Science Buddies: "Ask an Expert"

Hey i was just wondering,

How can B blood can be donated to someone with AB blood, but it is dangerous the other way around?

Surely the A antibodies from the type B blood would bind to the B antigens on AB red blood cells if you mix these blood types together, regardless of which is the recipient and donor?

I'm probably missing something...could someone please help me out?

Hi there,

The Science Buddies "Ask an Expert" forum is for K-12 students who are doing an independent science fair project and have questions or want assistance, not for general curiosities or homework questions. Please take note of this in the future and make posts elsewhere.

However, regarding this specific matter, this may help you: https://biology.stackexchange.com/quest ... ood-groups

Where your confusion is: antigens are on blood cells, antibodies are in plasma. Generally, when we talk about "blood transfusion," although the donor donates "whole blood," the recipient receives only a part (component) of the blood, like just RBCs or just platelets+plasma. So when you consider just RBCs, the donor's antibodies are taken out of the equation - when the blood bank processed the donor's blood, they (almost) literally took them out and put them separately.

Hope that was helpful, and if you have a specific project in the future, we'll be happy to help.

–Eugene

OK, here we go...
Type B rbc's can be donated to an AB person because that person lacks antibodies against both type A and type B antigens found on rbcs. For this reason, we regard type AB individuals as "universal recipients." If, however, you were to transfuse the serum or plasma from a type B person into a type AB individual, the anti-A antibodies in that serum/plasma would react with the recipient's type A antigens (not the B Ags as you stated), resulting in hemolysis.

On the other hand, type O people are universal donors because their rbcs lack both A and B Ags, so can be transfused into anyone (more or less). However, type O serum/plasma contains antibodies against both type A and type B Ags found on the rbcs, so a type O individual can only recieve type O rbcs. This is why type O blood donors are always in demand, because you can transfuse type O rbcs into anyone, regardless of their A or B blood type.

I hope this helps to clear up some of your confusion.

The above explanations are perfect! If you need a simpler explanation, however, I'll put one here:

Antibodies attach to foreign materials and clump them together. In blood, this would create a blood clot, which is dangerous because it could lead to major health conditions such as a stroke or pulmonary embolism (both of which are caused when blood flow is blocked from a certain area of the body). A person with type AB blood has A and B antigens and does not have A or B antibodies; a person with type B blood has B antigens and A antibodies.

When type B blood is introduced to type AB blood, it is not dangerous because there are not anti-B antibodies in the AB blood.

When type AB blood is given to someone with type B blood, however, the A antigens in the AB blood will be clumped together by the anti-A antibodies in the type B blood.

Think of it like this: a person can only receive the type of blood that is already in his/her body. Therefore, a person with AB blood already has B antigens and can be given more from someone with type B blood. Someone with type B blood, however, does not have A antigens already and will not react well if introduced to this antigen.

Hopefully this helps if you were still confused