Question

What is serology? In the ABO system of blood groups, how the blood groups are determined by antigens.

Answer 1

Hint: Serology is associated with the study of a component of blood and all the proteins present in that component. The ABO is based on the interaction of antigen-antibody because if two different blood groups are mixed, it will clot due to this interaction and may even lead to the death of the person.

Complete Answer:
Serology is the study of serum which is the fluid and solute component of the blood. It can also be defined as the blood plasma but without fibrinogens i.e. the clotting factors. The serum also does not contain any cell components such as leukocytes, erythrocytes, and platelets.
Serology is required in many diagnostic tests and blood typing (determination of the blood type). Diagnostic tests such as ELISA, agglutination, precipitation, etc are done by detecting antibodies and antigens in the serum.
ABO blood grouping is based on two surface antigens present on the cell membrane of red blood cells RBC known as A and B antigens. Consequently, the plasma produces two antibodies in response to these antigens known as anti-A and anti-B.
- A person with blood group A has the antigen A on RBC and the antibody anti- B in the plasma. Thus if blood with antigen B is given to such a person, it will be destroyed by the anti- B antibodies causing clots of the dead RBC.
- Similarly, a person with blood group B has the antigen B on RBC and the antibody anti- A in the plasma and thus cannot be given blood with A antigen.
- A person with AB blood group has both the antigens A and B and no antibodies in the plasma and thus can be given any blood group i.e. universal recipient.
- A person with O blood group does not have any antigens but has both antibodies anti-A and anti-B present thus any blood group other than O will be destroyed by these antibodies. But they can donate blood to all blood groups as they have no antigens i.e. universal donors.

Note:
- Serum is obtained by allowing the blood sample to clot and then separating the clot and cells portions from serum with the help of centrifugation.
- ABO blood group system was discovered by Landsteiner.
- Another blood group system is also present in the body known as Rh grouping and it is based on Rh antigen-antibody interaction.