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CARBOHYDRATE BLOOD GROUP ANTIGENS AND COLLECTIONS 35
C. B gene – encodes a glycosyltransferase that adds an N-acetylgalactosamine to
the pre-existing oligosaccharide precursor.
D. H gene – encodes a fucosyltransferase that adds a galactose molecule to the
pre-existing oligosaccharide precursor.
E. Se gene – encodes a glucosyltransferase that adds a glucose molecule to the
pre-existing oligosaccharide precursor.
B. The A and B antigens are very similar, differing only by the addition of an N-ace-
tyl group to the terminal galactose. The A gene encodes for a transferase that adds to
N-acetylgalactosamine as the terminal sugar conferring A specificity.
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Question 2: Which of the following statements about the ABO system is true?
A. The A and B genes have very little nucleotide sequence homology.
B. Anti-A and anti-B are naturally occurring, and are thought to be produced in
response to maternal poteins early in life.
C. In the absence of red cell exposure, levels of anti-A and anti-B continue to rise
throughout childhood and adulthood, reaching a peak in the sixth or seventh
decades.
D. Hemolytic disease of the fetus and newborn occurs more commonly in group
O mothers of Group A or B fetuses.
E. A
1
individuals have an A antigen that is similar to that of A
2
individuals.
D. Group O patients tend to have more IgG in their plasma, and IgG is the only
immunoglobulin that readily crosses the placenta.
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Question 3: Which statement is true about ABO typing of patients?
A. A
2
patients have a transferase (enzyme) that is less efficient at adding a sugar
residue than A
1
patients.
B. The vast majority of group A patients belong to subgroup A
2
.
C. About 90% of subgroup A
2
patients produce anti-A
1
.
D. In the event that there is a discrepancy between the ABO forward and reverse
typing, and emergency blood must be issued, group O-positive blood should
be given.
E. H-deficient (Bombay) phenotype is the universal recipient.
A. There are fewer A
2
antigens and more H antigen on A
2
red cells, reflecting less
efficient conversion of H to A by the enzyme responsible for the terminal sugar addi-
tion.
36 PRACTICAL SELF-ASSESSMENT FOR TRANSFUSION MEDICINE PROFESSIONALS
________________________________ _______________________________
夝
Question 4: Choose the most likely cause for the ABO forward and reverse typing
discrepancy based on the following information: forward typing indicates group A;
reverse typing indicates the presence of anti-A and anti-B.
A. Acquired B phenotype.
B. Individual is subgroup A
2
.
C. Individual is a newborn or elderly patient.
D. Individual has hypogammaglobulinemia.
E. None of the above could explain these results.
B. This the best possible explanation given these choices. An individual who is sub-
group A
2
would test as group A on forward typing. However, some A
2
individuals
make anti-A
1
(in addition to the anti-B that A individuals make). Therefore, on
reverse typing these individuals would have both anti-A and anti-B.
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夝
Question 5: ABO typing consists of forward (or front) and reverse (or back) typing
reactions. Why are A
1
RBCs used in reverse typing?
A. A
1
patient’s serum may contain anti-A
1
.
B. A
2
patient’s serum may contain anti-A
3
.
C. A
1
RBCs have the strongest expression of A antigen.
D. A
1
RBCs have the weakest expression of A antigen.
E. None of the above.
C. For reverse typing, the patient’s serum is tested with commercially prepared RBCs
to determine what antibodies are present in the patient’s serum. A
1
RBCs have stron-
ger expression of the A antigen compared to A
2
RBCs. If the patient has anti-A in his/
her serum (ie, B or O patients), they’ll be more likely to bind to the A
1
RBCs than the
A
2
RBCs, giving stronger positive reactions, resulting in fewer discrepancies between
the forward and reverse typing reactions.
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夝
Question 6: Which of the following statements is true about patients with the H-
deficient (Bombay) phenotype?
A. These individuals express the H gene (FUT1), which encodes a fucosyltransfer-
ase.
B. These individuals express the “secretor gene” (FUT2), which encodes a fucos-
yltransferase.
CARBOHYDRATE BLOOD GROUP ANTIGENS AND COLLECTIONS 37
C. These individuals forward and reverse type as group O.
D. These patients should be given group O RBCs if transfusion is needed.
E. Because these individuals do not carry normal A and B genes, their children
can have only group O or Bombay phenotypes.
C. Because the H gene (FUT1) and the Se gene (FUT2) are closely linked (within 100
kb) on chromosome 19, the mutation that causes the Bombay phenotype often
involves deletion of both of these genes. These patients have no ABH antigens on
red cells or in glandular secretions. This also means that they make anti-H, anti-A,(in
those with the B gene) and anti-B, (in those with the A gene). Recall that the H gene
product, a fucosyltransferase, must add a fucose to the oligosaccharide chain before
the A or B gene products can add their respective sugar molecules. If no H substrate
exists, then the individual cannot form A or B antigens. Lastly, if an individual with
Bombay phenotype mates with a non-Bombay individual, the children can inherit
an H allele from the non-Bombay parent. If the children also inherit an A or B allele
(different gene on a different chromosome), then they can have A, B, or O blood and
secretions.
________________________________ ________________________________
夝
Question 7: Which statement about the Ii blood group system is true?
A. I and i antigens are protein antigens encoded by two different alleles of the
same gene.
B. The i antigen is unbranched and predominates on adult red cells, whereas the I
antigen is branched and predominates on neonatal red cells.
C. Patients with “marrow stress” conditions have increased i antigen on their red
cells.
D. Cold agglutinin disease (cold autoimmune hemolytic anemia) may occur in
patients who lack anti-I.
E. Anti-I autoantibodies are associated with EBV infection; anti-i autoantibodies
are associated with mycoplasma infection.
C. These patients experience premature release of red cells from the marrow into the
bloodstream and have increased i antigen on their red cells. Most of the other
choices are reversed from their true associations.
________________________________ ________________________________
夝
Question 8: Which statement about the Lewis system is true?
A. Lewis antigens are intrinsic to the red cell membrane.
B. The Lewis (Le) gene encodes a fucosyltransferase that adds only fucose to
secreted type I oligosaccharide chains; this same gene is present in Le(a+) and
Le(b+) individuals.
38 PRACTICAL SELF-ASSESSMENT FOR TRANSFUSION MEDICINE PROFESSIONALS
C. The Le
a
antigen can be made only by secretors, whereas the Le
b
antigen can be
made only by nonsecretors.
D. Lewis antigens can be lost from red cells in patients with infectious mononu-
cleosis and pancreatitis, but persist in those with severe alcoholic cirrhosis.
E. The transfused patient cannot assume the Lewis phenotype of the donor.
B. The Lewis group is related to ABO. Lewis antigens are expressed on a number of
cells and tissues, but they are developmentally expressed. That is, most newborns
possess neither Le
a
nor Le
b
antigens de novo.
________________________________ _______________________________
夝
Question 9: A patient who requires a RBC transfusion is found to have anti-Le
a
.
Which of the following statements about anti-Le
a
is FALSE?
A. Le
a
antibodies that are reactive at 37 C and reactive at 4 C may cause severe
hemolysis.
B. Most Le
a
antibodies are not clinically significant.
C. Le
a
antibodies are not associated with hemolytic disease of the fetus and new-
born.
D. The transfused RBCs for this patient must be crossmatch-compatible.
E. The transfused RBCs for this patient must be Le
a
antigen-negative.
E. The transfused RBCs do not have to be Le
a
antigen negative in this situation. This
is because the Lewis antigens are soluble factors (not intrinsic to the red cell mem-
brane). Transfused RBCs are going to take on the Lewis phenotype of the patient.
Neonatal red cells do not have Lewis antigens. Lewis antibodies are naturally occur-
ring, generally IgM, and most often not clinically significant.
________________________________ _______________________________
夝
Question 10: Which of the following statements about the globoside (GLOB) blood
group antigen is NOT true?
A. The P
k
antigen is the immediate precursor to the P antigen, which is formed by
the addition of an N-acetylgalactosaminyl residue to the terminal galactosyl
residue of P
k
.
B. The P antigen is a high-incidence antigen in the population; it is absent in only
1 in 100,000 individuals.
C. Although rare, P antibodies are clinically significant IgM antibodies because
they can cause hemolytic transfusion reactions.
D. The P antigen is a receptor for EBV.
E. The P antigen is a receptor for nephritogenic E. coli.
CARBOHYDRATE BLOOD GROUP ANTIGENS AND COLLECTIONS 39
D. The P antigen is a receptor for B19 parvovirus and nephritogenic E. coli (think “P”
for parvovirus). All the other statements are true. P
1
is related to P and P
k
, but actu-
ally not a member of the globoside collection of antigens.
________________________________ ________________________________
夝
Question 11: Which antibody binds to red cells in the colder areas of the body and
then causes hemolysis as the cells circulate to the warmer central areas of the body
(paroxysmal cold hemoglobinuria)?
A. Donath-Landsteiner antibody (auto-anti-P IgG).
B. Anti-Ulex.
C. Anti-PIGA.
D. Anti-HP1a.
E. Paroxysmal cold hemoglobinuria is not antibody-based.
A. Paroxysmal cold hemoglobinuria is complement-dependent, facilitated by IgGs
(Donath-Landsteiner antibody) that bind the P antigen when cold (peripheral circu-
lation), but lyse via complement-mediated hemolysis when the complexes recircu-
late to warm central regions.
________________________________ ________________________________
夝
SUGGESTED READING
Beadling WV, Cooling L. Immunohematology. In: McPherson RA, Pincus MR, eds.
Henry’s clinical diagnosis and management by laboratory methods. 21st ed. Phila-
delphia: Saunders, 2007:618-69.
Daniels G. Human blood groups. 2nd ed. Oxford, England: Blackwell, 2002.
Issitt PD, Anstee DJ. Applied blood group serology. 4th ed. Durham, NC: Montgom-
ery Scientific Publications, 1998.
Klein HG, Anstee DJ. Mollison’s blood transfusion in clinical medicine. 12th ed.
Oxford, England: Wiley-Blackwell, 2011.
Marionneau S, Cailleau-Thomas A, Rocher J, et al. ABH and Lewis histoblood group
antigens: A model for the meaning of oligosaccharide diversity in the face of a
changing world. Biochimie 2001;83:565-73.
Reid ME, Lomas-Francis C, Olsson M. The blood group antigen factsbook. 3rd ed.
San Diego, CA: Academic Press, 2012 (in press).
Roback JD, Grossman BJ, Harris T, Hillyer CD, eds. Technical manual. 17th ed.
Bethesda, MD: AABB, 2011.
In: Leonard G, Licata M.
Practical Self-Assessment for Transfusion Medicine Professionals
Bethesda, MD: AABB Press, 2012
5
Polypeptide Blood Group Systems
QUESTIONS
Question 1: Which red cell antigen is correctly matched with one of its functions?
A. Duffy – Plasmodium vivax recognition site
B. Lewis – Yersinia enterocolitica recognition site.
C. P antigen – Streptococcus aureus recognition site.
D. Kell – Trichomonas vaginalis recognition site.
E. ABO – Plasmodium falciparum recognition site.
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Question 2: Which of the following is NOT a member of the MNS antigen system?
A. M antigen.
B. N antigen.
C. S antigen.
D. n antigen.
E. s antigen.
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夝
Question 3: Which of the following antigens are present on glycophorin A?
A. S antigen.
B. s antigen.
C. M antigen.
D. U antigen.
E. u antigen.
42 PRACTICAL SELF-ASSESSMENT FOR TRANSFUSION MEDICINE PROFESSIONALS
_____________________________ _____________________________
夝
Question 4: Which of the following is true about anti-M?
A. Occur naturally, non-RBC-stimulated.
B. Uncommon alloantibody specificity.
C. IgM only.
D. Frequent cause of HDFN.
E. Clinically significant.
________________________________ _______________________________
夝
Question 5: What is the most important distinction between patients with anti-M
and patients with anti-S?
A. Unlike anti-M, anti-S is rare.
B. Anti-S is similar to anti-M in that they only occur naturally.
C. Patients with anti-S must receive antigen-negative blood, unlike those with
anti-M, who can often safely receive crossmatch-compatible blood.
D. Anti-S is active only when warm; anti-M when cold.
E. Anti-S is never clinically significant.
_____________________________ _____________________________
夝
Question 6: Which of the following antibodies is described as of immune origin
solely, IgG only, may be clinically significant, and is extremely rare?
A. Anti-M.
B. Anti-N.
C. Anti-S.
D. Anti-n.
E. Anti-s.
_____________________________ _____________________________
夝
Question 7: Which of the following is NOT part of the Rh blood group system?
A. D antigen.
B. d antigen.
C. C antigen.
D. c antigen.
E. E antigen.
POLYPEPTIDE BLOOD GROUP SYSTEMS 43
_____________________________ _____________________________
夝
Question 8: Which of the following statements is true?
A. The RhCE protein is encoded by the same gene as RhD protein.
B. The C antigen is the most immunogenic of the Rh antigens.
C. Anti-D causes intravascular hemolysis.
D. Partial D is a recombinant RhD-RhCE protein.
E. Anti-f is a rare compound alloantibody.
_____________________________ _____________________________
夝
Question 9: Which of the following describes the Rh
null
phenotype?
A. All Rh antigens are expressed on the red cell surface.
B. Red cells exhibit stomatocytosis.
C. Red cells display decreased osmotic fragility.
D. The phenotype is fairly common.
E. The cells demonstrate extended red cell survival.
_____________________________ _____________________________
夝
Question 10: What is the main difference between “weak D” and “partial D” indi-
viduals?
A. Weak D phenotype results from a decreased number of epitopes on D antigen.
B. Partial D phenotype results from a decreased level of expression of D antigen.
C. Donors with weak D phenotype, but not partial D, should be categorized Rh-
positive.
D. Donors with partial D phenotype, but not weak D, should be categorized Rh-
positive.
E. Individuals with partial D phenotype, but not weak D, can make alloantibodies
to the D antigen when receiving D-positive RBCs.
________________________________ ________________________________
夝
Question 11: Which statement is true about the compound Rh antigens, “ce” (also
known as “f”), Ce, CE, and cE?
A. Compound antigens must be in cis configuration (on the same chromosome) to
be expressed.
B. Antibodies to compound antigens are not clinically significant.
C. A recipient who has anti-ce should not receive blood from a donor who has the
cE haplotype.
44 PRACTICAL SELF-ASSESSMENT FOR TRANSFUSION MEDICINE PROFESSIONALS
D. Compound antigens are the result of multiple amino acid polymorphisms.
E. Anti-c has been shown not to cause hemolytic transfusion reactions.
________________________________ _______________________________
夝
Question 12: Which statement about the G antigen is true?
A. It is found only on Rh
null
red cells.
B. Anti-G does not react with red cells that express C and/or D antigens.
C. G antibodies may cause severe neonatal alloimmune thrombocytopenia.
D. Recipients with G antibodies should not receive C-negative or D-negative
RBCs.
E. Current methods of antibody identification testing cannot distinguish anti-G
from a mixture of anti-C and anti-D.
________________________________ _______________________________
夝
Question 13: Which statement about the Kell blood group system is true?
A. Consists of 10 antigens found on a single transmembrane protein.
B. K antigen is the most potent immunogen of the non-ABO antigens.
C. K antigen is present on 90% of donated red cells, so it can be difficult to find K
antigen-negative RBC units.
D. Anti-K, -k, -Kp
a/b
, -Js
a/b
are typically immune-stimulated IgG antibodies detected
by the antiglobulin test that have been associated with hemolytic transfusion
reactions and HDFN.
E. Anti-K is an infrequent cause of HDFN.
________________________________ _______________________________
夝
Question 14: McLeod syndrome is caused by the absence of Kx antigen. In the
absence of Kx antigen, levels of Kell antigens are greatly reduced on red cells and
granulocytes. Which of the following is not associated with the McLeod syndrome?
A. Duchenne muscular dystrophy.
B. Chronic granulomatous disease.
C. Retinitis pigmentosa.
D. Stomatocytosis and decreased red cell production.
E. Acanthocytosis
________________________________ _______________________________
夝
Question 15: Which of the following is true about the Kidd blood group system?
POLYPEPTIDE BLOOD GROUP SYSTEMS 45
A. The Jk
null
phenotype is seen predominantly in those of African ethnicity.
B. Kidd antibodies are complement-fixing IgG.
C. JKA is a dominant allele, while JKB is recessive.
D. Jk
null
phenotype red cells are lysed by 2M urea.
E. Only anti-Jk
a
can cause hemolytic disease of the fetus and newborn.
_____________________________ _____________________________
夝
Question 16: Which of the following is true about Kidd antibodies?
A. A positive history of Kidd antibodies is not clinically significant if there is no
current evidence of Kidd antibodies.
B. Kidd antibodies are persistent and once detected in a patient they will be able
to be detected from that point on.
C. Crossmatch alone is sufficient to identify units to transfuse to patients with Kidd
antibodies.
D. Anti-Jk
a
is clinically significant; anti-Jk
b
is not.
E. Kidd antibodies can cause delayed hemolytic transfusion reactions.
________________________________ ________________________________
夝
Question 17:
Which of the following about the Duffy blood group system is NOT true?
A. The Duffy carrier protein is a chemokine receptor.
B. Anti-Fy
b
is more common than the anti-Fy
a
.
C. The Duffy carrier protein is the receptor for P. vivax.
D. Duffy antibodies can cause hemolytic transfusion reactions.
E. All of the above are true.
________________________________ ________________________________
夝
ANSWERS
Question 1: Which red cell antigen is correctly matched with one of its functions?
A. Duffy – Plasmodium vivax recognition site
B. Lewis – Yersinia enterocolitica recognition site.
C. P antigen – Streptococcus aureus recognition site.
D. Kell – Trichomonas vaginalis recognition site.
E. ABO – Plasmodium falciparum recognition site.
A. Duffy protein functions as a recognition site for Plasmodium vivax.