Blood Type Compatibility Question

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Okay, I understand the concept of blood compatibility and know how to determine it between potential donors/recipients. I understand that type O- is the universal donor because it doesn't have A/B antibodies or the Rh antigen, and therefore would not cause a reaction in a recipient who does have them. I also understand that type AB+ is the universal recipient because it already has both A/B antibodies and the Rh antigen, so receiving blood that has all or some of these antibodies/antigens would not cause a reaction.

My question is...why? If, for instance, a donor with type O- can give blood to an AB+ recipient without a reaction, why can't an AB+ donor give blood to an O- recipient without a reaction? Why does it make a difference who the recipient is and who the donor is if, in the end, you're combining both blood types anyway? :confused:

I posed this question to my A&P professor, and she admitted that she doesn't know. Really, I'm just curious--I like to understand why something is the way that it is. Please--can anyone help me?

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Specializes in med/surg, telemetry, IV therapy, mgmt.

Because you are giving AB+ blood to someone who doesn't have the Rh factor. Their O- blood recognizes that and begins the process to reject it. It all has to do with immunity. I'm surprised your instructor couldn't tell you that.

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Because you are giving AB+ blood to someone who doesn't have the Rh factor. Their O- blood recognizes that and begins the process to reject it. It all has to do with immunity. I'm surprised your instructor couldn't tell you that.

Hi Daytonite, thanks for your response. I think I used a poor example of what I'm trying to understand, so I'll try a different one: an A- donor can give blood to an AB- recipient, but an AB- donor can't give blood to an A- recipient. I realize that the AB- can't be a donor for an A- recipient, because the recipient has anti-B antibodies that would cause hemolysis. What I don't understand is why this doesn't happen when you have an A- donor and an AB- recipient. Why wouldn't the the anti-B antibodies of the donor's blood also cause hemolysis since the recipient has the B antigen? (And now that I think of it, I believe this is the example I gave that stumped the professor.) Maybe I'm overlooking something really obvious? Or just over-thinking it altogether? Again, thanks for your help :)

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OK here is your error....

AB type has A and B AntiGENS.

O type has A and B AntiBODIES.

That means that someone with O type blood has antiBODIES that fight A and B antigens which is why they can only receive O type blood.

AB has NO antiBODIES so it can accept O (no antigens), A (A antigens), B (B antigens).

It is the antibodies that cause the problem. AB has none. A type has B antibody so it cannot take B or AB blood since they both have B antigens that the A type will fight.

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OK here is your error....

AB type has A and B AntiGENS.

O type has A and B AntiBODIES.

That means that someone with O type blood has antiBODIES that fight A and B antigens which is why they can only receive O type blood.

AB has NO antiBODIES so it can accept O (no antigens), A (A antigens), B (B antigens).

It is the antibodies that cause the problem. AB has none. A type has B antibody so it cannot take B or AB blood since they both have B antigens that the A type will fight.

As I understand, the reason that O has no antigens is because it has both anti-A and anti-B antibodies. Therefore, the reason that type O cannot receive type AB is because the anti-A/anti-B antibodies of type O is killing off the AB antigens of the received blood. But then why is the reverse not true? Why is it that the antigens of an AB recipient's blood are not attacked by anti-A/anti-B antibodies of the donated type O blood? This is just something I can't seem to wrap my head around. Thank you very much for your help.

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Specializes in Emergency, Pre-Op, PACU, OR.

That is an interesting question! I hope this (I posted the complete link as well and put some parts in bold) can give you an answer!

6. Can a person safely receive a blood transfusion that doesn't exactly match his/her blood type?

Yes, if a small transfusion is administered slowly to the recipient of the blood, a person who is Type A, B, or AB can receive a donation of Type O blood. (However, the Type A, B or AB person could NOT safely receive non-matching blood from one of the other blood types because the antibodies in his/her blood would cause agglutination of the in-coming red blood cells.)

7. What is the Universal Donor? Since Type O blood does not contain RBC's with A or B antigens on their surface, small donations of this blood type can safely be given to the other 3 blood types; therefore, Type O has been called the "Universal Donor." If the transfusion is done slowly, the anti-A and anti-B antibodies in the Type O plasma will be diluted by the recipient's plasma so they don't cause the agglutination reaction (clumping) of the recipient's cells. Typically, however, every attempt is made to match the donor's blood as closely as possible.

http://www2.pvc.maricopa.edu/tutor/bio/bio160/blood.html

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I think you're on to something, One1--that sounds like it's the answer I'm looking for :)

Thanks for the help, you guys :up:

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"Why is it that the antigens of an AB recipient's blood are not attacked by anti-A/anti-B antibodies of the donated type O blood? This is just something I can't seem to wrap my head around. Thank you very much for your help."

Because we do not often transfer WHOLE blood unless it matches the blood type. Normally, when we give blood in the hospital, we are giving the extracted RBCs. Since we don't have the plasma from the O type and the O RBC do not have either antigen, the transfusion is accepted without issue.

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Because we do not often transfer WHOLE blood unless it matches the blood type. Normally, when we give blood in the hospital, we are giving the extracted RBCs. Since we don't have the plasma from the O type and the O RBC do not have either antigen, the transfusion is accepted without issue.

Ah, okay--this makes a lot of sense :idea: We didn't really learn about the practice of blood transfusion in my A&P class (only the basics of blood compatibility). But now I finally get it. Thank you, because now I can sleep soundly tonight :D

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Let me see if I've got this:

So, if the ABO matches, the Rh of the blood to be infused to an Rh positive pt. can be positive or negative, but the Rh negative pt. needs blood that is Rh negative as well as matching ABO-wise.

Is that right? Is there an easy way to explain that?

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I found it on ATI's "blood administration" module. It's just one more antigen:

A person who has the D antigen is classified Rh-positive; a person who does not have the D antigen is Rh-negative. Rh-negative individuals may donate to Rh-positive recipients, but should only receive Rh-negative blood to prevent the formation of anti-D antibodies.

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