I just went for a blood test and came back knowing I have type AB blood. However my blood can only be used by other people who share the same blood type with me but not others, while other people with type O, A, B they can share the blood with me. Why is that so?
In: Chemistry
While we all have blood, some peoples bodies make it with a *slightly* different mix. When talking about blood types, the most important distinction is some identification markers that sit on the outside of your red blood cells, kind of like name tags. The ones we’re interested in are called Antigen A, Antigen B, and the Rh factor (positive or negative). There is no Antigen O, it just means you don’t have A or B.
Why it’s important is that your body looks at the name tags of blood cells to see who’s supposed to be in the bloodstream and who’s not, kind of like a bouncer checking IDs at the club. If the bouncer finds people with the wrong name tags, it thinks the body is being invaded and starts a fight. If you got a blood donation, it would obviously be bad for your body to start destroying the new cells; you can become sick, and it might make your original problem come back or get worse.
So why are some blood types compatible and others not? Your body will only accept blood cells with the tags that it thinks belong there. The bouncer (your immune system) is only looking out to fight cells with tags that it knows don’t belong. Since you have AB, your body thinks any cells with tags A, or B, or both, are cool. If you had type B, your bouncer thinks Bs are cool, but As are not allowed so the fight is on. O is a special case because O has no tags. An O bouncer will only let in cells with no tags; if it sees A or B or both, the fight is on. But A or B bouncers don’t see any tags on an O cell, so they don’t start a fight. That’s why everyone can get O blood (no tags), but O people can’t get A or B blood. Rh is the same, but separate. If your body is Rh positive (you have it on your cells), you can take positive or negative blood, but if you’re negative, you can only take negative blood.
This is all a slightly complicated way of saying some peoples blood has different ID tags on it, and your body will fight any tags that it doesn’t like, but ignores cells without tags. AB type is alright because your body thinks all the other blood types are cool.
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