We’re the donors jabbees?
Your skin is easily damaged by the sun. So it has a special immune system in place to deal with the damage. When you have a transplant that is not from an identical twin you have to take immunosuppressive drugs or your body will quickly destroy the new organ. It still does, even with the drugs, but at a much slower rate.
The problem is that those drugs also take out your skin's special immune system that normally would sweep the cancer cells away.
So people who have had transplants need to be careful about light. I use that word because even the radiation from an artificial light does damage. Just less. Fire light is the least harmful but it is really not practical to stay indoors at all times and your only light be candles.