Lec 1-11 - Coico Q's

Question 1

Which of the following generally does not apply to bone

marrow (a primary lymphoid organ) but does apply to

secondary lymphoid organs?

A) cellular proliferation

B) differentiation of lymphocytes

C) cellular interaction

D) antigen-dependent response

Answer 1

D. Cellular proliferation, differentiation of lymphocytes, and

cellular interactions can take place in bone marrow. However,

antigen-dependent responses occur in the secondary lymphoid

organs, such as the spleen and lymph nodes.

Question 2

2. Which of the following is involved in recognition of

intracellular pathogens in innate immune cells?

A) Toll-like receptors (TLRs)

B) antibody

C) NOD-like receptors (NLRs)

D) complement

Answer 2

C. The NLRs are a group of cytosolic innate receptors that

recognize microbes that infect cells. Once ligated, they initiate a

set of cellular activities that facilitate inflammatory responses and

other host defense mechanisms.

Question 3

3. Which of the following is a correct statement about NK

cells?

A) They proliferate in response to antigen.

B) They kill target cells by phagocytosis and intracellular

digestion.

C) They are a subset of polymorphonuclear cells.

D) They kill target cells in an extracellular fashion.

E) They are particularly effective against certain bacteria.

Answer 3

D. NK cells are large granular lymphocytes. Their number does

not increase in response to antigen. Their killing is extracellular,

and their target cells are virus-infected cells or tumor cells. They

are not particularly effective against bacterial cells.

Question 4

Mature dendritic cells are capable of which of the

following?

A) activating naïve antigen-specific T cells

B) removing red blood cells

C) producing bradykinin

D) extracellular killing of target cells

Answer 4

A. When immature dendritic cells are activated following their

engulfment of pathogens (phagocytosis), they mature and become

more efficient at antigen presentation and, in fact, can activate

antigen-specific naïve T cells.

Question 5

Killer-cell inhibitory receptors (KIRs) expressed by NK

cells bind to which of the following to prevent killing of

normal cells:

A) complement receptors

B) MHC class I

C) immunoglobulin

D) Toll-like receptors

Answer 5

B. NK cells express KIRs, which allow them to bind to MHC

class I molecules expressed on all nucleated cells that would otherwise

be targets for killing when infected with certain viruses that

downregulate MHC class I expression.

Question 6

Which of the following applies uniquely with respect to

B cells found in secondary lymphoid organs?

A) present as precursor B cells

B) express only IgM

C) terminally differentiate into plasma cells

D) undergo proliferation

Answer 6

C. Terminal differentiation of B cells into plasma cells occurs only in secondary lymphoid organs, such as the spleen and lymph

nodes. Circulation of lymphocytes and cellular proliferation (but not antigen-dependent responses of terminal differentiation) also take place in the primary lymphoid organs, such as the bursa of Fabricius, or its equivalent, and the thymus. The bone marrow is the site where pluripotential stem cells differentiate into precursor

B and T cells.

Question 7

Which of the following sequence correctly describes

lymphocyte migration from lymph nodes to blood?

A) postcapillary venules, efferent lymphatic vessels, thoracic

duct, vena cava, heart

B) postcapillary venules, afferent lymphatic vessels, thoracic

duct, vena cava, heart

C) postcapillary venules, efferent lymphatic vessels,

vena cava, thoracic duct, heart

D) postcapillary venules, afferent lymphatic vessels,

vena cava, thoracic duct, heart

Answer 7

A. Blood lymphocytes enter the lymph nodes through the afferent

lymphatic vessel via postcapillary venules. They leave the

lymph nodes through efferent lymphatic vessels, which eventually

converge in the thoracic duct. This duct empties into the vena cava,

the vessel that returns the blood to the heart, thus providing for the

continual recirculation of lymphocytes.

Question 8

Clonal expansion of which of the following cells occurs

following their direct interaction with the antigen for

which they are specific?

A) macrophages

B) basophils

C) Bcells

D) T cells

E) mast cells

Answer 8

C. B cells bind directly to antigens recognized by their B-cell

receptors (BCRs). In contrast, T cells expressing T-cell receptors

(TCRs) are incapable of binding to antigen unless they are presented

by antigen-presenting cells in the context of MHC class I

(cytotoxic T cells) or MHC class II (helper T cells).

Question 9

A large glycoprotein has been enzymatically digested in

the laboratory to yield a mixture of glycopeptides ranging

in size from 4 to 6 amino acids in length. Which of the

following would be expected if the peptide mixture were

administered to an experimental animal together with an

adjuvant such as complete Freund’s adjuvant?

A) peptide-specific antibodies would be generated using

the peptide mixture alone

B) carbohydrate-specific antibodies would be generated

only if an adjuvant were administered with the peptide

mixture

C) peptide-specific antibodies would be generated only

if they were injected with a separate uncoupled

protein carrier

D) peptide-specific and carbohydrate-specific antibody

and T-cell responses would be generated using the

peptide mixture alone

E) there would be neither a humoral nor cell-mediated

immune response to the peptides in the mixture

Answer 9

E. Peptides ranging from 4 to 6 amino acids in length are low

molecular weight molecules that are unable to generate antibody

responses or T-cell responses due to their small size. If these peptides

were coupled or bound to a protein carrier, they could be

immunogenic. T cells do not generate T-cell responses to carbohydrates;

therefore D is incorrect.

Question 10

The protection against smallpox virus infection afforded

by prior infection with cowpox virus represents

A) antigenic specificity

B) antigenic cross-reactivity

C) enhanced viral uptake by macrophages

D) innate immunity

E) passive protection

Answer 10

B. The protection against smallpox provided by prior infection

with cowpox is an example of antigenic cross-reactivity. Immunization

with cowpox leads to the production of antibodies capable

of reacting with smallpox because the two viruses share several

identical, or structurally similar, determinants.

Question 11

Haptens

A) require carrier molecules to be immunogenic

B) react with specific antibodies when homologous

carriers are not employed

C) interact with specific antibody even if the hapten is

monovalent

D) cannot stimulate secondary antibody responses

without carriers

E) all of the above

Answer 11

E. Haptens are substances, usually of low molecular weight and

univalent that by themselves cannot induce immune responses

(primary or secondary), but can do so if conjugated to high molecular

weight carriers. The haptens can and do interact with the

induced antibodies without it being necessary that they be conjugated

to the carrier.

Question 12

An adjuvant is a substance that

A) increases the size of the immunogen

B) enhances the immunogenicity of haptens

C) increases the chemical complexity of the immunogen

D) enhances the immune response to the immunogen

E) enhances immunologic cross-reactivity

Answer 12

D. An immunologic adjuvant is a substance that, when mixed

with an immunogen, enhances the immune response against that

immunogen by mechanisms that depend upon the specific adjuvant

used (e.g., enhanced antigen presentation, delayed release of

antigen, etc.). It does not increase its size or chemical complexity.

In addition, it does not enhance the immune response against a

hapten, which requires its conjugation to an immunogenic carrier

to induce a response against the hapten. The adjuvant has no relevance

to possible toxicity of an immunogen

Question 13

A polyclonal antibody made against a large protein

antigen reacts with it even when it is denatured by disrupting

all disulfide bonds. Another monoclonal antibody

against the antigen fails to react when it is similarly

denatured. The most likely explanation can be stated as

follows:

A) The polyclonal antibody contains antibodies specific

for several non-conformational epitopes expressed by

the antigen.

B) The monoclonal antibody recognizes both conformational

and non-conformational epitopes.

C) The monoclonal antibody is specific for di sulfide

bonds.

D) The polyclonal antibody has a higher affinity for the

antigen.

Answer 13

A. Polyclonal antibodies are a mixture of antibodies produced

by multiple B-cell clones with B-cell receptors that react with

specific antigenic epitopes expressed by the antigen. Antibodies

can recognize single epitopes formed by primary sequence structures,

or secondary, tertiary, and quaternary conformational structures.

Denaturing a protein by disrupting disulfide bonds generally

destroys conformational determinants. Therefore it is likely that

the polyclonal antibody reacts with non-conformational epitopes

present on both native and denatured antigen, while the monoclonal

antibody reacts with a conformational determinant only on

the native antigen.

Question 14

Functional properties of immunoglobulins such as

binding to Fc receptors are associated with

A) light chains

B) J chains

C) disulfide bonds

D) heavy chains

E) variable regions

Answer 14

D. The C-terminal end of the constant region of the heavy

contains the domains that are associated with biologic activity of

immunoglobulins.

Question 15

The idiotype of an antibody molecule is determined by

the amino acid sequence of the

A) constant region of the light chain

B) variable region of the light chain

C) constant region of the heavy chain

D) constant regions of the heavy and light chains

E) variable regions of the heavy and light chains

Answer 15

E. The idiotype is the antigenic determinant of an Ig molecule,

which involves its antigen-combining site, which in turn consists

of contributions from the variable regions of both L and H chains.

Question 16

Which of the following would generate a polyclonal

rabbit antiserum specific for human γ heavy-chain, κ

chain, λ chain, and Fc regions of Ig:

A) Bench Jones proteins

B) pooled IgG

C) pepsin digested IgG

D) purified Fab

E) purified F(ab′ )2

Answer 16

B. Only pooled IgG containing the a mixture of IgG molecules

each expressing the γ heavy chain (thus the Fc region) and either

the κ or λ light chains would generate an antiserum to each of these

immunoglobulin components. None of the other answer choices

would stimulate antibodies to all of these components. Bench

Jones proteins are dimmers of light chains found in the urine of

patients with multiple myeloma. Pepsin treatment of IgG results

in the digestion of the Fc region. Purified Fab and F(ab′)2 fragments

lack the γ heavy chain (thus the Fc region).

Question 17

A polyclonal antiserum raised against pooled human

IgA will react with

A) human IgM

B) κ light chains

C) human IgG

D) J chain

E) all of the above

Answer 17

E. All are correct statements. Antibody to IgA will have antibody

specific for κ and λ light chains, which, of course, will react

with IgG and IgM, both of which have κ and λ chains. Antibody

will also be present against J chain if the IgA used for immunization

was dimeric.

Question 18

An individual was found to be heterzygous for IgG1

allotypes 3 and 12. The different possible IgG1 antibodies

produced by this individual will never have

A) two heavy chains of allotype 12

B) two light chains of either κ or λ

C) two heavy chains of allotype 3

D) two heavy chains, one of allotype 3 and one of

allotype 12

Answer 18

D. In any immunoglobulin produced by a single cell, the two

heavy chains and the two light chains are identical. Therefore, any

antibody molecule in this individual would have either allotype 3

heavy chains or allotype 12 heavy chains, not a mixture. Similarly,

the antibody would have either two κ or two λ chains.

Question 19

Papain digestion of an IgG preparation of antibody specific

for the antigen hen egg albumin (HEA) will

A) lose its antigen specificity

B) precipitate with HEA

C) lose all interchain disulfide bonds

D) produce two Fab molecules and one Fc fragment

E) none of the above

Answer 19

D. Papain digestion cleaves the IgG molecules above the hinge

region, generating two Fab molecules and an Fc fragment. The Fab

fragments can still bind to HEA, but since they are not held

together by disulfide binds, they cannot precipitate the antigen.

This contrasts with the effects of pepsin treatment of IgG, which

cleaves below the hinge region, leaving intact one divalent F(ab′)2

molecule capable of precipitating the antigen. Fragments of pepsintreated

HEA-specific antibody will have the same affinity for the

antigen as the original Fab regions of the antibody, since the CDR

regions of the molecules are preserved.

Question 20

If an individual who is highly allergic to cat dander is

exposed to a pet cat in a friend’s house, which class of

immunoglobulin would most likely be found to be elevated

soon after this exposure?

A) IgA

B) IgE

C) IgG

D) IgM

E) IgD

Answer 20

B. The major class of immunoglobulin produced in response to

allergens is IgE.

Question 21

Which of the following immunoglobulins can activate

complement as a single molecule when bound to an

antigen?

A) IgA

B) IgE

C) IgG

D) IgM

E) IgD

Answer 21

D. Only IgM can activate or fix complement when a single

molecule is bound to antigen. This is due to the pentameric form

of this immunoglobulin class

Question 22

The relative level of pathogen-specific IgM antibodies

can be of diagnostic significance because

A) IgM is easier to detect than the other isotypes

B) viral infection often results in very high IgM

responses

C) IgM antibodies are more often protective against

reinfections than are the other isotypes

D) relatively high levels of IgM often correlate with a

first and recent exposure to the inducing agent

Answer 22

D. Only the last statement is correct. Relatively high levels of

IgM often correlate with first recent exposure to an inducing agent,

since IgM is the first isotype synthesized in response to an immunogen.

All other statements are not true.

Question 23

Primary and secondary antibody responses differ in

A) the predominant isotype generated

B) the number of lymphocytes responding to antigen

C) the time it takes for measurable amounts of antibodies

to appear in the serum

D) the biologic functions manifested by the Ig isotypes

produced

E) all of the above

Answer 23

E

Question 24

In an individual predisposed to allergic responses,

which of the following statement best describes the

outcome of his/her exposure to an allergen:

A) Within weeks of exposure, large amounts of

allergen-specific IgM will be present in the

serum.

B) Clinical reactions such as wheezing and sneezing

may soon manifest soon after exposure due to the

presence of allergen-specific IgE that is retained

by cells such as mast cells that express Fcε

receptors.

C) IgG responses will control the allergic responses by

suppressing the ability of activated allergen-specific

B cells to undergo IgE class switching.

D) Circulating allergen-specific IgE will initiate an

inflammatory response that may manifest as runny,

itchy eyes.

E) all of the above

Answer 24

B. Individuals predisposed to allergic responses produce large

amounts of IgE antibodies with specificity for allergens. Once

produced, the IgE becomes bound for long periods of time (weeksto-

months) to various cells that express high affinity Fcε receptors
(e. g., tissue mast cells). When the allergens interact with the Fab

portions of these IgE molecules, cross-linking the cell-bound antibodies,

this results in destabilization of the cell membrane followed

by degranulization of the cell. Finally, this results in the

release of potent pharmacologically active agents that cause the

clinical symptom associated with allergies.

Question 25

Which of the following is required to ensure the integrity

and stability of immunoglobulin molecules but is not

associated with interactions between antigens and

antibodies?

A) covalent bonds

B) van der Waals forces

C) hydrophobic forces

D) electrostatic forces

E) a very close fit between an epitope and the antibody

Answer 25

A. No covalent bonds are involved in the interaction between

antibody and antigen. The binding forces are relatively weak and

include van der Waals forces, hydrophobic forces, and electrostatic

forces. A very

Question 26

Which of the following statements regarding B cell

hybridomas is true?

A) They are immortal cell lines that produce antibodies

with more than one specificity.

B) They are derived from B cells that are first cloned and

grown in cell culture for short periods.

C) They contain two nuclei.

D) They are derived by fusing B cells with malignant

plasma cells that are unable to secrete

immunoglobulin

Answer 26

D. The method used to generate B cell hybridomas employs the

fusion of B cells (e.g., from the spleen and lymph nodes) harvested

from immunized mice with a selected population of malignant

plasma cells unable to secrete immunoglobulin. The process yields

a monoclonal antibody secreted by cells that contain nuclei from

the B cell and plasma cell that have fused.

Question 27

The DNA for an H chain in a B-cell making IgG2 antibody

for diphtheria toxoid has the following structure:

5′ -V17 D5 J2 Cγ2 –Cγ4 –Cε –Cα2 –3′ . How many individual

rearrangements were required to go from the embryonic

DNA to this B-cell DNA?

A) 1

B) 2

C) 3

D) 4

E) none

Answer 27

C. Three DNA rearrangements are required. First, D5→J2 rearrangement

occurs, followed by V17→D5J2. This permits synthesis

of IgM and IgD molecules using V17D5J2. The third rearrangement

is the class switch of V17D5J2CμCδ to V17D5J2Cγ2, leading to the

synthesis of IgG2 molecules

Question 28

If you had 40V, 25D, and 6J regions able to code for an

H chain and 40V and 5J-region genes able to code for

an L chain, you could have a maximum repertoire of:

A) 76 + 45 = 121 antibody specificities

B) 76 x 45 = 3,420 specificities

C) (40 x 5) + (40 x 25 x 6) = 6200 specificities

D) (40 x 5) x (40 x 25 x 6) = 1,200,000 specificities

E) more than 1,200,000 specificities

Answer 28

E. While 1,200,000 would be the product of all possible combinations

of genes, many more antibody specificities are likely to

be generated as a result of junctional diversity at the sites of V, D,

and J gene segment joining (caused by imprecise joining, deletions,

and nucleotide insertions) and somatic hypermutation.

Question 29

The antigen specificity of a particular B cell:

A) is induced by interaction with antigen

B) is determined only by the L-chain sequence

C) is determined by H+ L-chain variable-region

sequences

D) changes after isotype switching

E) is determined by the H-chain constant region

Answer 29

C. The antigenic specificity is determined by the sequences and

hence the structure formed by the combination of H- and L-chain

variable regions

Question 30

If you could analyze at the molecular level a plasma cell

making IgA antibody, you would find all of the following

except :

A) a DNA sequence for V, D, and J genes translocated

near the Cα DNA exon

B) mRNA specific for either κ or λ L chains

C) mRNA specific for J chains

D) mRNA specific for μ chains

E) a DNA sequence coding for the T-cell receptor for

antigen

Answer 30

D. As a consequence of the rearrangement of the VDJ to Cα in

the IgA-producing cell, the Cμ gene will have been deleted. The

other DNA sequences and mRNA species will be found in the cell.

Question 31

The ability of a single B cell to express both IgM and

IgD molecules on its surface at the same time is made

possible by:

A) allelic exclusion

B) isotype switching

C) simultaneous recognition of two distinct antigens

D) alternative RNA splicing

E) use of genes from both parental chromosomes

Answer 31

D. The simultaneous synthesis of IgM and IgD is made possible

by the alternative splicing of the primary RNA transcript 5′–VDJ–

Cμ–Cδ–3′ to give either VDJCμ or VDJCδ mRNAs.

Question 32

Which of the following statements concerning the organization

of Ig genes is correct?

A) V and J regions of embryonic DNA have already

undergone a rearrangement.

B) Light-chain genes undergo further rearrangement

after surface IgM is expressed.

C) VH gene segments can rearrange with Jκ or Jλ gene

segments.

D) The VDJ segments coding for an Ig VH region may

associate with different H-chain constant-region

genes.

E) After VDJ joining has occurred, a further rearrangement

is required to bring the VDJ unit next to the Cμ

gene.

Answer 32

D. The association of VDJ segments coding for an Ig VH region

with different H-chain constant-region genes is the basis of isotype

or class switching.

Question 33

Which of the following does not contribute to the antigenbinding

site diversity of B-cell antigen receptors?

A) multiple V genes in the germline

B) random assortment of L and H chains

C) imprecise recombination of V and J, or V, D, and

J segments

D) inheritance of multiple C-region genes

E) somatic hypermutation

Answer 33

D. The presence of multiple CH-region genes does provide the

basis for functional diversity of Ig molecules but does not contribute

to the diversity of antigen-specific receptors.

Question 34

Which of the following statements regarding a B cell

expressing both IgM and IgD on its membrane is

incorrect?

A) The L chains of the IgM and IgD have identical

amino acid sequences.

B) The constant parts of the H chains of the IgM and

IgD have different amino acid sequences.

C) The IgM and IgD have different antigenic

specificities.

D) If it is triggered by antigen and T-cell signals to proliferate

and differentiate, it may differentiate into a

plasma cell that may secrete IgG, IgE, or IgA

antibodies.

E) The IgM on the surface will have either κ or λ L

chains, but not both.

Answer 34

C. The IgM and IgD expressed on a single B cell use the same

H- and L-chain V(D)J gene units and therefore have the same

antigenic specificity.

Question 35

Which of the following plays a role in changing the

antigen binding site of a B cell after antigenic

stimulation?

A) junctional diversity

B) combinatorial diversity

C) germline diversity

D) somatic hypermutation

E) differential splicing of primary RNA transcripts

Answer 35

D. Of the mechanisms described for generating diversity of Ig

molecules, only somatic hypermutation affects the antigen binding

site after antigen stimulation

Question 36

The earliest stages of B-cell differentiation:

A) occur in the embryonic thymus

B) require the presence of antigen

C) involve rearrangement of κ -chain gene segments

D) involve rearrangement of surrogate light-chain gene

segments

E) involve rearrangement of heavy-chain gene segments

Answer 36

E.
The earliest events in B-cell differentiation take place in fetal

liver and bone marrow in the adult and involve rearrangement of

heavy-chain V, D, and J gene segments.

Question 37

Which of the following is expressed on the surface of the

mature B lymphocyte?

A) CD40

B) MHC class II molecules

C) CD32

D) IgM and IgD

E) all of the above

Answer 37

E.

All the molecules are expressed on the surface of the mature

B cell.

Question 38

Which of the following statements is incorrect?

A) Antibodies in a secondary immune response generally

have a higher affinity for antigen than antibodies

formed in a primary response.

B) Somatic hypermutation of variable-region genes may

contribute to changes in antibody affinity observed

during secondary responses.

C) Synthesis of antibody in a primary response to a

thymus-dependent antigen occurs predominantly in

the blood.

D) Isotype switching occurs in the presence of antigen.

E) Predominantly IgM antibody is produced in the

primary response

Answer 38

C.

Antibody synthesis in the primary response to TD antigens

occurs predominantly in secondary lymphoid organs—the spleen

lymph nodes, and mucosa-associated lymphoid tissue.

Question 39

Immature B lymphocytes:

A) have rearranged only D and J gene segments

B) are progenitors of T as well as B lymphocytes

C) express both IgM and IgD on their surfaces

D) are at a stage of development where contact with

antigen may lead to receptor editing and deletion

E) must go through the thymus to mature

Answer 39

D.

In immature B cells, which express only IgM, contact with

cell-bound self-antigen initiates receptor editing—secondary rearrangement

of light-chain genes. If receptor editing results in a

receptor specific for self, the B cell is deleted.

Question 40

Antigen binding to the B-cell receptor:

A) transduces a signal through the antigen-binding

chains

B) invariably leads to B-cell activation

C) transduces a signal through the Igα and Igβ molecules

D) results in macrophage activation

E) leads to cytokine synthesis, which activates T cells

Answer 40

C.
The molecules Igα and Igβ, which are associated with the

surface Ig molecule, transduce a signal following antigen binding

to surface Ig.

Question 41

Which of the following would not be found on a memory B cell?

A) Igα and Igβ

B) γ heavy chains

C) ε heavy chains

D) surrogate light chains

E) κ light chains

Answer 41

D.
Surrogate light chains are expressed only at the pre-B-cell

stage of B-cell differentiation

Question 42

Germinal centers found in lymph nodes and spleen:

A) support the development of immature B and T cells

B) function in the removal of damaged erythrocytes

from the circulation

C) act as the major source of stem cells and thus help to

maintain hematopoiesis

D) are sites where antigen-activated mature B cells proliferate

and differentiate

E) exclude T cells

Answer 42

D.
Germinal centers are the areas of lymph node and spleen in

which antigen-activated B cells interact with T cells, proliferate,

undergo somatic hypermutation and class switch recombination,

and ultimately differentiate into memory or plasma cells.

Question 43

All the following are characteristics of both MHC class

I and II molecules except:

A) They are expressed codominantly.

B) They are expressed constitutively on all nucleated

cells.

C) They are polypeptides with domain structure.

D) They are involved in presentation of antigen fragments

to T cells.

E) They are expressed on the surface membrane of B

cells.

Answer 43

B.
MHC class I molecules are expressed on all nucleated cells,

but the constitutive expression of MHC class II molecules is

limited to APC such as B cells and dendritic cells. MHC class II

expression can be induced on other cell types such as endothelial

cells and fibroblasts by cytokines

Question 44

MHC class I molecules are important for which of the

following?

A) binding to CD8 molecules on T cells

B) presenting exogenous antigen (e.g., bacterial protein) to B cells

C) presenting intact viral proteins to T cells

D) binding to CD4 molecules on T cells

E) binding to Ig on B cells

Answer 44

A.
The interaction of CD8 expressed on the T cell and an invariant

region of an MHC class I molecule expressed on a host cell

plays a critical role in the triggering of CD8+ T cells (see also

Chapters 10 and 11).

Question 45

Which of the following is incorrect concerning MHC class II molecules?

A) B cells may express different allelic forms of MHC class molecules on their surface.

B) MHC class II molecules are synthesized in the endoplasmic reticulum of APCs.

C) Genetically different individuals express different MHC class II alleles.

D) MHC class II molecules are associated with β2 -microglobulin on the cell surface.

E) A peptide that does not bind to an MHC class II molecule will not trigger a CD4+ T-cell response.

Answer 45

D.

The MHC class I molecule, not the MHC class II molecule,

associates with β2-microglobulin.

Question 46

The peptide transporter TAP

A) binds β2 -microglobulin

B) prevents peptide binding to MHC molecules

C) is part of the proteasome

D) transports peptides into the endoplasmic reticulum for binding to MHC class I

E) transports peptides into the endoplasmic reticulum for binding to MHC class II

Answer 46

D.
The peptide transporter TAP selectively transports peptides

generated in the cytoplasm into the endoplasmic reticulum where

peptides 8–9 amino acids long, with the appropriate sequence, may bind to a newly synthesized MHC class I molecule

Question 47

Which of the following statements about HLA genes is incorrect ?

A) They code for complement components.

B) They code for both chains of every HLA class I molecule expressed.

C) They code for both chains of every HLA class II molecule expressed.

D) They are associated with susceptibility and resistance to different diseases.

E) The total set of HLA alleles on the chromosome is known as the HLA haplotype.

Answer 47

B.

HLA class I molecules are expressed at the cell surface with

β2-microglobulin; the gene coding for β2-microglobulin is located

outside the MHC, on a different chromosome.

Question 48

Which of the following is found on the surface of every

B cell, T cell, and pancreatic cell?

A) MHC class II molecules

B) a rearranged antigen-specific receptor

C) immunoglobulin

D) MHC class I molecules

E) CD19

Answer 48

D.
MHC class I molecules are expressed on these cells, and all

nucleated cells. MHC class II molecules are expressed constitutively

on APCs such as B cells, but not on T cells or pancreatic

cells. T cells and B cells express an antigen-specific receptor (see

also Chapters 8 and 10) but pancreatic cells do not. Ig and CD19

are expressed by B cells (Chapter 8).

Question 49

After a virus infects a boy’s liver cells, which of the following

about the processing and presentation of virus-derived

proteins is correct?

A) All the peptides derived from the processing associate

with his HLA class I molecules.

B) Processing occurs exclusively in acid vesicles.

C) The virus-derived peptides that bind to his HLA class

I molecules also bind to his sister’s HLA class I

molecules.

D) Some virus-derived peptides are presented to CD8+

T cells.

E) His HLA class I molecules preferentially bind virusderived

peptides 12–17 amino acids long.

Answer 49

D.

Because of the selectivity of binding of peptides to MHC

molecules, some but not all of the peptides derived from processing

the virus proteins are likely to associate with the boy’s HLA class

I molecules and activate a virus-specific CD8+ T-cell response. The

peptides that bind to HLA class I molecules are 8–9 amino acids

long. Because the boy’s sister is expected to have a different HLA

haplotype, a distinct set of virus-derived peptides will bind to her

HLA class I molecules

Question 50

Which of the following statements concerning T-cell development is correct?

A) Progenitor T cells that enter the thymus from the bone

marrow have already rearranged their TCR genes.

B) Interaction with thymic nonlymphoid cells is critical.

C) Maturation in the thymus requires the presence of foreign antigen.

D) MHC class II molecules are not involved in positive selection.

E) Mature, fully differentiated T cells are found in the cortex of the thymus.

Answer 50

B.

Interaction of thymocytes with thymic nonlymphoid cells—

cortical epithelial cells, dendritic cells and medullary epithelial

cells—is critical in T-cell development

Question 51

The development of self-tolerance in the T-cell compartment

is important for the prevention of autoimmunity.

Which of the following results in T-cell self-tolerance?

A) allelic exclusion

B) somatic hypermutation

C) thymocyte proliferation

D) positive selection

E) negative selection

Answer 51

E.

Negative selection removes developing T cells with potential

reactivity to self-molecules.

Question 52

Which of the following statements is correct?

A) The TCR chains transduce a signal into a T cell.

B) A cell depleted of its CD4 molecule would be unable to recognize antigen.

C) T cells with fully rearranged TCR chains are not found in the thymus.

D) T cells expressing the TCR are found only in the thymus.

E) CD4+ CD8+ T cells form the majority of T cells in the thymus.

Answer 52

E.

CD4+ CD8+ T cells = Double Positive form the majority of cells in the thymus.

Question 53

Which of the following is incorrect regarding mature

T cells that use αβ as their antigen-specific receptor?

A) They all express CD8 on the cell surface.

B) They may be either CD4+ or CD8+ .

C) They interact with peptides derived from nonself antigens.

D) They can further rearrange their TCR genes to express γδ as their receptor.

E) They circulate through blood and lymph and migrate to secondary lymphoid organs.

Answer 53

D.

The genes of T cells that use αβ as their receptor cannot

further rearrange to use γδ as their receptor; TCR δ gene segments

are interspersed with the α locus and are deleted when the α locus

rearranges.

Question 54

Which of the following statements is incorrect concerning TCR and Ig genes?

A) In both B- and T-cell precursors, multiple V-, D-, J-, and C-region genes exist in an unrearranged configuration.

B) Rearrangement of both TCR and Ig genes involves recombinase enzymes that bind to specific regions of the genome.

C) Both Ig and TCR are able to switch C-region usage.

D) Both Ig and the TCR use combinatorial associationof V, D, and J genes and junctional imprecision to generate diversity.

Answer 54

C.

The ability to change the heavy-chain constant region while

retaining the same antigen specificity is a property unique to Ig.

The other features are common to both the TCR and Ig.

Question 55

Which of the following statements is incorrect concerning antigen-specific receptors on both B and T cells?

A) They are clonally distributed transmembrane molecules.

B) They have extensive cytoplasmic domains that interact with intracellular molecules.

C) They consist of polypeptides with variable and constant regions.

D) They are associated with signal transduction molecules at the cell surface.

E) They can interact with peptides derived from nonself antigens.

Answer 55

B.
Both the TCR and Ig have short cytoplasmic tails. The signal

transduction molecules associated with the antigen-binding chains

interact with intracellular molecules.

Question 56

Which of the following is correct concerning the characteristics of T cells that exit the thymus?

A) They do not express CD4 or CD8 but express a TCR that has high affinity for MHC plus self-antigen.

B) They express CD4 and CD8 but no TCR and have low affinity for MHC plus self-antigen.

C) They express either CD4 or CD8 with a TCR that has high affinity for MHC plus self-antigen.

D) They express either CD4 or CD8 with a TCR that has low to moderate affinity for MHC plus self-antigen.

E) They express CD4, CD8, and a TCR that has high affinity for MHC plus self-antigen.

Answer 56

D.

T cells that use αβ as their TCR and emerge as the end stage

of differentiation in the thymus express either CD4 or CD8 (as well

as a TCR) and, as a result of thymic selection, have a low to intermediate

affinity for self-antigen associated with self-MHC (the

MHC molecules expressed by the individual’s thymic nonlymphoid

cells).

Question 57

The role of the APC in the immune response is all of the following except :

A) the limited catabolism of polypeptide antigens

B) to allow selective association of MHC gene products and peptides

C) to supply second signals required to fully activate T cells

D) to present nonself-peptides associated with MHC class I molecules to CD4+ T cells

E) to present peptide–MHC complexes to T cells with the appropriate receptor

Answer 57

D.
The APC presents peptide–MHC class I to CD8+ T cells and

peptide–MHC class II to CD4+ T cells. The other statements are

all features of an APC such as a dendritic cell.

Question 58

Which of the following statements about IL-2 is incorrect ?

A) It is produced primarily by activated macrophages.

B) It is produced by CD4+ T cells.

C) It can induce the proliferation of CD4+ T cells.

D) It binds to a specific receptor on CD4+ T cells.

E) It can activate CD8+ T cells in the presence of antigen.

Answer 58

A.
IL-2 is produced almost exclusively by activated T cells.

Question 59

Which of the following pairs of cell surface proteins do NOT interact with each other?

A) MHC class II and CD4

B) ICAM-1 (CD54) and LFA-1 (CD11a/CD18)

C) B7 (CD80 and CD86) and CD28

D) CD40 and CD40 ligand (CD154)

E) membrane Ig on the B cell and CD4 on the T cell

Answer 59

E.

The pairs of molecules in answers A–D are all important in

adhesion and/or co-stimulation for T cells with B cells and other

APCs; it is not thought that Ig interacts with CD4.

Question 60

Which of the following statements about the activation of CD4+ T cells is incorrect ?

A) Activation results in rapid phosphorylation of tyrosine residues in proteins associated with the TCR.

B) Intracellular calcium levels rise rapidly following activation.

C) The interaction between peptide–MHC class II on an APC and the TCR of an appropriate CD4+ T cell is necessary and sufficient for full T-cell activation.

D) Interaction of B7 and CD28 stabilizes IL-2 mRNA so that effective IL-2 translation occurs.

E) The activated cell synthesizes IL-2 and a receptor for IL-2.

Answer 60

C.

Peptide–MHC class II interacting with the TCR is the critical,

antigen-specific first signal required for CD4+ T-cell activation,

but co-stimulatory or second signals are required for full

activation.

Question 61

Which of the following statements about cytokines and subsets of CD4+ T cells is incorrect ?

A) TH 1 cells secrete cytokines that induce macrophage and NK-cell activation.

B) Cytokines produced by TH 2 cells are important in allergic responses.

C) The presence of IL-12 during the activation and differentiation of CD4+ T cells favors the development of TH 1 cells.

D) Cytokines synthesized by TH 1 and TH 2 cells inhibit the action of Treg cells.

E) Cytokines synthesized by TH 1 and TH 2 cells inhibit the action of TH 17 cells.

Answer 61

D.

Cytokines synthesized by Treg cells inhibit the action of TH1

and TH2 cells but not vice versa.

Question 62

Which of the following statements about CD8+ CTL is incorrect ?

A) They lyse targets via perforin and granzymes.

B) They cause target cell apoptosis.

C) They cannot kill CD4+ T cells.

D) They interact with their target through paired cell surface molecules.

E) They must be activated before exerting their cytotoxic function.

Answer 62

C.

A CD8+ CTL can kill any cell expressing an MHC class 1

molecule in association with a nonself-peptide, including, for

example, a CD4+ T cell infected with HIV.

Question 63

Infection with vaccinia virus results in the priming of virus-specific CD8+ T cells. If these vaccinia virusspecific CD8+ T cells are subsequently removed from the individual, which of the following cells will they kill in vitro ?

A) vaccinia-infected cells expressing MHC class II molecules from any individual

B) influenza-infected cells expressing the same MHC class I molecules as the individual

C) uninfected cells expressing the same MHC class I molecules as the individual

D) vaccinia-infected cells expressing the same MHC class I molecules as the individual

E) vaccinia-infected cells expressing the same MHC class II molecules as the individual

Answer 63

D.
The principle of MHC restriction indicates that the TCR of

CD8+ T cells interacts with target cells that express specific peptide

bound to self-MHC class I molecules. Thus, vaccinia-primed

CD8+ T cells recognize and hence kill only vaccinia-infected

targets that express self-MHC class I.