ELI5- What are blood groups? Why do they differ from person to person? Why can’t a person of one blood group receive blood from a person of a different blood group?

Question

Edit: Whoever it is, thank you very much for the silver! This the first award I’ve recieved on Reddit! I love you!

Edit: Whoever gave me the gold… You’re a legend! You’re a fucking legend!! Thanks a lot Redditor!! It means a lot!

In: Biology

Answer 1

The blood cells each contain a code on them somewhat like a key, this key only lines up with certain ‘locks’ in the body. This key can be used for your body to identify friendly blood cells from foreign ones. ( the body is hella xenophobic for obvious reasons)
Basically if the body recognizes a cell that is foreign (fungus, bacteria, anything without the key) it sends the security guard cells (WBC/phagocytes) to go and surround the foreign invader to keep it from causing trouble, eventually killing it.
If you where to trade blood with a person of a certain type of blood (ie You are A+ and he is B-) then your body would have bad reaction and you would likely die.
The A part is one part of the key, the + part is a separate part. If the receiving locks do not match either of these you will have a bad time.