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

First, that 3 year rule is basically nonsense. Cell turnover varies substantially between organs, tissues, and cell types. Second, the transplanted organ produces proteins that the host immune system identifies as foreign and attacks. Sure, the cells in the transplanted organ will divide and expand, but all the cells that are derived from the transplant contain the same incompatible proteins and will continue to be identified as foreign.