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

My cells have my unique DNA that’s a combo from my mom and dad. Your cells have your unique DNA that’s a combo from your mom and dad.

Let’s say we want to transplant your liver into my body. Your liver is made up of your cells, and your DNA. My body is made up of my cells and my DNA. If we stick your liver in my body, my body will think your DNA is a foreign invader, and will attack.

It’s not exactly the same concept, but a good analogy would be thinking about why our body responds to a bacterial/viral infection. Our body recognizes that the bacteria/virus is “foreign” because the genetic material is different than the DNA in our own cells, and activates the immune system to attack these invaders. Similarly, my body will recognize that your cells are “foreign” because it’s not the same DNA, and will activate the immune system.

As an aside, this is why we want organs donors to be a “match”. The closer the donor matches the recipient, the less likely the recipient’s immune system will think the organ is an invader, which means the organ is less likely to get rejected.

Also, idk where you got the 3 year cell turnover rule, but that’s not really accurate. Certain cells (for example, the heart and brain), essentially never regenerate. This is why heart attacks and strokes are bad—those cells are dead and can’t come back. Meanwhile, skin cells and cells in our intestines regenerate pretty rapidly.