Test bank for the immune system 4th edition by parham

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Test Bank for The Immune System 4th Edition by Parham
CHAPTER 5: ANTIGEN RECOGNITION BY T LYMPHOCYTES
5–1

T cells recognize antigen when the antigen

1. forms a complex with membrane-bound MHC molecules on another hostderived cell
2. is internalized by T cells via phagocytosis and subsequently binds to T-cell
receptors in the endoplasmic reticulum
3. is presented on the surface of a B cell on membrane-bound immunoglobulins
4. forms a complex with membrane-bound MHC molecules on the T cell
5. bears epitopes derived from proteins, carbohydrates, and lipids.

5–2
1.
2.
3.
4.
5.

T-cell receptors structurally resemble
the Fc portion of immunoglobulins
MHC class I molecules
secreted antibodies
a single Fab of immunoglobulins
CD3 ε chains.

5–3 If viewing the three-dimensional structure of a T-cell receptor from the side,

with the T-cell membrane at the bottom and the receptor pointing upwards, which
of the following is inconsistent with experimental data?
1. The highly variable CDR loops are located across the top surface.
2. The membrane-proximal domains consist of Cα and Cβ.
3. The portion that makes physical contact with the ligand comprises Vβand Cβ,
the domains farthest from the T-cell membrane.
4. The transmembrane regions span the plasma membrane of the T cell.
5. The cytoplasmic tails of the T-cell receptor α and β chains are very short.

5–4

Unlike B cells, T cells do not engage in any of the following processes except




1.
2.
3.
4.
5.

alternative splicing to produce a secreted form of the T-cell receptor
alternative splicing to produce different isoforms of the T-cell receptor
isotype switching
somatic hypermutation
somatic recombination

5–5 When comparing the T-cell receptor α-chain locus with the immunoglobulin
heavy-chain locus, all of the following are correct except

1. the T-cell receptor α locus differs because it has embedded within its
sequence another locus that encodes a different type of T-cell receptor chain
2. both are encoded on chromosome 14
3. the T-cell receptor α-chain locus does not contain D segments
4. the T-cell receptor α-chain locus contains more V and J regions
5. the T-cell receptor α-chain locus contains more C regions
6. they both contain exons encoding a leader peptide.

5–6 Unlike the C regions of immunoglobulin heavy-chain loci, the C regions of the
T-cell receptor β-chain loci
1.
2.
3.
4.

are functionally similar
do not contain D segments
are more numerous
are encoded on a different chromosome from the variable β-chain gene
segments of the T-cell receptor
5. do not encode a transmembrane region
6. possess non-templated P and N nucleotides.

5–7

Which of the following statements regarding Omenn syndrome is incorrect?

1. A bright red, scaly rash is due to a chronic inflammatory condition.
2. Affected individuals are susceptible to infections with opportunistic
pathogens.

3. It is invariably fatal unless the immune system is rendered competent
through a bone marrow transplant.
4. It is the consequence of complete loss of RAG function.
5. There is a deficiency of functional B and T cells.




6. It is associated with missense mutations of RAG genes.

5–8
1. Identify which features of the RAG genes have similarity to the transposase
gene of transposons.
2. Explain how the mechanisms for immunoglobulin and T-cell receptor
rearrangement may have evolved in humans.

5–9

All of the following statements regarding γ:δ T cells are correct except

1. they are more abundant in tissue than in the circulation
2. the δ chain is the counterpart to the β chain in α:β T-cell receptors because it
contains V, D, and J segments in the variable region
3. they share some properties with NK cells
4. activation is not always dependent on recognition of a peptide:MHC molecule
complex
5. expression on the cell surface is not dependent on the CD3 complex.

5–10 Match the term in Column A with its complement in Column B.

Column A

Column B

___a. T-cell receptor δchain gene

1.
positioned in the T-cell
receptor α-chain locus
between Vα and Jα gene
segments

___b. CD3 complex

2.
made up of γ, δ and ε
components




___c. T-cell receptor βchain gene

3.
located on
chromosome 7

___d. CD4

4.

counterpart to the Tcell receptor α-chain gene

___e. T-cell receptor γchain gene

5.
four extracellular
domains

5–11 During T-cell receptor _____-gene rearrangement, two D segments may be
used in the final rearranged gene sequence, thereby increasing overall variability of
this chain.
1.
2.
3.
4.
5.

α
β
γ
δ
ε.

5–12 The degradation of pathogen proteins into smaller fragments called peptides
is a process commonly referred to as
1.
2.
3.
4.
5.

endocytosis
promiscuous processing
antigen processing
antigen presentation
peptide loading.

5–13 All of the following are primarily associated with CD4 T-cell function except
1. improve phagocytic mechanisms of tissue macrophages
2. assist B cells in the production of high-affinity antibodies




3. kill virus-infected cells
4. facilitate responses of other immune-system cells during infection
5. assist macrophages in sustaining adaptive immune responses through their
secretion of cytokines and chemokines.

5–14 The primary reason for transplant rejections is due to differences in _____
between donor and recipient.
1.
2.
3.
4.
5.

CD3
MHC molecules
T-cell receptor α chains

γ:δ T cells
β2-microblobulin.

5–15 Explain the importance of promiscuous binding specificity exhibited by MHC
class I and class II molecules.

5–16 When describing the various components of the vesicular system, which of
the following is not included?
1.
2.
3.
4.
5.

nucleus
Golgi apparatus
endoplasmic reticulum
exocytic vesicles
lysosomes.

5–17 Which of the following is not a characteristic of immunoproteasomes?
1. They make up about 1% of cellular protein.
2. They consist of four rings of seven polypeptide subunits that exist in
alternative forms.
3. They are produced in response to IFN-γ produced during innate immune
responses.
4. They produce a higher proportion of peptides containing acidic amino acids
at the carboxy terminus compared with constitutive proteasomes.

5. They contain 20S proteasome-activation complexes on the caps.

5–18 Identify which of the following statements is true regarding the transporter
associated with antigen processing (TAP).
1. TAP is a homodimer composed of two identical subunits.
2. TAP transports proteasome-derived peptides from the cytosol directly to the
lumen of the Golgi apparatus.
3. TAP is an ATP-dependent, membrane-bound transporter.
4. Peptides transported by TAP bind preferentially to MHC class II molecules.
5. TAP deficiency causes a type of bare lymphocytes syndrome resulting in
severely depleted levels of MHC class II molecules on the surface of antigenpresenting cells.

5–19 All of the following are included in the peptide-loading complex except
1.
2.
3.
4.
5.

tapasin
calnexin
calreticulin
ERp57
β2-microglobulin.

5–20 Which of the following best describes the function of tapasin?
1. Tapasin is an antagonist of HLA-DM and causes more significant increases in
MHC class I than MHC class II on the cell surface.

2. Tapasin is a lectin that binds to sugar residues on MHC class I molecules, Tcell receptors, and immunoglobulins and retains them in the ER until their
subunits have adopted the correct conformation.
3. Tapasin is a thiol-reductase that protects the disulfide bonds of MHC class I
molecules.
4. Tapasin participates in peptide editing by trimming the amino terminus of
peptides to ensure that the fit between peptide and MHC class II molecules is
appropriate.
5. Tapasin is a bridging protein that binds to both TAP and MHC class I
molecules and facilitates the selection of peptides that bind tightly to MHC
class I molecules.




5–21 The mechanisms contributing to peptide editing include which of the
following? (Select all that apply.)
1. removal of amino acids from the amino-terminal end by endoplasmic
reticulum aminopeptidase (ERAP)
2. cathepsin S-mediated cleavage of invariant chain
3. the participation of tapasin in finding a ‘good fit’ for class I heterodimers
4. recycling an MHC class I heterodimer if the peptide falls out of its peptidebinding groove
5. upregulation of HLA-DM by interferon-γ.

5–22 Match the term in Column A with its description or function in Column B.
Column A

Column B

___a. cathepsin S

1.
a chaperone that
directs empty MHC class I
molecules to the inside of the
cell

___b. HLA-DM

2.
activated by
acidification in
phagolysosomes

___c. endoplasmic
reticulum
aminopeptidase (ERAP)

3.
a thiol-reductase in the
peptide-loading complex

___d. receptor-mediated
endocytosis

4.
removes class IIassociated invariant-chain
peptide (CLIP)

___e. ERp57

5.

internalization of




immunoglobulin:antigen
complexes by B cells

___f. HLA-G

6.
expressed only by
extravillous trophoblasts

___g. HLA-F

7.
trims peptides to fit
MHC class I molecules

5–23 Explain how mycobacteria avoid immune recognition by T cells during
infection.

5–24 Identify the three functions of the invariant chain.

5–25 Explain specifically how interferon-γ produced during an infection enhances
(A) antigen processing in the MHC class I pathway, and (B) antigen presentation in
the MHC class II pathway.

5–26 Discuss how T-cell receptors differ from immunoglobulins in the way that
they recognize antigen. Use the following terms in your answer: peptides, antigenpresenting cells, MHC molecules, and antigen-binding sites.

5–27 Pathogens that infect the human body replicate either inside cells (such as
viruses) or extracellularly, in the blood or in the extracellular spaces in tissues.
1. Identify (i) the class of T cells that are stimulated by intracellular pathogens,
(ii) their co-receptor, (iii) the MHC molecule used for recognition of antigen
and (iv) the T-cell effector function.




2. Repeat this for the classes of T cells that are stimulated by extracellular
pathogens. For the purposes of this question, count those pathogens (such as
mycobacteria) that can survive and live inside intracellular vesicles after
being taken up by macrophages as extracellular pathogens.

5–28 In contrast to immunoglobulins, α:β T-cell receptors recognize epitopes
present on _______ antigens:
1.
2.
3.
4.
5.

carbohydrate
lipid
protein
carbohydrate and lipid

carbohydrate, lipid, and protein.

5–29 Indicate whether each of the following statements regarding T cells is true
(T) or false (F).
1. __ T cells and B cells recognize the same types of antigen.
2. __ T cells and B cells require MHC molecules for the recognition of peptide
antigens.
3. __ T cells require an accessory cell called an antigen-presenting cell, which
bears MHC molecules on its surface.
4. __ T-cell receptor and immunoglobulin genes are encoded on the MHC.
5. __ The T-cell receptor has structural similarity to an immunoglobulin Fab
fragment.

5–30 Which of the following characteristics is common to both T-cell receptors
and immunoglobulins?
1. Somatic recombination of V, D, and J segments is responsible for the diversity
of antigen-binding sites.
2. Somatic hypermutation changes the affinity of antigen-binding sites and
contributes to further diversification.
3. Class switching enables a change in effector function.
4. The antigen receptor is composed of two identical heavy chains and two
identical light chains.




5. Carbohydrate, lipid, and protein antigens are recognized and stimulate a
response.

5–31 The antigen-recognition site of T-cell receptors is formed by the association

of which of the following domains?
1.
2.
3.
4.
5.

Vα and Cα
Vβ and Cβ
Cα and Cβ
Vα and Cβ
Vα and Vβ.

5–32 The most variable parts of the T-cell receptor are
1.
2.
3.
4.
5.

Vα and Cα
Vβ and Cβ
Cα and Cβ
Vα and Cβ
Vα and Vβ.

5–33 How many complementarity-determining regions contribute to the antigenbinding site in an intact T-cell receptor?
1.
2.
3.

4.
5.

2
3
4
6
12.

5–34 IgG possesses _______ binding sites for antigen, and the T-cell receptor
possesses _______ binding sites for antigen:
1. 1; 1
2. 2; 1
3. 1; 2




4. 2; 2
5. 2; 4.

5–35 In terms of V, D, and J segment arrangement, the T-cell receptor α-chain locus
resembles the immunoglobulin _______ locus, whereas the T-cell receptor β-chain
locus resembles the immunoglobulin _______ locus:
1.
2.
3.
4.
5.

λ light chain; κ light chain
heavy chain; λ light chain
κ light chain; heavy chain
λ light chain; heavy chain
κ light chain; λ light chain.

5–36 In B cells, transport of immunoglobulin to the membrane is dependent on
association with two invariant proteins, Igα and Igβ. Which of the following
invariant proteins provide this function for the T-cell receptor in T cells?
1.
2.
3.
4.
5.

CD3γ
CD3δ
CD3ε
ζ
All of the above.

5–37 Owing to the location of the δ-chain locus of the T-cell receptor on
chromosome 14, if the _______-chain locus rearranges by somatic recombination,
then the δ-chain locus is _______:
1.
2.
3.
4.
5.

α; also rearranged
α; deleted
α; transcribed
β; deleted
γ; also rearranged.




5–38 Explain how professional antigen-presenting cells optimize antigen
presentation to T cells despite the relatively limited capacity of any particular MHC
molecule to bind different pathogen-derived peptides.

5–39 Which of the following is not a characteristic of native antigen recognized by
T cells?
1.
2.
3.
4.
5.

peptides ranging between 8 and 25 amino acids in length
not requiring degradation for recognition
amino acid sequences not found in host proteins
primary, and not secondary, structure of protein
binding to major histocompatibility complex molecules on the surface of
antigen-presenting cells.

5–40 Which of the following statements regarding CD8 T cells is incorrect?
1. When activated, CD8 T cells in turn activate B cells.

2. CD8 is also known as the CD8 T-cell co-receptor.
3. CD8 binds to MHC molecules at a site distinct from that bound by the T-cell
receptor.
4. CD8 T cells kill pathogen-infected cells by inducing apoptosis.
5. CD8 T cells are MHC class I-restricted.

5–41 Antigen processing involves the breakdown of protein antigens and the
subsequent association of peptide fragments on the surface of antigen-presenting
cells with
1.
2.
3.
4.
5.

immunoglobulins
T-cell receptors
complement proteins
MHC class I or class II molecules
CD4.

5–42 Which of the following statements regarding T-cell receptor recognition of
antigen is correct?




1. α:β T-cell receptors recognize antigen only as a peptide bound to an MHC
molecule.
2. αβ T-cell receptors recognize antigens in their native form.

3. α:β T-cell receptors, like B-cell immunoglobulins, can recognize carbohydrate,
lipid, and protein antigens.
4. Antigen processing occurs in extracellular spaces.
5. Like α:β T cells, γ:δ T cells are also restricted to the recognition of antigens
presented by MHC molecules.

5–43 Which of the following describes a ligand for an α:β T-cell receptor?
1.
2.
3.
4.
5.

carbohydrate:MHC complex
lipid:MHC complex
peptide:MHC complex
all of the above
none of the above.

5–44 MHC class II molecules are made up of two chains called _______, whose
function is to bind peptides and present them to _______ T cells:
1.
2.
3.
4.
5.

alpha (α) and beta (β); CD4
alpha (α) and beta2-microglobulin (β2m); CD4
alpha (α) and beta (β); CD8

alpha (α) and beta2-microglobulin β2m); CD8
alpha (α) and beta (β); γ:δ T cells.

5–45 The complementarity-determining region (CDR) 1 and CDR2 loops of the Tcell receptor contact the _______:
1.
2.
3.
4.
5.

side chains of amino acids in the middle of the peptide
co-receptors CD4 or CD8
membrane-proximal domains of the MHC molecule
constant regions of antibody molecules
α helices of the MHC molecule.




5–46 The CDR3 loops of the T-cell receptor contact the _______:
1.
2.
3.
4.
5.

side chains of amino acids in the middle of the peptide
co-receptors CD4 or CD8
membrane-proximal domains of the MHC molecule
constant regions of antibody molecules

α helices of the MHC molecule.

5–47 The peptide-binding groove of MHC class I molecules is composed of the
following extracellular domains:
1.
2.
3.
4.
5.

α1:β1
β1:β2
α2:β2
α2:α3
α1:α2.

5–48 To which domain of MHC class II does CD4 bind?
1.
2.
3.
4.
5.

α1
β1
α2
β2
α3.

5–49 To which domain of MHC class I does CD8 bind?

1.
2.
3.
4.
5.

α1
β1
α2
β2
α3.

5–50 MHC molecules have promiscuous binding specificity. This means that




1.
2.
3.
4.

a particular MHC molecule has the potential to bind to different peptides
when MHC molecules bind to peptides, they are degraded
peptides bind with low affinity to MHC molecules
none of the above describes promiscuous binding specificity.

5–51 T-cell receptors interact not only with peptide anchored in the peptidebinding groove of MHC molecules, but also with
1.
2.

3.
4.
5.

anchor residues
peptide-binding motif
variable amino acid residues on α helices of the MHC molecule
β2-microglobulin
invariant chain.

5–52 Cross-priming of the immune response occurs when _____. (Select all that
apply.)
1. viral antigens are presented by MHC class I molecules on the surface of a cell
that is not actually infected by that particular virus
2. cytosol-derived peptides enter the endoplasmic reticulum and bind to MHC
class II molecules
3. phagolysosome-derived peptides bind to MHC class II molecules
4. peptides of nuclear or cytosolic proteins are presented by MHC class II
molecules.

5–53 In reference to the interaction between T-cell receptors and their
corresponding ligands, which of the following statements is correct?
1. The organization of the T-cell receptor antigen-binding site is distinct from
the antigen-binding site of immunoglobulins.
2. The orientation between T-cell receptors and MHC class I molecules is
different from that of MHC class II molecules.
3. The CDR3 loops of the T-cell receptor α and β chains form the periphery of
the binding site making contact with the α helices of the MHC molecule.
4. The most variable part of the T-cell receptor is composed of the CD3 loops of
both the α and β chains.

5. All of the above statements are correct.




5–54 The diversity of MHC class I and II genes is due to _____. (Select all that apply.)
1.
2.
3.
4.
5.

gene rearrangements similar to those observed in T-cell receptor genes
the existence of many similar genes encoding MHC molecules in the genome
somatic hypermutation
extensive polymorphism at many of the alleles
isotype switching.

5–55 The combination of all HLA class I and class II allotypes that an individual
expresses is referred to as their
1.
2.
3.
4.
5.

haplotype
allotype
isotype
autotype

HLA type.

5–56 All of the following are oligomorphic except
1.
2.
3.
4.
5.

HLA-G α chain
HLA-DO β chain
HLA-DQ β chain
HLA-A α chain
HLA-DR α chain.

5–57 All of the following are highly polymorphic except
1.
2.
3.
4.
5.

HLA-A α chain
HLA-DO α chain
HLA-B α chain
HLA-DR β chain
HLA-C α chain.

5–58 Of the following HLA α-chain loci, which one exhibits the highest degree of
polymorphism?
1.
2.
3.
4.
5.

HLA-A
HLA-B
HLA-C
HLA-DP
HLA-DR.

5–59 Which of the following are not encoded on chromosome 6 in the HLA
complex? (Select all that apply.)
1.
2.
3.
4.
5.
6.

β2-microglobulin
HLA-G α chain
TAP-1
invariant chain
tapasin
HLA-DR α chain.

5–60 The _____ refers to the complete set of HLA alleles that a person possesses on
a particular chromosome 6.
1.
2.
3.
4.
5.

isoform
isotype
oligomorph
allotype
haplotype.

5–61 Peptides that bind to a particular MHC isoform usually have either the same
or chemically similar amino acids at two to three key positions that hold the peptide
tightly in the peptide-binding groove of the MHC molecule. These amino acids are
called _____ and the combination of these key residues is known as its _____.
1.
2.
3.
4.

alleles; allotypes
anchor residues; peptide-binding motif
allotype; haplotypes
invariant chains; haplotypes

5. restriction residues; MHC allotype.

5–62 Provide an explanation of why it is believed that MHC class I genes are the
evolutionary ancestors of MHC class II genes.

5–63 Match the term in Column A with its description in Column B.
Column A

Column B

___a. MHC restriction

1.
mechanism enabling
extracellular antigens to
bind to MHC class I
molecules

___b. cross-presentation

2.
evolutionary
maintenance of divergent
MHC molecule phenotypes

___c. heterozygote
advantage

3.
recognition of
peptide antigen by a given
T-cell receptor when bound
to a particular MHC allotype

___d. balancing selection

4.
mechanism used to
increase polymorphisms of
HLA class I and class II
alleles involving
homologous recombination
between different alleles of
the same gene




___e. interallelic
conversion

5.
presentation of a
wider range of peptides
when MHC isotypes
inherited from each parent
are different

5–64 Directional selection is best described as
1. all polymorphic alleles preserved in a population
2. T-cell receptor interaction with peptide:MHC complexes directed to a planar
interface
3. a mechanism in T cells that is analogous to affinity maturation of
immunoglobulins
4. selected alleles increase in frequency in a population
5. selection of most appropriate transplant donor directed at the identification
of identical or similar combinations of HLA alleles compared with the
transplant recipient.

5–65 Describe (A) five ways in which T-cell receptors are similar to
immunoglobulins, and (B) five ways in which they are different (other than the way
in which they recognize antigen).

5–66 Compare the organization of T-cell receptor α and β genes (the TCRα and
TCRβ loci) with the organization of immunoglobulin heavy-chain and light-chain
genes.

5–67 T-cell receptors do not undergo isotype switching. Suggest a possible reason
for this.

5–68 The role of the CD3 proteins and ζ chain on the surface of the cell is to




1.
2.
3.

4.
5.

transduce signals to the interior of the T cell
bind to antigen associated with MHC molecules
bind to MHC molecules
bind to CD4 or CD8 molecules
facilitate antigen processing of antigens that bind to the surface of T cells.

5–69 Which of the following accurately completes this statement: “The function of
_______ T cells is to make contact with _______ and _______”? (Select all that apply.)
1.
2.
3.
4.
5.

CD8; virus-infected cells; kill virus-infected cells
CD8; B cells; stimulate B cells to differentiate into plasma cells
CD4; macrophages; enhance microbicidal powers of macrophages
CD4; B cells; stimulate B cells to differentiate into plasma cells
All of the above are accurate.

5–70 The immunological consequence of severe combined immunodeficiency
disease (SCID) caused by a genetic defect in either RAG-1 or RAG-2 genes is
1. lack of somatic recombination in T-cell receptor and immunoglobulin gene
loci
2. lack of somatic recombination in T-cell receptor loci
3. lack of somatic recombination in immunoglobulin loci
4. lack of somatic hypermutation in T-cell receptor and immunoglobulin loci

5. lack of somatic hypermutation in T-cell receptor loci.

5–71
1. (i) Describe the structure of an MHC class I molecule, identifying the different
polypeptide chains and domains. (ii) What are the names of the MHC class I
molecules produced by humans? Which part of the molecule is encoded
within the MHC region of the genome? (iii) Which domains or parts of
domains participate in the following: antigen binding; binding the T-cell
receptor; and binding the T-cell co-receptor? (iv) Which domains are the
most polymorphic?
2. Repeat this for an MHC class II molecule.




5–72 What is meant by the terms (A) antigen processing and (B) antigen
presentation? (C) Why are these processes required before T cells can be activated?

5–73
1. Describe in chronological order the steps of the antigen-processing and
antigen-presentation pathways for intracellular, cytosolic pathogens.
2. (i) What would be the outcome if a mutant MHC class I α chain could not
associate with β2-microglobulin, and (ii) what would happen if the TAP
transporter were lacking as a result of mutation? Explain your answers.

5–74 Which of the following removes CLIP from MHC class II molecules?
1.
2.
3.
4.

5.

HLA-DM
HLA-DO
HLA-DP
HLA-DQ
HLA-DR.

5–75
1. Describe in chronological order the steps of the antigen-processing and
antigen-presentation pathways for extracellular pathogens.
2. What would be the outcome (i) if invariant chain were defective or missing,
or (ii) if HLA-DM were not expressed?

5–76
1. What is the difference between MHC variation due to multigene families and
that due to allelic polymorphism?
2. How does MHC variation due to multigene families and allelic polymorphism
influence the antigens that a person’s T cells can recognize?




5–77 What evidence supports the proposal that MHC diversity evolved by natural
selection caused by infectious pathogens rather than exclusively by random DNA
mutations?

5–78 CD8 T-cell subpopulations are specialized to combat _______ pathogens,
whereas CD4 T-cell subpopulations are specialized to combat _______ pathogens:
1.

2.
3.
4.
5.

bacterial; viral
dead; live
extracellular; intracellular
intracellular; extracellular
virulent; attenuated.

5–79 Which of the following describes the sequence of events involved in
processing of peptides that will be presented as antigen with MHC class I?
1. plasma membrane →TAP1/2 →proteasome →MHC class I →endoplasmic
reticulum
2. TAP1/2 →proteasome →MHC class I →endoplasmic reticulum→plasma
membrane
3. proteasome →TAP1/2 →MHC class I →endoplasmic reticulum →plasma
membrane
4. proteasome →TAP1/2 →endoplasmic reticulum →MHC class I →plasma
membrane
5. endoplasmic reticulum →proteasome →MHC class I →TAP1/2 →plasma
membrane.

5–80 One type of bare lymphocyte syndrome is caused by a genetic defect in MHC
class II transactivator (CIITA), which results in the inability to synthesize MHC class
II and display it on the cell surface. The consequence of this would be that
1.
2.
3.

4.
5.

B cells are unable to develop
CD8 T cells cannot function
CD4 T cells cannot function
intracellular infections cannot be eradicated
peptides cannot be loaded onto MHC molecules in the lumen of the
endoplasmic reticulum.




5–81 Which of the following describes the sequence of events involved in the
processing of peptides that will be presented as antigen with MHC class II?
1. protease activity →removal of CLIP from MHC class II →binding of peptide to
MHC class II →endocytosis →plasma membrane
2. endocytosis →protease activity →removal of CLIP from MHC class II →binding
of peptide to MHC class II →plasma membrane
3. removal of CLIP from MHC class II →binding of peptide to MHC class II
→protease activity →endocytosis →plasma membrane
4. binding of peptide to MHC class II →endocytosis →removal of CLIP from MHC
class II →protease activity →plasma membrane
5. plasma membrane →endocytosis →protease activity →removal of CLIP from
MHC class II →binding of peptide to MHC class II.

5–82 Which of the following cell types does not express MHC class I?
1.
2.
3.

4.
5.

erythrocyte
hepatocyte
lymphocyte
dendritic cell
neutrophil.

5–83 Which of the following cell types is not considered a professional antigenpresenting cell?
1.
2.
3.
4.
5.

macrophage
neutrophil
B cell
dendritic cell
all of the above are professional antigen-presenting cells.

5–84 Match the answer on the right that best describes the function on the left.
More than one answer may be correct.




___ a. an intracellular,
monomorphic MHC class I

isotype whose function is
unknown

1. HLA-A, HLA-B, HLA-C

__ b. form ligands for
receptors on NK cells

2. HLA-E, HLA-G

__ c. participate in peptide
loading of MHC class II
molecules

3. HLA-F

__ d. present antigen to CD4
T cells

4. HLA-DP, HLA-DQ, HLADR

__ e. present antigen to CD8
T cells

5. HLA-DM, HLA-DO

5–85 Which of the following HLA-DRB genotypes is not possible in an individual?
(X: X represents diploid genotype.)
1.
2.

3.
4.
5.

DRB1: DRB1
DRB1, DRB3: DRB1, DRB4
DRB1: DRB1, DRB5
DRB1, DRB4: DRB1
DRB3: DRB1, DRB5.

5–86
1. How many HLA-DR α:β combinations can be made by an individual who is
heterozygous at all HLA-DRβ loci, inherits the DRβ haplotype DRB1 from their




mother, the DRβ haplotype DRB1, DRB4 from their father, and also inherits
different allelic forms of DRA from each parent?
2. Repeat this exercise given the same information except that the maternal DRβ
haplotype is DRB1, DRB3.

5–87 Which of the following is mismatched?
1. peptide-binding motif: combination of anchor residues in a peptide capable of
binding a particular MHC haplotype
2. MHC restriction: specificity of T-cell receptor for a particular peptide:MHC
molecule complex
3. balancing selection: maintenance of variety of MHC isoforms in a population
4. directional selection: replacement of older MHC isoforms with newer variants
5. interallelic conversion: recombination between two different genes in the

same family.

5–88 Which is the most likely reason that HIV-infected people with heterozygous
HLA loci have a delayed progression to AIDS compared with patients who are
homozygous at one or more HLA loci?
1. The greater number of HLA alleles provides a wider variety of HLA molecules
for presenting HIV-derived peptides to CD8 T cells even if HIV mutates during
the course of infection.
2. Heterozygotes have more opportunity for interallelic conversion and can
therefore express larger numbers of MHC alleles.
3. Directional selection mechanisms favor heterozygotes and provide selective
advantage to pathogen exposure.
4. As heterozygosity increases, so does the concentration of alloantibodies in the
serum, some of which cross-react with and neutralize HIV.

5–89
1. What is the maximum number of MHC class I and class II molecules that a
heterozygous individual could theoretically express? Explain your answer.
(Ignore the possibility of MHC class II molecules composed of chains from
different isotypes.)