Chapter 5 Flashcards
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.
True
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.
True
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
the 3’ side; both sides; the 5’ side
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
2; 1
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
Valpha and Vbeta
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.
The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.
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
side chains of amino acids in the middle of the peptide
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.
alpha:beta T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.
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
6
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.
It is the consequence of complete loss of RAG function.
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
expression on the cell surface is not dependent on the CD3 complex
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
P and N nucleotides
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
The portion that makes physical contact with the ligand comprises Vbeta and Cbeta, the domains farthest from the T-cell membrane.
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
delta
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
forms a complex with membrane-bound MHC molecules on another host-derived cell
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
HLA-DO beta chain
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
beta2-microglobulin and invariant chain
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
a particular MHC molecule has the potential to bind to different peptides
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
intracellular; extracellular
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
the existence of many similar genes encoding MHC molecules in the genome and extensive polymorphism at many of the alleles
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
anchor residues; peptide-binding motif
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
haplotype
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
variable amino acid residues on alpha helices of the MHC molecule
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
neutrophil
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
HLA-DQ beta chain
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
MHC class I or class II molecules
Which of the following cell types does not express MHC class I?
a. erythrocyte
b. hepatocyte
c. lymphocyte
d. dendritic cell
e. neutrophil
erythrocyte
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
alpha and beta; CD4
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
HLA type
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
HLA-B
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
MHC class I or class II molecules
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
proteasome -> TAP1/2 -> MHC class I -> endoplasmic reticulum -> plasma membrane
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
neutrophil
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
HLA-DM
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
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.
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.
alpha:beta T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.
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
intracellular; extracellular
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
endocytosis -> protease activity -> removal of CLIP from MHC class II -> binding of peptide to MHC class II -> plasma membrane
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.
The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.
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
HLA-DO beta chain
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
alpha and beta; CD4
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.
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.
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
HLA type
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
HLA-DQ beta chain
