Blood Groups

Blood Groups

  • Blood groups refer to the classification of blood based on the presence or absence of specific antigens and antibodies on the surface of red blood cells (RBCs) and in the plasma. 
  • Blood groups are classified into different types, with the most widely recognized systems being the ABO and Rh (Rhesus) systems.

 

ABO Blood Grouping:

  • ABO blood grouping is based on the presence or absence of two surface antigens (A and B) on the surface of red blood cells (RBCs). 
  • Each individual's blood is classified into one of four main groups: A, B, AB, or O, depending on the presence or absence of these antigens. 
  • Individuals with blood group A have antigen A on their RBCs and anti-B antibodies in their plasma. 
  • Individuals with blood group B have antigen B on their RBCs and anti-A antibodies in their plasma. 
  • Individuals with blood group AB have both antigens A and B on their RBCs but no antibodies against A or B in their plasma. 
  • Individuals with blood group O have neither antigen A nor B on their RBCs but have both anti-A and anti-B antibodies in their plasma. 
  • During blood transfusion, it is crucial to match the blood of the donor with that of the recipient to avoid severe problems such as clumping or destruction of RBCs. 
  • Compatibility for blood transfusion is determined based on the presence or absence of antigens and antibodies. 
  • Individuals with blood group O are considered universal donors because their blood can be donated to individuals with any other blood group. 
  • Individuals with blood group AB are considered universal recipients because they can accept blood from individuals with blood group AB as well as any other blood group.

 

Rh grouping

  • The Rh antigen, named after the Rhesus monkeys in which a similar antigen was first identified, is present on the surface of red blood cells (RBCs) in approximately 80% of humans. 
  • Individuals who possess the Rh antigen are classified as Rh-positive (Rh+ve), while those who lack it are classified as Rh-negative (Rh-ve). 
  • When an Rh-negative individual is exposed to Rh-positive blood, they may develop specific antibodies against the Rh antigen. 
  • This highlights the importance of matching Rh groups before blood transfusions to prevent adverse reactions. 
  • Rh incompatibility can pose risks during pregnancy, especially when an Rh-negative mother carries an Rh-positive fetus. 
  • During the first pregnancy, the maternal and fetal bloods are typically well-separated by the placenta, reducing the risk of Rh sensitization. 
  • However, exposure to Rh-positive fetal blood during delivery can lead to the mother producing Rh antibodies. 
  • In subsequent pregnancies with Rh-positive fetuses, these antibodies can cross the placenta and attack the fetal RBCs, causing a condition known as erythroblastosis fetalis. 
  • Erythroblastosis fetalis can result in fetal death or severe complications such as anemia and jaundice in the baby. 
  • Administration of anti-Rh antibodies to Rh-negative mothers immediately after the delivery of an Rh-positive baby can prevent sensitization and reduce the risk of erythroblastosis fetalis in subsequent pregnancies.