Question

A person with unknown blood group under ABO system, has suffered much blood loss in an accident and needs immediate blood transfusion. His one friend, who has a valid certificate of his own blood type, offers blood donation without delay. What would have been the type of blood group of the donor friend?

• A. Type B
• B. Type AB
• C. Type O
• D. Type A

Answer 1

The correct option is C Type O

Antigens are foreign substances that induce the immune system to produce antibodies. The "I${}^A$" and "I${}^B$" alleles are responsible for the production of the A and B antigens that are present on the surface of the erythrocytes. The antibodies are present in human blood without prior exposure to the antigen which means that people with a particular ABO antigen carry the antibody against the other antigen in their serum. The "A" and “B" blood groups carry "A", “B” antigen on their RBCs and anti-B antibodies and anti-A antibodiesin their serum respectively. Thus, if found foreign, the antigens can induce antibody production in recipient responsible for agglutination of blood type injected. This makes options A and D wrong. Similarly “AB” blood group has both “A” and “B” antigen on their RBC that can cause agglutination of blood if found foreign by the immune system of the recipient; option D is incorrect. Since type O persons do not have either antigen on their RBCs and thus cannot induce the agglutination reaction in the recipient. Hence, O blood group is known as a universal donor that can be transfused to a person with any blood group.