ABO and Rh Typing

Composition of Blood

ANTIGEN – substances that induces an immune response by causing production of antibodies

ANTIBODY - serum protein that is induced by, and reacts specifically with a foreign substance (Ag)

ABO Blood Group System• Discovered by Karl Landsteiner; on chromosome 9

• Single most important blood group for the selection and transfusion of blood

• Three antigens: A, B, H

• Two major antibodies: anti-A and anti-B

• Four phenotypes: A, B, AB, O

ABO AntigensPresent on the surface of red cells as well as

tissue and endothelial cells in the body

Found in soluble form in the plasma and other body secretions in people known as secretors

3 possible genes tat an be inherited: A, B, and O

ABO AntibodiesNatural antibodies antigenic stimulus is

environment exposure occur at birth

Newborns without ABO antibodies of their own; begin to produce wit detectable titers at 6 months age

According to the ABO blood typing system there are four different kinds of blood types: A, B, AB or O (null).

 

ABO blood grouping system

              

Blood group AIf you belong to the blood group A, you have A antigens on the surface of your RBCs and B antibodies in your blood plasma.

 

               Blood group BIf you belong to the blood group B, you have B antigens on the surface of your RBCs and A antibodies in your blood plasma.

AB0 blood grouping system

Blood Group

Antigens on RBCs

Antibodies in Serum

Genotypes

A A Anti-B AA or AO

B B Anti-A BB or BO

AB A and B Neither AB

O Neither Anti-A and anti-B OO

ABO Routine TestingIndirect/Reverse Typing

Known antigen (cell) vs unknown antibody (patient’s serum)

Serum is combined with cells having known antigen content in ratio 2:1 ratio

Uses commercially prepared reagents containing saline suspended A1 and B cells

Reaction Patterns for ABOBlood Group Agglutination w/ Anti-

AAgglutination w/ Anti-

B

A + -

B - +

AB + +

O _ _

ABO Routine TestingIndirect/Reverse Typing

Known antigen (cell) vs unknown antibody (patient’s serum)

Serum is combined with cells having known antigen content in ratio 2:1 ratio

Uses commercially prepared reagents containing saline suspended A1 and B cells

Reaction Patterns for ABOBlood Group Agglutination w/ A

cellsAgglutination w/ B

cells

A _ +

B + _

AB _ _

O + +

Slide Blood TypingThe slide is divided into halves.On one side a drop of anti-A is added, this will

attach to and cause clumping of rbcs possessing the A antigen.

On the other side a drop of anti-B is added which will cause clumping of rbcs with the B antigen.

A drop of rbcs is added to each side and mixed well with the reagent.

The slide is tilted back and forth for one minute and observed for agglutination (clumping) of the rbcs

Interpretation of Slide TypingTesting with Anti-A Anti-Serum

If an rbc contains the A antigen the red blood cells will be agglutinated by anti-A, a positive reaction.

If an rbc does not have the A antigen there will be no clumping, a negative reaction.

Interpretation of Slide TypingTesting with Anti-B Anti-SerumIf an rbc contains the B

antigen the red blood cells will be agglutinated by anti-B, a positive reaction.

If an rbc does not have the B antigen there will be no clumping by anti-B, a negative reaction.

Slide Blood Typing Group AAn unknown rbc suspension is added to known

anti-sera.The left hand of the slide contains anti-A which

reacts with the unknown cell.The right hand side contains anti-B which does

not react with the cell.

Slide Blood Typing Group BAn unknown rbc suspension is added to known

anti-sera.The left hand of the slide contains anti-A does

not react with the unknown cell.The right hand side contains anti-B which reacts

with the cell.

Slide Blood Typing Group OThe left hand of the slide contains anti-A

does not react with the unknown cell.The right hand side contains anti-B does

not react with the unknown cell.

Slide Blood Typing Group ABThe left hand of the slide contains anti-A

which reacts with the unknown cell.The right hand side contains anti-B

which reacts with the unknown cell.

Summary of Slide TypingAnti-A Anti-B Blood Group

NEG NEG O

POS NEG A

NEG POS B

POS POS AB

Example of Determining GenotypeMom’s phenotype is group A, genotype

AODad’s phenotype is group B, genotype

BO B O

A AB 25% AO 25% (Group A)

O BO 25% (Group B) OO 25% (Group O)

Rh Blood GroupAnother common way to group blood types is

using Rh antigensRh stands for ‘Rhesus’ because the Rh antigen

was first found in the Rhesus monkeyPeople with the Rh antigen are ‘Rh positive

(Rh+)’, whereas those without the antigen are ‘Rh negative (Rh -)’

Blood plasma does not normally contain anti-Rh antibodies

Hemolytic Disease of the Newborn: Rh Disease

If the fetus has Rh+ blood and the mother has Rh- blood, then the mother will make anti-Rh antibodies

However, contact between fetal and maternal blood is greatest during childbirth, and thus the firstborn baby is usually not affected

• The most common problem with Rh incompatibility is during pregnancy

• A small amount of blood from the fetus may contact the blood of the mother through the placenta

Treatment of HDN• If a woman has Rh- and gives birth to a child,

or if she has a miscarriage or abortion, she is given an injection of anti-Rh antibodies called anti-Rh gamma globulin or RhoGAM to prevent HDN.

• The antibodies bind to the fetal Rh antigens and inactivates them if they crossed the placenta during birth, and the mother’s immune system does not respond by producing antibodies.