Rh_Blood_Group_System__6.ppt

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Rh Blood Group System
DR. MOHAMMED H
SAIEMALDAHR
BB
Faculty of Applied Medical Sciences
MED TECH DEP

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The term Rh refers not only to a specific red cell antigen
but also to complex blood group system that is currently
comprised on more than 50 different antigenic specificities.
History of the Rh System
Levine and Stetson described a hemolytic transfusion
reaction in an obstetric patient following delivery of
stillborn infant. The women required transfusion. Her
husband, who had the same ABO type, was selected as
her donor, after transfusion the recipient, demonstrated
the classic symptoms of acute hemo]ytic transfusion
reaction.

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Subsequently an antibody was isolated from the mother’s
serum that react both at 37°C and 20 °C with the father’s
red cells. It was postulated that the fetus and the father
possessed a common factor that the mother lacked.
While the mother carry the fetus, the mother was
exposed to this factor and subsequently built up an
antibody that reacted against the transfused red cells from
the father and resulted in hemolytic transfusion reaction.

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Landsteiner and Wiener reported on an antibody by
guinea pigs and rabbits when they were transfused with
rhesus monkey red cells.
This antibody which agglutinated 85% of human red cells
was named Rh.
The name Rh was retained for the human produced
antibody.
Anti-rhesus formed by the animals was renamed anti-
LW (Landsteiner and Wiener).

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Nomenclature of the Rh System
The terminology used to describe the Rh system is derived
from 4 sets of investigators.
Two of the terminologies are based on the postulated
genetic mechanisms of the Rh system.
3rd terminology describes only the presence or absence
of a given antigen.
4th is result of the effort of the International Society of
Blood Transfusion (ISBT) Working Party on
Terminology for Red cell Surface antigens.

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Fisher-Race (DCE terminology)
In the early 1940s, Fisher and Race were investigating
the antigens found on human red cell including the newly
defined Rh antigen.
Thy postulated that the antigens from the system were
produced by 3 closely linked sets of alleles. Each gene
was responsible for producing a product (Ag) on the
red cell surface.

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Each antigen (Ag) and corresponding gene were given
the same letter designation. Fisher and Race named the
antigens of the system D, d, C, c, E, and e.
To date NO (d ) antigen has been found, and it is
considered an amorph (silent allele) or the absence of D
antigen.
The phenotype (blood type observed during testing) of a
given red cells is define by the presence or absence of D,
C, c, E, and e.

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According to the Fisher-Race proposal, each
person inherits a set of Rh genes from each
parent (one D, or d, one C or c, and one E or e).
Rh genes are co-dominant, each inherited gene
express its corresponding antigen on the red cell.
The combination of maternal and paternal haplotypes
(Possessing half the normal # of chromosome found on the cell)
determines one’s genotype (the Rh gene inherited from
each parent) and dictates one’s phenotype (the
antigens expressed on the red cell that can be detected
serologically).

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An individual’s Rh phenotype is reported as DCE
because Fisher-Race postulated that the C/c locus is lies
between D/d and E/e loci.
It is essential to remember that d doesn’t represent an
antigen but simply the absence of the D antigen.
C, c, E, e represent actual Ags recognized by specific
antibodies.

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2- Wiener (The Rh-Hr terminology)
Wiener believed that, the gene responsible for defining
Rh actually produced an agglutinogen (a substance that
stimulates the production of an agglutinin, thereby
acting as an antigen) that contained a series of blood
factors.
The agglutinogen may be considered the phenotypic
expression of the haplotype.
Each factor is an antigen recognized by an antibody.
Antibody can recognize a single or multiple factors (Ag)

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Agglutinogen Red cell surface
Rh gene
Factor Rh0
Factor hr′
Factor hr″
RH0
hr ′
hr ″

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Wiener (The Rh-Hr terminology)
Fisher-Race nomenclature may be converted to Wiener
nomenclature and vice versa.
It is important to remember that an agglutinogen in the
Wiener nomenclature actually represent the presence of
a single haplotype composed of three different antigens.
R= D antigen r = absence of the D antigen (d).
C= indicated by 1 or a single ( ′ ) c= when there is no 1 or (′)
E=is indicated by 2 or ( ″ ) e= there is no 2 or ( ″ )

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Example
R1 = DCe R0 =Dce r′ =dCe
E=is indicated by 2 or ( ″ ) e= there is no 2 or ( ″)
Example
R2=DcE r″ =dcE
When both C and E are present the letter Z or Y is used.
RZ=DCE rY=dCE
R1r =DCe/dce r′r =dCe/dce

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Rh Blood Group System (Wiener Rh)
When referring to the Rh Ag (factor) in wiener nomenclature the
single prime ( ' ) refers to either C or c.
The double prime ( ″ ) refers to either E or e.
If the r precedes the h ( rh′ or rh″ ) we are referring to C or E Ags
respectively.
When the h precedes the r we are referring to either c
( hr′ ) or e ( hr″ ) Ags.
Rho = D
There is no designation for the absence of D Ag.

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Rosenfield (Alpha numeric terminology)
In 1960s Rosenfield proposed a system that assigns a
number to each antigen of Rh system in order of its
discovery or recognized relationship to the Rh system.
This system has no genetic basis but simply
demonstrates the presence or absence of the Ags on the
red cells.

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Rosenfield
 A minus ( - ) sign preceding a number designated the
absence of the Ag.
 If Ag has not been typed for, its number will not appear
in the sequence .
 D is assigned =Rh1 C=Rh2
E=Rh3 c =Rh4 e = Rh5
 For cell that typed D+ C+ E+ c- e-, the Rosenfield
designation is Rh:1,2,3,-4,-5.

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Rosenfield
If the sample was not tested for e, the designation would
be Rh:1,2,3,-4.
All Rh system antigens have been assigned a number.

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International Society of Blood Transfusion
Numeric terminology
They adapted a six digit number for each blood group.
The first three number represent the system and the
remaining three represent the antigenic specificity.
The number 004 was assigned to the Rh blood group
system, then each antigen assigned to the Rh system was
given a unique number to complete the six digit
computer number.

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Biochemistry of Rh Antigens.
Understanding the results of gene action
The final result of gene action in red cell group is the
production of the biochemical structure.
Rh system is a non-glycosylated protein this mean that,
No carbohydrates attached to the protein
Rh Ags are transmembrane polypeptide (integral part of
the red cell membrane)
D associated protein is linked to the membrane skeleton.

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The number of D Ag sites, measured on a variety of Rh phenotype
# of D antigen sites
Rh phenotype
990,0-146,00
R1r
120,00-200,00
R0r
140,00-166,00
R2r
145,00-193,00
R1R1
230,00-310,00
R1R2
158,00-333,00
R2R2
110,000-202,000
D--

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The greatest number of D Ag site are on cells of the rare
Rh phenotype D --.
D-- cell carry only D Ag and completely lack C c and E e.
R2R2 cells possess the largest number of D Ag sites.

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Detection of Rh Antibodies and Antigens
 Are IgG, react optimally at 37 oC or following the
addition of antiglobulin reagent
 Produced after exposure of the individual’s immune
system to foreign red cells, either through transfusion or
pregnancy.
 Rh Abs often persists in the circulation for years
 Rh Abs are considered clinically significant, therefore, Ag
negative blood must be provided to any patient with a
history of Rh Ab sensitization.

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Detection of Rh antibodies and Antigens
Rh Abs do not bind complement. For complement to be
fixed, two IgG molecules must attach in close a proximity
on the red cell surface.
Red cell destruction due to Rh Abs is primarily extra-
vascular. This type of hemolysis classically characterizes
a delayed hemolytic transfusion reaction.

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Rh Antigens
Rh antigens are highly immunogenic, the D antigen is
most potent
D  c  E  C  e
Highly Rarely
Immunogenic
 Exposure to less than 1 ml of Rh positive red cells can
stimulate Ab production in an Rh negative person.

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Determination of D Status
Is essential when test donor blood sample.
Blood considered Rh positive if either the D or Du test is
positive
If any donor blood sample that types Rho(D) negative by
either slide or rapid method must be tested further by
indirect anti-globulin test (IDAT).
If both test results are negative, the donor sample is
considered Rh negative.

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Determination of Du Status
There are instance when an accurate Rh type can not be
determined through routine testing
 1- If the new-born’s cell are coated with maternal IgG
anti-D in utero, very few D Ag sites will be available to
react with reagent anti-D.
 Elution of the sensitizing Ab (removing the Ab) and
identifying it as anti-D will verify that the infant’s red cell
are D positive
 2- Warm autoimmune hemolytic anemia, Abs are
directed against the patient’s own red cell and react as
though they are Rh specific.

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Variation of the Rho (D) Antigen
Weak D overview
When Rh-positive red cell samples are typed for the D
Ag. It is expected that they will react strongly with anti-D
reagent.
However, with certain red cells the testing must be
carried through the AHG phase to demonstrate the
presence of the D Ag.
Red cells carrying the weaker D Ag have been referred to
as having the Du type.

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Three different mechanisms have been described that
can explain the weakened expression of the D Ag.
Genetic weak D
Inheritance of D genes that code for a weakened
expression of the D Ag.
The D Ag expressed appear to be complete but few in
number. Inheritance of these gene can be tracked from
one generation to the next and seen most frequently in
black.

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C Trans (a position effect or gene interaction effect)
The Rh Ag on the red cell is normal, but the steric
arrangement of the C Ag in relationship to the D Ag
appears to interfere with expression of the D Ag.
This interference with D expression does not occur when
the C gene is inherited in the cis (The location of two or
more genes on the same chromosome of a homologius
pair) .Family study can be distinguish which type of
weakened D Ag is being demonstrated.

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D Mosaic
One or more parts of the D Ag are missing
Wiener and Unger postulated that the complete D (Rho)
Ag had four parts designated RhA, RhB, RhC, RhD , a
lowercase superscript of a, b, c, and d is used to indicate
when the corresponding portion (s) of the mosaic is
missing.
Example, Rhb means the B portion is absent.

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Rh Reagents
 Coomb’s cells (C.C)
Control cellular used when AHG test is negative.
To confirm that washing has been adequate and the anti-
globulin reagent is reactive
 Control Cell
A group O Rh positive donor’s sample is mixed with 1:10
dilution of reagent anti-D and allowed to incubate.
After sensitization of RBC, they are washed with saline
and suspended to a 50% RBC suspension
These sensitized RBCs then used to confirm the anti-IgG
activity of the AHG.

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Rh Reagents
 Coomb’s cells (C.C)
They can be used to ensure that AHG test with neg
results are not false neg because of inactivation of the
AHG reagent.
When AHG test is neg , they should be free AHG reagent
in the test tube
When the CC are added, the free AHG in the test should
cause agglutination of the sensitized RBCs.
 This positive reaction is a mixed field in nature because;
half of RBCs in the mixture lack IgG on their surface and
are free cells
 2nd half of RBCs have IgG (CC) and are agglutinated

Rh_Blood_Group_System__6.ppt

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