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Old 11-22-2009
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Blood ABO compatibility confusion

Hi there,
I was reading Kaplan question and was confused with this
Serum from O person will agglutinate RBCs from AB person?

how is that possible
isnt it that O is a universal donor and AB is a universal acceptor?

Would appreciate a convincing explanation
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Old 11-22-2009
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When you give blood transfusion, you give RBCs you don't give serum.

Universal Donor: Blood group O persons will not have any antigen on their RBCs so when given to any patient it will not provoke antibodies. However, they have antibodies to A and B in the serum so they cannot accept any group other than Blood Group O.

Universal Recipient: Blood group AB persons will not have any antibodies in their serum (because they are self tolerant to their own A & B antigens) so they can accept any ABO blood group that you transfuse to them. However, you cannot give their blood to other groups as the A and B antigens on the surface of RBC will provoke the antibodies.

Your Kaplan Question is correct, the serum of Blood group O has antibodies to A & B and will certainly agglutinate an AB RBC. However, this is not the case in blood transfusion in which you give (O RBCs) to (AB RBCs and AB Serum which has no antibodies) patient.
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Old 11-22-2009
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To add to Sabio's answer;

Antibodies are always formed by the recipient (host) against the donor's (foreign) antigen. They cannot be formed by the donor (except in graft versus host disease in which you are transplanting the hematopoeitic origin itself).
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Old 11-25-2009
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The amount of antibodies in the donors blood is not enough to cause a reaction clinically. The problem arises not when the antibodies meet the antigen but when the lymphocytes do, get activated and start a type2 reaction, which happens if you donate those as been said by steptaker in bone marrow transplants.

Putting it simply, to avoid confusion ... the donor donates only the antigen not the antibodies, the recepient has both .

So in your example the serum of an O person which contains the antibodies is given only when he is the recepient.
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Old 02-14-2011
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Default Simplification

Quote:
Originally Posted by sabio View Post
when you give blood transfusion, you give rbcs you don't give serum.

universal donor: blood group o persons will not have any antigen on their rbcs so when given to any patient it will not provoke antibodies. However, they have antibodies to a and b in the serum so they cannot accept any group other than blood group o.

universal recipient: blood group ab persons will not have any antibodies in their serum (because they are self tolerant to their own a & b antigens) so they can accept any abo blood group that you transfuse to them. However, you cannot give their blood to other groups as the a and b antigens on the surface of rbc will provoke the antibodies.

Your kaplan question is correct, the serum of blood group o has antibodies to a & b and will certainly agglutinate an ab rbc. However, this is not the case in blood transfusion in which you give (o rbcs) to (ab rbcs and ab serum which has no antibodies) patient.
plasma or serum transfusion:
Donor ab
recepient o
rbcs or blood transfusion:
Donor
recepient:ab
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