Chapter 5 quiz

Question 1

T cells recognize antigen when the antigen ___________________.

a. forms a complex with membrane-bound MHC molecules on another host-derived cell.
b. is internalized by T cells via phagocytosis and subsequently binds to T-cell receptors in the endoplasmic reticulum
c. is presented on the surface of a B cell on membrane-bound immunoglobulins
d. forms a complex with membrane-bound MHC molecules on the T cell
e. bears epitopes derived from proteins, carbohydrates, and lipids

Answer 1

a. forms a complex with membrane-bound MHC molecules on another host-derived cell.

Question 2

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?

a. The highly variable CDR loops are located across the top surface.
b. The membrane-proximal domains consist of Cα and Cβ.
c. The portion that makes physical contact with the ligand comprises Vβ and Cβ, the domains farthest
from the T-cell membrane.
d. The transmembrane regions span the plasma membrane of the T cell.
e. The cytoplasmic tails of the T-cell receptor α and β chains are very short

Answer 2

c. The portion that makes physical contact with the ligand comprises Vβ and Cβ, the domains farthest
from the T-cell membrane.

Question 3

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

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

Answer 3

e. somatic recombination

Question 4

Unlike the C regions of immunoglobulin heavy-chain loci, the C regions of the T-cell receptor β-chain loci ______.

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

Answer 4

a. are functionally similar

Question 5

Which of the following statements regarding Omenn syndrome is incorrect?

a. A bright red, scaly rash is due to a chronic inflammatory condition.
b. Affected individuals are susceptible to infections with opportunistic pathogens.
c. It is invariably fatal unless the immune system is rendered competent through a bone marrow
transplant.
d. It is the consequence of complete loss of RAG function.
e. There is a deficiency of functional B and T cells.
f. It is associated with missense mutations of RAG genes.

Answer 5

d. It is the consequence of complete loss of RAG function.

Question 6

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

a. they are more abundant in tissue than in the circulation
b. 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
c. they share some properties with NK cells
d. activation is not always dependent on recognition of a peptide:MHC molecule complex
e. expression on the cell surface is not dependent on the CD3 complex

Answer 6

e. expression on the cell surface is not dependent on the CD3 complex

Question 7

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.

a. α
b. β
c. γ
d. δ
e. ε.

Answer 7

d. δ

Question 8

The degradation of pathogen proteins into smaller fragments called peptides is a process commonly referred to as

a. endocytosis
b. promiscuous processing
c. antigen processing
d. antigen presentation
e. peptide loading

Answer 8

c. antigen processing

Question 9

The primary reason for transplant rejections is due to differences in _____ between donor and recipient.

a. CD3
b. MHC molecules
c. T-cell receptor α chains
d. γ:δ T cells
e. β2-microblobulin

Answer 9

b. MHC molecules

Question 10

When describing the various components of the vesicular system, which of the following is not included?

a. Nucleus
b. Golgi apparatus
c. endoplasmic reticulum
d. exocytic vesicles
e. lysosomes

Answer 10

a. Nucleus

Question 11

Which of the following is not a characteristic of immunoproteasomes?

a. They make up about 1% of cellular protein.
b. They consist of four rings of seven polypeptide subunits that exist in alternative forms.
c. They are produced in response to IFN-γ produced during innate immune responses.
d. They produce a higher proportion of peptides containing acidic amino acids at the carboxy terminus
compared with constitutive proteasomes.
e. They contain 20S proteasome-activation complexes on the caps.

Answer 11

d. They produce a higher proportion of peptides containing acidic amino acids at the carboxy terminus
compared with constitutive proteasomes.

Question 12

Identify which of the following statements is true regarding the transporter associated with antigen processing (TAP).

a. TAP is a homodimer composed of two identical subunits.
b. TAP transports proteasome-derived peptides from the cytosol directly to the lumen of the Golgi
apparatus.
c. TAP is an ATP-dependent, membrane-bound transporter.
d. Peptides transported by TAP bind preferentially to MHC class II molecules.
e. TAP deficiency causes a type of bare lymphocytes syndrome resulting in severely depleted levels of
MHC class II molecules on the surface of antigen-presenting cells.

Answer 12

c. TAP is an ATP-dependent, membrane-bound transporter.

Question 13

All of the following are included in the peptide-loading complex except _____________.

a. tapasin
b. calnexin
c. calreticulin
d. ERp57
e. β2-microglobulin

Answer 13

b. calnexin

Question 14

Which of the following best describes the function of tapasin?

a. Tapasin is an antagonist of HLA-DM and causes more significant increases in MHC class I than MHC
class II on the cell surface.
b. Tapasin is a lectin that binds to sugar residues on MHC class I molecules, T-cell receptors, and
immunoglobulins and retains them in the ER until their subunits have adopted the correct
conformation.
c. Tapasin is a thiol-reductase that protects the disulfide bonds of MHC class I molecules.
d. 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.
e. 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.

Answer 14

e. 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.

Question 15

Which of the following characteristics is common to both T-cell receptors and immunoglobulins?

a. Somatic recombination of V, D, and J segments is responsible for the diversity of antigen-binding sites.
b. Somatic hypermutation changes the affinity of antigen-binding sites and contributes to further diversification.
c. Class switching enables a change in effector function.
d. The antigen receptor is composed of two identical heavy chains and two identical light chains.
e. Carbohydrate, lipid, and protein antigens are recognized and stimulate a response.

Answer 15

a. Somatic recombination of V, D, and J segments is responsible for the diversity of antigen-binding sites.

Question 16

The antigen-recognition site of T-cell receptors is formed by the association of which of the following domains?

a. Vα and Cα
b. VβandCβ
c. CαandCβ
d. VαandCβ
e. Vα and Vβ

Answer 16

e. Vα and Vβ

Question 17

How many complementarity-determining regions contribute to the antigen-binding site in an intact T-cell receptor?

a. 2
b. 3
c. 4
d. 6
e. 12

Answer 17

d. 6

Question 18

IgG possesses _______ binding sites for antigen, and the T-cell receptor possesses _______ binding sites for antigen:

a. 1;1
b. 2; 1
c. 1;2
d. 2;2
e. 2;4.

Answer 18

b. 2; 1

Question 19

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?

a. CD3γ
b. CD3δ
c. CD3ε
d. ζ
e. All of the above

Answer 19

e. All of the above

Question 20

Which of the following is not a characteristic of native antigen recognized by T cells?

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

Answer 20

b. not requiring degradation for recognition

Question 21

Which of the following statements regarding CD8 T cells is incorrect?

a. When activated, CD8 T cells in turn activate B cells.
b. CD8 is also known as the CD8 T-cell co-receptor.
c. CD8 binds to MHC molecules at a site distinct from that bound by the T-cell receptor.
d. CD8 T cells kill pathogen-infected cells by inducing apoptosis.
e. CD8 T cells are MHC class I-restricted.

Answer 21

a. When activated, CD8 T cells in turn activate B cells.

Question 22

Antigen processing involves the breakdown of protein antigens and the subsequent association of peptide fragments on the surface of antigen-presenting cells with ________________.

a. immunoglobulins
b. T-cell receptors
c. complement proteins
d. MHC class I or class II molecules
e. CD4.

Answer 22

d. MHC class I or class II molecules

Question 23

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

a. α:β T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.
b. αβ T-cell receptors recognize antigens in their native form.
c. α:β T-cell receptors, like B-cell immunoglobulins, can recognize carbohydrate, lipid, and protein
antigens.
d. Antigen processing occurs in extracellular spaces.
e. Like α:β T cells, γ:δ T cells are also restricted to the recognition of antigens presented by MHC
molecules.

Answer 23

a. α:β T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.

Question 24

Which of the following describes a ligand for an α:β T-cell receptor?

a. carbohydrate:MHC complex
b. lipid:MHC complex
c. peptide:MHC complex
d. all of the above
e. none of the above

Answer 24

c. peptide:MHC complex

Question 25

MHC class II molecules are made up of two chains called _______, whose function is to bind peptides and present them to _______ T cells.

a. alpha (α) and beta (β); CD4
b. alpha (α) and beta2-microglobulin (β2m); CD4
c. alpha (α) and beta (β); CD8
d. alpha (α) and beta2-microglobulin β2m); CD8
e. alpha (α) and beta (β); γ:δ T cells

Answer 25

a. alpha (α) and beta (β); CD4

Question 26

The CDR3 loops of the T-cell receptor contact the _______.

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

Answer 26

a. side chains of amino acids in the middle of the peptide

Question 27

MHC molecules have promiscuous binding specificity. This means that __________________.

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

Answer 27

a. a particular MHC molecule has the potential to bind to different peptides

Question 28

T-cell receptors interact not only with peptide anchored in the peptide-binding groove of MHC molecules, but also with ____________________.

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

Answer 28

c. variable amino acid residues on α helices of the MHC molecule

Question 29

Cross-priming of the immune response occurs when ______________________________.

a. viral antigens are presented by MHC class I molecules on the surface of a cell that is not actually infected by that particular virus, or peptides of nuclear or cytosolic proteins are presented by MHC class II molecules.
b. cytosol-derived peptides enter the endoplasmic reticulum and bind to MHC class II molecules
c. phagolysosome-derived peptides bind to MHC class II molecules
5
d. viral antigens are presented by MHC class II molecules on the surface of a cell that is not actually infected by that particular virus or peptides of nuclear or cytosolic proteins are presented by MHC class I molecules.
e. phagolysosome-derived peptides bind to MHC class III molecules

Answer 29

a. viral antigens are presented by MHC class I molecules on the surface of a cell that is not actually infected by that particular virus, or peptides of nuclear or cytosolic proteins are presented by MHC class II molecules.

Question 30

In reference to the interaction between T-cell receptors and their corresponding ligands, which of the following statements is correct?

a. The organization of the T-cell receptor antigen-binding site is distinct from the antigen-binding site of immunoglobulins.
b. The orientation between T-cell receptors and MHC class I molecules is different from that of MHC class II molecules.
c. 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.
d. The most variable part of the T-cell receptor is composed of the CD3 loops of both the α and β
chains.
e. All of the above statements are correct.

Answer 30

d. The most variable part of the T-cell receptor is composed of the CD3 loops of both the α and β
chains.

Question 31

The diversity of MHC class I and II genes is due to ___________________.

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

Answer 31

b. the existence of many similar genes encoding MHC molecules in the genome and extensive polymorphism at many of the alleles

Question 32

The combination of all HLA class I and class II allotypes that an individual expresses is referred to as their ____________.

a. haplotype
b. allotype
c. isotype
d. autotype
e. HLA type

Answer 32

e. HLA type

Question 33

All of the following are oligomorphic except ___________________.

a. HLA-G α chain
b. HLA-DO β chain
c. HLA-DQ β chain
d. HLA-A α chain
e. HLA-DR α chain

Answer 33

c. HLA-DQ β chain

Question 34

All of the following are highly polymorphic except _____________.

a. HLA-A α chain
b. HLA-DO α chain
c. HLA-B α chain
d. HLA-DR β chain
e. HLA-C α chain

Answer 34

b. HLA-DO α chain

Question 35

Of the following HLA α-chain loci, which one exhibits the highest degree of polymorphism?

a. HLA-A
b. HLA-B
c. HLA-C
d. HLA-DP
e. HLA-DR

Answer 35

b. HLA-B

Question 36

Which of the following is/are not encoded on chromosome 6 in the HLA complex?

a. β2-microglobulin and invariant chain
b. HLA-G α chain
c. TAP-1
d. tapasin
e. HLA-DR α chain

Answer 36

a. β2-microglobulin and invariant chain

Question 37

The _____ refers to the complete set of HLA alleles that a person possesses on a particular chromosome 6.

a. isoform
b. isotype
c. oligomorph
d. allotype
e. haplotype

Answer 37

e. haplotype

Question 38

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 _________________.

a. alleles; allotypes
b. anchor residues; peptide-binding motif
c. allotype; haplotypes
d. invariant chains; haplotypes
e. restriction residues; MHC allotype

Answer 38

b. anchor residues; peptide-binding motif

Question 39

Directional selection is best described as ______________________________.

a. all polymorphic alleles preserved in a population
b. T-cell receptor interaction with peptide:MHC complexes directed to a planar interface
c. a mechanism in T cells that is analogous to affinity maturation of immunoglobulins
d. selected alleles increase in frequency in a population
e. selection of most appropriate transplant donor directed at the identification of identical or similar
combinations of HLA alleles compared with the transplant recipient

Answer 39

d. selected alleles increase in frequency in a population

Question 40

The role of the CD3 proteins and ζ chain on the surface of the cell is to ___________________.

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

Answer 40

a. transduce signals to the interior of the T cell

Question 41

The immunological consequence of severe combined immunodeficiency disease (SCID) caused by a genetic defect in either RAG-1 or RAG-2 genes is _____________________.

a. lack of somatic recombination in T-cell receptor and immunoglobulin gene loci
b. lack of somatic recombination in T-cell receptor loci
c. lack of somatic recombination in immunoglobulin loci
d. lack of somatic hypermutation in T-cell receptor and immunoglobulin loci
e. lack of somatic hypermutation in T-cell receptor loci

Answer 41

a. lack of somatic recombination in T-cell receptor and immunoglobulin gene loci

Question 42

Which of the following removes CLIP from MHC class II molecules?

a. HLA-DM
b. HLA-DO
c. HLA-DP
d. HLA-DQ
e. HLA-DR

Answer 42

a. HLA-DM

Question 43

CD8 T-cell subpopulations are specialized to combat _______ pathogens, whereas CD4 T-cell subpopulations are specialized to combat _______ pathogens.

a. bacterial; viral
b. dead; live
c. extracellular; intracellular
d. intracellular; extracellular
e. virulent; attenuated

Answer 43

d. intracellular; extracellular

Question 44

Which of the following describes the sequence of events involved in processing of peptides that will be presented as antigen with MHC class I?

a. plasma membrane →TAP1/2 →proteasome →MHC class I →endoplasmic reticulum
b. TAP1/2 →proteasome →MHC class I →endoplasmic reticulum→plasma membrane
c. proteasome →TAP1/2 →MHC class I →endoplasmic reticulum →plasma membrane
d. proteasome →TAP1/2 →endoplasmic reticulum →MHC class I →plasma membrane
e. endoplasmic reticulum →proteasome →MHC class I →TAP1/2 →plasma membrane

Answer 44

c. proteasome →TAP1/2 →MHC class I →endoplasmic reticulum →plasma membrane

Question 45

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 ___________.

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

Answer 45

c. CD4 T cells cannot function

Question 46

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?

a. protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →endocytosis →plasma membrane
b. endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →plasma membrane
c. removal of CLIP from MHC class II →binding of peptide to MHC class II →protease activity →endocytosis →plasma membrane
d. binding of peptide to MHC class II →endocytosis →removal of CLIP from MHC class II →protease activity →plasma membrane
e. plasma membrane →endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II

Answer 46

b. endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →plasma membrane

Question 47

Which of the following cell types does not express MHC class I?

a. erythrocyte
b. hepatocyte
c. lymphocyte
d. dendritic cell
e. neutrophil

Answer 47

a. erythrocyte

Question 48

Which of the following cell types is not considered a professional antigen-presenting cell?

a. macrophage
b. neutrophil
c. B cell
d. dendritic cell
e. all of the above are professional antigen-presenting cells

Answer 48

b. neutrophil

Question 49

Which of the following is mismatched?

a. peptide-binding motif: combination of anchor residues in a peptide capable of binding a particular
MHC haplotype
b. MHC restriction: specificity of T-cell receptor for a particular peptide:MHC molecule complex
c. balancing selection: maintenance of variety of MHC isoforms in a population
d. directional selection: replacement of older MHC isoforms with newer variants
e. interallelic conversion: recombination between two different genes in the same family

Answer 49

e. interallelic conversion: recombination between two different genes in the same family

Question 50

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?

a. 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.
b. Heterozygotes have more opportunity for interallelic conversion and can therefore express larger numbers of MHC alleles.
c. Directional selection mechanisms favor heterozygotes and provide selective advantage to pathogen exposure.
d. As heterozygosity increases, so does the concentration of alloantibodies in the serum, some of which cross-react with and neutralize HIV

Answer 50

a. 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.