Blood Groups

Blood Groups-

 The discovery of blood groups by the Austrian Scientist Karl Landsteiner, in 1901. He was honored with Nobel Prize in 1930 for this discovery.More than 20 genetically determined blood group systems are known today. But, Landsteiner discovered two blood group systems called the ABO system and the Rh system. 

 ABO SYSTEM-

Based on the presence or absence of antigen A and antigen B, blood is divided into four groups:

  • ‘A’ group
  •  ‘B’ group
  •  ‘AB’ group
  •  ‘O’ group.
  1. Blood having antigen A belongs to ‘A’ group. This blood has β-antibody in the serum.
  2. Blood with antigen B and α-antibody belongs to ‘B’ group.
  3. If both the antigens are present, blood group is called ‘AB’ group and serum of this group does not contain any antibody.
  4. If both antigens are absent, the blood group is called ‘O’ group and both α and β antibodies are present in the serum. 

Antigen and Antibody present in ABO blood group-

Group Antigen in RBC Antibody in Serum
A A Anti-B
B B Anti-A
AB A $ B No antibody
O No antigen Anti A and Anti-B

 Importane of ABO group in Blood  Transfusion-

  • During blood transfusion, only compatible blood must be used. The one who gives blood is called the ‘donor’ and the one who receives the blood is called ‘recipient’.
  • While transfusing the blood, antigen of the donor and the antibody of the recipient are considered. The antibody of the donor and antigen of the recipient are ignored mostly.
  • Thus, RBC of ‘O’ group has no antigen and so agglutination does not occur with any other group of blood. So, ‘O’ group blood can be given to any blood group persons and the people with this blood group are called ‘universal donors’.
  • Plasma of AB group blood has no antibody. This does not cause agglutination of RBC from any other group of blood. People with AB group can receive blood from any blood group persons. So, people with this blood group are called ‘universal recipients’.

Rh Factor-

Rh factor is an antigen present in RBC. This antigen was discovered by Landsteiner and Wiener. It was first discovered in Rhesus monkey and hence the name ‘Rh factor’. There are many Rh antigens but only the D antigen is more antigenic in human.

The persons having D antigen are called ‘Rh positive’ and those without D antigen are called ‘Rh negative’. Among Indian population, 85% of people are Rh positive and 15% are Rh negative. Percentage of Rh positive people is more among black people. 

 Hemolytic Disease of Fetus and Newborn-

Hemolytic disease is the disease in fetus and newborn, characterized by abnormal hemolysis of RBCs. It is due to Rh incompatibility, i.e. the difference between the Rh blood group of the mother and baby. Hemolytic disease leads to erythroblastosis fetalis.

Erythroblastosis fetalis is a disorder in fetus, characterized by the presence of erythroblasts in blood. When a mother is Rh negative and fetus is Rh positive (the Rh factor being inherited from the father), usually the first child escapes the complications of Rh incompatibility. This is because the Rh antigen cannot pass from fetal blood into the mother’s blood through the placental barrier. 

Ultimately due to excessive hemolysis severe complica tions develop, viz.-  

  •  Severe anemia-Excessive hemolysis results in anemia and the infant dies when anemia becomes severe.
     
  •   Hydrops fetalis -Hydrops fetails is a serious condition in fetus, characterized by edema. Severe hemolysis results in the develop ment of edema, enlargement of liver and spleen and cardiac failure.
  •   Kernicterus. -Kernicterus is the form of brain damage in infants caused by severe jaundice. If the baby survives anemia in erythroblastosis fetalis (see above), then kernicterus develops because of high bilirubin content. 

Prevention or treatment for erythroblastosis fetalis- 

  • If mother is found to be Rh negative and fetus is Rh positive, anti D (antibody against D antigen) should be administered to the mother at 28th and 34th weeks of gestation, as prophylactic measure. If Rh negative mother delivers Rh positive baby, then anti D should be administered to the mother within 48 hours of delivery. This develops passive immunity and prevents the formation of Rh antibodies in mother’s blood. So, the hemolytic disease of newborn does not occur in a subsequent pregnancy.
  • If the baby is born with erythroblastosis fetalis, the treatment is given by means of exchange transfusion. Rh negative blood is transfused into the infant, replacing infant’s own Rh positive blood. It will now take at least 6 months for the infant’s new Rh positive blood to replace the transfused Rh negative blood. By this time, all the molecules of Rh antibody derived from the mother get destroyed. 

 

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