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Antibody And Antigen Reaction Multiple Choice Question And Answers

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Antigen And Antigen Reaction

Question 1. Specific site of antigen that reacts with antibody:

  1. Epitope
  2. Paratope
  3. Iditope
  4. Isotope

Answer. (1) (Epitope)

Read And Learn More: Micro Biology And Immunology Multiple Choice Question And Answers

Question 2. Smallest unit of antigenicity:

  1. Epitope
  2. Paratope
  3. Complex hapten
  4. Simple hapten

Answer. (1) (Epitope)

Epitope or antigenic determinant is the smallest unit of an antigen that binds to paratope of an antibody.

Question 3. Superantigens are produced by all the following pathogens, except:

  1. Staphylococcus aureus
  2. Enterococcus faecalis
  3. Rabies virus
  4. HIV

Answer. (2) (Enterococcus faecalis)

Question 4. All of the following statements about carbohydrate antigen are true except:

  1. It has lower immunogenicity
  2. Memory response is seen
  3. Cause polyclonal B-cell stimulation
  4. Does not require stimulation by T-cells

Answer. (2) Memory response is seen

  • Carbohydrate antigen like Lipopolysaccharide (LPS) is an example of T Independent Antigen
  • T Independent Antigen:
    • Directly stimulates B-cell for antibody production without participation of T-cell.
    • Dose-dependent immunogenic with Limited antibody response-IgM and IgG3
    • Lack memory response
    • LPS can cause polyclonal B-cell activation.

Question 5. Heterophile antibody is found in:

  1. Weil-Felix test
  2. Widal test
  3. Standard agglutination test
  4. All

Answer. (1) (Weil-Felix test)

  • Weil-Felix test is an example of heterophile agglutination test. Ricketssial antibodies are detected by using Proteus Ox2, Ox19 and OxK antigens.

Question 6. The main aim of an adjuvant is to increase:

  1. Distribution
  2. Absorption
  3. Antigenicity
  4. Metabolism

Answer. (3) (Antigenicity)

  • Adjuvant is any substance that enhances immunogenicity of Antigen.

Question 7. Papain cleaves the immunoglobin molecule into:

  1. 1 Fc and 1 Fab
  2. 1 Fc and 2 Fab
  3. 2 Fc and 1 Fab
  4. 2 Fc and 2 Fab

Answer. (2) (1 Fc and 2 Fab)

  • Papain cleaves Ig below hinge region: produces 2 Fab + 1 Fc fragments
  • Pepsin cleaves Ig above hinge region: produces one F(ab’2) fragment + many smaller fragments

Question 8. Variable portion of an immunoglobulin:

  1. Amino-terminal
  2. Carboxy terminal
  3. Acid terminal
  4. Amoxy terminal

Answer. (1) (Amino…)

  • Variable region end—Amino-terminal (NH4)
  • Constant region end—carboxy-terminal (CHO)

Question 9. Vaccination is based on the principle of:

  1. Agglutination
  2. Phagocytosis
  3. Immunological memory
  4. Clonal detection

Answer. (3) (Immunological memory)

Vaccination leads to production of memory cells against the immunogens which play an important role in prevention of the infection by producing antibodies on subsequent exposure of the organism.

Question 10. Antibody diversity is due to:

  1. Gene rearrangement
  2. Gene translocation
  3. Antigenic variation
  4. CD40 molecules
  5. Mutation

Answer. (1, 5) (Gene rearrangement, Mutation)

Somatic hypermutation and Recombination of V-(D)-J segments joining (Gene rearrangement) are the important mechanisms involved in Antibody diversity.

Antibody Diversity

  • There are 1010 antibodies that can be generated against various antigenic stimuli.
  • This antibody diversity is possible due to:
  • Presence of Multiple germ-line gene segments
  • Recombination of V-(D)-J Segments joining
  • Junctional flexibility
  • P-region nucleotide addition (P-addition)
  • N-region nucleotide addition (N-addition)
  • Somatic hypermutation
  • Combinatorial association of light and heavy chains.

Question 11. All of the following statements about hybridoma technology are true except:

  1. Specific antibody-producing cells are integrated with myeloma cells
  2. Myeloma cells in salvage pathway grows well in HAT medium
  3. Aminopterin, a folate antagonist, inhibits denovo pathway
  4. HGPRT ase and thymidylate synthetase are required for salvage pathway

Answer. (2) (Myeloma cells…)

‘Myeloma cells lacks HGPRT enzyme, hence they cannot grow well in HAT medium.’

Question 12. When Papain cleaves IgG antibody, it produces:

  1. 2 Fab and 1 Fc
  2. 2 Fab and 2 Fc
  3. 1 Fab and 1 Fc
  4. 1 Fab and 2 Fc

Answer. (1) (2 Fab and 1 Fc)

  • Papain cleaves antibody to: 2 Fab and 1 Fc
  • Pepsin cleaves antibody to: 2 (Fab)’.

Question 13. True about an immunoglobulin: (NEET Pattern Based)

  1. IgG has max conc. in serum
  2. IgM has max conc. in serum
  3. IgA has max conc. in serum
  4. IgE has max conc. in serum

Answer. (1) (IgG has…)

  • Decreasing order of Serum level of various immunoglobulin is GAMDE: That is highest is IgG and lowest is IgE
  • Decreasing order of Serum level of IgG subtypes: IgG1 > 2 > 3 > 4

Question 14. Ig that helps in Opsonization: (NEET Pattern Based)

  1. IgA
  2. IgG
  3. IgD
  4. IgE

Answer. (2) (IgG)

  • Most important for opsonization- C3b and Fc (IgG)
  • Examples of opsonin molecules include:
    • Antibodies: IgG and IgM
    • Components of the complement system: C3b, C4b, and iC3b
    • Mannose-binding lectin (initiates the formation of C3b).

Question 15. The serum concentration of which of the following human IgG subclass is maximum:

  1. IgG1
  2. IgG2
  3. IgG3
  4. IgG4

Answer. (1) (IgG1)

  • Serum level of IgG subtypes: IgG1—65%, IgG2—23%, IgG3—8%, IgG4—4%

Question 16. Which IgG can cross placenta most efficiently?

  1. IgG1
  2. IgG2
  3. IgG3
  4. IgG4

Answer. (1) (IgG1)

Question 17. Which of the following immunoglobulins can cross placenta?

  1. IgA
  2. IgM
  3. IgG
  4. IgD

Answer. (3) (IgG)

  • IgG is secreted in placenta, breast
  • Among the four subclasses: IgG2- poorly crosses placenta.

Question 18. True about antibody:

  1. IgM is produced in primary response
  2. IgD protects mucosa
  3. IgE is main antibody in secondary response
  4. IgG is main antibody in secondary response
  5. IgA protects body surface

Answer. (1, 4, 5) (IgM is produced in primary response, IgG is main antibody in secondary response, IgA protects body surface)

Question 19. Which antibody deficiency causes recurrent infection by organisms with polysaccharide capsule?

  1. IgA
  2. IgG1
  3. IgG2
  4. IgM

Answer. (3) (IgG2)

IgG2 subclass is the predominant antibody raised against the polysaccharise capsular antigens and its deficiency is associated with recurrent pyogenic infection due pyogenic capsulated bacteria.

20. Which of the following antibodies shows anamnestic response?

  1. IgA
  2. IgM
  3. IgG
  4. IgD

Answer. (3) (IgG)

Anamnestic response indicates secondary immune response which may be non-specific and mediated by IgG.

Question 21. Of all the IgG subclasses smallest is:

  1. IgG 1
  2. IgG 2
  3. IgG 3
  4. IgG 4

Answer. (4) (IgG 4)

Question 22. Antibody present in antigen binding site of B-cells?

  1. IgG
  2. IgM
  3. lg A
  4. lg D
  5. lg E

Answer. (2, 4) (IgM, IgD)

Question 23. The valency of IgM:

  1. 1
  2. 3
  3. 5
  4. 10

Answer. (4) (10)

5 IgM molecules join to form IgM antibody, therefore has a valency of 10

Question 24. Which antibodies are found in Cryoglobulinemia?

  1. IgG
  2. IgM
  3. IgE
  4. IgA

Answer. (2) (IgM)

Cryoglobulins usually consist of IgM directed against the Fc region of IgG.

Question 25. Cold antibody is:

  1. IgA
  2. IgG
  3. IgE
  4. IgM

Answer. (4) (IgM)

Cold agglutinin disease is an hemolytic disease, where high concentration of IgM antibodies are present against RBCs.

Question 26. Activator of classical pathway of complement:

  1. IgA
  2. IgG
  3. IgM
  4. IgE

Answer. (3) (IgM)

  • Classical complement is activated by both IgG and IgM. However, IgM is a powerful activator than IgG.

Question 27. Pentameric antibody with a J chain is:

  1. IgA
  2. IgG
  3. IgM
  4. IgE

Answer. (3) (IgM)

  • IgM is pentameric having a valency of 10, the five molecules of IgM are joined together by J-chain.

Question 28. Which immunoglobulin acts as receptor on B-cell?

  1. IgG
  2. IgA
  3. IgM
  4. IgE

Answer. (3) (IgM)

  • Immunoglobulin acts as receptor on B-cell (i.e. surface immunoglobulin)- IgM and IgD

Question 29. In utero infection leads to raise of which immunoglobulin first?

  1. IgG
  2. IgA
  3. IgG
  4. IgM

Answer. (4) (IgM)

  • IgM is phylogenetically oldest immunoglobulin and the earliest to be synthesized by the fetus, beginning by about 20 weeks.

Question 30. Rheumatoid arthritis is best diagnosed by:

  1. Anticitrulline antibody
  2. IgG antibody
  3. IgA antibody
  4. IgM antibody

Answer. (1) > (4) (Anticitrulline antibody > IgM antibody)

  • Anticitrulline antibodies
  • Autoantibodies that are frequently detected in the blood of rheumatoid arthritis patients.
  • Research suggests that in the joints of patients with rheumatoid arthritis, proteins may be changed to citrulline as part of the process that leads to inflammation of the rheumatoid joint.
  • When the citrulline antibody is found in a patient’s blood, there is a 90-95% likelihood that the patient has rheumatoid arthritis.
  • Rheumatoid arthritis is also diagnosed by detecting RF (Rheumatoid factor)
  • RF is a IgM antibody directed against Fc portion of IgG antibody.
  • RF is detected by passive agglutination tests like:
  • Rose-Waaler test
  • Latex agglutination test.

Question 31. Which antibody is elevated in primary immune response?

  1. IgA
  2. IgM
  3. IgG
  4. IgE

Answer. (2) (IgM)

  • IgM: Elevated in primary immune response
  • IgG: Elevated in secondary immune response

Question 32. Which is the first antibody elevated in fetal life?

  1. IgA
  2. IgM
  3. IgG
  4. IgE

Answer. (2) (IgM)

  • IgM: First antibody is elevated in fetal life
  • IgG: Only antibody that crosses placenta.

Question 33. Intestinal immunity is due to which Ig?

  1. IgM
  2. IgG
  3. IgA
  4. IgE

Answer. (3) (IgA)

Question 34. Synthesis of an immunoglobulin in membrane-bound or secretory form is determined by:

  1. One turn to two turn joining rule
  2. Class switching
  3. Differential RNA processing
  4. Allelic exclusion

Answer. (3) (Differential…)

  • ‘Differential RNA processing of a common primary transcript determines whether the secreted or membrane form of an immunoglobulin will be produced’…….
  • Membrane-bound or secreted form of immunoglobulin:
  • Mature naive B-cells produce only membrane-bound antibody (IgD or IgM), whereas differentiated plasma cells produce secreted antibodies (IgA).
  • Membrane-bound or secreted form of immunoglobulin is synthesized by alternate RNA splicing.

Question 35. Immunoglobulin in Peyer’s patch is:

  1. IgM
  2. IgG
  3. IgA
  4. IgD

Answer. (3)

  • Peyer’s patches are composed of 30-40 lymphoid follicles present in intestinal submucosa
  • They are required for intestinal secretory immunoglobulin A responses which provides local or intestinal immunity or mucosal immunity.
  • Peyer’s patches also contain Intra epithelial CD8 lymphocyte containing TCR ϒδ receptors

Question 36. Immunoglobulin present in local secretions is:

  1. IgG
  2. IgA
  3. IgM
  4. IgD

Answer. (2) (IgA)

Question 37. The Ig which activates alternate complement pathway:

  1. IgG
  2. IgE
  3. IgA
  4. IgM

Answer. (3) (IgA)

Question 38. Immunoglobulin that is inactive by heating is:

  1. IgG
  2. IgA
  3. IgM
  4. IgE

Answer. (4) (IgE)

Only heat labile immunoglobulin is IgE

Question 39. Immunoglobulin that is elevated in helminthic infection:

  1. IgG
  2. IgA
  3. IgM
  4. IgE

Answer. (4) (IgE)

Helminthic infection is characterized by an increase of IgE antibodies.

Question 40. IgE is secreted by:

  1. Mast cell
  2. Basophil
  3. Eosinophils
  4. Plasma cells
  5. Neutrophils

Answer. (4) (Plasma…)

  • IgE, like other immunoglobulins is secreted by plasma cells.
  • IgE after secreting from plasma cell, gets bound to mast cell by Fc portion. When antigen comes and binds to fab region of IgE, it in turn stimulates mast cell and mast cell degranulation occurs. (Type I hypersensitivity reaction)

Question 41. Which precipitates at 50 to 60°C but redissolve on heating?

  1. Bence Jones proteins
  2. Heavy chain
  3. Both light and heavy chains

Answer. (1) (Bence Jones…)

  1. Bence-Jones Protein:
  2. Abnormal immunoglobulin found in urine
  3. Coagulates at 50°C, redissolves at 70°C
  4. Elevated in Multiple myeloma

Question 42. The technique given in the picture is used for:

  1. Synthesis of monoclonal antibodies
  2. Preparing cell lines for viral culture
  3. Synthesis of vaccine
  4. Process of genetic engineering

Answer. (1) (Synthesis of monoclonal antibodies)

Question 43. Widal test is an example of:

  1. Slide flocculation test
  2. Precipitation
  3. Agglutination
  4. Complement fixation

Answer. (3) (Agglutination)

Question 44. A 20-year-old male with history of fever and enlarged lymph nodes and sore throat was suspected to have infectious mono-nucleosis and was ordered a Paul Bunnel test. Which of the following is the principle of the test?

  1. Heterophile agglutination test
  2. Neutralization test
  3. Complement-mediated cell damage
  4. Agglutination reaction

Answer. (1) (Heterophile agg..)

  • Paul-Bunnell test is an examples of Heterophile agglutination test; done for infectious mononucleosis (caused by Epstein-Barr virus). Here, sheep red blood cell (RBC) antigens are used to detect cross-reacting antibodies in patient’s sera.

Question 45. Which one is the example of gel precipitation test?

  1. Immunoelectrophoresis
  2. VDRL
  3. WIDAL
  4. Coomb’s test
  5. Elek’s test

Answer. (1, 5) (immunoelectrophoresis, Elek’s test)

  • VDRL is a flocculation test and Widal and Coomb’s tests are agglutination tests.

Question 46. Type of Ag-Ab reaction seen in VDRL:

  1. Agglutination
  2. Passive agglutination
  3. Flocculation
  4. Gel precipitation

Answer. (3) (Flocculation)

Question 47. Nagler’s reaction is example of: (NEET Pattern Based)

  1. Precipitation
  2. CFT
  3. Agglutination
  4. Neutralization

Answer. (4) (Neutralization)

Naegler reaction is an alfa toxin anti alfa toxin neutralization test

Question 48. Wasserman test is:

  1. Agglutination test
  2. Precipitation test
  3. Neutralization test
  4. Complement fixation

Answer. (4) (Complement fixation)

Question 49. All of the following interaction occurs between antigen antibody reaction except:

  1. Ionic bond
  2. Covalent bond
  3. Hydrogen bond
  4. van der Waals forces

Answer. (2) (Covalent bond)

The antigen-antibody reaction is reversible and the antigen and antibody molecules are bound together by weaker bonds such as ionic bond, van der Waal’s forces and hydrogen bond rather than stronger bond like covalent bond

Question 50. Which are example of agglutination test?

  1. Widal test
  2. VDRL test
  3. Kahn test
  4. Ascoli’s test

Answer. (1) (Widal test)

  • Widal test is an agglutination test
  • VDRL: Slide flocculation test (Precipitation test)
  • Kahn test: Tube flocculation test (Precipitation test)
  • Ascoli’s thermo precipitation test: Ring precipitation test done for Anthrax antigen detection

Question 51. Which of the following acts as an opsonin?

  1. C3a
  2. C3b
  3. C5a
  4. LTB4

Answer. (2) (C3b)

  • Opsonins (like Fc of IgG and complement factors like C3b, C4b and ic3b) play a very important role in uptake of bacteria by binding to the specific molecules on the surface of bacteria thus facilitating the engulfment by the phagocyte (which bear the receptors for the opsonins).

Question 52. The following methods of diagnosis utilize labeled antibodies except:

  1. ELISA (Enzyme-Linked Immunosorbent Assay)
  2. Hemagglutination inhibition test
  3. Radioimmunoassay
  4. Immunofluorescence

Answer. (2) (Hemagglutination inhibition test)

  • Hemagglutination inhibition test is detected by inhibition of hemagglutination of anti RBC antibody present in patient’s serum with respective RBC antigen.
  • Methods of diagnosis utilizing labeled antibodies:
  • Labeled antibodies are used for:
    • Antibody detection: Labeled anti-human gamma globulin is used to detect human gamma globulin present in patient’s serum.
    • Antigen detection: Labeled specific antibodies are used to detect corresponding antigens from the sample.

Question 53. Heterophile agglutination is/are used in all test except:

  1. Widal test
  2. Weil-Felix reaction
  3. Paulbunnel test
  4. ELISA
  5. Cold agglutination test

Answer. (1, 4) (Widal, ELISA)

Question 54. Antigen-antibody reaction is seen maximum in:

  1. Excess antibody
  2. Excess antigen
  3. Antigen and antibody are equal
  4. Antigen and antibody are low

Answer. (3) (Antigen and antibody are equal)

  • Antigen-antibody reaction results, when a large lattice is formed, consist of alternate antigen and antibody molecules which occur in the zone of equivalence.

Question 55. Opsonization is done by

  1. C3a
  2. C3b
  3. C5a
  4. C5b

Answer. (2) (C3b)

Common examples of opsonin which mediate opsonization include Fc portion of IgG, C3b and C4b.

Question 56. Complement constitutes how much of total serum protein?

  1. 5%
  2. 10%
  3. 15%
  4. 20%

Answer. (1) (5%)

Question 57. Complement which lead to killing of organism and protects us?

  1. C2345
  2. C56789
  3. C34567
  4. C3456

Answer. (2) (C56789)
C56789 is known as membrane attack complex, causes microbial lysis.

Question 58. Complement formed in liver: (NEET Pattern Based)

  1. C2, C4
  2. C3, C6, C9
  3. C5, C8
  4. C1

Answer. (2) (C3, C6, C9)
Site of Complement synthesis: Liver: C3, C6, C9, GIT- C1, Macrophage- C2, C4,Spleen-C5, C8

Question 59. Which compliment binds with Fc portion of IgM in Classic pathway or which of the following complement components attaches to the crystallizable fragment of IgM?

  1. C1
  2. C2
  3. C3
  4. C4

Answer. (1) (C1)

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