03 Rh Blood Group

Refers to the Rh Blood Group System and the presence or absence of the D antigen on RBCs.

The presence of the D antigen in the Rh Blood Group System.

The Rh Blood Group System is the second most important after the ABO Blood Group.

No, unlike the ABO system, there are no naturally occurring antibodies in the Rh Blood Group System.

Rh Blood Group System; D antigen.

Rh; second.

naturally occurring

D, C, E, c, and e antigens

The D antigen

When a corresponding antibody is detected and identified in the patient's serum (prior to transfusion).

The Rh system is complex with 49 antigens, including variants, rare antigens, and genes.

immunogenic

49

Mendelian inheritance patterns

Linked

Antigen (ag)

RHD and RHCE

RHD

RHCE

RHAG

As codominant alleles, where offspring inherit one haplotype from each parent.

RHD gene and RHCE gene.

Rh proteins are transmembrane proteins that span the RBC lipid bilayer and determine antigens in the Rh blood group system.

An amino acid substitution in the RHCE gene associated with the C/c antigens in the Rh protein.

An amino acid substitution in the RHCE gene associated with the E/e antigens in the Rh protein

Differences in antigens caused by mutations in Rh proteins, such as Ser103Pro and Pro226Ala.

A protein that spans the lipid bilayer of a cell membrane, such as Rh proteins in red blood cells.

Chromosome 1

RBC lipid bilayer

Ser103Pro

Pro226Ala

Antigenic variation

Antigens

The immunogenicity order from most to least is D > c > E > C > e.

The D antigen

The e antigen.

What does the immunogenicity order of Rh antigens indicate?

D

e

D, E, e.

Immunogenicity

Fisher-Race, Wiener, Rosenfield, and ISBT.

Antibodies can result from exposure to antigens (Ag) that are not present in the patient.

Developed antibodies recognize a single antigen.

Separate

Not present.

Single

It describes three closely linked genes (D, C/c, E/e) that produce the corresponding Rh antigens.

The D gene produces the D antigen

No, the "d" gene does not produce an antigen.

The C/c gene produces the C and c antigens.

The E/e gene produces the E and e antigens.

Three

D

Antigen

C and c

E and e

It describes multiple alleles at one complex locus that encode for an "agglutinogen," which consists of three factors (antigens/epitopes)

Antibodies can recognize single or multiple factors of the agglutinogen

Alleles

Agglutinogen

Single, multiple.

Antigens, epitopes

that a single gene, such as the Rho gene, encodes an agglutinogen with multiple factors (e.g., Rh₀, hr′, hr′′), which are expressed on the surface of red blood cells (RBCs).

The Rho gene encodes an agglutinogen that consists of factors Rh₀, hr′, and hr′′.

A protein complex made up of multiple factors (antigens) encoded by a single gene.

Antibodies recognize individual factors (e.g., Rh₀, hr′, hr′′) within the agglutinogen.

Gene

Rh₀, hr′, hr′′.

Factor

Surface

Factors, antigens.

A numerical Rh antigen system that makes no genetic assumptions and uses numbers to indicate the presence or absence of antigens.

•If a number is listed (e.g., Rh:1), the antigen is present.
•If a number is listed with a minus sign (e.g., Rh:-1), the antigen is absent.
•If not listed, the antigen was not determined.

Rh:1 indicates the presence of the D antigen, and Rh:-1 indicates its absence.

It adapts well to computer entry due to its straightforward numerical format.

Genetic

Presence

Absence

Determined

Computer

➢ Rh1: D
➢ Rh2: C
➢ Rh3: E
➢ Rh4: c
➢ Rh5: e

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

➢ First 3 digits indicate the blood group system, e.g., 004 = Rh;
001=ABO;

➢ Last 3 digits indicates the blood group ag specificity, e.g., 004001
= D ag of the Rh system; OR 001001 = A ag of the ABO system

➢ For recording of phenotypes, the system adopts the Rosenfield
approachs

Rh antigens play a functional role in maintaining membrane integrity and intracellular cation transport, making them different from ABO antigens.

The lack of some or missing Rh antigens is referred to as "deletion" for the absent antigens.

Rh null is the absence of all Rh system antigens, causing a membrane abnormality that shortens normal RBC survival.

Membrane integrity, intracellular cation.

Deletion

Rh null

Membrane

ABO

R^1r ( DCe/dce ).

1. Parental or paternity testing.
2. Predicting Hemolytic Disease of the Fetus/Newborn (HDFN).
3. Confirming Rh antibody (Ab) specificity.
4. Finding compatible blood for transfusion recipients with Rh antibodies.
5. Using published frequencies and subject information to determine possible genotypes and availability of antigen-negative blood.

find compatible blood for recipients with Rh antibodies.

It predicts the likelihood of Hemolytic Disease of the Fetus/Newborn by identifying the Rh status of the parents and fetus.

Parental, paternity

Hemolytic Disease of the Fetus/Newborn (HDFN)

Rh antibody (Ab)

Compatible

Genotypes, antigen.

Weak Rhₒ(D) refers to D antigen-positive cells that require further testing because they do not strongly agglutinate with Anti-D antisera at the immediate spin (IS) test phase.

37°C, AHG.

Hemagglutination

It is demonstrated by continuing testing through a 37°C incubation phase followed by the AHG (antihuman globulin) testing phase to confirm hemagglutination

Because weak D antigen expression may not produce strong hemagglutination during the IS test phase.

Immediate spin (IS).

IS (Immediate Spin).

1. Quantitative (genetic)
2. Position Effect
3. Partial / Mosaic D ag (missing parts)

is a genetically transmissible condition where the RHD gene codes for a weak expression of the D antigen. The D antigen is complete, but fewer antigen sites are present on the RBC surface.

•Normal D antigen sites: 15,000-33,000per RBC.

•Weak D antigen sites: 70-5,200 per RBC.

Yes, all epitopes of the D antigen are present; the difference lies in the reduced number of D antigen sites.

RHD

Epitopes

15,000; 33,000

70; 5,200

Genetically

It is an antiglobulin test that detects IgG antibodies bound to red cells to determine if D antigen expression is weak

A positive Rh control indicates that the cells have IgG antibodies already present, invalidating the test results.

The D antigen expression is weaker when the D and C genes are inherited on opposite chromosomes (trans position), compared to the cis position where both are on the same chromosome.

1. Anti-D positive, Rh control negative: Weak D positive.

2. Anti-D negative, Rh control negative: D negative.

3. Rh control positive: Unable to interpret.

Antiglobulin

Unable to interpret

Positional

Weak D positive

Cis

A condition where the D antigen is incomplete, with some epitopes missing from the red blood cell (RBC) surface.

The patient may develop an anti-D alloantibody against the missing epitope of the D antigen.

An antibody produced against antigens that are not part of the individual's own cells (e.g., missing portions of the D antigen).

D; epitopes

Anti-D alloantibody

Specificity

D-positive

C in the trans position to D creates a limiting effect on the expression of the D antigen, resulting in a weak D expression.

These represent partial locus deletions that can lead to:

•Unusually strong D antigen expression ("exalted D").

•Situations commonly observed in consanguineous relationships.

It refers to an unusually strong expression of the D antigen, typically associated with deletions of Cc and/or Ee.

Trans

Cc, Ee

Exalted D

Consanguineous

C/S-product antigens are formed when two genes are inherited on the same chromosome as a haplotype.

It represents the inheritance of c and e antigens as a haplotype (e.g., cde or cDe ).

It represents the inheritance of C and e antigens as a haplotype.

It represents the inheritance of c and E antigens on the same chromosome.

It represents the inheritance of C and E antigens on the same chromosome.

Chromosome

c, e

C, e.

c, E

C, E

❑ Not allelic to C & c

❑ C & Cw usually seen together, as in R1wR1 phenotype

❑ 2% of Caucasians; very rare in Afro-americans

❑ Anti-Cw may be naturally occurring & shows dosage

❑ When c & e are in cis position, e.g., dce or Dce haplotype

❑ Compound ag

❑ Anti-f antisera may be helpful in phenotyping

•Formed when C and e are in the cis position.

•A compound antigen.

•Antibodies against Ce are helpful in phenotyping.

•Always found with C-positive red blood cells and frequently found in D-positive cells.

•Anti-G appears to bind to D, C, and G antigens, resembling anti-C and anti-D but cannot be separated.

•Anti-G is commonly found in Rh-negative patients exposed to the C antigen only.

C, e, cis

Phenotyping

C, D.

D, C, G

Negative, C

Deleted Rh phenotypes lack many Rh antigens and may result from the rearrangement or replacement of large portions of the RHCE gene with the normal RHD gene.

Enhanced D antigen activity.

These phenotypes fail to produce some or all Rh CE antigens.

Deleted Rh phenotypes may result from rearrangement or replacement of large portions of the __________ gene with the __________ gene.

C/c , E/e

Rh CE

A syndrome characterized by a weakened expression of Rh antigens.

A syndrome where no Rh antigens are expressed at all.

Rh antigens

Rh antigens

Present, weakly

Rh

•An inherited characteristic causing a substantial decrease in all Rh antigen expression.

•Associated with a mutation in the RHAG gene.

•Leads to weakened Rh antigen expression and RBC abnormalities similar to Rh_{null} .

•Clinical symptoms are less severe and rarely remarkable.

•Expression varies between individuals.

RHAG

Rh antigen

Rh{null} .

Less severe, remarkable

Individual

An inherited condition where none of the Rh antigens are expressed.

•It has two genetic mechanisms:

1. Regulator Type:

•More common.

•Caused by a mutation in the RHAG gene, where no RHAG protein is expressed.

•Individuals can transmit normal RHD and RHCE genes.

2.Amorphic Type:
•Caused by mutations in each RHCE gene and a deletion in the RHD gene.

•The RHAG gene is normal.

Rh antigens

Regulator

RHAG

RHCE, RHD

RHAG

Fisher-Race expressed as "— / —" or Wiener Rh_{null} .

Features include:
•Mild hemolytic anemia and reticulocytosis (reticulo: immature RBC; cyto: cell; osis: abnormal condition).

•Increased level of Hemoglobin F (Hgb F).

•A potent anti-Rh29 antibody can be produced if normal Rh cells are transfused.

•Transfusion must use Rh_{null} RBCs.

"— / —"

Rh{null}

reticulocytosis

immature

Hemoglobin F (Hgb F)

Rh_{null}

•Add 1 drop of reagent antisera + 1 drop of patient cells

•Mix, spin, and read

•Add 1 drop of patient serum + 1 drop of red cell reagent

•Mix, spin, and read

•Same process as ABO Forward Typing

•Add 1 drop of reagent antisera + 1 drop of patient cells

•Mix, spin, and read

•No Reverse Typing performed

• Mix, spin, and read

The above test phase description is identified as Immediate Spin.

•Accurate Rh typing is the second of the primary foundations in pretransfusion testing and a safe transfusion.

•TJC & CAP PT: Rh typing test must be 100% correct/accurate at all times

1. Add 1 drop of reagent antisera + 1 drop of patient cells; mix, spin, and read.

2. Add 1 drop of patient serum + 1 drop of red cell reagent; mix, spin, and read.

Always add the clear substance(s) FIRST. This ensures the reagent or serum has been added to the test system.

Adding Cells Last

•Limited availability; high production cost.

•Lengthy incubation time.

•Cannot be used for weak-D typing.

•Potentiators increase likelihood of false positives.

•Manufacturer's control must be run.

•Can be used for weak-D typing.

•Relaxes antibody molecule by breaking disulfide bonds.

•Allows antibody to span distance between RBCs in low-protein medium.

•No manufactured control required (except AB+ uses saline control)

•Fewer false positives; usable for weak-D typing.

•Hybridized to increase antibody production and strength.

•Combines several clones to ensure reaction with all mosaic parts.

•Blends anti-IgM & IgG to enhance visualization.

This is a "negative" control and must remain negative throughout testing.

Step where patient red blood cells are added to tubes for testing.

Final step to determine the reaction of the samples after centrifugation.

Rh positive

Du Test

Incubate both tubes at 37°C for 15 minutes.

Spin, read, & grade reaction (rxn).

Spin, read, & grade reaction (rxn).

Rh positive

Continue testing

Removes unbound antibodies to ensure accurate results

Anti-human globulin step to detect incomplete antibodies.

Rh+

NOT

1.Normal D positive RBCs (depending on hospital policy).

2.D negative RBCs (especially for child-bearing-aged females).

Expectant mothers

NOT

A Du test is not required, and Rh-negative blood is given

Clinically significant

37°C

No, Rh Abs usually do not bind complement (C')

Extravascular

As little as 0.5 mL.

85%

Erythroblastosis Fetalis or Hydrops Fetalis

Rh-negative

Extravascular HTR

Intravascular

Antigen-negative RBCs