Why is the immune system an obstacle to organ transplantation?

Answer 1

The body triggers an immune response because it detects a foreign object in the body. It is the same concept of a splinter. The body detects it and tried to push it out because it knows it isn't supposed to be there. your brain isn't trained to know that an organ transplant is to help the body out so it just sees it as an invader

Answer 2

When an organ from one person is transplanted into another person, there are slight differences on the surfaces of the cells from the original organ and the new organ. The immune system is designed to distinguish between self and non-self. The new organ is non-self. As a result, a new organ may be attacked by the immune system.

The immune system tries to kill the cells in the transplanted organ. An interesting thing can happen in the liver. The liver constantly regenerates itself. Sometimes when the immune system attacks a transplanted liver, the person's own stem cells move to the liver and start replacing the destroyed cells. Eventually the liver becomes totally made of the persons own cells. One woman's liver became made from her child's cells and one from her husband's.