood typing and HLA (tissue antigen) typing before transplantation are done to help to ensure a close match. Suppressing the immune system is usually necessary for the rest of the transplant recipient's life to prevent the tissue from being rejected. Being careful to take post-transplant medications properly, and being closely monitored by your doctor may help prevent rejection.

ABO blood typing

This test is done to determine a person's blood type. Health care providers need to know your blood type when you get a blood transfusion or transplant, because not all blood types are compatible with each other. For example:

  • If you have type A blood, you can only receive types A and O blood.
  • If you have type B blood, you can you can only receive types B and O blood.
  • If you have type AB blood, you can only receive types A, B, AB, and O blood.
  • If you have type O blood, you can you can only receive type O blood.

Type O blood can be given to anyone with any blood type. That is why people with type O blood are called universal donors.

Donors can be of Live Related or Live Unrelated

Live Related Donor: A live related donor kidney comes from a blood relative, like a parent, brother, sister, or an adult child. Points to remember:

  • A kidney from a relative will be a better match. This means that there is less chance of rejection and you will not have to take as much (immunosuppressive) medicines.
  • There is no waiting time after the evaluation for a living related transplant unless the donor needs to have some medical problems taken care of.
  • You and the transplant team can plan when to have the transplant surgery.
  • Fewer people need temporary dialysis after a living related transplant than after a cadaver transplant.
  • The donor needs about 6-8 weeks to recover.

Cadaveric Donor: A cadaver donor kidney (kidney/pancreas) is one that comes from a person who has just died. This person has given permission for the kidneys, and possible other organs, to be donated for someone who is in need of a transplant.

Live Unrelated Donor: A live unrelated donor kidney comes from someone who is not related to the person, like a spouse or a friend.

  • There is no waiting time after the evaluation for a living unrelated transplant unless the donor needs to have some medical problems taken care of.
  • You and the transplant team can plan when to have the transplant surgery.
  • Fewer people need temporary dialysis after a living unrelated transplant than after a cadaver transplant.
  • The only difference is the donor will need about two months to recover.

Artificial implants (like pace makers, knee/hip joints) and corneal transplants are not rejected by our immune system? Why?

Pace makers - A small, battery-operated dvice that helps the heart beat in a regular rhythm

  • A pacemaker uses batteries to send electrical impulses to the heart to help it pump properly. An electrode is placed next to the heart wall and small electrical charges travel through the wire to the heart.

  • Most pacemakers are demand pacemakers. They have a sensing device. It turns the signal off when the heartbeat is above a certain level. It turns the signal back on when the heartbeat is too slow.


Pacemakers are designed in a way that it will rarely be rejected by the body’s immune system. As it is usually made of titanium, which is very static in the body. Titanium is also immune to corrosion by the body fluids.

Knee/Hip Implants

Likewise, for knees and hip implants. The implants are made from mostly Titanium and Cobalt-chrome. Titanium are used, for example it can make fiber metal which are layers of metal fibers bonded to the surface of an implant which allows the bone to grow into the implant or cement to follow into the implant for a better grip.

Corneal Transplants

They are rarely rejected because corneas have no blood supply. It gets oxygen and other nutrients from nearby tissues and fluid. Immune cells and antibodies do not reach the cornea to cause rejection, Tissues with a rich blood supply are more like to be rejected. In addition, transplants from one identical twin to another are almost never rejected.

Thank you for reading!

References

http://www.usckidneytransplant.org/patientguide/donor.html

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1677-55382005000600009

http://www.merck.com/mmhe/sec16/ch187/ch187h.html

http://www.nlm.nih.gov/medlineplus/ency/article/000815.htm

http://www.europeanmedicaltourist.com/heart-surgery/cardiac-pacemaker.html

http://www.hipsandknees.com/knee/kneeimplants.htm

http://www.zimmerindia.com/z/ctl/op/global/action/1/id/9480/template/PC

3:19 PM
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