Details about blood grouping and its composition.

 

BLOOD GROUPING

Blood is a fluid connective tissue and the most crucial component of the

circulatory system. In a healthy person, approximately 5 litters (12 pints) of

blood circulates throughout their body. 

                                                            Composition of blood

 It consists of erythrocytes,

leukocytes and platelets suspended in plasma along with the millions of

different molecules with its own specific roles and functions.

Even though components of blood are the same for all humans, there are various

blood types. In fact, there are more than 40 blood groups, but all of them are not

clinically significant. The discovery of the ABO blood group created great

excitement as until then, all blood had been assumed to be the same.

Blood Group System

Karl Landsteiner, an Austrian scientist discovered the ABO blood group system

in the year 1900. In his experiments, he mixed different blood types and noted

that the plasma from certain blood type produced agglutinates or formed

clusters which were caused by the absence of molecules on red blood cells and

resulting in antibodies to defeat that molecule. He then made a note of the

agglutination and divided the blood types into 4 different groups. For the

discovery of ABO blood group, he was awarded the Nobel Prize.

The blood grouping system is pivotal in blood transfusion. Our immune system

recognizes another blood type as foreign and attacks it if introduced in the body

causing a transfusion reaction. Any inappropriate match with the Rh and ABO

blood types, causes the most serious and life-threatening transfusion reactions.

Therefore, before blood transfusion, it is suggested to have a blood group

checked.

What are ABO and Rh blood groups?

During the blood transfusion, the two most important group systems examined

are the ABO-system and the Rhesus system.

The ABO blood group system consists of 4 types of blood group – A, B, AB,

and O and is mainly based on the antigens and antibodies on red blood cells and

in the plasma. Both antigens and antibodies are protein molecules in which

antigens are present on the surface of Red Blood Cells and antibodies are

present in the plasma which is involved in defending mechanisms.

On the other hand, the Rh blood group system consists of 50 defined blood

group antigens. In the Rh system, the most important antigens are D, C, c, E,

and e. The ABO and Rh blood systems are discussed in detail below.

ABO BLOOD GROUP  :- 

The basis of ABO grouping is of two antigens- Antigen A and Antigen B. The                                                                                      

ABO grouping system is classified into four types based on the presence or

absence of antigens on the red blood cells surface and plasma antibodies.

● Group A – contains antigen A and antibody B.

● Group B –contains antigen B and antibody A.

● Group AB –contains both A and B antigen and no antibodies (neither A

nor B).

● Group O – contains neither A nor B antigen and both antibodies A and

B.

The ABO group system is important during blood donation or blood transfusion

as mismatching of blood group can lead to clumping of red blood cells with

various disorders. It is important for the blood cells to match while transfusing

i.e. donor-recipient compatibility is necessary. For example, a person of blood

group A can receive blood either from group A or O as there are no antibodies

for A and O in blood group A.

As shown in the above table, individuals of blood group O are called

as universal donors, whereas individuals of blood group AB are universal

recipients. 

		GROUP A	GROUP B	GROUP AB	GROUP O
Red blood Cell type	A		B	AB	O
Antibodies In plasma	Anti -B		Anti - A	None	Anti – A and Anti – B
Antigens in red blood cell	A antigens		B antigens	A and B antigens	None

 

 

 Rh Blood Group System :-

In addition to the ABO blood grouping system, the other prominent one is the

Rh blood group system. About two-thirds of the population contains the third

antigen on the surface of their red blood cells known as Rh factor or Rh

antigen; this decides whether the blood group is positive or negative. If the Rh

factor is present, an individual is rhesus positive (Rh+ve); if an Rh factor is

absent individual is rhesus negative (Rh-ve) as they produce Rh antibodies.

Therefore, compatibility between donor and individual is crucial in this case as

well.