Why different blood types can't be mixed

Blood. It's pretty simple, right? It's the red crap that comes out when you fall down. Running low? Head to your local hospital and have them top you off. Got too much? Give some to your buddy or your dog.

Not so fast, Bleedy Gonzales. Before you get the old tissue oxygenation oil changed, there's a whole lot of science to be done, because even the slightest mistake in this relatively routine procedure can lead to ... and this is fun — a violent, horrifying death.

Bloody awful

Here are the bare bones basics, as presented by the helpful folks at the Australian Academy of Science: Everybody has a blood type, which indicates what sorts of antibodies in their blood. Antibodies are special proteins that work as your body's pit bosses, identifying problem customers like bacteria and viruses that make it into the works. A person with type A blood possesses antibodies which target specific antigens, a person with type B blood has a different set of antibodies.

These antibodies are sort of letter-of-the-law employees, and if they notice something that doesn't look right, they go on the attack lickety split. Their pedantry doesn't stop with germs, though. They'll lay the pain down on any cell that triggers their alarmingly touchy xenophobia, including any foreign blood cells that show up to the office with the wrong set of antigens attached.

When this happens, donor blood is rejected by the body in a pretty dramatic way. The recipient's immune system will attack the outsider blood, exploding the proteins in the foreign blood and sending the remains into the kidneys to be separated from the rest of the gang. The human kidney, while remarkable, isn't set up to handle the sudden rush of dead blood cells that occurs when a large transfusion goes wrong. Worst case scenario, they'll shut down entirely.

With that in mind, there's almost always a blood shortage at your local hospital, with rare blood types frequently in short supply. Want to do your good deed for the day? Get in contact with a blood bank and squirt out a pint for your fellow man.