How much of a non-compatible blood type (I’m O+, FTR) would have to be injected into me before it became a threat to my health and/or life? A few CC’s? A whole pint?
Also, do the blood types of donors & recipients play a part? For example, an AB+ can receive a whole pint of O+ before he gets into the danger zone, while a few drops of A+ will kill him? Or are the dangers pretty standard across blood types?
I’m not sure about the answer to the first part, but I’ll note that AB+ are “universal recipients” - they can receive any blood type because their own blood contains all of the antigens important to consider when matching for transfusion, A, B, and Rh+. The one who would have the most chances to get in danger with a screwed-up match is the “universal donor”, O-. They don’t have any of those antigens in their own blood, so their body would react to any blood containing A, B, or Rh+, in any combination.
I don’t know how much of a wrong donor blood type leads to a reaction, but with regard to what IS a wrong blood type:
Think of the A and B as little tags that hang off of blood cells. Someone with type A blood has A tags on their cells, with AB has both A and B tags on their cells. Rh+ (the plus in AB+) works the same way - someone with a B+ blood type has B and Rh+ tags on their blood cells. O is used to indicate the lack of A or B tags, and Rh- means the lack of an Rh tag, so someone with A- blood has A tags, but no Rh tags, and someone like me with O- blood has no tags at all on their blood cells.
These tags dictate what your immune system recognizes as being part of yourself. If somebody has A- blood, their immune system will attack a blood cell that has a B tag or an Rh+ tag, but anything with only A tags, or no tags at all, is fine.
Therefore, somebody who’s AB+ can receive a transfusion from anybody. Their immune system recognizes A, B, and Rh+ tags as ‘self.’ On the other side of it, people with O- blood can give blood to anybody, because their blood doesn’t have any tags on it at all, so nobody’s immune system rejects it as foreign. (There are rare exceptions, but I’ll skip those.) It’s not that B+ people can only receive B+ blood (they can get B+, B-, O+, or O-), so it’s not quite as simple as you’ve outlined.
I would guess that receiving a given volume of any ‘wrong’ blood type would be just as bad as any other (eg, it’d harm O- me just as quickly to get [whatever] volume of O+ blood as it would to get the same volume of AB+), but this is just a WAG.
I’m not a doctor, but comments from friends in the medical field indicated that one problem is that the mixed blood types start clumping together, and these clumps could block a blood vessel. And if that’s an important blood vessel, like the arteries around your heart, that’s a heart attack, or if arteries in your brain, that’s a stroke. (But those aren’t too likely – they are bigger, major arteries.)
So if this is accurate, it may depend more on where the transfusion goes than how much.
I thought that you were born with A or B or both antibodies (A if you were B, B if you were A, and A and B if you were O), but that you had to be exposed to Rh in order to develop the antibodies. Is that old information?
Yes, that’s right. A person’s immune system doesn’t make Rh antibodies until they’ve been exposed to Rh positive blood.
Nitpick: you are not born with anti-A or anti-B antibodies. You develop them usually within the first year of life, starting usually around 3 or more months of age. The last research I’ve read said that anti-A and anti-B were formed in response to bacteria and happen to cross react with ABO antigens. The fact that you are NOT born with anti-A or -B antibodies allows for ABO incompatible heart transplants to be performed on infants.
Interesting. I hadn’t heard of that.
Thanks, NB.
Am I getting confused? I thought blood type was genetic. Is it actually acquired?
Type is genetic, but the antibodies you have floating around depend on your exposure - you don’t manufacture them until after the exposure. This is true for most antibodies, including those for allergies and diseases.
Very interesting. I’m wondering how the Rh escaped.
For those confused, let’s lay it all out plainly. An antigen is defined as something that can be bound by an antibody. The name is derived from a contraction of “antibody-generating”. Antibodies are immune system particles that perform sentry-like duties in the body. If it finds something that matches the “shape” of it’s tip, it binds to it, inactivating both. This is then detected (I forget how) and the immune system makes more of those antibodies (“raises the alarm”) since it detects a problem. Antibodies exist in millions of varieties.
So an antigen can be part of a virus, a bacterium, or any bodily cell. IIRC, the cell wall is the most common antigen site. This includes your own red blood cells. They’re all copies of the same thing, you see, and therefore have the same antigens on the outside of it. You are not born with antibodies for the other kind, though. You build those up later, just as you acquire antibodies to fight the chicken pox, varicella, polio, etc (which is why you can’t get it twice and why vaccines work).
If you have A blood type, you have A antigens on your blood cells and anti-B antibodies floating around. If they find B blood cells, they’ll bind them all together, potentially forming a clot.
So, OP, I’d hazard a guess that you’d only need a clot-sized amount to be dangerous. The more blood, the more likely it is that it’ll form a clot big enough to block an important artery. Location, I’d think, would be important too. If put into the heart, you’re dead. A syringe full of air will cause a fatal embolism, so I’d make a WAG that it shouldn’t take much more blood than that either.
Oh, and I should mention that only the RBCs have the antigens on them. And antibodies exist in the blood serum. If the two were separated, a whole new cross-table of possibilities arises. In that case, you could put anti-A and anti-B from an AB person into an O person with no problems.