1. Blood group and ABO antigens
Lecturer Bahiya Osrah

2. History: Karl Landsteiner
Discovered the ABO Blood Group System in 1901
Blood types:
Type A, Type B, Type AB, & Type O
The identification of blood group depends on the antigen and antibodies produced by the immune system.

3. Introduction
Antigens: chemical structures imparting specific properties to the surface of the RBC
Antibodies: protein substance developed in response to foreign body substances
Three antigens we need to focus on: A, B, and H antigens that are usually expressed on the red blood cells surface.
The presence or absence of the A, B, and H antigens is controlled by the H and ABO genes

4. ABO 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.

5. H Antigen
The H gene codes for an enzyme that adds the sugar fucose to the terminal sugar of a precursor substance (PS)
The precursor substance (proteins and lipids) is formed on an oligosaccharide chain (the basic structure)

6. RBC Precursor Structure
Glucose
Galactose
Precursor Substance (stays the same)
N-acetylglucosamine
Galactose

7. Formation of the H antigen
RBC
Glucose
H antigen
Galactose
H enzyme is fucosyltransferase
N-acetylglucosamine
Galactose
Fucose

8. A and B Antigen
The “A” gene codes for an enzyme (transferase) that adds N-acetylgalactosamine to the terminal sugar of the H antigen
N-acetylgalactosaminyltransferase
The “B” gene codes for an enzyme that adds D- galactose to the terminal sugar of the H antigen
D-galactosyltransferase

9. Formation of the A antigen
RBC
Glucose
Galactose
N-acetylglucosamine
Galactose
N-acetylgalactosamine
Fucose

10. Formation of the B antigen
RBC
Glucose
Galactose
N-acetylglucosamine
Galactose
Galactose
Fucose

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

12. ABO Type Frequencies In U.S.
Per Cent O
45% A
40% B
11% AB 4%

13. Landsteiner’s Rule
Individual’s will form immune antibodies to ABO blood group antigens they do not possess.
Critical for understanding compatibility between ABO blood groups.

14. 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.

15. 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.

16. Group O Has NO antigens on RBC surface
Approximately 45% of the population is group O.
Has NO antigens on RBC surface
Has anti-A & anti-B antibodies in the plasma
Universal Donor: can be given to any blood type  no antigens on the RBCs
Genotype OO = Phenotype O

17. Group A Approximately 40% of the population is group A.
No B antigens present.
Has A antigens on the RBC surface
Has anti-B antibodies in the plasma
Genotypes AA & AO = Phenotype A

18. Group B Approximately 11% of the population is group B.
No A antigens present.
Has B antigens on the RBC surface
Has anti-A antibodies in the plasma
Genotype BB & BO = Phenotype B

19. Group AB Approximately 4% of the population is group AB.
Has A & B antigens on the RBC surface
Has NO antibodies in the plasma
Universal Recipient: can receive Type A, Type B, Type AB, or Type O blood  NO antibodies in plasma to react with antigens
Genotypes: AB = Phenotype AB
NOTE: This slide is in error as it only illustrates presence of one antigen not 2.

20. 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.

21. Summary A Anti-B A or O B Anti-A B or O AB A and B none AB, A, B or O
Blood Group
Antigens on cell
Antibodies in plasma
Transfuse with group A
Anti-B
A or O B
Anti-A
B or O AB
A and B
none
AB, A, B or O O
None
Anti-A & B

22. Rh (D) Antigen
Rh refers to the presence or absence of the D antigen on the red blood cell.
Discovered by Landsteiner & Wiener in 1937
Discovered in the Rhesus monkey
Rh is an antigen on the RBC surface
Rh + has the antigens on the RBC (85% of population)
Rh – does NOT have the Rh antigens
Rh + can accept Rh + or Rh – blood
Rh – can accept ONLY Rh - blood

23. Rh (D) Antigen
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.
Because the Rh(D) positive individuals already have D antigen and that will trigger the immune response of the negative individuals to the D-antigens and that will cause death

24. Erythroblastosis fetalis
Rh– mother and Rh+ father  Rh+ child 1st pregnancy
during pregnancy fetal Rh pos rbc’s escape into maternal circulation (antigents)
Mother develops antibodies to baby’s Rh+ antigens
2nd pregnancy with Rh+ child  mother’s anti-Rh antibodies attack unborn child’s RBCs
Prevention: shot of Rhogam shortly after birth of first Rh+ baby to block development of antibodies
Antigen-antibody reaction due to mixing of Rh+ blood of fetus with Rh- blood of mother during 2nd Rh+ pregnancy

25. 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.

26. 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

27. Interpretation of Slide Typing Testing 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.

28. Interpretation of Slide Typing Testing 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.

29. 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.

30. Slide Blood Typing Group B
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.

31. 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.

32. 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.

33. Summary of Slide Typing
Anti-A
Anti-B
Blood Group
NEG O
POS A B AB

34. Any questions??

35. References Cte.unt.edu/health/curriculum/blood_types.ppt
Cls.umc.edu/COURSE/CLS325/Week2/ABOsystem.ppt