Why do Lewis antibodies rarely shorten the survival of transfused red cells?

Lewis substance in donor plasma neutralizes them

Donor units are routinely typed Le(a-b-)

Lewis antigens are absent from adult red cells

Lewis antibodies are mainly of the IgG4 subclass

A pregnant woman has anti-M that reacts at immediate spin and weakly at the antiglobulin phase. After her plasma is treated with DTT, the antiglobulin reactions with M+ cells remain, and a control confirms that IgM activity was removed. The best interpretation is:

An IgG anti-M able to cross the placenta

IgM anti-M only, with no fetal risk

A failed DTT treatment of the plasma

Loss of M antigen from DTT-treated cells

Kidd antibodies are often missed in pretransfusion testing. Which combination of features explains this?

Weak reactions, dosage and a fast fall in titer

Strong IgM reactions seen at room temperature only

Loss of reactivity with enzyme-treated cells

Neutralization by Kidd substance in plasma

Anti-Fya is being excluded. The only nonreactive Fy(a+) panel cell types Fy(a+b-) and comes from a donor of African ancestry. Why is this a weak basis for ruling out anti-Fya?

It may carry only a single dose of Fya

Its Fya is a partial antigen, like partial D

Ficin is needed to expose its Fya antigen

Anti-Fya reacts only with Fy(a+b+) cells

Other blood group systems

18 DOH Abu Dhabi (HAAD) lab licensing practice questions on Other blood group systems, part of Blood Banking. The first 18 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
Why do Lewis antibodies rarely shorten the survival of transfused red cells?
1. ADonor units are routinely typed Le(a-b-)
2. BLewis substance in donor plasma neutralizes them
3. CLewis antigens are absent from adult red cells
4. DLewis antibodies are mainly of the IgG4 subclass
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Answer: B · Lewis substance in donor plasma neutralizes them
Lewis antigens circulate as glycolipids in plasma, so the plasma in a red cell unit neutralizes some of the recipient's antibody. Transfused red cells also lose their Lewis antigens within days and take on the recipient's Lewis type. Most Lewis antibodies are IgM and react best below 37 °C. Antigen-negative units are therefore not required; red cells compatible in an antiglobulin crossmatch at 37 °C are acceptable.
- A: Donor units are not routinely typed for Lewis antigens.
- C: Adult red cells carry Lewis antigens taken up from plasma.
- D: Most Lewis antibodies are IgM, not IgG4.
Question 2 · Hard
A pregnant woman has anti-M that reacts at immediate spin and weakly at the antiglobulin phase. After her plasma is treated with DTT, the antiglobulin reactions with M+ cells remain, and a control confirms that IgM activity was removed. The best interpretation is:
1. AIgM anti-M only, with no fetal risk
2. BA failed DTT treatment of the plasma
3. CAn IgG anti-M able to cross the placenta
4. DLoss of M antigen from DTT-treated cells
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Answer: C · An IgG anti-M able to cross the placenta
DTT breaks the disulfide bonds that hold IgM together, so reactivity that survives DTT treatment of the plasma comes from IgG. Most anti-M is IgM and harmless, but an IgG component can cross the placenta and has occasionally caused HDFN with fetal anemia. The IgG antibody should be titered at the antiglobulin phase and the pregnancy monitored. Because the antibody reacts at the antiglobulin phase, M-negative red cells are usually given if transfusion is needed.
- A: Reactivity that survives DTT shows an IgG component, so fetal risk cannot be excluded.
- B: The control shows the treatment worked and removed the IgM activity.
- D: The plasma, not the test cells, was treated, and M is not a DTT-sensitive antigen.
Question 3 · Medium
Kidd antibodies are often missed in pretransfusion testing. Which combination of features explains this?
1. AStrong IgM reactions seen at room temperature only
2. BLoss of reactivity with enzyme-treated cells
3. CNeutralization by Kidd substance in plasma
4. DWeak reactions, dosage and a fast fall in titer
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Answer: D · Weak reactions, dosage and a fast fall in titer
Anti-Jka and anti-Jkb are often weak and react more strongly with cells from people homozygous for the antigen, so they can be missed with heterozygous screening cells. They also fall below detectable levels within weeks to months and rise quickly after re-exposure, which makes them a leading cause of delayed hemolytic reactions. Enzyme-treated cells and polyspecific AHG help detect them. A record of a past Kidd antibody must be honored even when today's screen is negative.
- A: Kidd antibodies are usually IgG and react at the antiglobulin phase.
- B: Enzyme treatment enhances Kidd reactions.
- C: There is no soluble Kidd substance in plasma; that applies to Lewis antigens.
Question 4 · Easy
The P antigen (globoside, GLOB system) on red cell precursors is the cell receptor used by:
1. APlasmodium vivax
2. BEpstein-Barr virus
3. CHepatitis B virus
4. DParvovirus B19
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Answer: D · Parvovirus B19
Parvovirus B19 binds the P antigen (globoside) on erythroid precursors, then infects and kills them. Infection can stop red cell production for one to two weeks, causing an aplastic crisis in patients with short red cell survival, such as those with sickle cell disease or hereditary spherocytosis. People with the rare p phenotype lack globoside and resist infection. P is now in the GLOB system, separate from P1 in the P1PK system.
- A: Plasmodium vivax uses the Duffy glycoprotein to enter red cells.
- B: Epstein-Barr virus enters B cells through CD21 (complement receptor 2).
- C: Hepatitis B virus infects liver cells, not red cell precursors.
Question 5 · Hard
Anti-Fya is being excluded. The only nonreactive Fy(a+) panel cell types Fy(a+b-) and comes from a donor of African ancestry. Why is this a weak basis for ruling out anti-Fya?
1. AIt may carry only a single dose of Fya
2. BIts Fya is a partial antigen, like partial D
3. CFicin is needed to expose its Fya antigen
4. DAnti-Fya reacts only with Fy(a+b+) cells
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Answer: A · It may carry only a single dose of Fya
In people of African ancestry, FY*B often carries a GATA promoter change that silences it in red cells, so no Fyb is made. A cell typed Fy(a+b-) from such a donor is often FY*A paired with this silent allele, which gives a single dose of Fya, like an Fy(a+b+) cell. Anti-Fya can show dosage and may react weakly or not at all with single-dose cells. Duffy rule-outs should use cells known to be homozygous, ideally by genotype.
- B: Partial Fya is not a recognized cause of this pattern; the issue is antigen dose.
- C: Ficin destroys Duffy antigens rather than exposing them.
- D: Anti-Fya reacts with any Fy(a+) cell, but more strongly with a double dose.
Question 6 · Hard
An IgG alloantibody is tested with ficin-treated and DTT-treated panel cells. Which pattern fits anti-Jka?
1. ADestroyed by both ficin and DTT
2. BEnhanced by ficin; DTT has no effect
3. CDestroyed by ficin; DTT has no effect
4. DFicin has no effect; destroyed by DTT
Answer and explanation in LearnFree account
Question 7 · Medium
Kell antigens survive ficin treatment but are destroyed by DTT. This is because the Kell glycoprotein:
1. AIs fixed to the membrane by a GPI anchor
2. BIs taken up onto red cells from plasma
3. CIs rich in sialic acid, like glycophorin A and B
4. DNeeds its disulfide bonds to keep its shape
Answer and explanation in LearnFree account
Question 8 · Easy
Which antigens are usually absent or very weak on the red cells of newborn babies?
1. ALewis antigens (Lea and Leb)
2. BKell antigens (K and k)
3. CDuffy antigens (Fya and Fyb)
4. DKidd antigens (Jka and Jkb)
Answer and explanation in LearnFree account
Question 9 · Hard
A transfused man of West African ancestry has an antibody to a high-prevalence antigen. It reacts with all panel cells except a rare Js(a+b-) cell, and DTT-treated cells are nonreactive. Among donors of which ancestry are compatible units most likely to be found?
1. AEast Asian ancestry
2. BAfrican ancestry
3. CSouth Asian ancestry
4. DEuropean ancestry
Answer and explanation in LearnFree account
Question 10 · Medium
Compared with anti-M, anti-S is more likely to be:
1. AMade stronger by acidifying the plasma
2. BNeutralized by hydatid cyst fluid
3. CIgG and able to cause hemolytic reactions
4. DNaturally occurring and active only below 22 °C
Answer and explanation in LearnFree account
Question 11 · Medium
Red cells that do not react with anti-P1 but do react with anti-P have the phenotype:
1. AP1
2. BP2k
3. CP2
4. Dp
Answer and explanation in LearnFree account
Question 12 · Hard
A woman's red cells lack K, k, Kpb and Jsb. After her third pregnancy, her plasma reacts 3+ by AHG with every untreated panel cell, including K+k-, Kp(a+b-) and Js(a+b-) cells, but with no DTT-treated cell. Which specificity explains this?
1. AAnti-Jsb
2. BAnti-Ku
3. CAnti-k
4. DAnti-Kpb
Answer and explanation in LearnFree account
Question 13 · Medium
A patient on long-term hemodialysis, whose own red cells are N-positive, develops a cold-reacting anti-N-like antibody. What is the best-known cause?
1. AFormaldehyde used to sterilize reused dialyzers
2. BErythropoietin used to treat the anemia
3. CHeparin given at each dialysis session
4. DIron sucrose infusions given after dialysis
Answer and explanation in LearnFree account
Question 14 · Hard
A group A adult's red cells type Le(a-b-). Saliva contains A and H substances but no Lea or Leb. This person most likely has:
1. Ale/le with se/se
2. BFunctional Le and Se genes
3. Cle/le with a functional Se gene
4. DA functional Le gene with se/se
Answer and explanation in LearnFree account
Question 15 · Easy
Which red cell membrane protein carries the S, s and U antigens of the MNS system?
1. AThe Kidd glycoprotein
2. BBand 3 protein
3. CGlycophorin A
4. DGlycophorin B
Answer and explanation in LearnFree account
Question 16 · Hard
A woman with three early miscarriages has an antibody that reacts with every panel cell at room temperature, 37 °C and the antiglobulin phase, with some hemolysis. Her autocontrol is negative, and her red cells do not react with anti-P1, anti-P or anti-Pk. The antibody is most likely:
1. AAnti-Lea
2. BAnti-I
3. CAnti-P1
4. DAnti-PP1Pk
Answer and explanation in LearnFree account
Question 17 · Hard
A 36-year-old woman of Nigerian ancestry, transfused 4 red cell units after a postpartum hemorrhage 3 years ago, needs 2 units for a myomectomy. A panel identifies anti-Fya, all other common specificities are excluded, and the autocontrol is negative. Her red cells type Fy(a-b-). Red cell genotyping finds FY*B on both chromosomes, each with the GATA-box variant (c.-67T>C) that silences Duffy expression in red cell precursors but not in other tissues. The ABO-compatible units on the shelf include Fy(a+b+), Fy(a-b+) and Fy(a-b-) units. Which of these units are suitable?
1. AFy(a-b-) units only
2. BFy(a-b+) units only
3. CFy(a+b+) and Fy(a-b+) units
4. DFy(a-b+) and Fy(a-b-) units
Answer and explanation in LearnFree account
Question 18 · Hard
A 41-year-old woman of Thai ancestry, with two previous pregnancies, needs 2 red cell units before a hysterectomy for bleeding fibroids; hemoglobin 72 g/L (7.2 g/dL). Her antibody screen, using three group O cells from European donors, is negative, and an 11-cell panel from the same supplier is also negative. Of four ABO-compatible units crossmatched by the antiglobulin method, one, from a donor of Thai ancestry, is 2+ incompatible at immediate spin and at the antiglobulin phase; the other three are compatible. The donor unit's DAT is negative, and her autocontrol is negative. Which specificity is most likely?
1. AAnti-Kpa (Kell system)
2. BAnti-Jsa (Kell system)
3. CAnti-Wra (Diego system)
4. DAnti-Mur (MNS system)
Answer and explanation in LearnFree account

Other blood group systems

Why do Lewis antibodies rarely shorten the survival of transfused red cells?

A pregnant woman has anti-M that reacts at immediate spin and weakly at the antiglobulin phase. After her plasma is treated with DTT, the antiglobulin reactions with M+ cells remain, and a control confirms that IgM activity was removed. The best interpretation is:

Kidd antibodies are often missed in pretransfusion testing. Which combination of features explains this?

The P antigen (globoside, GLOB system) on red cell precursors is the cell receptor used by:

Anti-Fya is being excluded. The only nonreactive Fy(a+) panel cell types Fy(a+b-) and comes from a donor of African ancestry. Why is this a weak basis for ruling out anti-Fya?

An IgG alloantibody is tested with ficin-treated and DTT-treated panel cells. Which pattern fits anti-Jka?

Kell antigens survive ficin treatment but are destroyed by DTT. This is because the Kell glycoprotein:

Which antigens are usually absent or very weak on the red cells of newborn babies?

A transfused man of West African ancestry has an antibody to a high-prevalence antigen. It reacts with all panel cells except a rare Js(a+b-) cell, and DTT-treated cells are nonreactive. Among donors of which ancestry are compatible units most likely to be found?

Compared with anti-M, anti-S is more likely to be:

Red cells that do not react with anti-P1 but do react with anti-P have the phenotype:

A woman's red cells lack K, k, Kpb and Jsb. After her third pregnancy, her plasma reacts 3+ by AHG with every untreated panel cell, including K+k-, Kp(a+b-) and Js(a+b-) cells, but with no DTT-treated cell. Which specificity explains this?

A patient on long-term hemodialysis, whose own red cells are N-positive, develops a cold-reacting anti-N-like antibody. What is the best-known cause?

A group A adult's red cells type Le(a-b-). Saliva contains A and H substances but no Lea or Leb. This person most likely has:

Which red cell membrane protein carries the S, s and U antigens of the MNS system?

A woman with three early miscarriages has an antibody that reacts with every panel cell at room temperature, 37 °C and the antiglobulin phase, with some hemolysis. Her autocontrol is negative, and her red cells do not react with anti-P1, anti-P or anti-Pk. The antibody is most likely: