ABO Blood Grouping

 

Blood Grouping

Aim

To understand the ABO blood group system and to determine the blood group.

Principle

The ABO blood grouping system was discovered in the year 1901 by Karl Landsteiner. ABO Blood Group System is based on the presence or absence of two specific antigens and antibodies - A and B: The presence or absence of these two similar carbohydrate antigens located on the surface of red blood cells is determined using specific antisera. 

Haemagglutination occurs when anti A antiserum is mixed with type A red blood cells. People with blood type AB possess both A and B antigens on their red blood cells and those with O blood type lack A and B antigens.  Agglutination reactions occur between high molecular weight particulate antigen and antibody. Because many antigens are there on cells, agglutination reaction leads to clumping or agglutination of cells. When the clumping involves red blood cells, it is called haemagglutination. Haemagglutination reactions are used in the typing of blood.

Many other antigens exist on human red blood cells. Another surface antigen on red blood cells is designated as Rh factor or D antigen. Individuals are Rh positive when D antigen is present. The presence of Rh factor is determined by a haemagglutination reaction between antigen D antiserum and red blood cells with antigen D on their surface.

A person possess antibodies to the alternate antigen. Thus people of blood type A have antibody to the B antigen in their sera. Rh negative individuals do not naturally have anti D antibody in their sera. Anti D antibodies are produced when red blood cells with D antigen are introduced into Rh negative individuals.

Type O (O-ve) blood group is called the universal donor, because type O blood group have neither A or B antigens. It can be donated to recipients of any blood type. Type AB (AB-ve) blood group is called the universal recipient. They lack anti-A nor anti-B antibodies in their plasma and can receive blood from the donors of any blood type. AB-negative is considered to be the rarest blood type. 

ABO and Rh blood types are important as they are essential during the blood transfusions and to avoid further complications.  An incompatible transfusion results when the antigens of the donor red blood cells react with the antibodies in the recipient’s serum or induce the formation of antibodies. Small samples of the recipient's and donor's blood are mixed to check compatibility in a process known as cross-matching before transfusion.

Materials Required

• Sterile cotton balls
• Sterile lancet
• Clean glass slide
• Anti-A, B, and D antiserum
• 70% alcohol
• Marking pen

Procedure

1. With the marking pen three circles are drawn in a clean glass slide and labelled A, B and D.
2. The ring finger disinfected with the cotton ball dipped in 70% alcohol
3. The ring fingertip pricked with the lancet and added a drop of the blood each to the circles labelled A, B and D
4. The bleeding stopped using a sterile cotton ball and a bandage applied to the wound
5. To the circle labelled A, added one drop of anti A antiserum, to the circle labelled B, added Anti-B and to the third circle labelled D, added Anti-D with the help of a dropper.
6. Mixed each suspension gently with the help of a toothpick and observed the result.

Observation

The test sample showed no agglutination in the circles “A” (with anti A) and “B” (with anti B) and agglutination in circle D (with anti D)

Result

The tested sample is O+

 

ABO blood grouping (left hand side)

Blood Group	Antigen	Antibody
A	A	B
B	B	A
AB	A and B	neither A nor B antibodies
O	No A or B antigens	both A and B antibodies
Rh+	D antigen	No D antibody
Rh-	No D antigen	No D antibody in usual cases, till an exposure to D antigen occurs