Week 1 ABO blood group system 1 PDF

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Summary

ABO BLOOD GROUP SYSTEM⮚ ISBT - International Society of Blood Transfusion ⮚ 35 blood group system ⮚ More than 300 antigens ⮚ designates specific number/specific type of blood group ⮚ ABO Blood group is designated as 001 because it is the first blood group to be discovered. ISBT 001 ⮚ ISBT advocates ...

Description

ABO BLOOD GROUP SYSTEM ⮚ ⮚ ⮚ ⮚ ⮚

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ISBT - International Society of Blood Transfusion 35 blood group system More than 300 antigens designates specific number/specific type of blood group ABO Blood group is designated as 001 because it is the first blood group to be discovered. ISBT 001 ISBT advocates standardization and harmonisation in the field of blood transfusion. ISBT designates 6 digits = first 3 for specific blood group and the other 3 is for the specific antigen under the blood group

Karl Landsteiner - Discovered the ABO Blood Group System in 1901 ⮚

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They extracted blood from each other separated RBC from plasma or serum and then mixed each others blood It was the first demonstration of the forward and reverse typing (a method in detecting the ABO types). Antigen - present on RBC Antibody - present on plasma or serum When antigen and antibody mixed together randomly, there will be an antibody-antigen reaction that will lead to agglutination (clumping).

Jan Jansky (1907) - Designated his own nomenclature for ABO - He designated it as Type 1, Type 2, Type 3 and Type 4. (Type A, B, AB, O) - Alfred von Decastello and Adriano Sturli, AB group William Lorenzo Moss - Also designated nomenclature for the ABO type (1,2,3,4) but the conversion is not the same. Why is it important? - Most IMMUNOGENIC blood group ⮚ IMMUNOGENIC - capability of the substance or antigen to elicit first stimulating in response. ⮚ Example is antigen ⮚ NOT ALL ANTIGENS ARE IMMUNOGEN, for example: Hapten is an antigen but not considered as immunogen because it is a low molecular weight molecule and is not capable of raising antibody production/immune response. - With EXPECTED antibodies / multiple match early occurring antibodies (naturally occuring

antibodies) (starting from birth present on your plasma) ⮚ Antibody is produced in the absence of antigen. - ABO antibodies can activate Complement ⮚ Because it is pentameric in nature meaning

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has 10 binding cites; more efficient in activating the complement. End product of compliment activation is (red) cell lysis. IgG (monomer) is also capable of to activate complement but it is not efficient like Igm.

ABO antigens: - Biochemical & Genetic Considerations ABO antigens are… ● Glycosphingolipids (or glycoproteins) - ABO/ABH antigens present on the RBC are made up of glycosphingolipids & glycoproteins. But if ABH antigen is present on body fluids (ex. synovial fluid, urine, plasma) they are made up of glycoproteins only. ● Histoblood group antigens - Solve organs also has ABH antigens (in organ transplantation it must be compatible) - Should be type specific. - To avoid Graft vs Host Disease (GvHD): ABH blood group not compatible ●

Controlled by ABO gene located on the long arm of chromosome 9 ABO Blood Group Antigens -A -B - AB -O

*The ABH antigens are present on the RBC surface. ⮚

Group O was also called group C before.

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Type A has increased risk for gastric cancer. Forward and reverse method used to detect ABH antigen or ABO type of individual. Forward typing - detect specific ABO or ABH antigen present for RBC antigen’s surface Reverse typing - for specific antibody. Determine expected antibody present on the plasma. Both are done in laboratory. Reverse typing is done to validate the result of forward typing.

FORMATION of ABH antigens H gene (HH/Hh) – chromosome 19 - foundation of the ABH antigens. Without H gene, there will be no A, B & H antigen. - How to inherit H gene? Either homozygous for dominant H (HH) or heterozygous for dominant H (Hh) - When the dominant and recessive genes are combined only dominant gene will be expressed. - If you inherit only recessive H (hh), you will not produce H antigen. ABO genes – chromosome 9 - A and B gene are dominant gene while O is recessive gene called amorphous silent because even when you inherit O genes it’ll not produce enzyme. If it doesn’t produce enzyme it will not produce dominant sugar, it will not produce an antigen. - A and B gene has enzyme to produce. For them to produce antigen. Se gene (SeSe/Sese) – chromosome 19 - Se gene will be expressed if the inherited genes that is homozygous (SeSe) for Se gene or heterozygous (Sese) for dominant Se. - Secretory gene Purpose: express ABH antigens in the secretions and body fluids. - if both recessive Se genes are inherited, you can’t produce Se gene.

Type 2 precursor

RBC Precursor Structure

- The presence or absence of the ABH antigens on the red blood cell membrane is controlled by the H gene - The presence or absence of the ABH antigens in secretions is indirectly controlled by the Se gene H Antigen - The H gene codes for an enzyme (L fucosyltransferase) that adds the sugar L-fucose to the terminal (dulo) sugar of a precursor substance type 2 (PS2) ⮚

Components of PS2 - glucose, galactose, Nacetylglucosamine. (Oligosaccharide chain)

Formation of the H antigen

- The H antigen is found on the RBC when you have the Hh or HH genotype, but NOT from the hh genotype. ⮚

When L-fucose attach to the terminal portion precursor substance type 2 (PS2) by the enzyme (L fucosyltransferase) it will now be converted into H antigen.

- The A antigen is found on the RBC when you have the Hh, HH, and A/A, A/O, or A/B genotypes. - The B antigen is found on the RBC when you have the Hh, HH, and B/B, B/O, or A/B genotypes.

Formation of the A antigen Gene H A

B

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If A gene is inherited from the parent you will produce enzyme (N-acetyl-D-galactosamine) add to the terminal portion of H antigen. Now the H antigen will be converted into A antigen.

AB

Glucosyl Transferase L-fucosyl transferase N-acetyl galactose Aminyl transferase D-galactosyl transferase Both A and B

Immunodominant Sugar L-fucose

Antige n H

NOe

A

acetyl-Dgalactosamin

D-galactose

B

Both A and B

AB

H antigen Certain blood types possess more H antigen than others: Greatest amount of H

Formation of the B antigen

Least amount of H

O>A2>B>A2B>A1>A1B

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B gene will produce enzyme B galactosyl transferase will add the immunoglobulin sugar D galactose to the terminal portion of the antigen / precursor substance. The H antigen will now be converted into B antigen.

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When you are type O you only have H antigen (no A & B) and produce enzyme Lfucosyltransferase, if AB you both have A and B antigen. Bombay Phenotype - means a person has no A,B, and H antigen (recessive genes only). You will not produce H gene>no H antigen>nothing to convert. If you can’t make H, you can’t make A or B. You will produce anti A, anti B & anti H.  discovered in Bombay, India

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Genetics - Summary

- Most of the H antigen sites in a Group A individual have been converted to the A antigen. (if you are Type A, you have A antigens on the RBC surface and due to the process of conversion, the H antigen will be converted into A. However, not all H are converted. The antigens present on your RBC surface are A (predominant) and H (not converted). ⮚

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A1B is at the least amount of H because A1 is very efficient in converting H into A1. Almost all of the H antigens are converted. O has the highest amount of H because all of its binding site from RBC surface containing only H. Not all H antigens are converted. Some remains as H.

A and B Antigens - Not fully developed at (full: 2-4 years of age) birth, fewer copies of antigen on the cells. - Antigens are detectable as early at 37th day after conception.

- Human typing sera may give weaker, or very rarely negative, reactions. ABO Antigens in Secretions ⮚ ⮚

During testing for newborns (3-6months) the ideal test to be done is only forward typing. Reverse typing is not used for newborns because the baby in less than 3-6 months of age doesn’t have enough antibodies. In reverse typing the plasma is test for antibodies. There will be discrepancy when it comes to the forward and reverse typing.

- Secretions include body fluids like plasma, saliva, synovial fluid, digestive juices, amniotic fluid, milk etc. - Blood Group Substances are soluble antigens (A, B, and H) that can be found in the secretions. ⮚

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In determining the secretor status terms are: A secretor, B secretor, AB secretor, ABH secretor. The specimen of choice is saliva because it is the most accessible and easier sample to use. The principle or test done to determine secretor status is agglutination inhibition (test for secretion). Substance/secretor (referring to antigens present on body fluids or secretions)

Secretor Status - The Se gene is responsible for the expression of the H antigen on glycoprotein structures located in body secretions. - If the Se allele is inherited as SeSe or Sese, the person is called a “secretor” - 80% of the population are secretors ⮚

Blood type A = A secretors.

BOMBAY PHENOTYPE ABO subgroup ABO Lectins: A1 - Dolichos biflorus B - Bandeiraea simplicifolia O - Ulex europeaus A SUBGROUPS - Von Dungern (1911) - described 2 different A antigens based on reactions between group A RBCs and anti-A and anti-A1. Blood group

Frequency

A1 A2

80%...