Rh Blood group system 149 – 172
Blood group terminology 173 – 211
Detection and identification of antibodies 232 255
RH Blood Group System
Introduction:

The Rh blood group is highly
complex, and the alloimmunization to
Rh blood group antigens can complicate
transfusion and pregnancy. It is
imperative
to
have
a
basic
understanding of Rh, as RhD typing is a
critical component of pretransfusion and
prenatal testing.

The term Rh refers to a specific
red blood cell (RBC) antigen (D) and to a
complex blood group system currently
composed of 61 different antigenic
specificities.

Rh is the second in importance
only to ABO blood group system in terms
of transfusion, as the Rh system antigens
are very immunogenic. Unlike ABO
antibodies that are routinely found in
individuals who lack the corresponding
antigen, Rh antibodies are produced
only after exposure to foreign red blood
cells

The terms Rh-positive and Rhnegative are used to describe the
presence or absence of the D antigen.
Rh-positive indicates that an individual’s
red blood cells possess one particular Rh
antigen, the D antigen. Rh-negative
indicates that the red blood cells lack the
D antigen
Terminology
There are four terminologies used to
describe the Rh system.
Two are based on postulated genetic
theories of Rh inheritance. The third
common terminology used describes
only the presence or absence of a given
antigen. The fourth was established by
the International Society of Blood
Transfusion (ISBT) Committee on
Terminology for Red Cell Surface
Antigens.




It is important for the student to
distinguish between phenotype
and genotype before exploring
the Rh nomenclature.
The phenotype of a given RBC is
defined by the serologic
detection of antigens using
specific antisera.
an Rh phenotype represents the
results for serologic testing of
RBC for D, C, c, E, and e antigens
A genotype is an individual’s
actual genetic makeup. An RH
genotype refers to the actual RH
genes inherited by the individual
from his parents. Serologic
results may not exactly
correspond with the genetic
expression.
Fisher-Race: DCE Terminology

In the mid-1940s Fisher and
Race defined the five common Rh
antigens and postulated that the
antigens of the system were produced
by three closely linked genes

Each gene was responsible for
producing one antigen on the RBC
surface.

Each antigen 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.

According to the Fisher-Race
theory, an individual inherits a set of RH
genes from each parent (i.e., one D or d,
one C or c, and one E or e). The
combination of genes inherited from
one parent is called a haplotype.

There are rare phenotypes that
involve deletions of specific genes, and
in those cases the deletion is
represented with a dash.
For example, an individual having only D
and no C/c and E/e, the Fisher-Race
haplotype is written as D–. Placing
parenthesis around (D), (C), and (e)
indicates weakened antigen expression
WIENER: RH-HR TERMINOLOGY
Wiener believed there was one gene
responsible for defining Rh that produced an
agglutinogen containing three Rh factors5
(Fig. 7–2)
Summary of the nomenclature for the
common agglutinogens (Table 7-2)


Modified Wiener terminology allows
one to convey Rh antigens inherited
on one chromosome or haplotype
and makes it easier to discuss a
genotype.
In the Wiener nomenclature, there
is no designation for the absence of
D antigen. By using these
designations, the laboratorian
should be able to recognize
immediately which antigens are
present on the RBCs.
Rosenfield
and
Coworkers:
Alphanumeric Terminology

In the early 1960s, Rosenfield
and associates proposed a system that
assigned a number to each antigen of
the Rh system in order of its discovery or
recognized relationship to the Rh system

This system has no genetic basis,
nor was it proposed based on a theory of
Rh inheritance, but it simply
demonstrates the presence or absence
of the antigen on the RBC

Each antigen is assigned a
number. A minus sign preceding a
number designates the absence of the
antigen. If an antigen has not been
phenotyped, its number will not appear
in the sequence.

An
advantage
of
this
nomenclature is that the RBC phenotype
is thus succinctly described.

For the five major antigens, D is
assigned Rh1, C is Rh2, E is Rh3, c is Rh4,
and e is Rh5. For RBCs that type
Dpositive, C-positive, E-positive, cnegative, and e-negative, the Rosenfield
designation is Rh: 1, 2, 3, –4, –5.

If the sample was not tested for
e, the designation would be Rh: 1, 2, 3, –
4.

The numeric system is well
suited to electronic data processing. Its
use expedites data entry and retrieval.
Its primary limiting factor is that there is
a similar nomenclature for numerous
other blood groups, such as Kell, Duffy,
Kidd, and more.

Therefore, when using the
Rosenfield nomenclature on the
computer, one must use both the alpha
(Rh:) and the numeric (1, 2, –3, etc.) to
denote a phenotype.

Table 7-3 lists common Rh
genotypes
comparing
the
nomenclatures of Wiener, Fisher-Race,
and Rosenfield

Genetics
Rh Genes

RHD and RHCE are two closely
linked genes located on chromosome 1
that control expression of Rh proteins.

RHD codes for the presence or
absence of the RhD protein, and the
second gene RHCE codes for either
RhCe, RhcE, Rhce, or RhCE proteins (Fig.
7–3). RHD and RHCE are codominant,
which means that all products inherited
typically produce antigens detectable on
RBCs. RHD and RHCE genes each have 10
exons and are 97% identical.

Each gene has a number of
alleles, most of which have been
identified through molecular testing
techniques

Numerous mutations have been
described in the RH genes. Greater than
250 alleles have been determined in the
RHD gene, and 50 alleles have been
found in the RHCE allele and the number
continues to grow
Rh-Associated Glycoprotein (RHAG)

Another gene important to Rh
antigen expression is RHAG, and it
resides on chromosome 6.

The product of this gene is Rhassociated glycoprotein (RHAG)

This polypeptide is very similar
in structure to the Rh proteins, with the
difference being that it is glycosylated
(carbohydrates attached).

Within the RBC membrane, it
forms complexes with the Rh proteins.
RhAG is termed a coexpressor and must
be present for successful expression of
the Rh antigens. However, by itself, this
glycoprotein does not express any Rh
antigens.

When mutations in the RHAG
gene occur, it can result in missing or

significantly altered RhD and
RhCE proteins, affecting antigen
expression.

In rare instances, individuals
express no Rh antigens on their RBCs.
Rh-Positive Phenotypes

RH genes are inherited as
codominant
alleles.
Rh-positive
individuals inherit one or two RHD
genes, which result in expression of RhD
antigen and are typed Rh-positive.

Figure 7–4 is an example of a
normal Rh inheritance pattern

Numerous mutations in the RHD
gene have been discovered that cause
weakened expression of the RhD antigen
detected in routine testing.
Rh-Negative Phenotypes

Rh-negative phenotypes are so
called because the RBCs lack detectable
D antigen. Rh-negative individuals can
arise from several pathways.

The most common Rh-negative
phenotype results from the complete
deletion of the RHD gene—that is, the
individuals possess no RHD gene but
have inherited two RHCE genes.
Rh Deficiency Syndrome: Rhnull and
Rhmod

Rare individuals have Rh
deficiency or Rhnull syndrome and fail to
express any Rh antigens on the RBC
surface.

Rhnull syndrome is inherited in
one of two ways—amorphic and
regulator. Other rare individuals exhibit
a severely reduced expression of all Rh
antigens, a phenotype called Rhmod.

Individuals who lack all Rh
antigens on their RBCs are said to have
Rhnull syndrome, which can be
produced by two different genetic
mechanisms.

In the regulator-type Rhnull
syndrome, a mutation occurs in the
RHAG gene. This results in no RhAG
protein expression and subsequently no
RhD or RhCE protein expression on the
RBCs, even though these individuals
usually have a normal complement of
RHD and RHCE genes.

These individuals can pass
normal RHD and RHCE genes to their
children.

In the second type of Rhnull
syndrome (the amorphic type), there is a
mutation in each of the RHCE genes
inherited from each parent as well as the
deletion of the RHD gene found in most
D-negative individuals. The RHAG gene is
normal

It should be noted that Rhnull
individuals of either regulator or
amorphic type are negative for the highprevalence antigen LW and for FY5, an
antigen in the Duffy blood group system.
S, s, and U antigens found on
glycophorin B may also be depressed.

Individuals
with
Rhnull
syndrome
demonstrate
a
mild
compensated
hemolytic
anemia,
reticulocytosis, stomatocytosis, a slightto-moderate decrease in hemoglobin
and hematocrit levels, an increase in
hemoglobin F, a decrease in serum
haptoglobin, and possibly an elevated
bilirubin level.

The severity of the syndrome is
highly variable from individual to
individual, even within one family.
Rhnull individuals, if exposed to normal
Rh cells through transfusion or
pregnancy, can produce a potent
antibody, anti-Rh29, which reacts with
all cells except for those that are Rhnull.

Individuals of the Rhmod
phenotype have a partial suppression of
RH gene expression caused by mutations
in the RHAG gene.

When the resultant RhAG
protein is altered, normal Rh antigens
are also altered, often causing weakened
expression of the normal Rh and LW
antigens.
Unusual Phenotypes and Rare Alleles

Several of the less frequently
encountered Rh antigens are described
briefly in the following paragraphs.

While the antibodies directed
against these antigens are less
commonly encountered, they can be
clinically significant and, in some cases,
cause transfusion reactions, HDFN, or
both.
Cw

Cw was originally considered an
allele at the C/c locus. Later studies
showed that it can be expressed in
combination with both C and c and in the
absence of either allele.

It is now known that the
relationship between C/c and Cw is only
phenotypic and that Cw is antithetical to
the high-prevalence antigen MAR.

Cw results from a single amino
acid change most often found on the
RhCe protein.

Anti-Cw has been identified in
individuals without known exposure to
foreign RBCs and after transfusion or
pregnancy.

Anti-Cw may show dosage (i.e.,
reacting more strongly with cells from
individuals who are homozygous for
Cw). Commercial anti-Cw reagent is not
readily available, but because of the low
prevalence of the Cw antigen RBCs
compatible at the crossmatch in the
antiglobulin phase may be selected for
transfusion.

Anti-Cw may not always be
detected on routine antibody screens
because the low frequency of the
antigen means that some screening cell
sets may not have a Cw-positive cell
included.
f(ce)

The f antigen is expressed on the
RBC when both c and e are present on
the same haplotype.

The antigen f was included in a
series of these compound antigens,
which were previously referred to as cis
products to indicate that the antigens
were on the same haplotype.

Anti-f is generally a weakly
reactive antibody often found with other
antibodies. It has been reported to cause
HDFN and transfusion reactions

In case of transfusion, f-negative
blood should be provided. Anti-f is not
available as a reagent.

It is adequate to provide either
c-negative or e-negative blood since all
c-negative or e-negative individuals are
f-negative.
rhi (Ce)

Similar to f, rhi was considered a
compound antigen present when C and
e are on the RhCe protein.

Therefore anti-rhi would only
react with cells from an individual with a
haplotype of DCe or Ce (Table 7-10)

Antigens cE (RH27) and CE
(Rh22) also exist, but antibodies
produced to these antigens are not
commonly seen (Table 7–10)

For transfusion purposes, it is
not necessary to discriminate anti-D and
anti-C from anti-G, as the patient would
receive D-negative and C-negative blood
regardless if the antibody is anti-D, antiC, or anti-G.
Rh17 (Hr0)

Rh17, also known as Hr0, is an
antigen present on all RBCs with the
“common” Rh phenotypes (e.g., R1R1,
R2R2, rr).

In essence, this antibody is
directed to the entire protein resulting
from the RHCE genes.

When RBCs phenotype as D–
(i.e. D+C-E-c-e-) the most potent
antibody they make is often one
directed against Rh17 (Hr0), which
would react with all cells except D–.
Rh23, Rh30, Rh40, and Rh52
G

G is an antigen present on most
D-positive and all C-positive RBCs.

The antigen results from the
amino acid serine at position 103 on the
RhD, RhCe, and RhCE proteins.

G was originally described in an
rr person who received D+C–E–c+e+
RBCs.

Subsequently, the recipient
produced an antibody that appeared to
be antiD plus anti-C, which should be
impossible because the C antigen was
not on the transfused RBCs.

Anti-G versus anti-D and anti-C is
important when evaluating obstetric
patients. If the patient has produced
anti-G and not anti-D, then she is
considered a candidate for Rhimmune
globulin.

Rh23, Rh30, and Rh40 are all
low-prevalence antigens associated with
a specific category of partial D.

These low prevalence antigens
result from the formation of the hybrid
proteins seen in individuals with partialD phenotypes.

Rh23 (also known as Wiel and
Dw) is an antigenic marker for category
Va partial-D.

Rh30 (also known as Goa or
Dcor) is a marker for partial DIVa.Rh40
(also known as Tar or Targett) is a marker
for partial DVII. Rh52 or BARC is
associated with some partial-DVI types.
Rh33 (Har)

The low-prevalence antigen
Rh33 is most often found in whites and
is associated with the rare variant
haplotype called R0Har. R0Har gene
codes for normal amounts of c, reduced
amounts of e, reduced f, reduced Hr0,
and reduced amounts of D antigen
written as (D)c(e).

The D reactions are frequently
so weak that the cells are often typed as
Rhnegative. As previously discussed,
R0Har or DHAR results from a hybrid
gene RHCE-RHD-RHCE in which only a
small portion of RHD is inserted into the
RHCE gene.
Rh32

Rh:32 is a low-prevalence
antigen associated with a variant of the
R1[D(C)(e)] haplotype called R = N
(pronounced “R double bar N”).

The C antigen and e antigen are
expressed weakly. The D antigen
expression is exaggerated or exalted.
This gene has been found primarily in
African Americans.
Rh43 (Crawford)

Rh43, also known as the
Crawford antigen, is a low-prevalence
antigen on a variant Rhce protein.

The Crawford (ceCF) antigen is
of very low prevalence found in
individuals of African descent
e Variants

Like the variant D antigen seen
in individuals possessing a hybrid or
mutated RHD gene, some individuals of
African or mixed ethnic backgrounds
possess e antigen that exhibits similar
qualities as those described for partial-D
phenotypes and that is, an individual
may have a phenotype of e-positive but
produce antibodies behaving as anti-e.

These variant types result from
multiple mutations in the RHCE gene.
Individuals who possess two altered
RHCE genes may have a phenotype of epositive but produce antibodies
behaving as anti-e.

The Rh antigens hrB (Rh31) and
hrS (Rh19 )are rarely encountered in
routine blood banking.

They are normally present in
individuals who possess normal RhCe or
Rhce protein but are lacking in
individuals with normal RhcE or RhCE
proteins (i.e., e-negative).

Several antigens, most notably
hrB and hrS, are lacking on the Rhce
proteins because of a variant RHCE gene.
If individuals with these variant genes
who are hrB-negative or hrS-negative
are immunized, they may produce antihrB or anti-hrS.

In
a
routine
antibody
identification, these antibodies are
generally nonreactive with e-negative
red blood cells (and therefore are also
hrBnegative
and
hrS-negative),
appearing to have anti-e-like specificity.