ABO/D Blood Groups

Understanding Critical For Safe Transfusions

ABO Biochemical Basics

Blood group antigens are actually sugars attached to the red blood cell.

Antigens are “built” onto the red cell. Individuals inherit a gene which codes

for specific sugar(s) to be added to the red cell.

The type of sugar added determines the blood group.

This diagram illustrates the terminal sugar for each blood group.

Blood Group Basics

All normal blood groups have “H”. If only H is added to the red blood cell the

person is group O. If N-acetylgalactosamine is added to H, the

person is group A. If D-galactose is added to H, the person is

group B. If both N-acetylgalactosamine and D-galactose

are added the person is AB.

ABO Type Frequencies In U.S.

ABO Type Per Cent

O 45%

A 40%

B 11%

AB 4%

Landsteiner’s Rule

Individual’s will form immune antibodies to ABO blood group antigens they do not possess.

Substances are present in nature which are so similar to blood group antigens which result in the constant production of antibodies to blood group antigens they do not possess.

Critical for understanding compatibility between ABO blood groups.

Antibody clinical significance Immunizations are frequently done to protect

us from disease.• Receive Hepatitis B immunization.• Actual bits of hepatitis virus injected.• Body recognizes as foreign and produces an immune

antibody.• Subsequent exposure to real Hepatitis B virus will

result in destruction of the virus by immune antibodies. ABO antibodies are immune and will result in

destroying incompatible cells which may result in the death of the recipient.

Inheritance

Blood group antigens are “codominant”, if the gene is inherited, it will be expressed.

Some aberrant genotypes do occur but due to the rarity will not be discussed.

Understanding of basic inheritance important.

Genetics Two genes inherited, one from each parent. Individual who is A or B may be homozygous

or heterozygous for the antigen. Heterozygous: AO or BO Homozygous: AA or BB Phenotype is the actual expression of the

genotype, ie, group A Genotype are the actual inherited genes which

can only be determined by family studies, ie, AO.

Example of Determining Genotype

Mom’s phenotype is group A, genotype AO Dad’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)

Other Examples

Mom Dad Offspring Blood Group

AA BB 100% AB

BO OO 50% each of B or O

OO OO 100% O

OO AO 50% each of A or O

Group O

Approximately 45% of the population is group O.

No A or B antigens present, think of as “0” antigens present.

These individuals form potent anti-A and anti-B antibodies which circulate in the blood plasma at all times.

Group O For red blood cell transfusions Group O

individuals CAN ONLY RECEIVE Group O. Transfusion of any other blood group will

probably result in death of the recipient due to the anti-A and anti-B antibodies present in their blood plasma.

As DONORS, this blood group is considered the “universal donor” since there are no A or B antigens present this blood can be transfused safely to all other blood groups.

Group A

Approximately 40% of the population is group A.

No B antigens present. These individuals form

potent anti-B antibodies which circulate in the blood plasma at all times.

Group A

For red blood cell transfusions Group A individuals can receive either Group A or Group O

Transfusion of Group B will result in death of the recipient due to the anti-B antibodies present in their blood plasma reacting with the B antigens present on the transfused red blood cells.

Group B

Approximately 11% of the population is group B.

No A antigens present. These individuals form potent

anti-A antibodies which circulate in the blood plasma at all times.

Group B

For red blood cell transfusions Group B individuals can receive either Group B or Group O

Transfusion of Group A will result in death of the recipient due to the anti-A antibodies present in their blood plasma reacting with the A antigens present on the transfused red blood cells.

Group AB

Approximately 4% of the population is group AB.

Both A and B antigens present.

These individuals possess no ABO antibodies.

NOTE: This slide is in error as it only illustrates presence of one antigen not 2.

Group AB

For red blood cell transfusions Group AB can receive ANY blood Group.

Considered the “Universal Recipient”. Because they have no anti-A, can receive

group A, no anti-B, can receive group B. So even though the rarest blood group, finding

compatible blood is not a problem.

Hemolysis

If an individual is transfused with an incompatible blood group destruction of the red blood cells will occur.

This may result in the death of the recipient.

Summary

Blood Group Antigens on cell Antibodies in plasma

Transfuse with group

A A Anti-B A or O

B B Anti-A B or O

AB A and B none AB, A, B or O

O None Anti-A & B O

Rh (D) Antigen

Of next importance is the Rh type.• Term “Rh” is a misnomer.

• Rh is a blood group system with many antigens, one of which is D.

• Re-education of public is difficult.

Rh refers to the presence or absence of the D antigen on the red blood cell.

Rh (D) Antigen (continued)

Unlike the ABO blood group system, individuals who lack the D antigen do not naturally make it.

Production of antibody to D requires exposure to the antigen.

The D antigen is very immunogenic, ie, individuals exposed to it will very likely make an antibody to it.

For this reason all individuals are typed for D, if negative must receive Rh (D) negative blood.

Rh (D) Antigen (continued)

The most important patient population to consider is females of child-bearing age.

If immunized to Rh (D) antigen the antibody can cross the placenta and destroy Rh (D) positive fetal cells resulting in death.

This is why Rh negative women are given Rhogam after birth of Rh positive baby.

Hemolytic Disease of the Neborn – How it Occurs A child is Rh pos B during pregnancy fetal Rh pos rbc’s escape into maternal

circulation C Mother produces antibodies to Rh (D) antigen D Second pregnancy with Rh (D) pos child results in

destruction of fetal D pos rbcs

Rh (D) Antigen (continued)

For transfusion purposes Rh (D) negative individuals must receive Rh negative blood.

Rh (D) positive individuals can receive EITHER Rh (D) negative or Rh (D) positive blood.

VERY IMPORTANT concept to remember when determining blood compatibility.

Blood Typing

There are 2 components to blood typing:• Test unknown cells with known antibodies

• Test unknown serum/plasma with known rbc’s

The patterns are compared and the blood group is determined.

Slide Blood Typing

Very rudimentary method for determining blood groups.

CANNOT be used for transfusion purposes as false positives and negatives do occur.

A “false positive” is when agglutination occurs not because the antigen is present, but cells may already be clumpled.

A “false negative” is one in which the cells are not clumped because there are too many cells or not enough reagent.

Slide Blood Typing - continued The 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-Serum

If 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 A An 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 A An 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 O

The 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 AB

The 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 Typing

Anti-A Anti-B Blood Group

NEG NEG O

POS NEG A

NEG POS B

POS POS AB

Tube Typing

Could not find pictures of tube typing, but most common procedure and much more graphicly illustrative of what goes on.

Will be added to this presentation