Why does our body reject other people’s donated organs and require immunosuppressants to be taken but getting someone else’s blood is ok?

Question

Why does our body reject other people’s donated organs and require immunosuppressants to be taken but getting someone else’s blood is ok?

In: 157

Answer 1

People are talking about A,B,O antigens and red blood cells not having a nucleus, but that’s not the main reason.

The single most important factor for organ rejection is MHC-1 (this is the thing that’s being tested when you test if you’re a match for organ donation). Red blood cells don’t express it.

Slower rejection based on more subtle mismatches don’t really matter because you don’t need the donor cells to survive long term anyway.