Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Hillyer > Part III Pretransfusion Testing and Blood Group Antigens > Flashcards

Part III Pretransfusion Testing and Blood Group Antigens Flashcards

1
Q

More than 1/3 SCD patients with apparent C+ phenotype make anti-C or anti-Ce, because:

A

They do not have a conventional RhCe protein; the C antigen is expressed from a hybrid RHD gene that has lost expression of D, but encodes a C epitope. These patients are better served on C- rather than C+ transfusion protocols.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Does ACOG recommend the use of RhIG in patients with weak expression of D?

A

No, because the majority of weak D are not at risk of sensitization; need genotyping to distinguish from partial D. Partial D are at risk of sensitization.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Rh haplotype frequencies in Caucasian, AA and AS?

A

CC: R1 (42%) > r (37%) > R2 > R0 (1r20)
AA: R0 (44%) > r (26%) > R1 > R2 (0r12)
AS: R1 (70%) > R2 (21%) > r = R0
Based on this, you can calculate that ~15% of CC and ~5% of AA are RhD negative.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is McLeod Syndrome?

A

Weak expression of Kell system antigens and absence of Kx antigen; >30 different mutations in an X-linked gene, XK; late onset myopathy, neurodegeneration, and CNS symptoms in the 4th decade; sequencing of XK has prognostic value.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Prevalence of weak D RBCs not detected by serologic reagents is approximately ___

A

0.1%, this has been associated with alloimmunlization and can be improved by RHD genotyping.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

ABO: frequencies in CC, AA and AS

A

O, A, B, AB (CC has more As, AA and AS have more Bs)
CC: 45, 40, 11, 4
AA: 49, 27, 20, 4
AS: 43, 27, 25, 5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the function of H gene (FUT1)?

A

Add terminal fucose to type 2 precursor&raquo_space; H antigen on RBCs; loss of function of H and Se gene&raquo_space; Bombay phenotype.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the function of Se gene (FUT2)?

A

Add terminal fucose to type 1 precursor&raquo_space; H antigen in secretion; loss of function of Se gene&raquo_space; cannot make Le(b)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the terminal CH groups of A, B and O antigens?

A

A: GalNAc (N-acetylgalactosamine)
B: Gal (galactose)
O (H): Fuc (fucose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

FUT3 (LE) is different from FUT1 and FUT2 in what aspect?

A

FUT3 transfer a fucose to the subterminal N-acetylglucosamine (GlcNAc), rather than a fucose to the terminal galactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does FUT1 and FUT2 genes interact to determine Bombay/Para-Bombay phenotype?

A

hh/sese: Bombay (strong anti-H)

hh/Sese or hh/SeSe or H(minimal)h/sese: Para-Bombay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is non-secretor phenotype?

A

20% of individuals have a defective FUT2 gene: sese. They have H antigen on RBCs but not in secretions, and they cannot make Le(b).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the phenotype corresponding to Sese/lele?

A

Le(a)-Le(b)-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the phenotype corresponding to sese/Lele?

A

Le(a)+Le(b)-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the phenotype corresponding to Sese/Lele?

A

Le(a)+Le(b)+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the carrier of ABO in secretions?

A

Type 1 glycoproteins. They are produced in epithelial cells and reside on mucins in secretions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Rank the amount of H antigen by ABO blood groups:

A

O > A2 > B > A2B > A1 > A1B

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What percentage of group A individuals are A1?

A

80%; ~20% are A2; A3, Ael and Ax are much less frequent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the prevalence of anti-A1 in A2 and A2B individuals?

A

1-8% of A2 individuals and ~30% of A2B individuals have anti-A1 due to structural difference between A1 and A2.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which lectin, at a suitable dilution, can agglutinate A1 but not A2 or weaker subgroup RBCs?

A

Dolichos biflorus

Depends more on the quantitative than the qualitative difference between A1 and A2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the molecular mechanism of A2?

A
  • Absence of Type 4A glycolipids in A2, which are dominant in the A1
  • Loss of stop codon&raquo_space; extra 21 residues at C-terminus; Pro156Leu
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Lack of RhAG causes what phenotype?

A

Rh null or marked reduction of Rh expression;

RhAG is important for brining the RhD and RhCE proteins to the membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the function of RhAG?

A

Ammonia/ammonium transport and cation balance in RBCs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Is RhAG immunogenic and clinically significant?

A

Antigen of high prevalence: RHAG1 and RHAG3
Antigen of low prevalence: RHAG2 and RHAG4
RHAG4 has been associated with strong DAT in a baby thus requiring exchange transfusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Molecular mechanism of weak-D?
- Over 75 different mutations in RHD - RHC in trans to RHD (Dce/Ce) - Del (?)
26
What is the most common form of partial D in CC and AA?
CC: DVI; routine testing with IgM monoclonal anti-D reagent does not detect it. AA: DIIIa; these give strong reactions in serologic tests using anti-D.
27
What is the mechanism of partial D?
Many arise as a result of nucleotide exchange between RHCE and RHD; less often they result from single-point mutations in RHD
28
What is the difference between big C and little c?
6 nucleotide substitutions >> 4 aa changes
29
What is the difference between big E and little e?
1 nucleotide substitution >> Pro226Ala
30
What is G antigen?
The 4 aa shared by RhD and RhC, encoded by exon 2; anti-G mimicks anti-D plus anti-C; pregnant women with anti-G (but without anti-D) are still candidates for RhIG to prevent anti-D.
31
What is V antigen?
Low-freq antigen present in 30% AA; results from Leu245Val in the Rhce protein
32
What are partial e antigens?
Individuals of African descent often have altered RHCE*ce genes encoding partial antigens. The RBCs phenotype as e positive, but they can make alloantibodies with e-like specificities (e.g. anti-hr(s), -hr(B), -RH18 and -RH34)
33
Most individuals, especially of European descent, who are D-negative have what kind of change to the RHD gene?
Deletion. D-negative phenotype can also result from various mutations in RHD (premature stop codons, insertions, deletions, or RHD/RHCE hybrid alleles)
34
Where and when are RhD, RhCE and RhAG proteins expressed?
Where: erythroid and myeloid cells When: during late erythropoiesis with RhAG expressed earlier
35
What is the rate of alloimmunization to RhD in D-negative individuals?
Hospital setting: 20% | Healthy male volunteers: 80% (in response to as little as 0.5 mL of D-positive RBCs)
36
Antibodies specific to which Rh antigens can cause severe HDFN?
Anti-D and anti-c. | Anti-C, -E and -e usually cause no or mild HDFN.
37
Autoantibodies that seem to target Rh antigens may be an artifact of what?
Using Rh-null RBCs in the testing. These cells have dcreased expression of other proteins in the Rh complex (CD47, LW, GPB-SsU antigens, and RhAG). Extended antigen-match should be the way to go for transfusion support.
38
What antibody can people with Jk(a-b-) make?
Anti-Jk3; Jk(a-b-) is rare among both white and black people.
39
What is the null phenotype lacking M and N antigens and high prevalence antigen(s)?
En(a-)
40
What are the features of the extracellular segment of glycophorin B?
N (Leu-Ser-Thr-Thr-Glu) > S/s > U
41
What is the phenotype of M(k)M(k) RBCs?
Lack both MN and Ss antigens
42
What is the physiological function of GPA?
receptor for bacteria, viruses and P. falciparum; chaperone for Band 3 transport to RBC membrane; major contributor to the negatively charged RBC glycocalyx; may also regulate complement
43
What is the physiological function of GPB?
Member of the Rh-complex; null phenotypes are not associated with known health defects
44
What does FYX allele encode?
Weak expression of Fy(b); found in whites; due to a single point mutation in the 1st intracellular loop
45
What is the greatest variation between whites and blacks regarding Duffy antigen frequency?
49% of whites are Fy(a+b+), 68% of blacks are Fy(a-b-)
46
What is the major mechanism for the Fy(a-b-) phenotype in blacks?
A mutation in the promoter region of FYB that disrupts a binding site for GATA-1 >> loss of Duffy expression on RBCs
47
What is the physiological function of Duffy antigen?
DARC (a promiscuous chemokine receptor binding both C-X-C and C-C; receptor for P. vivax and P. knowlesi
48
Which gene is responsible for I antigens?
IGnT (GCNT2) encode the acetyl-glucosamine transferase that increase branching of straight chain (i) to form I antigen
49
What is the gene and its encoded enzyme underlying P(k) and P1 (originally named P)?
A4GALT (4-alpha-galactosyltransferase): Gal alpha(1-4)-Gal beta(1-4)-...
50
What is P antigen? What is the genetic basis?
Defined by terminal GalNAc residuals on top of P(k); now belongs to the GLOB system; enzyme encoded by beta3GALNT1
51
What is p phenotype or Tj(a-)? Why is it clinically important?
Null of the system (inactivating mutations in A4GALT); can form alloanti-PP1P(K) which is hemolytic and of clinical significance; associated with a high rate of spontaneous abortion
52
What is the difference between P1 and P2 phenotype and the molecular basis?
Changes in exon2a of A4GALT results in transcriptional down regulation in P2.
53
The rare p phenotype is resistant to which viral infection?
Parvovirus B19; P antigen is the receptor for B19 parvovirus
54
P1 is the receptor for which microorganisms?
E. coli and Streptococcus suis
55
What autoantibody causes paroxysmal cold hemoglobinuria (PCH)?
Autoanti-P (biphasic IgG antibody, Donath-Landsteiner antibody)
56
What is the ISBT definition of a blood group system?
Consists of one or more antigens controlled at a single gene locus, or by two or more very closely linked homologous genes with little or no observable recombination between them.
57
What is the ISBT definition of a collection?
Consists of serologically, biochemically or genetically related antigens (controlled by unknown genes)
58
Inactivating mutations in which gene define the Jr(a-) or null phenotype?
ABCG2 (ATP-binding cassette, subfamily G, member 2): involved in transport of urate and possibly other compounds
59
Which glycoprotein is defective in Glanzmann's thrombasthaenia?
GPIIb/IIIa: receptor for fibrinogen (also fibronectin, vitronectin and vWF)
60
Which glycoprotein is defective in Bernard-Soulier syndrome?
GPIb/V/IX: receptor for vWF; show defect in platelet aggregation assay with ristocetin.
61
What are the top three antigens involved in NAIT?
HPA-1a (68%) > HPA-5b (15%) > HPA-1b (6%) (BCW data)
62
Immunization to HPA-1a is highly correlated with which HLA allele?
HLA-DRB3*01:01 and HLA-DRB4*01:01 (need to verify this; read the original reports)

Hillyer (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions