Blood Groups PDF

## Blood Groups The ABO system of blood grouping was discovered by Karl Landsteiner, who won the Nobel Prize for his work on blood groups in 1931. Blood groups are created by molecules present on the surface of red blood cells (and often on other cells as well). Antibodies are proteins produced by...

## Blood Groups The ABO system of blood grouping was discovered by Karl Landsteiner, who won the Nobel Prize for his work on blood groups in 1931. Blood groups are created by molecules present on the surface of red blood cells (and often on other cells as well). Antibodies are proteins produced by certain white blood cells in response to a foreign substance, the antigen. Each antibody can bind only to a specific antigen. The purpose of this binding is to help destroy the antigen. Antigens are any foreign substances that, when introduced into the body, cause the immune system to create an antibody. The antigens are present on the red blood corpuscles while the antibodies are present in the plasma. There are two types of antigens and two types of antibodies. Antigens are antigen-A and antigen-B. The antibodies are anti-A and anti-B. Based on compatibility, four blood groups have been recognized in human beings. They are A, B, AB and O. The antigen and antibody of each type of blood group is summarized below: | Blood group | Antigen on red cells | Antibody in plasma | Donate to | Receive from | |---|---|---|---|---| | A | A | Anti-b | A and AB | A and O | | B | B | Anti-a | B and AB | B and O | | AB | A and B | Nil | All groups | AB only | | O | Nil | Anti-a and Anti-b | All groups | O only | A person with AB type of blood group is called **Universal recipient** because it can receive blood from all types whereas a person with O type of blood group is called **Universal donor** because it can donate blood to all types. ### Rhesus system: In 1940, Landsteiner and Wiener discovered the presence of another factor in the RBC of Rhesus monkeys called the Rh factor at the antigen. Normally, no antibody for this antigen is found in blood. This Rh factor is present in 85% of the whole population. If the Rh factor is present in the **RBC**, the individual is referred to as **Rh+**, if not then **Rh-**. Erythroblastosis foetalis is a haemolytic disease caused due to Rh incompatibility. The Rh factor may cause a serious problem if an Rh- woman marries an Rh+ man. If the woman conceives an Rh+ foetus, the Rh factor passes into her circulatory system and triggers the formation of Rh antibodies in her blood (mother's blood). During the second pregnancy, conception of an Rh+ foetus again would result in an emergency because a large number of Rh antibodies would pass into the foetal blood and cause agglutination of its RBCs. It may also be fatal. This can be avoided by complete replacement of the foetal blood. ### Blood Transfusion In cases of serious loss of blood arising as a result of injuries and various diseases (haemorrhage in stomach, loss of blood in complicated births, etc.) and in serious forms of anemia, transfusion of blood is the only way by which lives can be saved. A person who donates the blood is called the donor and the one who receives is a recipient. Transfusing a patient with the incorrect ABO group blood may have fatal consequences. Donor's red blood cells may be destroyed by an antibody in the recipient's plasma. Before blood transfusion, blood of the donor and the recipient must be tested to see whether any agglutination takes place or not. For this purpose, the blood samples are diluted with saline and then are mixed together and observed under a microscope. If the corpuscles form clusters, then the donor's blood is considered to be unsuitable for transfusion. Individuals having the O group are termed **universal donors** since their blood can be administered to any individual, irrespective of the recipient's blood group. Can you guess why the O group is called the universal donor group? Persons having the AB blood group are referred to as **universal recipients** because they can receive blood from any other blood group. Can you guess why AB is called the universal recipient?