system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens when a person is given a wrong type of blood.

For example: If someone who requires O- ,gets O+
gpt
If given the wrong blood type their body will react to the blood as it would any other invading organism, with the immune system breaking down the blood cells as fast as it can. This can cause clotting throughout the body which can lead to organ failure, and the mess from all of the dead cells needs to be cleaned up by the kidneys which might be overwhelmed and damaged. The clotting factors might all be temporarily used up and leave the patient open to excessive bleed (which is why they presumably were given blood in the first place).