Exam 2 Flashcards
T cells recognize antigen when the antigen
forms a complex with membrane-bound MHC molecules on another host-derived cell
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
fromtheT-cellmembrane.
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
C) The portion that makes physical contact with the ligand comprises Vβ and Cβ, the domains farthest
fromtheT-cellmembrane.
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
E) Somatic Recombination
Unlike the C regions of immunoglobulin heavy-chain loci, the C regions of the T-cell receptor β-chain loci ______.
Functionally similar
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.
D) It is the consequence of the complete loss of RAG function.
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
E) Expression on the cell surface is not dependent on the CD3 complex.
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.
D) δ
The degradation of pathogen proteins into smaller fragments called peptides is a process commonly referred to as
Antigen processing
The primary reason for transplant rejections is due to differences in _____ between donor and recipient.
MHC Molecules
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
Nucleus
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.
D) They produce a higher proportion of peptides containing acidic amino acids at the carboxy-terminus compared with constitutive proteasome.
Identify which of the following statements is true regarding the transporter associated with antigen processing (TAP).
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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.
C) TAP is an ATP-dependent, membrane-bound transporter.
All of the following are included in the peptide-loading complex except _____________.
a. tapasin
b. calnexin
c. calreticulin
d. ERp57
e. β2-microglobulin
B) Calnexin
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.
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.
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.
A) somatic recombination of V,D, and J segments is responsible for the diversity of antigen-binding sites.
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
E) Vα and Vβ
How many complementarity-determining regions contribute to the antigen-binding site in an intact T-cell receptor?
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IgG possesses _______ binding sites for antigen, and the T-cell receptor possesses _______ binding sites for antigen:
2;1
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
E) All of the above
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.
B) not requiring degradation for recognition
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.
A) When activated, CD8 T-cels in turn activate B cells
Antigen processing involves the breakdown of protein antigens and the subsequent association of peptide fragments on the surface of antigen-presenting cells with ________________.
MHC class I or MHC class II molecules
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.
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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.
A) α:β T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.
- 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
C) peptide:MHC complex
MHC class II molecules are made up of two chains called _______, whose function is to bind peptides and present them to _______ T cells.
alpha (α) and beta (β); CD4
The CDR3 loops of the T-cell receptor contact the _______.
side chains of amino acids in the middle of the peptide.
MHC molecules have promiscuous binding specificity. This means that
a particular MHC molecule has the potential to bind to different peptides.
T-cell receptors interact not only with peptide anchored in the peptide-binding groove of MHC molecules, but also with ____________________.
variable amino acid residues on α helices of the MHC molecule
Cross-priming of the immune response occurs when ______________________________.
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.
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.
D) The most variable part of the T-cell receptor is composed of the CD3 loops of both the ∂ and ß chains.
The diversity of MHC class I and II genes is due to ___________________.
the existence of many similar genes encoding MHC molecules in the genome and extensive
polymorphism at many of the alleles
The combination of all HLA class I and class II allotypes that an individual expresses is referred to as their ____________.
HLA type
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
C) HLA-DQ β chain
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
B) HLA-DO α chain
Of the following HLA α-chain loci, which one exhibits the highest degree of polymorphism? 6 a. HLA-A b. HLA-B c. HLA-C d. HLA-DP e. HLA-DR
B) HLA-B
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
A) β2-microglobulin and invariant chain
The _____ refers to the complete set of HLA alleles that a person possesses on a particular chromosome 6.
Haplotype
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 _________________.
anchor residues; peptide-binding motif
Directional selection is best described as ______________________________.
selected alleles increase in frequency in a population
The role of the CD3 proteins and ζ chain on the surface of the cell is to ___________________.
transduce signals to the interior of the T cell
The immunological consequence of severe combined immunodeficiency disease (SCID) caused by a genetic defect in either RAG-1 or RAG-2 genes is _____________________.
lack of somatic recombination in T-cell receptor and immunoglobulin gene loci
Which of the following removes CLIP from MHC class II molecules?
a. HLA-DM correct
b. HLA-DO
c. HLA-DP
d. HLA-DQ
e. HLA-DR
E) HLA-DR
CD8 T-cell subpopulations are specialized to combat _______ pathogens, whereas CD4 T-cell subpopulations are specialized to combat _______ pathogens.
intracellular; extracellular
Which of the following describes the sequence of events involved in processing of peptides that will be presented as antigen with MHC class I?
proteasome →TAP1/2 →MHC class I →endoplasmic reticulum →plasma membrane
