ABO and Rh Blood Group System MCQ - Practice Questions with Answers

 Blood groups: ABO Blood Groups

• There are more than 30 antigens present on the surfaces of blood cells. These antigens give rise to blood groups 
• Antigens can induce an immune response by secreting a class of proteins called antibodies that bind in a specific fashion with antigens. 
• Depending on the nature of antigens present on the membrane of RBCs various types of blood grouping has been done. Two such blood group systems are ABO ( antigen A, B)  and Rh (antigen Rh)  blood grouping.

ABO blood group:

• ABO blood groups in human beings were reported for the first time by Karl Landsteiner. According to this system, humans can have 4 types of blood groups, A, B, AB and O
• A,  B and O blood groups were discovered by Landsteiner while AB blood group was discovered by de Castello and Steini.
• ABO blood groups are determined by the gene Ig which has three alleles Ia, Ib, and Io of this gene 
• Allele Ia and Ib produce antigen A and antigen B respectively. 
• RBCs of each blood group contain some antigens and they possess antibodies against other antigens in their plasma. 
   

• During blood transfusion it is very important to know the blood groups to avoid clumping reactions
• Clumping is also known as Agglutination. It occurs when Antibodies stick to wrong Antigens and this can result in clumps which can be fatal. Hence blood group recognition is very important before transfusion (Antigens are Agglutinogen and Antibodies are Agglutinins)
• Since individuals with blood group AB  do not have antibodies against any of the antigens, it can receive blood from individuals with A, B and O blood groups. This is why blood group AB is called the universal recipient
• Individuals with blood group O does not have any kind of Antigen and thus can donate blood to individuals with A, B and AB blood groups. Hence, blood group O is called the universal donor.

 Rh Blood group  

• It was discovered by Landsteiner and Wiener in the blood of Rhesus monkey
• Rh antigen has also been observed on the surfaces of the RBCs of human beings.
• The individuals with Rh antigen are called Rh-positive while those lacking it are called Rh-negative.
• Rh+ is dominant on Rh-. 
• Both Rh+ and Rh- persons are normal however, Rh incompatibility becomes a constraint during blood transfusion and pregnancies

Rh incompatibility During pregnancy

• During pregnancy, Rh incompatibility is seen when the father’s blood is Rh+ while the mother’s blood is Rh-. 
• Therefore, if a father’s blood is Rh+ and the mother’s blood is Rh-, the blood of their baby will be Rh+ ( Rh+ is dominant over Rh- ). 
• In such interaction, generally, the first child does not suffer, however, the subsequent foetuses do
• In the subsequent foetuses, anti-Rh factors of mothers blood attack and destroy the RBCs of foetus. This leads to haemolytic disease of the newborn or HDN
• This condition is called erythroblastosis foetalis.
• The newborns that survive are anaemic 
• To prevent HDN, Rh- mothers are injected with a defective anti-Rh-antibody during all pregnancies carrying Rh+ foetus. Marriage between Rh- woman and Rh+ man is not recommended. 

Rh incompatibility During blood transfusion

• During the first blood transfusion of Rh+ blood to the person with Rh- blood no abnormalities are seen. However, Rh- person develops anti-Rh factors or antibodies in his/her blood.
• During the second blood transfusion of Rh + blood to the Rh- person, the anti-Rh factors developed( during the first transfusion) in the blood of a person with Rh- blood,  attack and destroy the RBCs of the donor.