Test 2: Rh Blood Group System Flashcards
Rh specific antigens reside on ________ versus the
carbohydrate antigens ABO and Hh.
proteins
True or false, Rh antigens are very immunogenic.
TRUE
What are the most important Rh antigens?
D / d
C / c
E / e
Rh antibodies are only produced when?
after exposure to foreign red blood cells. They are not naturally occurring.
ex: transfusion, pregnancy
Rh system is a complex blood group system composed of over ____ different RBC antigens.
50
What is considered a positive Rh test?
1-4+ (because it is IgG)
You must have a ___________ Rh control to have a valid test.
negative
(must have a negative control for anyone that is AB+, due to everything reacting)
What is Tippett’s Current theory?
two closely linked genes control the expression of all Rh antigens (codominant alleles)
_____ gene: determines the expression of the D protein (antigen)
RHD
_____ gene: determines the expression of the C, c, E, and e polypeptides (antigens)
RHCE
What is Fisher-Race theory?
- Rh antigens are controlled by 3 closely linked loci (D/d, C/c, E/e)
What is Wiener theory?
Rh antigens are controlled by alleles at one gene locus
What is the Rh frequency in the Caucasian population?
- D: 85%
- Absence of D: 15% (sometimes documented as d)
What is the frequency of C, E, c, and e?
- C: 70%
- E: 30%
- c: 80%
- e: 98%
Only ___ % of population will make antibodies to Rh antibodies, especially if they have never been pregnant
30
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)
C
The order of the genes is usually _____, but they are
sometimes ordered alphabetically as CDE
DCE
___________ – combination of genes inherited by one
parent
Haplotype
Fisher-Race:
Deletions are indicated with…
weakened expression with…
a dash “-“
parenthesis ()
According to Wiener, ___ alleles exist at the single Rh gene locus
8
R0, R1, R2, Rz, r, r′, r″, ry
Wiener:
Each gene encodes an _________ (made of factors) that correlates with Rh antigens
agglutinogen
Example 1: R1 —> Rh1(Rh0, rh′
, hr″ ) —> D, C, e (long hand notation, do not memorize)
converting Wiener terminology to Fisher-Race terminology:
R?
D
converting Wiener terminology to Fisher-Race terminology:
r?
no D
converting Wiener terminology to Fisher-Race terminology:
1 and ‘ ?
C
converting Wiener terminology to Fisher-Race terminology:
2 and “ ?
E
converting Wiener terminology to Fisher-Race terminology:
0?
ce
converting Wiener terminology to Fisher-Race terminology:
z or y?
CE
-Indicates phenotype information more suited for computerized data entry
-Antigens are designated by number
Rosenfield Terminology
What are the assigned numbers in Rosenfield terminology?
–Rh1:D
–Rh2:C
–Rh3:E
–Rh4:c
–Rh5:e
a negative before the number means absence
What is ISBT? and what is it used for?
-International Society of Blood Transfusion
the label system used on blood transfusion bags. Six-digits are assigned to each blood group specificity
What patients are the most common to develop antibodies due to the amount of transfusions?
sickle cell patients
Genotypes can be predicted based on what?
the race of the individual
What is the common genotype for Caucasians? (Wiener)
R1, r, R2, R0
What is the common genotype for blacks? (Wiener)
R0, r, R1, R2
What Wiener genotype is rarely encountered?
–r′, r″, Rz, and ry
What antibodies could an DCe individual make?
anti E and c
What gene is needed to express the Rh system?
What chromosome is it on?
RhAG (Rh-associated glycoprotein)
chromosome 6
What type of protein is RHAG?
transmembrane protein
RhAG is termed __________ and must be present for successful expression of the Rh antigens.
coexpressor
By itself RhAG… does not express what
does not express any Rh antigens
What can result from mutations in the RHAG gene?
- missing or significantly altered RhD and RhCE proteins, affecting antigen
expression.
-Consideration of the Rh(null) phenotype. (neg. for everything, not usual)
Rh antigens are non-glycosylated proteins.
* Rh antigens reside on _____________ proteins and are an integral
part of the RBC membrane.
transmembrane
-Only small loops of Rh proteins are exposed on the surface of the
RBC.
The number of D antigen sites vary depending on…
Rh phenotype
What are the functions of Rh proteins?
-play a role in maintaining the structural integrity of the RBC
-may also act as molecular transporters
Why are high-protein-based Rh reagents not used?
can produce false positives
-low-protein-based is typically used because it quick and accurate
What is low-protein-based Rh typing reagents composed of?
saline-based, chemically modified, monoclonal, or blends of monoclonals.
D antigen testing:
RBCs that test positive only by the indirect antiglobulin test (IAT) are called…
weak D antigens
(Newer monoclonal reagents have enhanced the detection of weak D antigens without the IAT)
Weak D testing:
must run a control with this, even with every patient , with patients red cells and __________
???
What are the steps for the weak D test?
-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.
What test is required for individuals that possess weaker expression of D antigen?
indirect antiglobulin test
What are the different categories of phenotypes defined as weakened D?
- C in trans to RHD
- Weak D
- Partial D
- D(el)
What population is weak D antigen more common in?
the black population
Weak D antigen is due to the inheritance of a weaker from of the D antigen, often the ______ haplotype.
cDe
Can weak D antigen patients receive D-positive blood?
yes
Donors are considered D positive
The D antigen may appear
weak when the C antigen…
is inherited trans to D
(CIs C and D together is stronger)
Weak D could be also be caused when Ce (r′) gene is paired with either _____ or ____.
DCe (R1) or cDe (R0)
Can someone with weak D due to partial D antigens receive D positive blood?
No.
What is it called when an individual is D positive but are missing parts of the D antigen?
partial D antigen
*When exposed to the “whole D antigen,”
individuals may produce anti-D toward the missing part
Partial D antigen reacts strongly with ________ reagents.
monoclonal
What should you suspect if a D-positive individual makes anti-D and it does not react with his or her own RBCs
Partial D antigen
What does AABB require to be tested for on all donor cells if they are initially negative for the D antigen?
tested for weak D antigen
What are Weak D (Du-positive) donors labeled as?
D-positive
Why is testing for weak D antigen on recipient samples not required?
Patients are classified as D-negative and transfused with D-negative blood
What is it called when two genes inherited on the same chromosome may form additional antigen products?
Compound antigens (cis-product antigens)
What is an example of a Compound antigen (cis-product antigen)?
c and e antigens on same
haplotype cause “f” to be inherited
Almost all genes that code for the C or D antigen will code for the ____ antigen
G
______ D positive cells and ____ C positive cells are G positive
most, ALL
Anti-G antibody will mimic anti-___ and
anti-___ antibodies
D, C
Anti-G looks like a combination of
________ and ________ on an antibody identification panel
anti-D and anti-C
If anti-G antibody is present, what blood do you give them?
give D-negative and C-negative blood
Unusual Phenotypes:
-No reactions with
anti-E, anti-e, anti-C, or
anti-c
-Stronger D antigen
activity
D-deletion (-D- or D–)
-Transfuse only D-deleted cells
Unusual Phenotypes:
What is it called when no Rh antigens are present?
Rh(null)
What are the two possible genetic mechanisms for Rh(null)?
- Regulator gene:
RHAG - Amorph (r=)
Unusual Phenotypes:
- Similar to Rh(null)
- Most Rh antigen
expression is
missing; the RHAG
gene also controls
this phenotype
Rh(mod)
How do you find out a patient has D-deletion?
Only know this once the patient starts making antibodies ???
-freeze red cells with glycerol (up to 10 years)
Individuals who lack all Rh antigens on their RBCs are said to have what syndrome?
Rh(null) syndrome
These individuals have a partial suppression of the RH gene expression caused by mutations in the RHAG gene
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
***What are LW antigens and antibodies similar to?
are they genetically related?
Rh antigens
not genetically related
What will Anti-LW antibody react with?
D-positive (strong) and D-negative (weak) cells
What are the LW alleles?
Lwa
, LWb
, and LW
What is the most common LW phenotype?
LW(a+b-)
What does anti-LW react with? What does it not react with?
-strongly with most D-positive RBCs
-weakly (sometimes not at all) with Rh-negative RBCs
-never with Rh(null) cells
Anti-LW usually shows stronger positive reactions with D-____________
RBCs than with D-________ adult RBCs
positive, negative
Anti-LW reacts equally well with _____ cells regardless of their D type.
cord
Most Rh antibodies are what immunoglobulin type?
IgG1
Rh antibody agglutination is best observed by….
IAT
Rh antibodies:
___________ are useful for
identification.
Enzymes enhance Rh and destroy some of the other systems.
Potentiators
Rh antibodies to C, c, E,
and e react stronger
to ___________
antigens
homozygous (dosage)
Do Rh antibodies activate compliment?
no
___-negative and ___-negative
blood is sometimes given
when anti-E antibody is
identified (weak anti-c
antibody is often seen with
anti-E antibody)
E, c
What are symptoms of delayed transfusion reaction?
Unexplained fever, a mild bilirubin elevation, and a decrease in hemoglobin and haptoglobin
With delayed transfusion reaction, the _____ is usually positive.
DAT
- Antibody screen may demonstrate circulating antibody
- Elution studies may be helpful
Why is HDFN caused by Rh antibodies often severe?
-Rh antigens are well developed on fetal cells
-Rh antibodies are transplacental IgG
What is given to D-negative woman during pregnancy and after delivery of a D-positive fetus?
Rh-immune globulin, a purified preparation of IgG anti-D
-It is only effective in preventing RhD HDFN
