Chapter 5

Question 1

The rejoining and repair of DNA during the recombination process leads to additional variation in sequence at the junctions between the rearranged gene segments. This is called junctional diversity and contributes considerably to the final diversity of T cell receptor specificities. Two sources of junctional diversity are introduced: P (palindromic) and N (nontemplated) nucleotides. P nucleotides are generated through endonuclease activity and repair around a hairpin loop at the ends of the gene segments to be joined. N nucleotides are nucleotides added at random at the junctions by terminal deoxynucleotidyl transferase (TdT) activity.

Answer 1

True

Question 2

Gene rearrangement by somatic recombination involves recombination signal sequences (RSSs) that flank V, D, and J segments and are recognized by the enzymes involved in cutting and rejoining the gene segments. An RSS is composed of a conserved nonamer sequence and heptamer sequence separated by a spacer region. There are two types of RSS, one with a spacer of 12 bp and one with a spacer of 23 bp. To ensure that segments are brought together in the right order, an RSS with a 12-bp spacer is always brought together with one with a 23-bp spacer. This is called the 12/23 rule. This ensures that in the beta-chain locus, V rearranges to DJ and not directly to J or another V, and in the alpha-chain locus, V rearranges to J and not to another V.

Answer 2

True

Question 3

On the beta-chain gene locus, recombination signal sequences flank _______ of the V segment, _______ of the D segment, and _______ of the J segment.

a. the 5’ side; both sides; the 3’ side
b. the 5’ side; the 5’ side; the 5’ side
c. the 3’ side; both sides’; the 3’ side
d. both sides; both sides; both sides
e. the 3’ side; both sides; the 5’ side

Answer 3

the 3’ side; both sides; the 5’ side

Question 4

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 4

2; 1

Question 5

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

a. Valpha and Calpha
b. Vbeta and Cbeta
c. Calpha and Cbeta
d. Valpha and Cbeta
e. Valpha and Vbeta

Answer 5

Valpha and Vbeta

Question 6

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 alpha and beta chains form the periphery of the binding site making contact with the alpha helices of the MHC molecule.
d. The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.
e. The most constant part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.

Answer 6

The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.

Question 7

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. alpha helices of the MHC molecule

Answer 7

side chains of amino acids in the middle of the peptide

Question 8

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

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

Answer 8

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

Question 9

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 9

6

Question 10

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.

Answer 10

It is the consequence of complete loss of RAG function.

Question 11

All of the following statements regarding gamma:delta T cells are correct except ___________.

a. they are more abundant in tissue than in the circulation
b. the delta chain is the counterpart to the beta chain in alpha:beta 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 11

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

Question 12

Junctional diversity during gene rearrangement results from the addition of __________________.

a. switch region nucleotides
b. P and N nucleotides
c. V, D, and J nucleotides
d. recombination signal sequences
e. mutations in complementarity-determining regions

Answer 12

P and N nucleotides

Question 13

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 Calpha and Cbeta.
c. The portion that makes physical contact with the ligand comprises Vbeta and Cbeta, 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 alpha and beta chains are very short

Answer 13

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

Question 14

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. alpha
b. beta
c. gamma
d. delta
e. epsilon

Answer 14

delta

Question 15

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 15

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

Question 16

All of the following are highly polymorphic except _____________.

a. HLA-A alpha chain
b. HLA-DO beta chain
c. HLA-B alpha chain
d. HLA-DR beta chain
e. HLA-C alpha chain

Answer 16

HLA-DO beta chain

Question 17

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

a. beta2-microglobulin and invariant chain
b. HLA-G alpha chain
c. TAP-1
d. tapasin
e. HLA-DR alpha chain

Answer 17

beta2-microglobulin and invariant chain

Question 18

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 18

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

Question 19

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 19

intracellular; extracellular

Question 20

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 20

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

Question 21

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 21

anchor residues; peptide-binding motif

Question 22

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 22

haplotype

Question 23

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 alpha helices of the MHC molecule
d. beta2-microglobulin
e. invariant chain

Answer 23

variable amino acid residues on alpha helices of the MHC molecule

Question 24

Which of the following cell types is(are) not considered a professional antigen-presenting cell(s)?

a. macrophage
b. neutrophil
c. B cell
d. dendritic cell
e. neutrophil and B cell

Answer 24

neutrophil

Question 25

All of the following are oligomorphic except ___________________. a. HLA-G alpha chain b. HLA-DO beta chain c. HLA-DQ beta chain d. HLA-A alpha chain e. HLA-DR alpha chain

Answer 25

HLA-DQ beta chain

Question 26

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 26

MHC class I or class II molecules

Question 27

Which of the following cell types does not express MHC class I? a. erythrocyte b. hepatocyte c. lymphocyte d. dendritic cell e. neutrophil

Answer 27

erythrocyte

Question 28

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 and beta; CD4 b. alpha and beta2-microglobulin; CD4 c. alpha and beta; CD8 d. alpha and beta2-microglobulin; CD8 e. alpha and beta; gamma:delta T cells

Answer 28

alpha and beta; CD4

Question 29

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 29

HLA type

Question 30

Of the following HLA-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 30

HLA-B

Question 31

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 31

MHC class I or class II molecules

Question 32

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 32

proteasome -> TAP1/2 -> MHC class I -> endoplasmic reticulum -> plasma membrane

Question 33

Which of the following cell types is(are) not considered a professional antigen-presenting cell(s)? a. macrophage b. neutrophil c. B cell d. dendritic cell e. neutrophil and B cell

Answer 33

neutrophil

Question 34

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 34

HLA-DM

Question 35

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 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 35

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 36

Which of the following statements regarding T-cell receptor recognition of antigen is correct? a. alpha:beta T-cell receptors recognize antigen only as a peptide bound to an MHC molecule. b. alpha:beta T-cell receptors recognize antigens in their native form. c. alpha:beta T-cell receptors, like B-cell immunoglobulins, can recognize carbohydrate, lipid, and protein antigens. d. Antigen processing occurs in extracellular spaces. e. Like alpha:beta T cells, gamma:delta T cells are also restricted to the recognition of antigens presented by MHC molecules.

Answer 36

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

Question 37

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 37

intracellular; extracellular

Question 38

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 38

endocytosis -> protease activity -> removal of CLIP from MHC class II -> binding of peptide to MHC class II -> plasma membrane

Question 39

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 alpha and beta chains form the periphery of the binding site making contact with the alpha helices of the MHC molecule. d. The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains. e. The most constant part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.

Answer 39

The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.

Question 40

All of the following are highly polymorphic except _____________. a. HLA-A alpha chain b. HLA-DO beta chain c. HLA-B alpha chain d. HLA-DR beta chain e. HLA-C alpha chain

Answer 40

HLA-DO beta chain

Question 41

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 and beta; CD4 b. alpha and beta2-microglobulin; CD4 c. alpha and beta; CD8 d. alpha and beta2-microglobulin; CD8 e. alpha and beta; gamma:delta T cells

Answer 41

alpha and beta; CD4

Question 42

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. e. The lower 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.

Answer 42

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.

Question 43

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 43

HLA type

Question 44

All of the following are oligomorphic except ___________________. a. HLA-G alpha chain b. HLA-DO beta chain c. HLA-DQ beta chain d. HLA-A alpha chain e. HLA-DR alpha chain

Answer 44

HLA-DQ beta chain

Question 45

Which of the following describes a typical ligand for an alpha:beta T-cell receptor? a. carbohydrate:MHC complex b. lipid:MHC complex c. peptide:MHC complex d. DNA:MHC complex e. RNA:MHC complex

Answer 45

peptide:MHC complex

Question 46

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 46

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

Question 47

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

Answer 47

a single Fab of immunoglobulins

Question 48

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 48

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

Question 49

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 49

somatic recombination

Question 50

When comparing the T-cell receptor α-chain locus with the immunoglobulin heavy-chain locus, all of the following are correct except a. 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 b. both are encoded on chromosome 14 c. the T-cell receptor α-chain locus does not contain D segments d. the T-cell receptor α-chain locus contains more V and J regions e. the T-cell receptor α-chain locus contains more C regions f. they both contain exons encoding a leader peptide

Answer 50

the T-cell receptor α-chain locus contains more C regions

Question 51

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 51

are functionally similar

Question 52

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 52

It is the consequence of complete loss of RAG function.

Question 53

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 53

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

Question 54

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 54

δ

Question 55

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 55

antigen processing

Question 56

All of the following are primarily associated with CD4 T-cell function except a. improve phagocytic mechanisms of tissue macrophages b. assist B cells in the production of high-affinity antibodies c. kill virus-infected cells d. facilitate responses of other immune-system cells during infection e. assist macrophages in sustaining adaptive immune responses through their secretion of cytokines and chemokines

Answer 56

kill virus-infected cells

Question 57

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 57

MHC molecules

Question 58

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 58

nucleus

Question 59

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 59

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

Question 60

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 60

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

Question 61

All of the following are included in the peptide-loading complex except a. tapasin b. calnexin c. calreticulin d. ERp57 e. β2-microglobulin

Answer 61

calnexin

Question 62

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 62

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 63

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

Answer 63

a. removal of amino acids from the amino-terminal end by endoplasmic reticulum aminopeptidase (ERAP) c. the participation of tapasin in finding a ‘good fit’ for class I heterodimers d. recycling an MHC class I heterodimer if the peptide falls out of its peptide-binding groove

Question 64

In contrast to immunoglobulins, α:β T-cell receptors recognize epitopes present on _______ antigens: a. carbohydrate b. lipid c. protein d. carbohydrate and lipid e. carbohydrate, lipid, and protein

Answer 64

protein

Question 65

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 65

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

Question 66

The antigen-recognition site of T-cell receptors is formed by the association of which of the following domains? a. Vα and Cα b. Vβ and Cβ c. Cα and Cβ d. Vα and Cβ e. Vα and Vβ

Answer 66

Vα and Vβ

Question 67

The most variable parts of the T-cell receptor are a. Vα and Cα b. Vβ and Cβ c. Cα and Cβ d. Vα and Cβ e. Vα and Vβ

Answer 67

Vα and Vβ

Question 68

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 68

6

Question 69

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 69

2; 1

Question 70

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: a. λ light chain; κ light chain b. heavy chain; λ light chain c. κ light chain; heavy chain d. λ light chain; heavy chain e. κ light chain; λ light chain

Answer 70

κ light chain; heavy chain

Question 71

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 71

All of the above

Question 72

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 _______: a. α; also rearranged b. α; deleted c. α; transcribed d. β; deleted e. γ; also rearranged

Answer 72

α; deleted

Question 73

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 73

not requiring degradation for recognition

Question 74

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 74

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

Question 75

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 75

MHC class I or class II molecules

Question 76

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 76

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

Question 77

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 77

peptide:MHC complex

Question 78

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 78

alpha (α) and beta (β); CD4

Question 79

The complementarity-determining region (CDR) 1 and CDR2 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 79

α helices of the MHC molecule

Question 80

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 80

side chains of amino acids in the middle of the peptide

Question 81

The peptide-binding groove of MHC class I molecules is composed of the following extracellular domains: a. α1:β1 b. β1:β2 c. α2:β2 d. α2:α3 e. α1:α2

Answer 81

α1:α2

Question 82

To which domain of MHC class II does CD4 bind? a. α1 b. β1 c. α2 d. β2 e. α3

Answer 82

β2

Question 83

To which domain of MHC class I does CD8 bind? a. α1 b. β1 c. α2 d. β2 e. α3

Answer 83

α3

Question 84

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

Answer 84

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

Question 85

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 85

variable amino acid residues on α helices of the MHC molecule

Question 86

Cross-priming of the immune response occurs when _____. (Select all that apply.) 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 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 d. peptides of nuclear or cytosolic proteins are presented by MHC class II molecules

Answer 86

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 d. peptides of nuclear or cytosolic proteins are presented by MHC class II molecules

Question 87

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 87

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

Question 88

The diversity of MHC class I and II genes is due to _____. (Select all that apply.) 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 c. somatic hypermutation d. extensive polymorphism at many of the alleles e. isotype switching

Answer 88

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

Question 89

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 89

HLA type

Question 90

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 90

HLA-DQ β chain

Question 91

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 91

HLA-DO α chain

Question 92

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 92

HLA-B

Question 93

Which of the following are not encoded on chromosome 6 in the HLA complex? (Select all that apply.) a. β2-microglobulin b. HLA-G α chain c. TAP-1 d. invariant chain e. tapasin f. HLA-DR α chain

Answer 93

a. β2-microglobulin | d. invariant chain

Question 94

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 94

haplotype

Question 95

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 95

anchor residues; peptide-binding motif

Question 96

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 96

selected alleles increase in frequency in a population

Question 97

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 97

transduce signals to the interior of the T cell

Question 98

Which of the following accurately completes this statement: “The function of _______ T cells is to make contact with _______ and _______”? (Select all that apply.) a. CD8; virus-infected cells; kill virus-infected cells b. CD8; B cells; stimulate B cells to differentiate into plasma cells c. CD4; macrophages; enhance microbicidal powers of macrophages d. CD4; B cells; stimulate B cells to differentiate into plasma cells e. All of the above are accurate

Answer 98

a. CD8; virus-infected cells; kill virus-infected cells c. CD4; macrophages; enhance microbicidal powers of macrophages d. CD4; B cells; stimulate B cells to differentiate into plasma cells

Question 99

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 99

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

Question 100

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 100

HLA-DM

Question 101

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 101

intracellular; extracellular

Question 102

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 102

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

Question 103

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 103

CD4 T cells cannot function

Question 104

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 104

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

Question 105

Which of the following cell types does not express MHC class I? a. erythrocyte b. hepatocyte c. lymphocyte d. dendritic cell e. neutrophil

Answer 105

erythrocyte

Question 106

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 106

neutrophil

Question 107

Which of the following HLA-DRB genotypes is not possible in an individual? (X: X represents diploid genotype.) a. DRB1: DRB1 b. DRB1, DRB3: DRB1, DRB4 c. DRB1: DRB1, DRB5 d. DRB1, DRB4: DRB1 e. DRB3: DRB1, DRB5

Answer 107

DRB3: DRB1, DRB5

Question 108

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 108

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

Question 109

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 109

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.

Question 110

Which of the following cell types do not express MHC class I? a. Erythrocyte b. Hepatocyte c. Lymphocyte d. Dendritic cell e. Neutrophil

Answer 110

Erythrocyte

Question 111

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 111

HLA type