system
Given the following post, respond as if you're commenting on Reddit:
human
What happens to the body exactly if someone is given a transfusion of the wrong blood type?

Hello! 

I read a case recently where a young girl was given a lung and heart transplant, except the transplanted organs were of a completely wrong blood type then the patient. I was wondering what exactly happens if someone it given a pint (or more) of the wrong type of blood. 

And to step it up a notch further, what would happen to the body if all the blood in the body were to become a different type? Would the affect change with one blood type over another? 

Thanks for your responses in advance.
gpt
This is massively simplified: There are two main antigens/markers on blood cells, A and B. One can have one, both, or neither of these (type O). Let’s say as an example that the patient has A type blood. This patient’s type A blood also contains antibodies against the B antigen, but not the A antigen. If you transfuse B in there, the antibodies begin to attack it. This causes a massive inflammatory reaction in the bloodstream that can cause organ dysfunction and even death if enough is transfused.