Lec 1-11 - Coico Q's Flashcards
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
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.
- 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
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.
- 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.
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.
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
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.
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
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.
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
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.
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
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.
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
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).
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
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.
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
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.
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
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.
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
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
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.
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.
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
D. The C-terminal end of the constant region of the heavy
contains the domains that are associated with biologic activity of
immunoglobulins.
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
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.
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
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).
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
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.
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
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.
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
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.
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
B. The major class of immunoglobulin produced in response to
allergens is IgE.
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
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
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
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.
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
E
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
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.
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
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
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
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.
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
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
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
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.
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
C. The antigenic specificity is determined by the sequences and
hence the structure formed by the combination of H- and L-chain
variable regions
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
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.
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
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.
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.
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.
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
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.
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.
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.
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
D. Of the mechanisms described for generating diversity of Ig
molecules, only somatic hypermutation affects the antigen binding
site after antigen stimulation
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
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.
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
E.
All the molecules are expressed on the surface of the mature
B cell.
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
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.
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
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.
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
C.
The molecules Igα and Igβ, which are associated with the
surface Ig molecule, transduce a signal following antigen binding
to surface Ig.
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
D.
Surrogate light chains are expressed only at the pre-B-cell
stage of B-cell differentiation
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
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.
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.
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
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
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).
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.
D.
The MHC class I molecule, not the MHC class II molecule,
associates with β2-microglobulin.
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
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
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.
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.
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
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).
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.
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
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.
B.
Interaction of thymocytes with thymic nonlymphoid cells—
cortical epithelial cells, dendritic cells and medullary epithelial
cells—is critical in T-cell development
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
E.
Negative selection removes developing T cells with potential
reactivity to self-molecules.
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.
E.
CD4+ CD8+ T cells = Double Positive form the majority of cells in the thymus.
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.
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.
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.
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.
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.
B.
Both the TCR and Ig have short cytoplasmic tails. The signal
transduction molecules associated with the antigen-binding chains
interact with intracellular molecules.
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.
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).
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
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.
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.
A.
IL-2 is produced almost exclusively by activated T cells.
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
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.
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.
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.
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.
D.
Cytokines synthesized by Treg cells inhibit the action of TH1
and TH2 cells but not vice versa.
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.
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.
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
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.
