Structure And Function Of Immune System Multiple Choice Question And Answers

Lymphoid Organ

Question 1. Nude mice can accept xenograft because it lacks:

1. T cell
2. B cell
3. Dendritic cell
4. Memory cell

Answer. (1) (T cell)

Nude mice are the mice that undergo thymectomy and therefore they lack T cells.

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Question 2. All are peripheral lymphoid organ except:

1. LN
2. Spleen
3. MALT
4. Thymus
5. Bone marrow

Answer. (4, 5) (Thymus, Bone marrow)

Lymphoid Organ:

• Central/Primary: Thymus and Bursa of fabricus (birds) / Bone Marrow (human)
• Peripheral/Secondary: Spleen, Lymph Node, MALT (GIT and Respiratory mucosa).

Question 3. T-cell dependent region in lymph node:

1. Cortex
2. Medulla
3. Paracortical area
4. Mantle layer

Answer. (3) (Paracortical area)

• Lymph node 
  • T-cell area- Paracortical area
  • B-cell area- Cortex and medulla
• Spleen
  • T-cell area- Periarteolar lymphoid sheath
  • B-cell area- marginal zone

Question 4. Antibody-dependent killing:

1. NK cell
2. NK cell only
3. Macrophage
4. NK cell, neutrophils & macrophage

Answer. (4) (NK cell, neutrophils & macrophage)

• Antibody-dependent killing is called as ADCC (antibody-dependent cell-mediated cytotoxicity) which involves killing of the virus-infected or tumor cells through antibody-mediated mechanisms involving cells such as NK cells, macrophages, neutrophils or eosinophils.

Question 5. γδ T cell is associated with?

1. CD4
2. CD5
3. Cd8
4. First-line defense against bacterial peptides

Answer. (4) (First-line defense against bacterial peptides)

• γδ T cells represent a small subset of T cells (5%) that possess a distinct TCR which lack both CD4 and CD8 molecules.
• They differ from the conventional αβ T cells as- they do not require antigen processing and MHC presentation of peptides
• They are part of innate immunity as the first line of defense as they exhibit limited diversity for the peptide and lipid antigens
• They are usually found in the gut mucosa, within a population of lymphocytes known as IELs

Question 6. Innate immunity active against viral cells:

1. Cytotoxic-T cell
2. B cell
3. NK cells
4. Memory B-cell

Answer. (3) (NK cells)

Question 7. T-cell and B cell share many of the receptor but which one is specific only for B-Cell?

1. Sheep RBC
2. Concavallin
3. EAC rosette
4. Maturation-Thymus

Answer. (3) (EAC rosette)

• EAC rosette is specific for B cell. Whereas sheep RBC rosette is a feature of T cell.
• T cell maturation takes place in thymus
• T cells undergo blast transformation when exposed to concovalin.

Question 8. Which is not an example of antigen-presenting cells (APC)?

1. M cells
2. Thymocytes
3. Langerhan cells
4. Macrophages

Answer. (2) (Thymocytes)

Thymocytes are the T cells present in thymus, and T cells NEVER act as APC; in fact APCs present the antigen to T cells.

Question 9. True regarding thymus is:

1. Mature thymocytes express CD 4 and CD 8
2. Thymocytes whose T-cell receptor bind with high affinity to self-antigens and MHC
3. Complexes are clonally deleted
4. Mature thymocytes express surface IgM and IgD
5. CD 4 and CD 8 double-positive cells are completely eliminated by a process of negative selection

Answer. (2) (Thymocytes whose T-cell receptor bind with high affinity to self-antigens and MHC)

CD 4 and CD 8 double positive (DP) T-cells are not eliminated completely. They have three fates:

Positive selection: The 5% of DP T-cells, whose αβ receptors are capable of recognizing their MHC molecules are positively selecteThis results in MHC restriction.

• Death by neglect: Majority of DP cells (95%) fail positive selection because they do not specifically recognize their MHC molecules.
• Negative selection: The survived cells that undergo positive selection (5%) are MHC restricteHowever, some of these surviving cells (2–5%) react to the self antigens and therefore, they are selected to be killed by apoptosis and removed (negatively selection).
• The remaining DP T-cells (2–5%) having αβ type TCR selectively loose either CD4 or CD8 and become single positive mature T-cells
• About Other options:
• Mature thymocytes are single positive; i.they express either CD 4 or CD 8; but never both.
• Mature B cells (not thymocytes) express surface IgM and IgD.

Question 10. Which of the following features is not shared between ‘T-cells’ and ‘B-cells’?

1. Positive selection during development
2. Class I MHC expression
3. Antigen-specific receptors
4. All of the above

Answer. (1) (Positive selection during development)

• During embryonic life, for deletion of self-reacting clones, T-cells undergo positive selection followed by negative selection whereas B-cells undergo only negative selection.
  About Other Options
• Class I MHC molecules are expressed on all nucleated cells. Both T and B-cells being nucleated, so they express class I MHWhereas class II MHC are expressed on all
  APCs (so present on B-cells but not on T-cells).
• Antigen-specific receptor:
• Antigen-specific receptor on T-cell- TCR (T-cell receptor)
  • Antigen-specific receptor in B-cell- BCR (B-cell receptor), i.surface immunoglobulins like IgM and IgD

Question 11. Cell-mediated immunity is by virtue of:

1. Helper T-cell
2. Suppressor T-cells
3. Cytotoxic T-cells
4. All of the above

Answer. (4) (All of the above)

• Cell-mediated immunity refers to specific immune response mediated by effector T-cells (both T-helper, Cytotoxic T-cells and Suppressor T-cells) generated against an antigen.

Question 12. Most potent stimulator of Naive T-cells:

1. Mature dendritic cells
2. Follicular dendritic cells
3. Macrophages
4. B-cells

Answer. (1) (Mature dendritic cells)

• Mature dendtritic cells possess higher level of MHC-II & costimulatory B-7 molecules, hence they are the most potent stimulator of T-cells.

Question 13. All of the following are functions of CD4 helper cells, except:

1. Immunogenic memory
2. Produce immunoglobulins
3. Activate macrophages
4. Activate cytotoxic cells

Answer. (2) (Produce immunoglobulins)

• When resting Th cell binds to a MHC class II- antigen complex on APC, that initiates the activation of Th cell.
• The activated Th cell divides many times to produce effector Th cell and memory Th cell.
• Effector Th cell further divides to Th 1 and 2 and perform the following actions:
  • Activation and proliferation of Tc cell
  • Regulate monocyte-macrophage system
  • Helps in activation of B-cell to produce plasma cell that secretes immunoglobulins,(but CD4 TH cells never produce immunoglobulins).

Question 14. NK cells marker is/are:

1. CD 4
2. CD 1
3. CD 16
4. CD 56
5. CD 20

Answer. (3, 4) (CD16, CD 56)..

Question 15. True statement/s regarding NK cells are:

1. Also called large granular lymphocyte
2. Can kill virus-infected cell
3. Forms first line of defence
4. Can kill tumour cell
5. No role in cell-mediated immunity

Answer. (1, 2, 3, 4) (Also called large granular lymphocyte, Cankill virus-infected cell, Formsfirst line of defence, Cankill tumour cell)

NK cell is an important component of CMI along with TC cell and ADCC.

Question 16. A New agent was developed to increase the recognition of foreign antigens by Antigen-presenting cells. True regarding the physiological aspects of APCs:

1. Antigen is presented via MHC–I complexes
2. APCs are required before a response to viruses are generated
3. Direct antibody stimulation still requires APC’s
4. Antigen processed by APC are recognized by CD 4+ T Cells

Answer. (4) (Antigen processed by APC are recognized by CD 4+ T Cells)

Exogenous (foreign) antigens are first phagocytosed by APCs, then they are processed by APCs and presented on the surface of APCs along with MHC II to be recognized by CD 4+T Cells.

Question 17. Macrophages are major source of:

1. IL-1
2. IL-5
3. IL-7
4. IFN-Y

Answer. (1) (IL-1)

Macrophage produces various secretory molecules:

• Enzymes- Lysozyme, proteases, elastases, collagenases, plasminogen activator,
• Cytokines-IL-1, 8, 12, TNF-α, TGF-β, prostaglandins
• Platelet-derived growth factor (PDGF), Platelet activated factor (PAF),
• CSF (colony-stimulating factor), ACE (Angiotensin Converting Enzyme)
• Complements- C2, C4
• Reactive O2 species- H2O2, NO, OH

Question 18. The role played by MHC 1 and 2 is to:

1. Stimulate interleukin production
2. Immunoglobulin class switch over
3. Transduce the signal to T-cell following antigen binding
4. Presenting the antigen for recognition by T-cell antigen binding receptors

Answer. (4) (Presenting the antigen for recognition by T-cell antigen binding receptors)

The major function of MHC I and II molecule is to present the peptide antigen to the T-cell receptors of T-cells.

• MHC I molecule presents the peptide antigen to Tc cells.
• MHC II molecule presents the peptide antigen to T helper cells.

Question 19. MHC molecules are coded by:

1. Chromosome-6
2. Chromosome-7
3. Chromosome-8
4. Chromosome-9

Answer. (1) (Chromosome-6)

• MHC genes are located on short arm of Chromosome-6

Question 20. Gene coding for MHC-I include: (NEET Pattern Based)

1. A, B, C
2. DR
3. DP
4. DQ

Answer. (1) (A, B, C)

• Class I MHC gene includes- A, B, C
• Class II MHC gene includes DP, DQ, DR
• Class III MHC gene includes- genes for certain complement factors, Heat shock protein, TNF

Question 21. Peptide binding site on MHC-I for presenting processed antigen to CD8 T-cells is formed by:

1. Junction of proximal domains made-up of Alpha subunit
2. Junction of distal domains made-up of Alpha subunit
3. Junction of proximal domains made-up of beta subunit
4. Junction of distal Proximal domains made-up of beta subunit

Answer. (2) (Junction of distal domains made-up of Alpha subunit )

• Binding sites of MHC I & II molecules:
• The antigen binding site:
  • For MHCI- groove between α1 and α2
  • For MHCII- groove between α1 and b1
  • Bothe these grooves lie in the distal part of MHC molecules
• The co-receptor binding site:
  • For MHCI- α3 domain binds to CD8 of Tc cell
  • For MHCII- β2 domain binds to CD4 of TH cell
  • Bothe these grooves lie in the proximal part of MHC molecules.

Question 22. MHC II are presented on:

1. Macrophages
2. Dendritic cells
3. Lymphocytes
4. Eosinophils
5. Platelet

Answer. (1, 2) (Macrophages, Dendritic cells)

• MHC I molecules are present on all nucleated cells (RBC and platelets are non-nucleated, so MHC I molecules are not found)
• MHC II molecules are more restricted in distribution, present on macrophages, dendritic cells and B-cells.

Question 23. MHC III codes for:

1. Complements
2. Interleukin
3. Prostaglandins
4. Interferon

Answer. (1) (Complements)

• MHC III codes for Complements C2, C4, C3 convertase, factor B, properdin, HSP and TNF.

Question 24. Th1 cell produces:(JIPMER December 2016 pattern)

1. IL1
2. IL 2
3. IL3
4. IL4

Answer. (2) (IL 2)

• Th1 cell produce IL2, IFN- γ, and TNF- β whereas Th2 cells produce IL4,5,6 and 10.

Question 25. IL–2 produced by:

1. T-cells
2. B-cells
3. Monocytes
4. Neutrophils

Answer. (1) (T-cells)

Question 26. Most important chemical mediators of gram-negative septicemia:

1. IL-2B
2. TNF-α
3. TGB-β
4. IL-20

Answer. (2)(TNF-α)

• Bacterial septic shock apparently develops because bacterial cell-wall endotoxins stimulate macrophages to overproduce IL-1 and TNF-α to higher levels that cause septic shock
• TNFα is the principle cytokines involved in gram-negative septic shock.
• TNFα is primarily responsible for Shwartzman reaction, in which repeated injection of LPS (obtained from gram-negative cell wall) into a solid tissue leads to hemorrhagic infarction.