Why does organ transplant work well with relatives?

Answer 1

For kidney transplants, which require a tissue match as well as a blood type match, it is more likely that a sibling/parent/relative will have the right type of tissue. Waiting for a non-related organ to become available can take 3-5 years, by which point the patient can be really ill. Plus dialysis many times a week is a nuisance.

With a donated kidney from someone related, you know what day you're having the surgery (no waiting for a random phone call), you know that somebody did not have to die for it and you don't need to spend years on dialysis.

Most other organ transplants do not require tissue typing (i.e heart, lungs, liver, pancreas), but still blood typing and size matching, which means that a stranger is just as likely to be a match as a realtive. But for hearts, lungs etc... you clearly can't take these from a living sibling. (You can take part of a liver, or rarely part of a lung, but not an entire lung, since this would compromise their quality of life). In these cases, a cadaveric donation is necessary.

There are some major negatives of getting an organ from a sibling. If the transplant your require is for an autoimmune disease, getting an organ that is related to you will usually mean that the disease will recur in the transplanted organ. (Since you're body thinks it's too genetically similar to your own.) Related transplants for autoimmune diseases typically have really bad outcomes (retransplantation or death). That's the major downside. Others include possilby compromising the sibling's health.

Answer 2

If the individuals are related, the genetic make-up of the organs are likely to be similar, so in theory the organ should be less likely to be rejected.

However... if the recipient is being transplanted because an auto-immune condition (a condition where your body attacks part of your own body) prevented their original organ functioning properly, transplanting an organ which is related to that person is generally a bad idea. Since the organs would be similar, the recipients body is likely to attack the new organ because it is too similar to the original. In these instances, outcomes are generally better if donor and recipient are not related.