ABO BLOOD GROUP SYSTEM

Karl Landsteiner

He discovered the first human blood group system. First individual to perform FORWARD and REVERSE typing from drawing blood from himself and five associates (Stetson, Levinson, Fisher, Race, and Weiner).

Forward Typing

using known sources of commercial antisera (anti-A and anti-B) to detect antigens on an individual's RBC.

Anti A (color)

blue

Anti-B color

yellow

Sample in Forward Grouping

red cells

Reverse Typing

detecting ABO antibodies in the patient's serum by using known reagent RBCs

Sample in Reverse Typing

Serum

ABO Theory of Inheritance

Individual inherits 1 ABO gene from each parent and these 2 genes determine which ABO antigens are present on the RBC membrane

A and B antigens / genes

Autosomal Codominant genes

O phenotype / genes

Autosomal recessive

Amorph gene / silent gene

Location of ABO Gene

Chromosome 9 (formation of the ABO antigen)

Location of Fut 1 (H) gene

Chromosome 19 (formation of the ABO red cells)

Location of Fut 2 (Se) Gene

Chromosome 19 (formation of ABO on secretions)

A Genes and Immunodominant sugar

gene: a-3-N-Galactosaminyltransferase

immunodominant sugar: N-acetylgalactosamine

B Gene and Immunodominant sugar

gene: a-3-D-galactosyltransferase

immunodominant sugar: D-galactose

O Gene and Immunodominant sugar

gene: NONE (since amorph/ silent)

immunodominant sugar: L- fucose

H gene

transfer enzyme to transfer L-fucose to galactose terminal

immunodominant sugar of AB group

D-galactose and N-acetylgalactosamine

Number of H genes (highest to lowest amount of H)

O > A2 > B > A2B > A1 > A1B

A lectin

Dolichos biflorus

B lectin

Griffonia (Bandeiraea) simplicifolia

O Lectin

Ulex europaeus

Slide (Direct) Method Principle

Detection of A and B antigens on Erythrocyte Surface

Known and Unknown in Slide (Direct) Method

Known: Antibodies (Reagent)

Unknown: Antigen (RBC surface)

Reagents in Slide Method

Anti-A, Anti-B, Anti-AB

Tube (Direct) Method Principle

Traditional testing method to detect clinically significant antibodies

Principle of AHG Reagent (Coomb's Reagent)

Create a bridge between sensitized reagent RBCs, resulting in observable agglutination

Enhancement reagents

Added to the test system prior to 37C incubation phase to increase sensitivity and decrease zeta potential.

shortens incubation time

22% Bovine Albumin

gives positive ions

30-60 mins incubation

Low Ionic Strength Solution (LISS)

increases the uptake of antibody onto the RBC during sensitization phase

Polyethylene Glycol (PEG)

removes excess water

AHG reagent

added to the test system as it allows for agglutination of incomplete antibodies

Monospecific AHG reagent

contains only ONE antibody specificity, either anti-IgG or antibodies to complement components (C3 and C4 or C3b and C3d)

Polyspecific AHG

contains anti- IgG and anti-complement

not often used because it leads to the detection of clinically significant antibodies

Blood Type O

Universal red cell Donor and universal plasma receiver

No antigens

Antibodies: Anti-A and Anti- B

Blood Type AB

Universal red cell receiver and universal plasma donor

Antigens : A and B

Antibodies: none

Secretor genes

SeSe or Sese

Nonsecretor genes

sese

A blood type in secretors

A and H

B blood type in secretors

B and H

AB blood type in secretors

A, B and H

O blood type in secretors

H only (many concentrating factors)