ABO BLOOD GROUP SYSTEM
1) The oldest known blood group system is the ABO,OR ABH system, discovered by Landsteiner in 1990.
2) The ABO system consists of four main groups: A , B , AB , & O.These are determined by the presence or absence on the red cell of two antigens: A & B.
3) Group AB red cells possess both antigens, group A cells possess the A antigen,group B cells possess the B ANTIGEN , and group O cells possess neither A nor B.
4) The serum of an individual contains antibodies against the antigens lacking in his red cells.
5) Group A person lacks the B antigen. His serum contains anti-B antibodies (agglutinins ).
6) Group B person lacks the A antigen. His serum contains anti-A antibodies (agglutinins).
7) Group O person who lacks both A and B antigens contains anti-A and anti-B antibodies (agglutinins).
8) Group AB persons have neither antibody in their serum.
ABO BLOOD GROUP
BLOOD GROUP ANTIGEN RBC’s ANTIBODY IN SERUM
A A Anti-B
B B Anti-A
AB A&B None
O None Anti-A & anti- B
ABO ANTIGENS
The antigens of the ABO system develop early in the foetus.The antigens are not only present in the red blood cells,but are found in practically all tissues, and body fluids in 78% of people.
The production of A and B antigen is regulated by the H gene, determining the conversion of ‘precursor substance’ (P.S) into H substance. In presence of H substance the A gene regulates the production of A and H antigen, and the B gene regulates the production of B and H antigen. In absence of both the A and B genes only the H antigen will be responsible for blood group O.In the absence of the H gene, a homozygous hh situation, there will be no conversion of precursor substance into H substance. This means that even in the presence of A and/or B genes there will be no production of A and /or B antigen. such a situation is very rare, and is known as Oh or Bombay group.
Substance Genes Substance Genes Antigens
A A+H
H B B+H
AB A+B+H
H O H
Precursor
Substance
-PS-
hh P.S A.B.AB.O None
Bombay
Blood group
BOMBAY GROUP (Oh) : This can be summarized as follows:-
Persons who do not inherit H gene ( very rare hh genotype) are unable to produce H substance, and therefore even when A and B genes are inherited, A , and B antigen cannot be formed .This rare group is called Bombay group (Originally recognized in Marathi-speaking people in India.Antibodies anti-A, and anti-B are present in the blood of Oh Bombay persons.
WHAT IS BOMBAY PHENOTYP?
The blood group Oh, in which there are no detectable A ,B , or H antigens on the Red blood Cells , and there is anti A, anti B, and anti H {ABS} in the plasma .So called because the few cases reported have nearly all been found in India round Bombay.
DISCUSS THE ROLE OF GENE H IN THE EXPRESSION OF A AND B GENES?
1) The expression of A and B antigens is determined by H genes, which is inherited independently:this gene codes for an enzyme that converts a carbohydrate precursor on red cell into H substance. This enzyme is called TRANSFERASE.
2) The H substance is partly converted by the A or B genes into A or B antigen, some H substance remains unconverted. (The presence of the A and B genes results in the addition of sugars to the H substance to produce the A and B antigens :- N-acetyl-D-galactosamine in the case of A gene,and –D-galactose in the case of the B gene.
3) The O gene being amorphic,affects no conversion of H substance.
4) ‘h’ is an amorphic gene,the phenotype hh is extremely rare {BOMBAY PHENOTYPE}.
ABO ANTIBODIES (anti-A,anti-B)
A feature of the ABO system is the regular occurance of anti-A ,anti-B in the absence of the corresponding red cell antigens.
This allows for reverse (serum) grouping as a means of confirming the red cell phenotype.The antibodies are a potential cause of dangerous haemolytic reactions if transfusions are given without regard to ABO compatibility.Anti-A, and anti-B are always naturally occurring IgM class.Although they react best at low temperature , they are haemolytic at 37C.Hyperimmune anti-A, and anti-B occur less frequently ,usually in response to transfusion or pregnancy ,but may also be formed following the injection of some toxoids, and vaccines,they are IgG class, and are produced by group O and sometimes group A2 individuals.Hyperimmune IgG anti-A, and/or anti-B from group A2 mothers may cross the placentas , and cause haemolytic disease of the new born (HDN).Group O donors should always be screened for hyperimmune anti-A and anti –B antibodies which cause haemolysis when group O whole blood is transfused to recipients with A and B phenotypes. These dangerous ‘’universal’’donors should be reserved for group O recipients only,or the blood should be used as packed red cells.
1) The oldest known blood group system is the ABO,OR ABH system, discovered by Landsteiner in 1990.
2) The ABO system consists of four main groups: A , B , AB , & O.These are determined by the presence or absence on the red cell of two antigens: A & B.
3) Group AB red cells possess both antigens, group A cells possess the A antigen,group B cells possess the B ANTIGEN , and group O cells possess neither A nor B.
4) The serum of an individual contains antibodies against the antigens lacking in his red cells.
5) Group A person lacks the B antigen. His serum contains anti-B antibodies (agglutinins ).
6) Group B person lacks the A antigen. His serum contains anti-A antibodies (agglutinins).
7) Group O person who lacks both A and B antigens contains anti-A and anti-B antibodies (agglutinins).
8) Group AB persons have neither antibody in their serum.
ABO BLOOD GROUP
BLOOD GROUP ANTIGEN RBC’s ANTIBODY IN SERUM
A A Anti-B
B B Anti-A
AB A&B None
O None Anti-A & anti- B
ABO ANTIGENS
The antigens of the ABO system develop early in the foetus.The antigens are not only present in the red blood cells,but are found in practically all tissues, and body fluids in 78% of people.
The production of A and B antigen is regulated by the H gene, determining the conversion of ‘precursor substance’ (P.S) into H substance. In presence of H substance the A gene regulates the production of A and H antigen, and the B gene regulates the production of B and H antigen. In absence of both the A and B genes only the H antigen will be responsible for blood group O.In the absence of the H gene, a homozygous hh situation, there will be no conversion of precursor substance into H substance. This means that even in the presence of A and/or B genes there will be no production of A and /or B antigen. such a situation is very rare, and is known as Oh or Bombay group.
Substance Genes Substance Genes Antigens
A A+H
H B B+H
AB A+B+H
H O H
Precursor
Substance
-PS-
hh P.S A.B.AB.O None
Bombay
Blood group
BOMBAY GROUP (Oh) : This can be summarized as follows:-
Persons who do not inherit H gene ( very rare hh genotype) are unable to produce H substance, and therefore even when A and B genes are inherited, A , and B antigen cannot be formed .This rare group is called Bombay group (Originally recognized in Marathi-speaking people in India.Antibodies anti-A, and anti-B are present in the blood of Oh Bombay persons.
WHAT IS BOMBAY PHENOTYP?
The blood group Oh, in which there are no detectable A ,B , or H antigens on the Red blood Cells , and there is anti A, anti B, and anti H {ABS} in the plasma .So called because the few cases reported have nearly all been found in India round Bombay.
DISCUSS THE ROLE OF GENE H IN THE EXPRESSION OF A AND B GENES?
1) The expression of A and B antigens is determined by H genes, which is inherited independently:this gene codes for an enzyme that converts a carbohydrate precursor on red cell into H substance. This enzyme is called TRANSFERASE.
2) The H substance is partly converted by the A or B genes into A or B antigen, some H substance remains unconverted. (The presence of the A and B genes results in the addition of sugars to the H substance to produce the A and B antigens :- N-acetyl-D-galactosamine in the case of A gene,and –D-galactose in the case of the B gene.
3) The O gene being amorphic,affects no conversion of H substance.
4) ‘h’ is an amorphic gene,the phenotype hh is extremely rare {BOMBAY PHENOTYPE}.
ABO ANTIBODIES (anti-A,anti-B)
A feature of the ABO system is the regular occurance of anti-A ,anti-B in the absence of the corresponding red cell antigens.
This allows for reverse (serum) grouping as a means of confirming the red cell phenotype.The antibodies are a potential cause of dangerous haemolytic reactions if transfusions are given without regard to ABO compatibility.Anti-A, and anti-B are always naturally occurring IgM class.Although they react best at low temperature , they are haemolytic at 37C.Hyperimmune anti-A, and anti-B occur less frequently ,usually in response to transfusion or pregnancy ,but may also be formed following the injection of some toxoids, and vaccines,they are IgG class, and are produced by group O and sometimes group A2 individuals.Hyperimmune IgG anti-A, and/or anti-B from group A2 mothers may cross the placentas , and cause haemolytic disease of the new born (HDN).Group O donors should always be screened for hyperimmune anti-A and anti –B antibodies which cause haemolysis when group O whole blood is transfused to recipients with A and B phenotypes. These dangerous ‘’universal’’donors should be reserved for group O recipients only,or the blood should be used as packed red cells.
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