INNATE IMMUNITY

1 Which of the following does not protect body surfaces:

A Skin.

B Mucus.

C Gastric acid.

D Salivary amylase

E Gut microflora.
Correct. The enzyme splits starch and is of importance for digestion but not for protection

2 Pattern recognition receptors (PRR) include:

A LPS.

B PAMPs.

C Lipoteichoic acid.

D Lectin-like molecules.

E Unmethylated CpG sequences.

Correct. Many PRR are lectin-like in that they recognize exposed microbial sugars

3 The mononuclear phagocyte system does not include:

A Monocytes.

B Kupffer cells.

C Kidney mesangial cells.

D Lymph node medullary macrophages.

E Endothelial cells.
Correct. Endothelial cells are not essentially phagocytic although they do contribute by the production of mediators
of the inflammatory process, particularly acute inflammation and were previously lumped together with the
mononuclear phagocyte system in what was known as the reticuloendothelial system (RES).

4 A polymorphonuclear neutrophil (PMN):

A Is a bone marrow stem cell.

B Is closely similar to a mast cell.

C Contains microbicidal cytoplasmic granules.

D Is not a professional phagocytic cell.

E Has granules which stain with eosin.

Correct. The granules contain a wide spectrum of microbicidal agents.
5 Which of the following is not produced following activation of the NADPH oxidase microbicidal pathway

A O2 –

B O2

C H2O2

D NO

E OH
Correct. NO is produced following the induction of nitric oxide synthase

6 Neutrophil defensins are:

A Anti-toxins.

B Oxygen-dependent.

C Enzymes.

D Glycolipids.

E Peptide antibiotics.
Correct. The defensins are peptide antibiotics present in the granules in extremely high concentration.

7 The TLR9 pattern recognition receptor recognises:

A CpG motifs.

B Gram +ve peptidoglycan.

C Mycobacterial lipoarabinomannan.

D Gram –ve LPS.

E dsRNA.
Correct. Toll-like receptor 9 recognition of these microbial dinucleotide sequences leads to activation of the NF B
transcription factor.

8 Complement component C3 is cleaved by:

A C3b

B C3bBb

C Factor B

D Factor D

E Factor H
Correct. This is the C3 convertase enzyme generated in the alternative complement pathway and is responsible for
splitting off the small peptide C3a leaving C3b as a residue.
9 The membrane attack complex consists of:

A OH.

B Colicins

C C3b3b,Bb

D C5b,6,7,8,9

E Properdin
Correct. These terminal components form a complex which inserts into the membrane to form a transmembrane ion
channel which leads to lysis of the cell.

10 C3b:

A Is chemotactic.

B Is an anaphylatoxin.

C Opsonizes bacteria.

D Directly injures bacteria.

E Is the inactive form of C3.

Correct. Bacteria coated with C3b adhere to C3b receptors on professional phagocytic cells

11 Acute inflammation characteristically involves:

A Constriction of arterioles.

B Capillary endothelial cell enlargement.

C Influx of macrophages.

D Influx of mast cells.

E Influx of neutrophils.
Correct. Neutrophils are chemotactically attracted to the site of inflammation by C5a and mast cell chemotactic
factors such as leukotriene B4

12 Lysozyme:

A Is a cytoplasmic organelle.

B Activates complement.

C Is a proteolytic enzyme.

D Splits peptidoglycan.

E Is released by mast cells.

Correct. Lysozyme splits the peptidoglycan of bacterial cell walls.

13 Which of the following is not an acute phase protein:

 A Serum amyloid P component.

B Chondroitin sulfate.

C C-reactive protein.

D Mannose binding lectin.

E Fibrinogen.
Correct. This is a cell matrix component.

14 Interferons:

A Are found only in mammalian species.

B Are divided into 5 main families.

C Induce enzyme synthesis in the target cell.

D Only affect infected cells.

E Are specific for individual viruses.

Correct. Derepression of genes in the target cell result in the synthesis of a protein kinase and an endonuclease

15 Natural killer (NK) cells do not:

A Respond to interferon.

B Contain perforin.

C Contain tumor necrosis factor (TNF).

D Kill only by damaging the target cell outer membrane.

E Contain serine proteases.

Correct. Perforin inserts into the target cell membrane thereby facilitating entry of TNF and granzymes into the
target cell.

16 Eosinophils do not:

A Stain with basic dyes.

B Contain a major basic protein.

C Contain peroxidase.

D Give a respiratory burst on activation.

E Have C3b receptors.

Correct. They do stain with acidic dyes.

17 Polymorphonuclear neutrophils attack bacteria:

A Exclusively by oxygen-dependent mechanisms.

B Exclusively by oxygen-independent mechanisms.

 C By phagocytosis.

D By secreting complement.

E By secreting interferon.
Correct. The ability to ingest bacteria and kill them is a major feature of these professional phagocytic cells. Loss of
neutrophils renders the host very susceptible to overwhelming infection

18 A complement component which is strongly chemotactic for neutrophils is:

A C9

B C5a

C C3

D C3b

E C5b
Correct. C5a is a powerful chemotactic agent and also an anaphylatoxin

19 Acute inflammation can be initiated by:

A Mast cell activation.

B Influx of neutrophils.

C An increase in vascular permeability.

D C3.

E Lysozyme.
Correct. Activation of mast cells releases chemotactic factors for neutrophils and also vasoactive mediators such as
histamine.

SPECIFIC ACQUIRED IMMUITY

1 The initial complement component that is bound by complement-fixing antibodies is:

A C1q

B C1s

C C3b

D C5a

E C9
Correct. The constant region of IgM and of IgGI, IgG2 and IgG3 antibodies binds C1q after the antibody has
complexed with antigen. This eventually leads to the generation of a C4b2b convertase which splits C3.

2 Several of the complement components are:

A Glycolipids

B Cytokines
 C Enzymes

D Hormones

E Antibodies
Correct. They act in a sequential proteolytic cascade which gives tremendous amplification of the response.

3 The classical and alternative pathways meet at complement component:

A C4

B C4b

C Factor D

D C5

E C3
Correct. Each pathway of complement activation produces a C3 convertase, either C4b2b (classical and lectin
pathways) or C3bBb (alternative pathway), which cleaves C3 into C3a and C3b.

4 Clonal selection occurs when antigen is encountered by:

A Neutrophils

B Mast cells

C T-cells

D Basophils

E Eosinophils
Correct. Both T-cells and B-cells possess antigen-specific receptors and clones of these lymphocytes will be selected
to proliferative when specific antigen is encountered.

5 Plasma cells:

A Have a thin layer of cytoplasm

B Are derived from T-cells

C Develop into B-cells

D Secrete large amounts of gamma interferon

E Have a highly developed rough endoplasmic reticulum

Correct. Plasma cells secrete large amounts of antibody and therefore require well developed ER in order to make
sufficient amounts of this protein.

6 Specific antibodies are readily detectable in serum following primary contact with antigen after:

A 10 min

B 1h

C 5–7 days
 D 3–5 weeks

E Only following a second contact with antigen

Correct. 5 days or more are required for B-cell proliferation, differentiation into plasma cells, and the secretion of a
large enough amount of antibody for it to be readily detected systemically.

7 A plasma cell secretes:

A Antibody of a single specificity related to that on the surface of the parent B-cell

B Antibody of two antigen specificities

C The antigen it recognizes

D Many different types of antibody

E Lysozyme
Correct. A single plasma cell secretes millions of molecules of antibody but they are all identical and will be related
to the single specificity of antibody used as the antigen receptor on the B-lymphocyte from which the plasma cell
was derived.

8 Adoptive transfer of acquired immune responsiveness involves the transfer of:

A Antibody

B Complement

C Phagocytes

D Lymphocytes

E Serum
Correct. Adoptive transfer experiments helped establish that immunological memory, one of the hallmarks of the
adaptive immune response, is a property of the small lymphocyte.

9 The main reason an experimental animal treated with X-rays can act as a living test tube for lymphocyte transfer
experiments is because:

A It is microbiologically sterile

B Complement components will be inactivated

C The host lymphocytes are destroyed or unable to divide

D Only non-dividing cells are affected

E The requirement for T-cell help is overcome

Correct. Lymphocytes are highly sensitive to radiation and if the host's lymphocytes are destroyed or unable to
divide following treatment with x-rays, then any immune response observed following lymphocyte transfer will be
of donor, not recipient, origin.

10 Immunological unresponsiveness to self antigens is called:

A Tolerance

B Tolerogen

C Memory
 D Acquired immunity

E ADCC
Correct. Tolerance is a specific immunological non-responsiveness. Whilst tolerance can be induced to any antigen,
the mechanism is thought to have evolved as a means of preventing the maturation of pathogenic self-reactive
lymphocytes.

11 Edward Jenner vaccinated against smallpox using:

A Killed smallpox virus

B A recombinant protein derived from smallpox

C An unrelated virus

D Toxoid

E Cowpox
Correct. The smooth unblemished skin of milkmaids gave Jenner the idea of using cowpox. The cowpox virus is
non-virulent in man but shares antigens with the related smallpox virus and is therefore able to elicit protection
against subsequent infection with smallpox.

12 Protective antibodies against infectious agents are often:

A Autoantibodies

B Neutralizing

C Toxoids

D Natural Killer

E Non-specific
Correct. They protect by neutralizing a function of the pathogen such as the harmful part of a toxin or a viral coat
protein which binds to a cell-surface viral receptor on the host cells.

13 Intracellular parasites within macrophages are killed more readily in the presence of:

A Antibody

B Kinins

C Properdin

D Gamma-interferon

E Anaphylatoxin
Correct. Gamma-interferon activates microbicidal mechanisms within the macrophage, thereby leading to the death
of intracellular parasites.

14 T cell surface receptors for antigen partly recognize:

A Cytokines

B MHC

C ADCC
 D Antibody

E IL-2
Correct. T-cells recognize processed antigen plus the major histocompatibility complex (MHC) molecules which act
as a marker to inform the T-cell that it is in contact with another cell.

15 An immune response against grass pollen often involves:

A Pathogen-associated molecular patterns

B Breakdown of self tolerance

C A hypersensitivity reaction

D Reaction against MHC

E Persistent infection by the pollen

Correct. Hypersensitivty to otherwise innocuous antigens can lead to tissue damage.

16 Secondary antibody responses are better because:

A They provide defense against unrelated antigens

B The antibody can be made by both T and B cells

C Complement-fixing antibodies are made

D They do not require T-cell help

E They are stronger and faster

17 Which cell type produces antibodies?:

A Macrophages

B T-lymphocytes

C NK

D Plasma cells

E Eosinophils
Correct. B-lymphocytes have antibody on their cell surface which acts as an antigen receptor. Upon activation they
differentiate into plasma cells which secrete large amounts of antibody.

18 Clonal selection occurs when a B-lymphocyte encounters:

A Cytokines

B Antigen

C T-lymphocytes

D Complement

E Chemotactic factors
Correct. Antigen selects the few B-lymphocytes, out of many millions, which have cell surface antibody which best
'fits' the antigen.

19 The secondary, but not the primary, immune response is based on:
 A Memory

B The bonus effect of multivalency

C Complement activation

D Mast cell degranulation

E Clonal selection
Correct. The clonal proliferation that occurs during a primary immune response produces both effector lymphocytes
and memory cells. These memory cells constitute an expanded population of specific lymphocytes which form the
basis of the secondary immune response.

20 Protection against microorganisms inside cells is provided by:

A T-cells

B Antibody

C C3b

D C1q

E The membrane attack complex

Correct. T-lymphocytes are specialized for recognizing peptides derived from intracellular infectious agents which
are exhibited on the surface of an infected cell together with MHC class I & II molecules.

ANTIBODIES
1 The basic Ig unit is composed of:

A 2 identical heavy and 2 identical light chains.

B 2 identical heavy and 2 different light chains.

C 2 different heavy and 2 identical light chains.

D 2 different heavy and 2 different light chains.

E Non-covalently bound polypeptide chains.

Correct.