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Blood banking: blood groups, antigens and antibodies

40 Kerala PSC Lab Technician Gr II practice questions on Blood banking: blood groups, antigens and antibodies, part of Pathology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

  1. Question 1 · Medium

    A D-negative woman forms anti-D after delivering a D-positive baby. Anti-D is called an immune antibody because it:

    1. AIs directed against her own cells
    2. BIs present from early infancy
    3. CComes from the baby's plasma
    4. DForms only after exposure to red cells
    Show answer

    Answer: D · Forms only after exposure to red cells

    Immune (unexpected) antibodies such as anti-D form only after a person is exposed to foreign red cell antigens through transfusion or pregnancy. Here fetal D-positive cells entered her circulation, usually at delivery. Regular ABO antibodies, in contrast, appear in infancy without any red cell exposure. Anti-D immunoglobulin given within 72 hours of delivery prevents this sensitisation.

    • A: An antibody against one's own cells is an autoantibody; this anti-D targets fetal cells.
    • B: Antibodies present from infancy without exposure are regular ABO antibodies.
    • C: The baby does not make anti-D; the mother makes it against the baby's cells.

  2. Question 2 · Easy

    According to Landsteiner's rule, a person's plasma contains:

    1. ANo ABO antibodies until adult life
    2. BABO antibodies only after transfusion
    3. CAntibodies to the ABO antigens they lack
    4. DAntibodies to their own ABO antigens
    Show answer

    Answer: C · Antibodies to the ABO antigens they lack

    Landsteiner's rule states that a healthy person has regular anti-A and/or anti-B against the ABO antigens absent from their own red cells. A group A person has anti-B, a group B person anti-A, a group O person anti-A, anti-B and anti-A,B, and a group AB person neither. These antibodies appear without transfusion, starting a few months after birth. This is the basis of reverse (serum) grouping.

    • A: ABO antibodies appear from about 3-6 months of age, not in adult life.
    • B: ABO antibodies appear naturally in infancy, without transfusion.
    • D: People do not normally make antibodies to their own ABO antigens.

  3. Question 3 · Hard

    A woman is group A and her baby is group B. The alleged father is group O. Assuming no rare ABO variants, what can be concluded?

    1. AHe is excluded as the father
    2. BABO cannot exclude paternity
    3. CHe could be the father
    4. DThe baby's B came from the mother
    Show answer

    Answer: A · He is excluded as the father

    A group B child must have inherited a B allele from one parent. The mother is group A (genotype AA or AO), so she cannot pass B, and a group O man (OO) can pass only O. The alleged father is therefore excluded, unless a rare variant such as cis-AB is present, which DNA testing would settle. ABO typing can exclude paternity but can never prove it.

    • B: ABO typing can exclude paternity, as it does here.
    • C: An OO man can pass only O, so he cannot give the child a B allele.
    • D: A group A mother carries no B allele to pass on.

  4. Question 4 · Easy

    On which chromosome is the ABO gene located?

    1. A9
    2. B6
    3. C1
    4. D19
    Show answer

    Answer: A · 9

    The ABO gene lies on the long arm of chromosome 9 (9q34). Its A and B alleles code for glycosyltransferases, while the O allele codes for an inactive enzyme. The RH genes are on chromosome 1 and the HLA genes on chromosome 6. The H (FUT1) and secretor (FUT2) genes are on chromosome 19.

    • B: Chromosome 6 carries the HLA genes.
    • C: Chromosome 1 carries the RHD and RHCE genes.
    • D: Chromosome 19 carries the H, secretor and Lewis genes.

  5. Question 5 · Easy

    A and B antigens are made by adding sugars to which precursor?

    1. AH substance
    2. BP antigen
    3. CI antigen
    4. DLewis substance
    Show answer

    Answer: A · H substance

    The H gene (FUT1) adds fucose to a precursor chain to make H substance. The A transferase then adds N-acetylgalactosamine, and the B transferase adds D-galactose, to H. Group O cells have the most unconverted H and A1B cells the least. People with the Bombay phenotype make no H, so they cannot make A or B even if they inherit those genes.

    • B: P antigens belong to separate blood group systems.
    • C: The I antigen is a separate carbohydrate antigen, not the ABO precursor.
    • D: Lewis substances are made by a different enzyme and adsorbed from plasma.

  6. Question 6 · Medium

    ABH substances appear in the saliva of people who inherit the:

    1. ASecretor (Se) gene
    2. BLewis (Le) gene
    3. CKell (K) gene
    4. DBombay (h) allele

    Answer and explanation in LearnFree account

  8. Question 8 · Medium

    Compared with ABO antigens, Rh antigens are:

    1. AFound on most body tissues
    2. BProteins found only on red cells
    3. CWeakly developed at birth
    4. DSugars also present in saliva

    Answer and explanation in LearnFree account

  9. Question 9 · Hard

    Two parents are group A and group B. Their first child is group O. What are the parents' genotypes?

    1. AAA and BO
    2. BAO and BO
    3. CAO and BB
    4. DAA and BB

    Answer and explanation in LearnFree account

  10. Question 10 · Hard

    A woman's blood gives: anti-A negative, anti-B negative, anti-H lectin negative; her serum agglutinates A1, B and group O cells (4+ each); autocontrol negative. Her blood group is most likely:

    1. ABombay phenotype (Oh)
    2. BGroup O
    3. CGroup O with cold autoantibody
    4. DWeak A subgroup (Ax)

    Answer and explanation in LearnFree account

  11. Question 11 · Medium

    Lewis antigens on red cells differ from ABO antigens because Lewis antigens are:

    1. AMade by red cell precursors
    2. BTaken up from the plasma
    3. CProteins, not carbohydrates
    4. DFully developed at birth

    Answer and explanation in LearnFree account

  13. Question 13 · Medium

    Seven days after a transfusion, a woman becomes jaundiced and her hemoglobin falls. Her antibody screen was negative before transfusion and is now positive. Which antibody most often causes this picture?

    1. AAnti-Jka
    2. BAnti-Lea
    3. CAnti-M
    4. DAnti-A

    Answer and explanation in LearnFree account

  14. Question 14 · Easy

    In group A and group B people, naturally occurring anti-B and anti-A are mainly of which class?

    1. AIgA
    2. BIgG3
    3. CIgG1
    4. DIgM

    Answer and explanation in LearnFree account

  15. Question 15 · Medium

    The P antigen (globoside) on red cell precursors acts as the cell receptor for:

    1. APlasmodium vivax
    2. BCytomegalovirus
    3. CDengue virus
    4. DParvovirus B19

    Answer and explanation in LearnFree account

  16. Question 16 · Hard

    A group O woman's husband is group AB. Which ABO groups are possible in their children?

    1. AA, B or AB
    2. BA or B only
    3. CO or AB only
    4. DA, B, AB or O

    Answer and explanation in LearnFree account

  17. Question 17 · Easy

    The A and B genes code for which type of enzyme?

    1. AProteases
    2. BLipases
    3. CKinases
    4. DGlycosyltransferases

    Answer and explanation in LearnFree account

  18. Question 18 · Medium

    Anti-Lea found in a pregnant woman does not cause hemolytic disease of the newborn. Why?

    1. AIt is IgM, and fetal cells carry little Lewis antigen
    2. BIt reacts only with white cells
    3. CIt is an IgG subclass that cannot bind cells
    4. DIt is neutralised by the baby's own saliva

    Answer and explanation in LearnFree account

  19. Question 19 · Medium

    A patient's anti-Jka reacts 3+ with Jk(a+b-) cells but only 1+ with Jk(a+b+) cells. This difference is called:

    1. ADosage effect
    2. BProzone effect
    3. CRouleaux formation
    4. DMixed-field reaction

    Answer and explanation in LearnFree account

  20. Question 20 · Medium

    Naturally occurring anti-A and anti-B are thought to form in infancy because of exposure to:

    1. AA- and B-like substances in gut bacteria
    2. BMaternal red cells during delivery
    3. CAntigens in breast milk only
    4. DTransfused red cells

    Answer and explanation in LearnFree account

  21. Question 21 · Medium

    IgM anti-A agglutinates saline-suspended cells directly, while IgG anti-D usually does not. The reason is that IgM:

    1. ABinds more firmly than any IgG
    2. BLowers the zeta potential of the cells
    3. CHas two antigen-binding sites only
    4. DIs large enough to bridge the gap between cells

    Answer and explanation in LearnFree account

  22. Question 22 · Easy

    Red cells of the Duffy phenotype Fy(a-b-) resist invasion by:

    1. AParvovirus B19
    2. BPlasmodium vivax
    3. CBabesia microti
    4. DPlasmodium falciparum

    Answer and explanation in LearnFree account

  23. Question 23 · Hard

    In a population, 4% of people are D negative. Treating D and d as a simple pair of alleles, what percentage of people are heterozygous Dd?

    1. A64%
    2. B32%
    3. C16%
    4. D96%

    Answer and explanation in LearnFree account

  25. Question 25 · Medium

    Why is reverse (serum) grouping not used to confirm the ABO group of a newborn?

    1. AThe baby has not yet made ABO antibodies
    2. BCord serum always hemolyses the cells
    3. CNewborn IgM blocks the reagent cells
    4. DNewborn red cells lack A and B antigens

    Answer and explanation in LearnFree account

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