Rh Blood Group System Flashcards
What are the 5 antigens in the Rh blood group system?
D, C, c, E, e
What is the most common Rh phenotype?
dce
Which chromosome are the Rh genes located?
Chromosome 1
Which gene controls the expression of Rh antigens?
RHAg
Which Rh gene do individuals either possess or lack?
RhD
Which Rh gene expresses all alleles inherited - where all alleles are co-dominant?
RHCE
What type of antibody (immune or natural) are anti-D, C, c, E, e?
Immune. Exposure must occur in order for them to form.
What is an amorph?
Only a dominant form of the allele exists. An individual either has the gene or lacks the gene.
Which Rh gene is an amorph?
RhD
Which Rh antigen is the most important to test for, especially in child-bearing age women?
D
What percentage of D-negative individuals who receive a single unit of D-positive blood will develop anti-D?
80%
Which nomenclature suggested that Rh antigens were determined by 3 genes?
Fischer-Race
Explain how Fisher-Race nomenclature suggested the inheritance of Rh genes.
The 3 Rh genes (D, C and c, E and e) occupy loci in close proximity to one another, so close that they never separate and are passed on to each generation.
True or False: Crossing-over occurs in the Rh system.
False
Determine the phenotype and possible genotypes of an individual that had the following antisera results:
anti-D 4+ anti-C 4+ anti-c 0 anti-E 0 anti-e 4+
Phenotype: DCe
Possible Genotypes: DCe/DCe or DCe/dCe
Determine the phenotype and genotype of an individual that had the following antisera results:
anti-D 4+ anti-C 0 anti-c 4+ anti-E 0 anti-e 4+
Phenotype: Dce
Possible genotypes: Dce/Dce or Dce/dce
Determine the phenotype and genotype of an individual that had the following antisera results:
anti-D 4+ anti-C 4+ anti-c 4+ anti-E 0 anti-e 4+
Phenotype: DCce
Possible Genotypes: DCe/Dce or DCe/dce or Dce/dCe
Translate the Fischer-Race nomenclature to the Wiener nomenclature for the following: Dce DCe DcE DCE
Dce - R0
DCe - R1
DcE - R2
DCE - Rz
Translate the Fischer-Race nomenclature to the Wiener nomenclature for the following: dce dCe dcE dCE
dce - r
dCe - r’
dcE - r’’
dCE - ry
Which nomenclature postulated that two genes, one on each chromosome pair, controls the entire expression of the Rh system?
Wiener
Using both the Fisher-Race and Wiener nomenclature, which genotypes are the most common for D-positive and D-negative individuals?
D-positive: R2/r - DcE/dce
D-negative: r/r - dce/dce
Rosenfeld nomenclature is based only upon…
serologic (agglutination) reactions
Describe how the Rosenfeld system works.
The antigens are labeled: D=1, C=2, E=3, c=4, e=5
When tested, if agglutination occurs, the number is listed as is. If no reaction occurs, a negative number is indicated.
If not tested, simply omit the number.
Use the Rosenfeld nomenclature to describe the following results:
anti-D 4+ anti-C 0 anti-E 3+ anti-c 4+ anti-e 0
1, -2, 3, 4, -5
How does the International Society of Blood Transfusion label blood group systems?
Via a 6 digit code
First 3 numbers indicate the blood group system (004 = Rh)
Second 3 numbers indicate the specific antigen (004001 = D)
Reactions with antisera only determine
phenotype
What phenotype testing is used for parentage testing, predicting HDFN, locating compatible blood for recipients, and confirming Rh antibody specificity?
Rh phenotyping
If a patient tests D-negative with anti-D, what is the next step that should be taken?
Perform a weak D test (Du)
Describe the process for weak D (Du) testing.
Incubate cells with anti-D at 37 degrees C.
Wash cells 3X with saline.
Add AHG to bind anti-D bound to RBCs.
Agglutination = Weak D positive
List 3 mechanisms for Weak D
Genetic
Mosaic
Position Effect
Which mechanisms for weak D are quantitative?
Genetic
Position Effect
Which Weak D mechanism is qualitative and can be capable of producing anti-D?
Mosaic
If an individual inherits a D gene that codes for lowered densities of D antigen on RBC membranes, how will they type?
Weak D
What is the position effect?
The position of the C gene in correlation to the D gene
What is the C-trans position effect?
The C gene is on a different haplotype from the D gene
Ex: DcE/dCE
What is the C-cis position effect?
The C gene is located on the same haplotype as the D gene
Ex: DCE/dcE
Which position effect results in a weak-D expression due to steric hindrance?
C-trans
The absence of a portion(s) of the D antigen is termed as
Partial D (Mosaic D)
Can an individual with Partial D develop anti-D?
Yes, to the portion of the antigen that they lack.
Do normal D and Weak D have the same level of immunogenicity?
No. Weak D is substantially less immunogenic than Normal D.
Is weak D capable of producing a transfusion reaction?
Yes, in patients with anti-D
Failure to express Rh antigens on RBC surface is considered
Rh null
What are the two mechanisms can cause Rh null?
Regulator-type or amorph-type
A mutation in the RHAG gene results is what type of genetic mutation?
Regulator-type
Mutations in each of the RHCE genes inherited from each parent along with the deletion of the RHD gene is considered what type of genetic mutation?
Amorph-type
Partial suppression of Rh antigen expression is considered
Rh mod
A mutation in the RhAG gene will cause
Rh mod
In Rh null, which other antigens will test negative and which will be depressed?
negative: LW and FY5
depressed: S, s, U
Which phenotype exhibits similar clinical symptoms as Rh null, but is less severe and is rarely clinically significant?
Rh mod
Anti-LW will react more strongly in D-positive or negative individuals?
D-positive
An unusual phenotype that occurs from a single amino acid change most often found on RhCe protein
Cw
True or False: Cw can be expressed in the presence of C and c or in the absence of C and/or c.
True
The F antigen will be expressed when?
When d and c are expressed on the same haplotype
d and c are expressed on the same haplotype and the F antigen can be expressed. This occurrence can be termed…
compound antigen
rh1 phenotype occurs when
C and e are expressed on the same RhCe protein
anti-rh1 only reacts with which genotype?
DCe/dce
If an RBC expresses D and/or C, it will also express which unusual antigen?
G antigen
Anti-G can mimic
anti-C and anti-D
What occurrence can result in excess expression of the D antigen due to a lack of Cc or Ee reactivity?
deletion
D-deletion RBCs can only be transfused with
D-deletion RBCs
Rh antibodies are typically which class of Ig?
IgG
Order of Rh antigen immunogenicity
D > c > E > C > e
Rh antibodies are unable to bind
complement (due to the location on the RBC)
Most frequently encountered Rh antibody
Anti-E (followed by anti-c)
Anti-C rarely occurs by itself, but may occur in the presence of
anti-D
If anti-D is present, which other Rh antibody can be present?
anti-G (anti-D and anti-C)
R1/R1 individuals who generate anti-E will frequently also make
anti-c
Patients with anti-E should automatically be phenotyped for
c antigen
Antibodies that tend to occur together are termed
concomitant
What are the 4 types of anti-D reagent?
High protein, IgM anti-D, Chemically modified, monoclonal anti-D
Autoagglutinins, abnormal serum proteins, antibodies to additives, and using unwashed RBCs can result in false positives with which anti-D reagent?
High protein
IgG anti-D potentiated with high protein and other macromolecules
High protein anti-D
Prepared from predominantly IgM antibodies and is only used when false positives occur with high protein anti-D
IgM anti-D (low protein/saline)
Which anti-D reagent requires a diluent control?
high protein
The other reagents only require a control when AB positive
Which anti-D reagents cannot be used in the weak-D test?
IgM anti-D
IgG converted to saline agglutinin by weakening disulfide bonds at the hinge region, which produces stronger reactivity than IgM antibodies
Chemically modified anti-D
Prepared from a blend of monoclonal IgM and polyclonal IgG and is used most frequently
Monoclonal anti-D
IgM and IgG react when?
IgM - initial spin
IgG - AHG
The control diluent used for protein reagents has protein concentration equaling
human serum
What is a way you can tell if a false positive has occurred?
The forward type will appear AB positive and the control is positive
How often is QC performed on anti-D?
daily
Sources for false positives
spontaneous agglutination contaminated reagents use of wrong serum/reagents autoagglutinins or abnormal serum proteins coating the RBCs Not following manufacturer instructions
An IAT only needs to be performed only if
it is indicated in the manufacturer insert
