The Rh Blood Group

Brian Poirier, MD

UCDavis Medical Center

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Topics

• Terminology systems

• Rh antibodies

• Consequences of Rh incompatibility

• Unusual phenotypes

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Objectives

• Explain the derivation of the term Rh

• Differentiate Rh from LW

• Compare and convert the major genotypes among Fisher-Race, Wiener, and Rosenfield terminologies

• Define the basic biochemical structure of Rh

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Objectives (Continued)

• Describe and differentiate three mechanisms that result in weak D expression on rbcs

• Describe 3 characteristics of Rh antibodies

• Describe how to prevent Rh D immunization

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Rh Blood Group

• Second most important blood group (after ABO)

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History of the Rh System

• 1939 Levine described a HTR in an OB patient:– After delivery of a still born infant, a woman

required transfusions. – After receiving her husband’s blood (ABO

compatible), she demonstrated the acute HTR.

– An antibody was isolated from mom’s serum that reacted both at 37 C and 20 C with father’s rbcs.

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History of the Rh System (continued)

History of the Rh System (continued)

• 1940 Landsteiner and Wiener reported:– An antibody made by guinea pigs and rabbits

when they were transfused with rhesus monkey rbcs.

– The antibody agglutinated 85% of human rbcs, was named “Rh.”

– The antibody was renamed as anti-LW (Landsteiner and Wiener).

– The name Rh was retained for human-produced antibody.

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Nomenclatures of the Rh system

• Fisher-Race: The DCE Terminology

• Wiener (Rh-Hr): The Rh-Hr Terminology

• Rosenfield: Alpha/Numeric Terminology

• ISBT (International Society of Blood Transfusion): Numeric Terminology

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Fisher-Race (DCE or CDE)

• 5 major antigens: D, C, E, c, e– Rh positive really means D positive.– Absence of D designated “d” (later found not

to be a real antigen- an “amorph”).

• 8 potential haplotypes named based on presence of genes for above antigens (eg, Dce, dce).

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Wiener (Rh-Hr)

• Different names for the 5 main antigens– Rho=D– rh’=C– rh”=E– hr’=c– hr”=e

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Wiener (Rh-Hr) (continued)

• Gave shorthand names to the 8 potential combinations alluded to above; still in use

R1=DCe r’=dCe

R2=DcE r”=dcE

Ro=Dce r=dce

Rz=DCE ry=dCE

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Converting Wiener (Rh-Hr) to Fisher-Race

Fisher-Race terminology is easier to use:

• R=D, r=d

• 1 or prime=C

• 2 or double prime=E

• 0 or blank=ce

• any superscript letter =CE

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Rosenfield Terminology (alpha/numeric)

• Rosenfield system has no genetic basis, only demonstrates the presence or absence of the antigen on the red cells.

• A minus sign preceding a number designates absence of the antigen. The absence of the number indicates the antigen has not been typed.

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Rosenfield Terminology (Continued)

• D is assigned Rh1; C is assigned Rh2; E is assigned Rh3; c is assigned Rh4; e is assigned Rh5

• Example 1: D+ C- E+ c+ e+ would be: Rh: 1, -2, 3, 4, 5

• Example 2: DCe/dcE would be: Rh: 1, 2, 3, 4, 5

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ISBT Terminology

• ISBT adopted a six-digit number for each blood goup specificiy.

• First 3 numbers represent the system and the remaining 3 the antigen specificity.

• 004 was assigned to the Rh blood group system; each antigen assigned to the Rh system was given a unique number to complete the 6-digit computer number.

• Example: “D” antigen would be “004001”

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“The Big Four Rh Phenotypes

• R1, R2, R0, and r are most frequently encountered phenotypes.

• R0 most common in blacks, least common in whites.

• R1> R2

• r is always second in frequency

• Whites: R1 > r > R2 > R0

• Blacks: R0 > r > R1 > R2

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Gene Frequency of Rh Antigens

Gene Frequency %

D 85

d 15

C 70

E 30

c 80

e 9819

Common Rh Types by 3 Nomenclatures

Wiener Fisher-Race Rosenfield %R1r DCe/dce Rh: 1,2,-3, 4,5

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R1R1 DCe/DCe Rh: 1,2,-3, -4,5 18

rr dce/dce Rh: -1,-2,-3, 4,5 15

R1R2 DCe/DcE Rh: 1,2,3, 4,5 11

R2r DcE/dce Rh: 1,-2,3, 4,5 9

R2R2 DcE/DcE Rh: 1,-2,3, 4,-5 2

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Rh Antigens

• Non-glycosylated proteins in the red cell membrane.

• Inherited as codominant alleles.• Are transmembrane polypeptides and are an

integral part of the red cell membrane.• All Rh antigens (D,C,E) are very similar; differ

by only 44 base pair.• C and c differ in 4 a.a.• E and e differ in 1 a.a.

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Rh Antigens

Hillyer et al 2009

Rh Antigens (continued)

• Rh antigens are highly immunogenic:D > c > E > C > e

• The D antigen is the most immunogenic antigen outside the ABO system.

• As little as 0.5 ml will elicit anti-D allo-immunization in healthy volunteers (Gunson et al 1970).

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Rh Antibodies

• Do not bind complement

• Extravascular

• IgG

• Can cross placenta and cause HDFN

• HTR

• Exposure required (pregnancy or transfusion)

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Consequences of Rh Incompatibility

• Unexposed: 80% of healthy D negative individuals make anti-D with one unit transfused. Approximately 22% of hospitalized (non-oncology) patients (Yazer et al 2007).

• Exposed: HTRs with extravascular hemolysis

• Most severe HDFN

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Prevention of D Immunization:RhIgG

• Macro dose (300 g): protect against 30 mL of WB or 15 mL of packed RBCs

• Micro dose (50 g): protect against 5 mL of WB; sufficient for abortion, amniocentesis, and ectopic rupture at up to 12 weeks gestation

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Unusual Rh Phenotypes

• Weak D phenotype Du

• Rhnull phenotype

• Compound Rh antigens

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Weak D phenotype (Du)• Some D positive individuals require AHG

phase to demonstrate D antigen• Reasons:

– C opposite chromosome to D (C in trans position): eg, Dce/dCe

– Genetic weak D (weakened D expression)– Partial D (“Mosaic”)

• (most prone to making anti-D)

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Determination of D Status

• Donors: D neg donors must be confirmed by AHG test

• Recipients: D neg recipients do not need to be confirmed by AHG (though most are)

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Rh antigen typing reagents

• Saline anti-D (IgM, can’t be used for Du)

• High protein anti-D (requiring Rh control)

• Chemically modified anti-D (low protein)

• Monoclonal anti-D

• Blend of Monoclonals (anti-IgM and anti-IgG anti-D)

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Rhnull Phenotype

• Lacks all Rh antigens

• Rhnull syndrome demonstrates a mild compensated hemolytic anemia with stomatocytosis, spherocytosis and reticulocytosis

• Transfuse with Rhnull blood

• The clinical symptoms of Rhmod phenotype are less severe and rarely clinically remarkable.

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Compound Rh Antigens

• f = antigen present when c and e are on the same chromosome

• G: G is present on most D pos and all C pos RBCs. Anti-G originally appeared to be anti-D+C; further investigation showed that anti-G was directed toward D+G.

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The LW System

• LW antigens

• Anti- LW

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LW Antigens (normal pathway)

Precursor substance

DCE genes

normal Rh antigens

LWa LWb genes LW genes

LW pos LW neg

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Anti- LW:

– Reacts strongly with most D pos rbcs.– Reacts weakly with D neg rbcs.

– No reaction with Rhnull rbcs.

– Reacts equally well with cord cells regardless of D typing.

– Rarely clinically significant.

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Objectives

• Explain the derivation of the term Rh

• Differentiate Rh from LW

• Compare and convert the major genotypes among Fisher-Race, Wiener, and Rosenfield terminologies

• Define the basic biochemical structure of Rh

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Objectives (Continued)

• Describe and differentiate three mechanisms that result in weak D expression on rbcs

• Describe 3 characteristics of Rh antibodies

• Describe how to prevent Rh D immunization

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THANKS TO

• Rosemary Howard, CLS

• Dr Chris Gresens

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References

• Transfusion Medicine and Hemostasis, Hillyer et al, 2009, Elsevier Pub.

• Yazer et al, (2007), Detection of anti-D in D- recipients transfused with D + red cells, Transfusion 47 2197-2201

• Avent ND, Reid (2000) The Rh blood group system: a review Blood 95 375-387.

• Gunson et al (1970) The Anti-Rh0(D) Responses of Immunized Volunteers following Repeated Antigenic Stimuli, BJH

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