If most organ cells, like in the liver, are replaced every three years or so, why isn’t a transplant eventually accepted by the new body?

Question

If most organ cells, like in the liver, are replaced every three years or so, why isn’t a transplant eventually accepted by the new body?

In: 350

Answer 1

Because the replacement cells are still made by the donor organ.

The problem with transplants is that host’s immune system recognizes them as foreign and wants to attack them. If Alice received a kidney from Bob, Alice’s immune system recognizes the cells in Bob’s kidney as not-Alice. When Bob’s kidney’s cells get replaced over time, it’s Bob’s kidney that’s doing the replacement. So all the new cells have “Bob” written all over them, and not “Alice”, because they were built based on Bob’s blueprints (DNA) and not Alice’s.