Test 2: Rh Blood Group System Flashcards by Sarah King | Brainscape

Q

Rh specific antigens reside on ________ versus the
carbohydrate antigens ABO and Hh.

A

proteins

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Q

True or false, Rh antigens are very immunogenic.

A

TRUE

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Q

What are the most important Rh antigens?

A

D / d
C / c
E / e

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Q

Rh antibodies are only produced when?

A

after exposure to foreign red blood cells. They are not naturally occurring.

ex: transfusion, pregnancy

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Q

Rh system is a complex blood group system composed of over ____ different RBC antigens.

A

50

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Q

What is considered a positive Rh test?

A

1-4+ (because it is IgG)

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Q

You must have a ___________ Rh control to have a valid test.

A

negative

(must have a negative control for anyone that is AB+, due to everything reacting)

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Q

What is Tippett’s Current theory?

A

two closely linked genes control the expression of all Rh antigens (codominant alleles)

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Q

_____ gene: determines the expression of the D protein (antigen)

A

RHD

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Q

_____ gene: determines the expression of the C, c, E, and e polypeptides (antigens)

A

RHCE

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Q

What is Fisher-Race theory?

A

Rh antigens are controlled by 3 closely linked loci (D/d, C/c, E/e)

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Q

What is Wiener theory?

A

Rh antigens are controlled by alleles at one gene locus

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Q

What is the Rh frequency in the Caucasian population?

A

D: 85%
Absence of D: 15% (sometimes documented as d)

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Q

What is the frequency of C, E, c, and e?

A

C: 70%
E: 30%
c: 80%
e: 98%

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Q

Only ___ % of population will make antibodies to Rh antibodies, especially if they have never been pregnant

A

30

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Q

Each gene expresses an antigen that is given the same letter as the italicized letter of the gene name (e.g., the ___ gene produces the C antigen)

A

C

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Q

The order of the genes is usually _____, but they are
sometimes ordered alphabetically as CDE

A

DCE

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Q

___________ – combination of genes inherited by one
parent

A

Haplotype

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Q

Fisher-Race:

Deletions are indicated with…

weakened expression with…

A

a dash “-“

parenthesis ()

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Q

According to Wiener, ___ alleles exist at the single Rh gene locus

A

8

R0, R1, R2, Rz, r, r′, r″, ry

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Q

Wiener:

Each gene encodes an _________ (made of factors) that correlates with Rh antigens

A

agglutinogen

Example 1: R1 —> Rh1(Rh0, rh′
, hr″ ) —> D, C, e (long hand notation, do not memorize)

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Q

converting Wiener terminology to Fisher-Race terminology:

R?

A

D

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Q

converting Wiener terminology to Fisher-Race terminology:

r?

A

no D

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Q

converting Wiener terminology to Fisher-Race terminology:

1 and ‘ ?

A

C

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Q

converting Wiener terminology to Fisher-Race terminology:

2 and “ ?

A

E

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Q

converting Wiener terminology to Fisher-Race terminology:

0?

A

ce

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Q

converting Wiener terminology to Fisher-Race terminology:

z or y?

A

CE

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Q

-Indicates phenotype information more suited for computerized data entry
-Antigens are designated by number

A

Rosenfield Terminology

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Q

What are the assigned numbers in Rosenfield terminology?

A

–Rh1:D
–Rh2:C
–Rh3:E
–Rh4:c
–Rh5:e

a negative before the number means absence

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Q

What is ISBT? and what is it used for?

A

-International Society of Blood Transfusion

the label system used on blood transfusion bags. Six-digits are assigned to each blood group specificity

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Q

What patients are the most common to develop antibodies due to the amount of transfusions?

A

sickle cell patients

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Q

Genotypes can be predicted based on what?

A

the race of the individual

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Q

What is the common genotype for Caucasians? (Wiener)

A

R1, r, R2, R0

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Q

What is the common genotype for blacks? (Wiener)

A

R0, r, R1, R2

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Q

What Wiener genotype is rarely encountered?

A

–r′, r″, Rz, and ry

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Q

What antibodies could an DCe individual make?

A

anti E and c

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Q

What gene is needed to express the Rh system?
What chromosome is it on?

A

RhAG (Rh-associated glycoprotein)

chromosome 6

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Q

What type of protein is RHAG?

A

transmembrane protein

Q

RhAG is termed __________ and must be present for successful expression of the Rh antigens.

A

coexpressor

Q

By itself RhAG… does not express what

A

does not express any Rh antigens

Q

What can result from mutations in the RHAG gene?

A

missing or significantly altered RhD and RhCE proteins, affecting antigen
expression.
-Consideration of the Rh(null) phenotype. (neg. for everything, not usual)

Q

Rh antigens are non-glycosylated proteins.
* Rh antigens reside on _____________ proteins and are an integral
part of the RBC membrane.

A

transmembrane

-Only small loops of Rh proteins are exposed on the surface of the
RBC.

Q

The number of D antigen sites vary depending on…

A

Rh phenotype

Q

What are the functions of Rh proteins?

A

-play a role in maintaining the structural integrity of the RBC
-may also act as molecular transporters

Q

Why are high-protein-based Rh reagents not used?

A

can produce false positives

-low-protein-based is typically used because it quick and accurate

Q

What is low-protein-based Rh typing reagents composed of?

A

saline-based, chemically modified, monoclonal, or blends of monoclonals.

Q

D antigen testing:

RBCs that test positive only by the indirect antiglobulin test (IAT) are called…

A

weak D antigens

(Newer monoclonal reagents have enhanced the detection of weak D antigens without the IAT)

Q

Weak D testing:

must run a control with this, even with every patient , with patients red cells and __________

A

???

Q

What are the steps for the weak D test?

A

-label one tube “anti-D” and one “control”
-one drop of cell suspension in each tube
-one drop of the anti-D into one tube and one drop of control into the other tube
-incubate 15-30 min at 37 decrees
-wash 3X with saline
-add 1-2 drops of antiglobulin reagent IgG
-mix and centrifuge
-gently resuspend and examine for agglutination. record
-Add IgG-coated control cells to negative results, spin, and read.

Q

What test is required for individuals that possess weaker expression of D antigen?

A

indirect antiglobulin test

Q

What are the different categories of phenotypes defined as weakened D?

A

C in trans to RHD
Weak D
Partial D
D(el)

Q

What population is weak D antigen more common in?

A

the black population

Q

Weak D antigen is due to the inheritance of a weaker from of the D antigen, often the ______ haplotype.

A

cDe

Q

Can weak D antigen patients receive D-positive blood?

A

yes

Donors are considered D positive

Q

The D antigen may appear
weak when the C antigen…

A

is inherited trans to D

(CIs C and D together is stronger)

Q

Weak D could be also be caused when Ce (r′) gene is paired with either _____ or ____.

A

DCe (R1) or cDe (R0)

Q

Can someone with weak D due to partial D antigens receive D positive blood?

A

No.

Q

What is it called when an individual is D positive but are missing parts of the D antigen?

A

partial D antigen

*When exposed to the “whole D antigen,”
individuals may produce anti-D toward the missing part

Q

Partial D antigen reacts strongly with ________ reagents.

A

monoclonal

Q

What should you suspect if a D-positive individual makes anti-D and it does not react with his or her own RBCs

A

Partial D antigen

Q

What does AABB require to be tested for on all donor cells if they are initially negative for the D antigen?

A

tested for weak D antigen

Q

What are Weak D (Du-positive) donors labeled as?

A

D-positive

Q

Why is testing for weak D antigen on recipient samples not required?

A

Patients are classified as D-negative and transfused with D-negative blood

Q

What is it called when two genes inherited on the same chromosome may form additional antigen products?

A

Compound antigens (cis-product antigens)

Q

What is an example of a Compound antigen (cis-product antigen)?

A

c and e antigens on same
haplotype cause “f” to be inherited

Q

Almost all genes that code for the C or D antigen will code for the ____ antigen

A

G

Q

______ D positive cells and ____ C positive cells are G positive

A

most, ALL

Q

Anti-G antibody will mimic anti-___ and
anti-___ antibodies

A

D, C

Q

Anti-G looks like a combination of
________ and ________ on an antibody identification panel

A

anti-D and anti-C

Q

If anti-G antibody is present, what blood do you give them?

A

give D-negative and C-negative blood

Q

Unusual Phenotypes:

-No reactions with
anti-E, anti-e, anti-C, or
anti-c
-Stronger D antigen
activity

A

D-deletion (-D- or D–)

-Transfuse only D-deleted cells

Q

Unusual Phenotypes:

What is it called when no Rh antigens are present?

A

Rh(null)

Q

What are the two possible genetic mechanisms for Rh(null)?

A

Regulator gene:
RHAG
Amorph (r=)

Q

Unusual Phenotypes:

Similar to Rh(null)
Most Rh antigen
expression is
missing; the RHAG
gene also controls
this phenotype

A

Rh(mod)

Q

How do you find out a patient has D-deletion?

A

Only know this once the patient starts making antibodies ???
-freeze red cells with glycerol (up to 10 years)

Q

Individuals who lack all Rh antigens on their RBCs are said to have what syndrome?

A

Rh(null) syndrome

Q

These individuals have a partial suppression of the RH gene expression caused by mutations in the RHAG gene

A

Rh(mod) phenotype

-* When the resultant RhAG protein is altered, normal Rh antigens are also altered often causing weakened expression of the normal Rh and LW antigens

Q

***What are LW antigens and antibodies similar to?
are they genetically related?

A

Rh antigens

not genetically related

Q

What will Anti-LW antibody react with?

A

D-positive (strong) and D-negative (weak) cells

Q

What are the LW alleles?

A

Lwa
, LWb
, and LW

Q

What is the most common LW phenotype?

A

LW(a+b-)

Q

What does anti-LW react with? What does it not react with?

A

-strongly with most D-positive RBCs
-weakly (sometimes not at all) with Rh-negative RBCs
-never with Rh(null) cells

Q

Anti-LW usually shows stronger positive reactions with D-____________
RBCs than with D-________ adult RBCs

A

positive, negative

Q

Anti-LW reacts equally well with _____ cells regardless of their D type.

A

cord

Q

Most Rh antibodies are what immunoglobulin type?

A

IgG1

Q

Rh antibody agglutination is best observed by….

A

IAT

Q

Rh antibodies:

___________ are useful for
identification.
Enzymes enhance Rh and destroy some of the other systems.

A

Potentiators

Q

Rh antibodies to C, c, E,
and e react stronger
to ___________
antigens

A

homozygous (dosage)

Q

Do Rh antibodies activate compliment?

A

no

Q

___-negative and ___-negative
blood is sometimes given
when anti-E antibody is
identified (weak anti-c
antibody is often seen with
anti-E antibody)

A

E, c

Q

What are symptoms of delayed transfusion reaction?

A

Unexplained fever, a mild bilirubin elevation, and a decrease in hemoglobin and haptoglobin

Q

With delayed transfusion reaction, the _____ is usually positive.

A

DAT

Antibody screen may demonstrate circulating antibody
Elution studies may be helpful

Q

Why is HDFN caused by Rh antibodies often severe?

A

-Rh antigens are well developed on fetal cells
-Rh antibodies are transplacental IgG

Q

What is given to D-negative woman during pregnancy and after delivery of a D-positive fetus?

A

Rh-immune globulin, a purified preparation of IgG anti-D
-It is only effective in preventing RhD HDFN