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.
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
- With
the marking pen three circles are drawn in a clean glass slide and
labelled A, B and D.
- The
ring finger disinfected with the cotton ball dipped in 70% alcohol
- The
ring fingertip pricked with the lancet and added a drop of the blood each
to the circles labelled A, B and D
- The
bleeding stopped using a sterile cotton ball and a bandage applied to the
wound
- 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.
- 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 |
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