Why is blood transfusion a specific immune response

Answer 1

If I'm understanding the question correct, it seems like we're being asked why a blood transfusion can elicit an immune response. The reason for this is that there are different blood types, which determine the antigen on the blood cells, and the present antibodies. For example, someone with Type A blood has the Type A antigen on their blood cells, and also has the antibody that would recognize the Type B antigen. If those antibodies from the Type A person recognize a Type B antigen, coagulation will occur. Type AB has both antigens, yet neither of the antibodies to recognize said antigens, and a Type O person has neither antigen, but both antibodies are present.

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