The ABO System

Arezoo RastiTehran University of Medical Sciences

Faculty of Nursing & MidwiferyAprill 2008

Discovery of the ABO system: In 1900, a German scientist, Karl Landsteiner, discovered that blood groups differ from one individual to another

The fourth type of red cells, “AB”, was discovered in 1902 by Von Decastelloand Sturli, associates of Landsteiner

Landsteiner's rules for the ABO Blood Group

A person does not have antibody to his own antigensEach person has antibody to the antigen he lacks (only in the ABO system) Below are the four blood groups and the antigens and the expected, naturally-occurring antibodies present

ABO Blood Group System

ABNeither Anti-A nor Anti-BA and B

OAnti-A, Anti-B, Anti-A,BNeither A nor B

BAnti-AB

AAnti-BA

ABOBlood Group

Antibodies in Serum

Antigen onRed Cells

Importance of Understanding the ABO System

Blood DonorsTransfusion recipientsTransplant Candidates and DonorsPrenatal PatientsNewbornsPaternity testing

Compatibility of the ABO system is essential for all other pre-transfusion testing

Solid organ and bone marrow transplants

ABO antigenic determinants (epitopes) are found on many tissues and body fluids in addition to red cells

ABO phenotypes and genotypesGroup A phenotype = A/A or A/O genotype

Group B phenotype = B/B or B/O genotype

Group O phenotype = O/O genotype

Group AB phenotype = A/B genotype

Genes in ABO SystemA, B, and OThe ABO locus is on chromosome number 9

H gene HH , Hh or hH , hhSe genes SeSe , Se se or se Se , sese

Hh and Se genes are closely linked on chromosome 19

Production of A, B, and H antigens

H gene fucosyl transferasesA gene N-acetyl-galactosamine transferasesB gene D-galactose transferases

The production of A, B and H antigens are controlled by the action of transferases

BIOCHEMISTRY of ABO antigens

Characteristics of ABO antigenspresence on red blood cells soluble antigens can be present in plasma, saliva, and other secretions These antigens are also expressed on tissues other than red cells ABO antigens are only moderately well developed at birth

Subgroups of A and BAmounts of antigen on the red blood cells The most common are subgroups of A. Approximately 80% of the A's and AB's have a normal expression of A1. Most of the other 19% are either A2 or A2BA3; A int; Am, Ax; AelWeak variant forms of the B antigen (B3, Bx, and Bel) exsist

Why Knowledge of A Subgroups Is Important For Laboratorians

The antigen may be so weak that it is not detected and the red cells are mistyped as group O Problems may arise because the serum of an A2 or A2B, A3 or Ax individual might contain anti-A1Anti-A1 is produced by about 1-2% of group A2

persons and about 25% of group A2B persons

Bombay blood grouplacks H gene (hh)cells type as Oserum has anti-A, anti-B, and anti-H Anti-H agglutinates O cells transfusionAutologus or other Bombay blood people since they lack the H antigen

Characteristics of ABO antibodiesNaturallyoccurring

Anti- AAnti- B

Their production is thought to be stimulated by bacteria which have been shown to contain substances that are chemically similar to human A and B antigens

"Immune" ABO Antibodiespregnancy with an ABO incompatible fetustransfusion of ABO incompatible red cells

Immunoglobulin M antibodies Ig M, predominantly

Their optimum temperature is less than 30 0C, but reactions do take place at body temperature

They are absent at birth and start to appear around 3-6 months as result of stimulus by bacterial polysaccharides.(For this reason, newborn blood is only forward typed.)

AB00AB++

B0+B+0

A+0A0+

O++O00

B Cells

ACells

Anti-BAnti-A

Reverse ABO

Group

Reaction of Serum Tested

Against

Red Cell ABO

Group

Reaction of Cells Tested

With

Errors in ABO typingCord blood samplingWharton ,s Jelly

Newborns hypogammaglobulinemia, some leukemias, lymphomasAcute leukemia

Pseudo B Gr - Bacteria …….

Acetylase

Cis AB

Pseudo mucinous ovarian cyst , GI cancers

Weak H geneA h Anti A AntiH

Mixed fieldBlood Transfusion

O….....A or B or ABBone marrow transplantation A3IUT transfusion Chimerism

Washed cellsMultiple myelomaRadiography

Dangerous OO…………….

Anti A , Anti B , Anti ABCold agglutinins

Infections Lymphoma Infectious mono nucleosis

Why Knowledge of A Subgroups Is Important For Laboratorians

The antigen may be so weak that it is not detected and the red cells are mistyped as group O Problems may arise because the serum of an A2 or A2B, A3 or Ax individual might contain anti-A1Anti-A1 is produced by about 1-2% of group A2

persons and about 25% of group A2B persons

ABO Antibodies and Aging ABO antibodies are not usually produced by an infant until 3 to 6 months of age

Antibodies found in the sera of newborns are almost always IgG, passively acquired from the mother. Thus, serum testing of newborns is not performed. Anti-A and anti-B titers are highest at ages 5-10 years and then they gradually decrease. Thus, in elderly patients, ABO antibodies may be difficult to detect.

ABO SYSTEM & Disease

ABO & IQ

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