2. BLOOD GROUP
• Definition
• BLOOD GROUP is one of the classes
(such as those designated A, B, AB, or O)
into which individuals or their blood can
be separated on the basis of the presence
or absence of specific antigens in
the blood. — also called BLOOD TYPE.
4. ABO blood group system
• It is a major human blood
group system. The ABO type of a
person depends on the presence
or absence of three genes, A and
B and O. These genes determine
the configuration of the
red blood cell surface.
5. HISTORYThe ABO blood types were first discovered by an Austrian Physician Karl Landsteiner working at the
Pathological-Anatomical Institute of the University of Vienna in1900.
In 1900, he found that blood sera from different persons would clump together (agglutinate) when mixed in
test tubes, and not only that some human blood also agglutinated with animal blood.
This was the first evidence that blood variation exists in humans ,but before it was believed that all
humans have similar blood.
In 1901, he made a definitive observation that blood serum of an individual would not agglutinate with only
those of certain individuals.
Based on this he classified human bloods into three groups, namely group A, group B, and group C.
He defined that group A blood agglutinates with group B, but never with its own type. Similarly, group B
blood agglutinates with group A. Group C blood is different in that it agglutinates with both A and B.
His third group (C) indicated absence of both A and B antigens, but contains anti-A and anti-B, thus
designated as O (null) group
The following year, his students Adriano Sturli and Alfred von Decastello discovered the fourth
type ,designated as AB group containing both A and B antigen but no antibody
6.
7. BLOOD ANTIGEN
An antigen is a substance foreign to the body that causes an immune response.
The ABO antigen is a glycosyl-transferase that is encoded, for which three are major alleles, A, B and O.
The A and B alleles catalyze addition of different carbohydrate residues (N-acetyl glactosamine for group
A and d-glactose for group B) to a basic antigenic glycoprotein or glycolipid with terminal sugar1-fucose
on the red cell, known as the H SUBSTANCE.
The O allele is non-functional that’s why doesn’t modify the H substance.
The A allele actually itself has 2 variant, A1 and A2 , which further complicates the issue but they are of
minor clinical significance . A2 cell react more weakly than A1 cells with anti-A, patients who are A2B can
be wrongly grouped as B.
The A,B and H antigens are present on most body cells including white cells and platelets .
In 80% of population who posses secretor genes, these antigens are also found in soluble form in
secretions and body fluids ( e.g. plasma, saliva, semen, and sweat).
8. BLOOD GROUP ANTIBODIES
Antibodies, also known as immunoglobulins, are Y-shaped proteins that are
produced by the immune system to help stop intruders from harming the
body.
The most of the natural antibodies are anti-A and anti-B .The natural
antibodies are usually immunoglobulin M (IgM) and react optimally at cold
temperature(4 C) so, although reactive at 37C are called COLD ANTIBODIES
The immune antibodies develop in response of transfusion and
transplacental passage during pregnancy .these are commonly IgG, although
some IgM may also develop , usually in early phase of immune response.
These antibodies react optimally at 37C called warm antibodies.
Only IgG antibodies are capable of transplacental passage from mother to
fetus and the most important immune antibody is the Rh antibody, anti-D.
