Why is organ transplantation possible?

Question

Just part of my science homework that's i'm having trouble with...

Answer 1

Because of advances in medicine. Back in the days when immunosuppression was still not particularly understood, organ transplantation would have been impossible. You see, even if the organ to be transplanted was obtained from the closest possible donor, the body of the recipient would still react negatively to transplant, since the recipient's body would recognize it as non-self. The body will then do everything to reject the transplanted organ. Since the development of immunosuppresive agents, doctors have found a way to keep this reaction to a minimum, thus letting the recipient's body to to accept the transplanted organ without much reaction.

Answer 2

Based on the fact that you are questioning this, you must understand that the body has an immune system, and that the immune system destroys objects that are NOT identified as self.
Basically, it is impossible to find exact matches for organ donors (even identical twins have some immunological differences that make transplants not 100% perfect).

Since most cells of organs from person to person pretty much express the same surface molecules (antigens), the problem will be with something called MHC, which is involved with the immune system recognizing antigen. Basically every cell expresses MHC I, which allows the host to recognize self, and special immune cells express MHC II. MHC are encoded by genes of the HLA haplotype, and are evolutionarily conserved, meaning a lot of people share HAPLOTYPES. So when performing a transplant, they set out to find donors and recipients with compatible HLA haplotypes so the host immune system will recognize the donor cells as SELF.

Of course even before HLA is considered, blood group antigens (ABO) must be considered, or it will be rejected in seconds and minutes (hyperacute rejection) if there is not a match.

Now, even if good HLA matches are found, there will still be some immunological activity directed against the donor cells since they are not an exact match. Immunosuppressive therapy is used to counteract this, by blocking IL-2 receptors on T-Cells, T-Cell activity is slowed.

Answer 3

For medical transplantation to be successful, physicians must elude the combative efforts of the body’s complex immune system, which fights to protect the body from infections of all sorts. Central to the functioning of the immune system is its ability to distinguish between invading or foreign matter, which should be attacked, and matter that is a normal part of the body, which should not be attacked. This recognition system uses specific markers called histocompatibility antigens that are on the surface of all cells in an individual’s body. The immune system attacks anything that lacks these histocompatibility antigens or has antigens different from those found in the rest of the body, such as those found on invading viruses, bacteria, or other microorganisms. This recognition system causes the immune system to attack transplanted tissues that have different antigens because it has no way to distinguish between harmful and beneficial foreign matter.

The odds that two unrelated people will have the same set of histocompatibility antigens are about one in 30,000.

There are over 200 different histocompatibility antigens, with each individual having a specific set of them. The odds that two unrelated people will have the same set of histocompatibility antigens are about one in 30,000. Transplant surgeons attempt to match histocompatibility antigens of the donor and the recipient as closely as possible in order to minimize rejection. In most cases, the match will not be exact, and the recipients must take drugs to suppress the immune response. The first drugs that were used were azathioprine and prednisone. But these drugs suppress the entire immune system, leaving the recipient vulnerable to infections and certain cancers. They also have toxic side effects.

A major breakthrough in immune suppression was the development of cyclosporine, a natural product derived from a fungus found in soil. Cyclosporine suppresses the part of the immune system involved in organ rejection with less severe impact on other parts of the immune system. A few years later, the drug tacrolimus (FK-506) was found to be even more effective for kidney, liver, heart, and lung transplants. However, patients who take these two drugs still face some increased risk of infection and cancer, and the drugs can cause kidney damage. Doctors often use a combination of immune-suppressing drugs to limit these side effects.

Answer 4

►because we have a common genetic system..........