1. The Rhesus (Rh) Blood Group system
Mohammed Laqqan

2. The Rh(D) Antigen
Rh is the most complex system, with over 45 antigens.
The complexity of the Rh blood group Ags is due to the highly polymorphic genes that encode them.
Discovered in 1940 after work on Rhesus monkeys.
The 2nd most important after ABO in the crossmatch test.
Only the most clinically significant Ags will be discussed.
It received its name in 1940, when Landsteiner and Wiener immunized rabbits with red blood cells from rhesus monkeys and found that the rabbit antirhesus antibody agglutinated approximately 85 percent of human red blood cells tested. They gave the name "Rh" to this determinant present on all rhesus monkey cells and apparently present on 85 percent of human red blood cells.
Mohammed Laqqan

3. Rh Genetics
The genes that control the system are autosomal codominant located on the short arm of chromosome 1.
Mohammed Laqqan

4. Rh blood group antigens are proteins
The antigens of the Rh blood group are proteins.
The RhD gene encodes the D antigen, which is a large protein on the red blood cell membrane, & the most important.
RHD gene
RHCE gene
Chromosome 1
Proteins
Mohammed Laqqan

5. Rh Antigen Frequency D antigen – 85% d antigen – 15% C antigen – 70%
Rh Positive
Rh Negative
D antigen – 85%
d antigen – 15%
C antigen – 70%
c antigen – 80%
E antigen – 30%
e antigen – 98%
The presence or absence of D Ag determines if the person is Rh+ or Rh-
Mohammed Laqqan

6. Nomenclature of the RH system
3 Different nomenclatures:
1- Fisher-Race
2- Weiner
3- Rosenfield Nomenclature
Mohammed Laqqan

7. Fisher-Race Theory
Rh inheritance is controlled by 3 closely linked loci on each chromosome of a homologous pair
Each locus has its own set of alleles which are: Dd , Cc , and Ee .
The D gene is dominant to the d gene, but Cc and Ee are co-dominant co-dominant.
The 3 loci are so closely linked that crossing over does NOT occur, and the 3 genes on one chromosome are always inherited together.
Mohammed Laqqan

8. “d” antigen not produced
Fisher-Race D d C c E e
3 closely linked genes
“d” antigen not produced
Produces D antigen
Produces C/c antigen
Produces E/e antigen
Mohammed Laqqan

9. Fisher-Race There are 8 gene complexes at the Rh locus
Fisher-Race uses DCE as the order
Others alphabetize the genes as CDE
DCe
dCe
DcE
dCE
Dce
dcE
DCE
dce
Mohammed Laqqan

10. Fisher-Race Nomenclature
Antigens
Gene Combination
D, c, e
Dce
D, C, e
DCe
D, c, E
DcE
D, C, E
DCE
c,e
dce
C,e
dCe
c,E
dcE
C,E
dCE
Mohammed Laqqan

11. Fisher-Race Example:
DCe/DCe individual is homozygous for D, C, and e genes
DCe/dcE individual is heterozygous for D, C, e, d, c, and E genes
Mohammed Laqqan

12. Fisher-Race: Genetics/Terminology
Rh phenotype is designated by the presence or absence of Rh antigens: D, C, c, E, e
little d: Indicates the ABSENCE of the D antigen and nothing more.
There is NO little d antigen or allele.
Many blood bankers today are leaving the ‘d’ out the the nomenclature entirely.
Phenotype example: R1 phenotype is D, C, e
Rh genes are codominant.
Mohammed Laqqan

13. In the Fish-Race theory the D gene codes for the D antigen
In the Fish-Race theory the D gene codes for the D antigen. The C gene codes for the C antigen, etc.
Mohammed Laqqan

14. Wiener Theory Good for describing phenotype
There is one Rh locus at which occurs one Rh gene, but this gene has multiple alleles.
For example, one gene R1 produces one agglutinogen (antigen) Rh1 which is composed of three "factors"
The three factors are analogous to C, D, and e respectively
The main difference between the Fisher-Race and Wiener theories is that the:
Fisher-Race theory has three closely linked loci,
the Wiener theory has only one gene locus at which multiple alleles occur.
Mohammed Laqqan

15. Produces D antigen on RBC
Wiener Theory
Single gene at Rh locus R’ r’ R0 r” R”
Produces D antigen on RBC
Produces C antigen on RBC
Mohammed Laqqan

16. Wiener
Wiener further theorized that 8 major genes led to different combinations of antigens (D, C, E, c, e):
R0, R1, R2, Rz
r, r′, r″, ry
Mohammed Laqqan

17. 2- Weiner Nomenclature D present R D absent r C Prime ′ or 1 E
Nomenclature expressed by the use of a single letter.
D present R
D absent r C
Prime ′ or 1 E
Double ″ or 2
Mohammed Laqqan

18. Conversion of Wiener to Fisher-Race
R in Wiener = D in Fisher-Race
r is absence of D (d)
0 or no symbol implies c and e
1 or ′ implies C and e
2 or ″ implies c and E
z or y implies C and E
Mohammed Laqqan

19. Fisher-Race and Wiener Nomenclature
(Weiner Gene)
Antigens
Fisher-Race R0
D, c, e
Dce R1
D, C, e
DCe R2
D, c, E
DcE Rz
D, C, E
DCE r
c,e
dce r′
C,e
dCe r″
c,E
dcE ry
C,E
dCE
Mohammed Laqqan

20. Converting Wiener into Fisher-Race or vice versa
R  D
r  no D
1 and ′  C
2 and ″  E
Example: DcE  R2
r″  dcE
Written in shorthand
Mohammed Laqqan

21. Rosenfield Nomenclature
Each antigen assigned a number
Rh 1 = D
Rh 2 = C
Rh 3 = E
Rh 4 = c
Rh 5 = e
In writing the phenotype, the prefix “Rh” is followed by colon, then number (if negative, number is preceded by -)
e.g. D+, C+, E-, c+, e+ is written as
Rh:1,2,-3,4,5
Mohammed Laqqan

22. Significance
After ABO, the Rh system is the second most important system. This is because:
The D antigen is extremely immunogenic.
It causes the production of anti-D in % of Rh(D) negative people who are exposed to the D antigen.
Moreover, anti-D is the most common cause of severe HDN and can cause in Utero death.
Because of this, in blood transfusion, the patient and donor are matched for Rh(D) type as well as ABO groups.
The C and E Ags are not as immunogenic as D, routine typing for these Ags is not performed
Capable of inducing an immune response; antigenic
Mohammed Laqqan

23. Rh Deleted Red cells that express no Ags at the C & E loci ( D )
Number of D Ags greatly increase
Anti-D IgG Abs can agglutinate these cells
Mohammed Laqqan

24. Rh null
RH null: individual that appears to have no Rh antigens ( , , )
RBC has fragile membrane- short lived
Must use autologous blood products
No D, C, c, E, e antigens present on the RBC membrane
Demonstrate mild hemolytic anemia (Rh antigens are integral part of RBC membrane and absence results in loss of membrane integrity)
Stomatocytosis.
When transfusion is necessary ONLY Rh Null blood can be used to transfuse.
Mohammed Laqqan

25. Clinically Significant Transfusion Reactions
Rh antibodies
Result from the exposure to Rh antigens
IgG form
Bind at 37°C
Form agglutination in IAT phase
Rh Abs
Clinically Significant
Yes
Abs class
IgG
Thermal range
4 - 37
HDNB
Transfusion Reactions
Extravascular
Intravascular No
Mohammed Laqqan

26. Clinical Significance of Rh antibodies
Related to Hemolytic transfusion reactions
Re-exposure to antigen cause rapid secondary response
Always check patients history for previous transfusion or pregnancy to avoid re-exposure.
Mohammed Laqqan

27. Hemolytic disease of the Newborn (HDN)
Usually related to D antigen exposure and the formation of anti-D
Usually results from D negative female and D positive male producing and offspring.
The baby will probably be D positive.
1st pregnancy not effected, the 2nd pregnancy and on will be effected-results in still birth, severe jaundice, anemia related to HDN.
To prevent this occurrence the female is administered RH-IG.
Mohammed Laqqan

28. Rh factor First pregnancy Placenta Rh+ antigens
Rh factor can cause complications in some pregnancies.
Placenta
Rh+ antigens
Mother is exposed to Rh antigens at the birth of her Rh+ baby.
Mohammed Laqqan

29. Mother makes anti-Rh+ antibodies.
Possible subsequent pregnancies
Anti-Rh+ antibodies
During the mother’s next pregnancy, Rh antibodies can cross the placenta and endanger the fetus.
Mohammed Laqqan

30. Weak D Phenotype
Most D positive rbc’s react macroscopically with Reagent anti-D at immediate spin
These patients are referred to as Rh positive
Reacting from 1+ to 3+ or greater
HOWEVER, some D-positive rbc’s DO NOT react (do NOT agglutinate) at Immediate Spin using Reagent Anti-D. These require further testing (37oC and/or AHG) to determine the D status of the patient.
Mohammed Laqqan

31. Variants of D Weak expression of the Rh system on the RBC, (Du)
Du red cells can be classified into three categories according to the mechanism that account for the Weak D antigen
Mohammed Laqqan

32. Categories of Du red cells
1- Acquired Du (Position Effect)
2- Du Variant (Partial D)
3- Hereditary Du (Genetically Transmissible)
Mohammed Laqqan

33. 1- Acquired Du (Position Effect)
C allele in trans position to D allele
Example: Dce/dCe, DcE/dCE In both of these cases the C allele is in the trans position in relation to the D allele.
D antigen is normal, C antigen appears to be crowding the D antigen. (Steric hindrance)
Does NOT happen when C is in cis position
Example: DCe/dce
Can safely transfuse D positive blood components.
Mohammed Laqqan

34. 2- Du Variant (Partial D)
The D- Ag consists of at least 4 parts
Missing one or more PARTS (epitopes) of the D antigen remaining Ag is weakly expressed
Alloantibodies are produced to the missing parts
Du variants should receive Rh –ve blood when transfused
Mohammed Laqqan

35. Partial D: Multiple epitopes make up D antigen
Partial D: Multiple epitopes make up D antigen. Each color represents a different epitope of the D antigen. A.
Patient B lacks one D epitope. B.
The difference between Patient A and Patient B is a single epitope of the D antigen. The problem is that Patient B can make an antibody to Patient A even though both appear to have the entire D antigen present on their red blood cell’s using routine anti-D typing reagents..
Mohammed Laqqan

36. 3- Hereditary Du (Genetically Transmissible)
The RHD gene codes for weakened expression of D antigen in this mechanism.
D antigen is complete, there are just fewer D Ag sites on the rbc. Quantitative!
Common in Black population (usually Dce haplotype). Very rare in White population.
Agglutinate weakly or not at all at immediate spin phase.
Agglutinate strongly at AHG phase.
Can safely transfuse D positive blood components.
Mohammed Laqqan