ABO BLOOD GROUP SYSTEM

• ABO blood group system


  Classification of human blood based on the inherited properties of RBC as determined by the presence or absence of the antigens A and B, which are caused on the surface of the red cells. Persons may thus have type A, type B, type O or type AB blood.

  
• Identification of blood groups

  1. Agglutination test

  2. Antibody cross-linkage when different specific combining sites of one antibody react with antigen on two different red cells

  3. Mixing red cells (antigen) and serum (antibody) to determine type of antigen or type of antibody
• Agglutination test


  • A volume of serum containing antibody is added to a thin suspension (2-3%) of red cell suspended in saline solution in a small tube with a narrow diameter
  • After incubation, the red cells will have settled at the bottom of the tube
  • Sedimented red cells are examined macroscopically (with the naked eye) for agglutination, or they may be spread on a slide and viewed through a low-power microscope
• Complete antibody


  An antibody that agglutinates red cells when they are suspended in saline solution
• Matings


  • O x O
  • O x A
  • O x B
  • O x AB
  • A x A
  • A x B
  • A x AB
  • B x B
  • B x AB
  • AB x AB
• Possible children


  • O
  • A
  • B
  • AB
• Impossible children


  • A, B, AB
  • B, AB
  • A, AB
  • O
  • B, AB
  • O
• Exclusions of paternity on the ABO system