The Rhesus (Rh) The Rhesus (Rh) Blood Group Blood Group

systemsystem

The Rh(D) AntigenThe Rh(D) Antigen Rh is the most complex system, with Rh is the most complex system, with

over 45 antigensover 45 antigens The complexity of the Rh blood group The complexity of the Rh blood group

Ags is due to the highly polymorphic Ags is due to the highly polymorphic genes that encode them.genes that encode them.

Discovered in 1940 after work on Discovered in 1940 after work on Rhesus monkeysRhesus monkeys

The 2The 2ndnd most important after ABO in most important after ABO in the crossmatch testthe crossmatch test

Only the most clinically significant Only the most clinically significant Ags will be discussedAgs will be discussed

Rh GeneticsRh Genetics

The genes that control the system The genes that control the system are autosomal codominant located are autosomal codominant located on the short arm of chromosome 1.on the short arm of chromosome 1.

Rh blood group antigens are Rh blood group antigens are proteinsproteins

The antigens of the Rh blood group are proteins.The antigens of the Rh blood group are proteins. The RhD gene encodes the D antigen, which is a The RhD gene encodes the D antigen, which is a

large protein on the red blood cell membrane, & large protein on the red blood cell membrane, & the most important.the most important.

RHD gene RHCE gene

Chromosome 1

Proteins

Rh Antigen FrequencyRh Antigen Frequency

D antigen – 85%D antigen – 85% d antigen – 15%d antigen – 15% C antigen – 70%C antigen – 70% c antigen – 80%c antigen – 80% E antigen – 30%E antigen – 30% e antigen – 98%e antigen – 98%

The presence or absence of D Ag The presence or absence of D Ag determines if the person is Rh+ or Rh-determines if the person is Rh+ or Rh-

Rh PositiveRh Positive

Rh NegativeRh Negative

3 Different nomenclatures:3 Different nomenclatures:1- Fisher-Race1- Fisher-Race2- Weiner2- Weiner3- Rosenfield Nomenclature3- Rosenfield Nomenclature

Nomenclature of the RH systemNomenclature of the RH system

Fisher-Race TheoryFisher-Race Theory

Rh inheritance is controlled by 3 closely Rh inheritance is controlled by 3 closely linked loci on each chromosome of a linked loci on each chromosome of a homologous pairhomologous pair

Each locus has its own set of alleles which Each locus has its own set of alleles which are: are: Dd Dd , , Cc Cc , and , and Ee Ee . .

The The D D gene is dominant to the gene is dominant to the d d gene, but gene, but Cc Cc and and Ee Ee are co-dominant.are co-dominant.

The 3 loci are so closely linked that crossing The 3 loci are so closely linked that crossing over does NOT occur, and the 3 genes on one over does NOT occur, and the 3 genes on one chromosome are always inherited together.chromosome are always inherited together.

Fisher-RaceFisher-Race

Dd

C

c

E

e

3 closely linked genes

“d” antigen not produced

Produces D antigen

Produces C/c antigen

Produces E/e antigen

Dd

C

c

E

e

Fisher-RaceFisher-Race

There are 8 gene There are 8 gene complexes at the complexes at the Rh locusRh locus

Fisher-Race uses Fisher-Race uses DCEDCE as the order as the order

Others alphabetize Others alphabetize the genes as the genes as CDECDE

DCeDCe dCedCe

DcEDcE dCEdCE

DceDce dcEdcE

DCEDCE dcedce

Fisher-Race NomenclatureFisher-Race Nomenclature

Gene Gene CombinatiCombinati

ononAntigensAntigens

Dce Dce D, c, e D, c, e

DCe DCe D, C, e D, C, e

DcE DcE D, c, E D, c, E

DCE DCE D, C, E D, C, E

dce dce c,e c,e

dCe dCe C,e C,e

dcE dcE c,Ec,E

dCEdCE C,EC,E

Fisher-Race Example:Fisher-Race Example:

DCe/DCe individual is homozygous DCe/DCe individual is homozygous for D, C, and e genesfor D, C, and e genes

DCe/dcE individual is heterozygous DCe/dcE individual is heterozygous for D, C, e, d, c, and E genesfor D, C, e, d, c, and E genes

Fisher-Race: Fisher-Race: Genetics/TerminologyGenetics/Terminology

Rh phenotype is designated by the presence Rh phenotype is designated by the presence or absence of Rh antigens: D, C, c, E, eor absence of Rh antigens: D, C, c, E, e• little d: Indicates the ABSENCE of the D little d: Indicates the ABSENCE of the D

antigen and nothing more. antigen and nothing more. • There is There is NONO little d antigen or allele. little d antigen or allele. • Many blood bankers today are leaving the Many blood bankers today are leaving the

‘d’ out the the nomenclature entirely. ‘d’ out the the nomenclature entirely.

• Phenotype example: RPhenotype example: R11 phenotype is D, C, e phenotype is D, C, e Rh genes are Rh genes are codominant.codominant.

In the Fish-Race theory the D gene codes for the D antigen. The C gene codes for the C

antigen, etc.

Wiener TheoryWiener Theory Good for describing phenotypeGood for describing phenotype There is one Rh locus at which occurs one Rh There is one Rh locus at which occurs one Rh

gene, but this gene has multiple alleles.gene, but this gene has multiple alleles. For example, one gene For example, one gene R1 R1 produces one produces one

agglutinogen (antigen) Rh1 which is composed of agglutinogen (antigen) Rh1 which is composed of three "factors"three "factors"

The three factors are analogous to C, D, and e The three factors are analogous to C, D, and e respectivelyrespectively

The main difference between the Fisher-Race and The main difference between the Fisher-Race and Wiener theories is that the: Wiener theories is that the: • Fisher-Race theory has three closely linked Fisher-Race theory has three closely linked

loci, loci, • the Wiener theory has only one gene locus at the Wiener theory has only one gene locus at

which multiple alleles occurwhich multiple alleles occur..

Wiener TheoryWiener Theory

Single gene at Rh locus

R’

r’

R0

r”

R”

Produces D antigen on RBC

Produces C antigen on RBC

WienerWiener

Wiener further theorized that Wiener further theorized that 88 major major genes genes led to different combinations led to different combinations of antigens (D, C, E, c, e):of antigens (D, C, E, c, e):• RR00, R, R11, R, R22, R, Rzz

• r, r′, r″, rr, r′, r″, ryy

2- Weiner Nomenclature2- Weiner Nomenclature

Nomenclature expressed by the use of a single letter.Nomenclature expressed by the use of a single letter.

R R D presentD present

r r D absentD absent

Prime Prime ′ or 1 ′ or 1 CC

Double ″ Double ″ or 2 or 2 EE

Conversion of Wiener to Fisher-Conversion of Wiener to Fisher-RaceRace

R in Wiener = D in Fisher-RaceR in Wiener = D in Fisher-Race r is absence of D (d)r is absence of D (d) 0 or no symbol implies c and e0 or no symbol implies c and e 1 or ′ implies C and e1 or ′ implies C and e 2 or ″ implies c and E2 or ″ implies c and E z or y implies C and Ez or y implies C and E

Fisher-Race and Wiener NomenclatureFisher-Race and Wiener Nomenclature

Fisher-RaceFisher-Race AntigensAntigens (Weiner Gene)(Weiner Gene)

Dce Dce D, c, e D, c, e RR00

DCe DCe D, C, e D, C, e RR11

DcE DcE D, c, E D, c, E RR22

DCE DCE D, C, E D, C, E RRzz

dce dce c,e c,e rr

dCe dCe C,e C,e r′r′

dcE dcE c,Ec,E r″r″

dCEdCE C,EC,E rryy

Converting Wiener into Fisher-Converting Wiener into Fisher-Race or vice versaRace or vice versa

R R D D

r r no D no D

11 and and ′′ C C

22 and and ″″ E E

Example: DcE Example: DcE RR2 2

r″ r″ dcE dcE

Written in shorthand

Rosenfield NomenclatureRosenfield Nomenclature Each antigen assigned a numberEach antigen assigned a number Rh 1 = DRh 1 = D Rh 2 = CRh 2 = C Rh 3 = ERh 3 = E Rh 4 = cRh 4 = c Rh 5 = eRh 5 = e In writing the phenotype, the prefix “Rh” is In writing the phenotype, the prefix “Rh” is

followed by colon, then number (if negative, followed by colon, then number (if negative, number is preceded by -)number is preceded by -)

e.g. D+, C+, E-, c+, e+ is written as e.g. D+, C+, E-, c+, e+ is written as Rh:1,2,-3,4,5Rh:1,2,-3,4,5

SignificanceSignificance After ABO, the Rh system is the second most After ABO, the Rh system is the second most

important system. This is because:important system. This is because: The D antigen is extremely immunogenic.The D antigen is extremely immunogenic. It causes the production of anti-D in 50 - 70% of It causes the production of anti-D in 50 - 70% of

Rh(D) negative people who are exposed to the D Rh(D) negative people who are exposed to the D antigen. antigen.

Moreover, anti-D is the most common cause of Moreover, anti-D is the most common cause of severe HDN and can cause severe HDN and can cause in Uteroin Utero death. death.

Because of this, in blood transfusion, the patient Because of this, in blood transfusion, the patient and donor are matched for Rh(D) type as well as and donor are matched for Rh(D) type as well as ABO groups.ABO groups.

The C and E Ags are not as immunogenic as D, The C and E Ags are not as immunogenic as D, routine typing for these Ags is not performed routine typing for these Ags is not performed

Weak D PhenotypeWeak D Phenotype Most Most D positiveD positive rbc’s react macroscopically rbc’s react macroscopically

with Reagent anti-D at immediate spinwith Reagent anti-D at immediate spin• These patients are referred to as These patients are referred to as Rh positiveRh positive• Reacting from 1+ to 3+ or greaterReacting from 1+ to 3+ or greater

HOWEVER,HOWEVER, some D-positive rbc’s some D-positive rbc’s DO DO NOTNOT react (do react (do NOTNOT agglutinate) at agglutinate) at Immediate Spin using Reagent Anti-D. Immediate Spin using Reagent Anti-D. These require further testing These require further testing (37(37ooC and/or C and/or AHG)AHG) to determine the D status of the to determine the D status of the patient.patient.

• Weak expression of the Rh system on Weak expression of the Rh system on the RBC, the RBC, (D(Duu))

• DDuu red cells can be classified into red cells can be classified into three categories according to the three categories according to the mechanism that account for the mechanism that account for the Weak D antigenWeak D antigen

Variants of D

Categories of DCategories of Duu red cells red cells

1- Acquired D1- Acquired Duu (Position Effect) (Position Effect)

2- D2- Duu Variant (Partial D) Variant (Partial D)

3- Hereditary D3- Hereditary Du u (Genetically (Genetically Transmissible)Transmissible)

1- Acquired D1- Acquired Du u (Position Effect)(Position Effect) C allele in transC allele in trans positionposition to D alleleto D allele

• Example:Example: D Dce/dce/dCCe, DcE/dCE e, DcE/dCE In both of these cases the C allele is in the In both of these cases the C allele is in the trans position in relation to the D allele.trans position in relation to the D allele.

D antigen is normal, C antigen appears to D antigen is normal, C antigen appears to be crowding the D antigen. (Steric be crowding the D antigen. (Steric hindrance)hindrance)

Does Does NOTNOT happen when C is in happen when C is in ciscis positionposition• Example: DCe/dceExample: DCe/dce

Can safely transfuse D positive blood Can safely transfuse D positive blood components.components.

2- D2- Duu Variant (Partial D) Variant (Partial D) The D- Ag consists of at least 4 partsThe D- Ag consists of at least 4 parts Missing one or more PARTS Missing one or more PARTS

(epitopes) of the D antigen (epitopes) of the D antigen remaining Ag is weakly expressedremaining Ag is weakly expressed

Alloantibodies are produced to the Alloantibodies are produced to the missing partsmissing parts

DDuu variants should receive Rh –ve variants should receive Rh –ve blood when transfusedblood when transfused

Partial D: Multiple epitopes make up D antigen. Each color represents a different epitope of the D antigen.

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..

A.

B.Patient B lacks one D epitope.

3- Hereditary D3- Hereditary Duu (Genetically Transmissible (Genetically Transmissible))

The The RHD RHD gene codes for weakened gene codes for weakened expression of D antigen in this expression of D antigen in this mechanism.mechanism.• D antigen is complete, there are just fewer D D antigen is complete, there are just fewer D

Ag sites on the rbc. Quantitative!Ag sites on the rbc. Quantitative!• Common in Black population (usually Dce Common in Black population (usually Dce

haplotype). Very rare in White population.haplotype). Very rare in White population. Agglutinate weakly or not at all at Agglutinate weakly or not at all at

immediate spin phase.immediate spin phase. Agglutinate strongly at AHG phase.Agglutinate strongly at AHG phase. Can safely transfuse D positive blood Can safely transfuse D positive blood

components.components.

Rh DeletedRh Deleted

Red cells that express no Ags at the Red cells that express no Ags at the C & E loci ( D ) C & E loci ( D )

Number of D Ags greatly increaseNumber of D Ags greatly increase Anti-D IgG Abs can agglutinate these Anti-D IgG Abs can agglutinate these

cellscells

RH null: individual that appears to have no Rh RH null: individual that appears to have no Rh antigens antigens

RBC has fragile membrane- short livedRBC has fragile membrane- short lived Must use autologous blood productsMust use autologous blood products

• NoNo D, C, c, E, e antigens present on the RBC D, C, c, E, e antigens present on the RBC membrane membrane

DemonstrateDemonstrate mild hemolytic anemia (Rh antigens mild hemolytic anemia (Rh antigens are integral part of RBC membrane and absence are integral part of RBC membrane and absence results in loss of membrane integrity)results in loss of membrane integrity)• Stomatocytosis.Stomatocytosis.

When transfusion is necessary When transfusion is necessary ONLYONLY Rh Null Rh Null blood can be used to transfuse.blood can be used to transfuse.

Rh nullRh null

Rh antibodiesRh antibodies

Result from the Result from the exposure to Rh exposure to Rh antigensantigens

• IgG formIgG form• Bind at 37Bind at 37°C°C• Form agglutination Form agglutination

in IAT phasein IAT phase

Rh AbsRh AbsClinically Clinically SignificanSignifican

tt

YesYes

Abs classAbs class

IgGIgG

Thermal Thermal rangerange

4 - 374 - 37

HDNBHDNB

YesYes

Transfusion ReactionsTransfusion Reactions

ExtravasculExtravascularar

IntravasculIntravascularar

YesYes NoNo

• Related to Hemolytic transfusion Related to Hemolytic transfusion reactionsreactions

• Re-exposure to antigen cause rapid Re-exposure to antigen cause rapid secondary responsesecondary response

• Always check patients history for Always check patients history for previous transfusion or pregnancy to previous transfusion or pregnancy to avoid re-exposure.avoid re-exposure.

Clinical Significance of Rh Clinical Significance of Rh antibodiesantibodies

Usually related to D antigen exposure and the Usually related to D antigen exposure and the

formation of anti-Dformation of anti-D

Usually results from D negative female and D Usually results from D negative female and D

positive male producing and offspring. positive male producing and offspring.

• The baby will probably be D positive.The baby will probably be D positive.

11stst pregnancy not effected, the 2 pregnancy not effected, the 2ndnd pregnancy and pregnancy and

on will be effected-results in still birth, severe on will be effected-results in still birth, severe

jaundice, anemia related to HDN.jaundice, anemia related to HDN.

To prevent this occurrence the female is To prevent this occurrence the female is

administered RHIG.administered RHIG.

Hemolytic disease of the Newborn Hemolytic disease of the Newborn (HDN)(HDN)

Rh factor can Rh factor can cause cause complications in complications in some some pregnancies.pregnancies.

Mother is Mother is exposed to Rh exposed to Rh antigens at the antigens at the birth of her Rhbirth of her Rh++ baby.baby.

First pregnancy

PlacentaRh+ antigens

Rh factorRh factor

Anti-Rh+ antibodies

Possible subsequent pregnancies

Mother makes Mother makes anti-Rhanti-Rh++ antibodies.antibodies.

During the During the mother’s next mother’s next pregnancy, Rh pregnancy, Rh antibodies can antibodies can cross the placenta cross the placenta and endanger the and endanger the fetus.fetus.