Sunday, August 11, 2013

blood groups types explained and test methodology

blood groups test - blood groups types - blood groups explained

overview

What is a blood group?
Red blood cells contain certain proteins on their surface. These proteins are called antigens.
There are various types of red blood cell antigens  -  the ABO and rhesus types are the most important

ABO antigens
The two major antigens or surface identifierson human RBCs are the A and B antigens.Blood is grouped according to the presence orabsence of these antigens.

ABO antibodies (Isohaemagglutinins)
Anti-A and Anti-B, the common IgM antibodies   to the RBC surface antigens of the  ABO blood   group system, are sometimes described as   being "naturally occurring";  however, this is a   misnomer, because these antibodies are   formed in infancy by sensitization in the same   way as other antibodies.  The theory that explains how these antibodies   are developed states that antigens similar to the A and B antigens occur in nat ure, including in   food, plants, and bacteria. After birth   (during  the first years of life)  an infant's gut becomes   colonized with normal flora that express these A-like and B-like antigens, causing the immune   system to make antibodies to those antigens that the red blood cells do not possess. People   who are blood type A will have Anti-B antibodies, blood type B will have Anti-A antibodies, blood   type O will have both Anti-A and Anti-B antibodies, and blood type AB will have neither. 

These antibodies are of the IgM class, which have the capability of agglutinating (clumping) and   damaging red blood cells within the blood vessels, possibly leading to death.  The ABO system



The ABO system

According to the AB0 blood group system there are four different kinds of blood groups: A, B,
AB or O
  • A blood group individuals will have type A antigens on the surface of red blood cells and anti-B antibodies in plasma.  
  • B blood group individuals will have type B antigens on the surface of red blood cells and anti-A antibodies in your plasma.
  • AB blood group are those who will have type A and type B antigens on the surface of red blood cells and no antibodies to A or B antigens in plasma.
  • O blood group are those who will have neither type A or type B antigens on the surface of red blood cells but will have anti-A and anti-B antibodies in plasma.

when to get tested?
When need to be transfused with blood or blood components
Cases in which blood or blood products are needed for treatment may include:
  • Severe anemia 
  • Surgical patients with intra-operative or post-operative bleeding Injury or trauma patients with excessive blood loss 
  • Bleeding disorders such as hemophilia
who can receive blood from whom?
Of course you can always give A blood to persons with blood group A, B blood to a person with blood group B and so on. But in some cases you can receive blood with another type of blood group, or donate blood to a person with another kind of blood group.

Universal blood donor
 A universal blood donor is someone who has an O blood   type and is Rh negative. This means that they have no A or   B antigens or Rh factor on their red blood cells. Their red   blood cells can be given to a patient with any ABO or Rh   blood type

Universal blood recipient
 A universal recipient is a person who has an AB blood type   and is Rh positive. They can receive red blood cells of any   ABO or Rh type with no risk




what happens when blood clumps or agglutinate?

For a blood transfusion to be successful, ABO  and Rh blood groups must be compatible   between the donor blood and the patient blood. If they are not, the red blood cells from the   donated blood will clump or agglutinate. 

The A antigen and the A antibodies can bind to each other in the same way that the B antigens   can bind to the B antibodies. The red blood cells will be linked together, , by the antibodies.

The agglutinated red cells can clog blood vessels and stop the circulation of the blood to various   parts of the body. The agglutinated red blood cells also crack and its contents leak out in the   body. The red blood cells contain hemoglobin which becomes toxic when outside the cell. This   can have fatal consequences for the patient.

sample
Whole blood (EDTA   anticoagulant)

procedures

Reagents for ABO Typing
The monoclonal Anti-A, Anti-B reagents are murine monoclonal   antibodies of IgM  class, secreted by mouse hybridoma cell lines,   which were selected for their ability to agglutinate specifically   human RBCs bearing blood group antigens A and B on direct   agglutination tests (slide, microplate and tube test).

Assay method

  • On  a clean  slide, carefully put  two  drops of blood and makesure that the drops do not touch one another.
  • Add a drop of anti-A to the first  blood drop ,mix the two drops,using a wooden stick. Check and see if agglutination occurred. 
  • Add a drop of anti-B  to  the second  blood  drop ,mix the two drops, using  a  wooden stick.   Check and see if agglutination occurred.
Results






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