Exam 2 Flashcards
T-cell receptors structurally resemble ______.
a. the Fc portion of immunoglobulins
b. MHC class 1 molecules
c. secreted antibodies
d. a single Fab of immunoglobulins
e. CD3 ε chains
d. a single Fab of immunoglobulins
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
e. the T-cell receptor α-chain locus contains more C regions
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
a. are functionally similar
All of the following statements regarding γ:δ T cells are correct except:
a. activation is not always dependent on recognition of a peptide:MHC molecule complex
b. they are more abundant in tissue than in the circulation
c. expression on the cell surface is not dependent on the CD3 complex
d. they share some properties with NK cells
e. 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. expression on the cell surface is not dependent on the CD3 complex
The degradation of pathogen proteins into smaller fragments called peptides is a process commonly referred to as ____.
a. endocytosis
b. antigen processing
c. promiscuous processing
d. antigen presentation
e. peptide loading
b. antigen processing
All of the following are primarily associated with CD4 T-cell function except:
a. kill virus-infected cells
b. assist macrophages in sustaining adaptive immune responses through their secretion of cytokines and chemokines
c. improve phagocytic mechanisms of tissue macrophages
d. assist B cells in the production of high-affinity antibodies
e. facilitate responses of other immune-system cells during infection
a. kill virus-infected cells
Which of the statements below is false regarding MHC molecule:
a. MHC molecules have promiscuous binding specificity, which means that one MHC molecule is able
to bind a wide range of peptides with different sequences.
b. The consequence of MHC promiscuity is that humans need only encode a relatively small number of
MHC molecules in their genome if they are to bind to the huge number of pathogen-derived
peptides encountered during a lifetime of infections.
c. MHC molecules are coexpressed on the cell surface. This also ensures that an appropriate density of
MHC molecules populates the cell surface to ensure efficient T-cell engagement and subsequent
activation.
d. Each MHC molecule can bind only to a very restricted number of peptides. This is why we need to expressed so many MHC molecules per cell
e. MHC I molecule are found is most nucleated cells, whereas MHC II are expressed almost exclusively by antigen-presenting cells (APCs), such as B cells, dendritic cells and macrophages.
d. Each MHC molecule can bind only to a very restricted number of peptides. This is why we need to expressed so many MHC molecules per cell
Which of the following is not a characteristic of immunoproteasomes?
a. They produce a higher proportion of peptides containing acidic amino acids at the carboxy terminus compared with constitutive proteasomes.
b. They contain 205 proteasome-activation complexes on the caps.
c. They consist of four rings of seven polypeptide subunits that exist in alternative forms.
d. They make up about 1% of cellular protein.
e. They are produced in response to IFN-γ
produced during innate immune responses.
a. They produce a higher proportion of peptides containing acidic amino acids at the carboxy terminus compared with constitutive proteasomes.
Identify which of the following statements is true regarding the transporter associated with antigen processing (TAP).
a. TAP is an ATP-dependent, membrane-bound transporter
b. TAP is a homodimer composed of two identical subunits
c. TAP transports proteasome-derived peptides from the cytosol directly to the lumen of the Golgi apparatus
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.
a. TAP is an ATP-dependent, membrane-bound transporter
Which of the following characteristics is common to both T-cell receptors and immunoglobulins?
a. Somatic hypermutation changes the affinity of antigen-binding sites and contributes to further
diversification.
b. Class switching enables a change in effector function.
c. The antigen receptor is composed of two identical heavy chains and two identical light chains.
d. Somatic recombination of V, D, and J segments is responsible for the diversity of antigen-binding sites
e. Carbohydrate, lipid, and protein antigens are recognized and stimulate a response
d. Somatic recombination of V, D, and J segments is responsible for the diversity of antigen-binding sites
Which of the following statements is false regarding MHC class I:
a. The complete MHC class I molecule is a heterodimer made up of one α chain and a smaller chain called β-microglobulin. The α chain consists of three extracellular domains α1, α2, and α3—a transmembrane region and a cytoplasmic tail. b. β2-Microglobulin is a single-domain protein covalently associated with the extracellular portion of the α chain, providing support and stability. c. The polymorphic class I molecules in humans are called HLA-A, HLA-B, and HLA-C. The α chain is encoded in the MHC region by an MHC class I gene. The gene for β2-microglobulin is elsewhere in the genome. d. The antigen-binding site is formed by the α1 and α2 domains, the ones farthest from the membrane, which create a peptide-binding groove. The region of the MHC molecule that binds to the T-cell receptor encompasses the α helices of the α1 and α2 domains that make up the outer surfaces of the peptide-binding groove. The α3 domain binds to the T-cell co-receptor CD8. e. The most polymorphic parts of the α chain are the regions of the α1 and α2 domains that bind antigen and the T-cell receptor. β2-Microglobulin is invariant; that is, it is the same in all individuals.
b. β2-Microglobulin is a single-domain protein covalently associated with the extracellular portion of the α chain, providing support and stability.
Which of the following statements is false regarding MHC class II:
a. MHC class II molecules are heterodimers made up of an α chain and a β chain. The α chain consists of α1 and α2 extracellular domains, a transmembrane region, and a cytoplasmic tail. The β chain contains β1 and β2 extracellular domains, a transmembrane region, and a cytoplasmic tail. b. In humans there are three polymorphic MHC class II molecules called HLA-DP, HLA-DQ, and HLA-DR. c. Both chains of an MHC class II molecule are encoded by genes in the MHC region. d. Antigen binds in the peptide-binding groove formed by the α2 and β2 domains. The α helices of the α2 and β2 domains interact with the T-cell receptor. The β1 domain binds to the T-cell co-receptor CD4. e. With the exception of HLA-DRα, which is dimorphic, both the α and β chains of MHC class II molecules are highly polymorphic. Polymorphism is concentrated around the regions that bind antigen and the T-cell receptor in the α1 and β1 domains.
d. Antigen binds in the peptide-binding groove formed by the α2 and β2 domains. The α helices of the
α2 and β2 domains interact with the T-cell receptor. The β1 domain binds to the T-cell co-receptor
CD4.
Identify which of the following statements is false regarding T-cell receptors.
a. The antigen-recognition site of T-cell receptors is formed by the association of which of the Vα and
Vβ domains.
b. Six complementarity-determining regions contribute to the antigen-binding site in an intact T-cell
receptor
c. In B cells, transport of immunoglobulin to the membrane (B-cell receptor) is dependent on
association with two invariant proteins, Igα and Igβ. This function for the T-cell receptor in T cells is
provided by the invariant proteins CD3γ, CD3δ, CD3ε, and ζ.
d. α:β T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.
e. Like α:β T cells, γ:δ T cells are also restricted to the recognition of peptides presented by MHC
molecules.
e. Like α:β T cells, γ:δ T cells are also restricted to the recognition of peptides presented by MHC
molecules.
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. phagolysosome-derived peptides bind to MHC class III molecules
c. 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.
d. cytosol-derived peptides enter the endoplasmic reticulum and bind to MHC class II molecules
e. phagolysosome-derived peptides bind to MHC class II molecules
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.
Identify which of the following statements is false in regard to the binding of peptides to the groove of MHC I and MH II molecules.
a. For all MHC molecules, only a few of the amino acids in the antigen peptide are critical for binding to amino acids in the peptide-binding groove.
b. The critical amino acids in the peptide are called anchor residues; they are the different in all peptides that bind to a given MHC molecule. The other amino acid residues in the peptides must be similar.
c. The pattern of anchor residues that binds to a given MHC molecule is called the peptide-binding motif. Hence, a very large number of discrete peptides can bind to each MHC isoform, the only constraint being the possession of the correct anchor residues at the appropriate positions in the peptide.
d. MHC class I molecules bind peptides that are 8-10 (mostly 9) amino acids long.
e. MHC class II molecules bind longer peptides with a range of lengths, usually from 13 to 25 amino
acids long.
b. The critical amino acids in the peptide are called anchor residues; they are the different in all peptides that bind to a given MHC molecule. The other amino acid residues in the peptides must be similar.
Identify which of the following statements is false regarding the diversity and polymorphism of human leukocyte antigen (HLA) and MHC molecules.
a. 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.
b. The combination of all HLA class I and class II allotypes that an individual expresses is referred to as their HLA type.
c. Interallelic conversion is a recombination between homologous alleles of the same gene. Gene conversion is a recombination between non-homologous alleles of different genes.
d. MHC polymorphisms are non-randomly localized, predominantly to the region of the molecule that makes contact with peptide and T-cell receptors. Random DNA mutations, in contrast, would be scattered through the gene, giving rise to amino acid changes throughout MHC molecules and not just in those areas important for peptide binding and presentation.
e. Directional selection is best described as all polymorphic alleles preserved in a population.
e. Directional selection is best described as all polymorphic alleles preserved in a population.
The role of the CD3 proteins and ζ chain on the surface of the cell is to ___________________.
a. bind to antigen associated with MHC molecules
b. bind to MHC molecules
c. bind to CD4 or CD8 molecules
d. transduce signals to the interior of the T cell
e. facilitate antigen processing of antigens that bind to the surface of T cells
d. transduce signals to the interior of the T cell
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. endoplasmic reticulum →proteasome →MHC class I →TAP1/2 →plasma membrane
b. plasma membrane →TAP1/2 →proteasome →MHC class I →endoplasmic reticulum
c. proteasome →TAP1/2 →MHC class I →endoplasmic reticulum →plasma membrane
d. TAP1/2 →proteasome →MHC class I →endoplasmic reticulum→plasma membrane
e. proteasome →TAP1/2 →endoplasmic reticulum →MHC class I →plasma membrane
c. proteasome →TAP1/2 →MHC class I →endoplasmic reticulum →plasma membrane
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. plasma membrane →endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II
b. protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →endocytosis →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. endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →plasma membrane
e. endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →plasma membrane
Identify which of the following statements is false regarding inheritance of MHC/HLA genes.
a. Allotype is any of the genetically determined variants in the constant region of a given subclass of a
protein that is detectable as an antigen by members of the same species having a different constant
region.
b. Haplotype is one complete set of MHC genes, which is inherited from either one’s mother or one’s
father.
c. Mice and humans are diploid organisms, and therefore have two complete sets of chromosomes
(one maternally-inherited and one paternally-inherited). Therefore, each cell of a human or a mouse
actually possesses two MHC haplotypes - a maternal haplotype and a paternal haplotype.
d. Inbred mouse strains, however, are homozygous at all genetic loci, thus we typically only state the
MHC haplotype once, since both haplotypes are identical.
e. Human populations must maintain a homogenous, less diverse population of HLA class I and II allotypes to increase the chances of surviving many epidemics of infectious disease.
e. Human populations must maintain a homogenous, less diverse population of HLA class I and II allotypes to increase the chances of surviving many epidemics of infectious disease.
Regarding the distinct phases of B-cell development, which of the statements below is incorrect?
a. Repertoire assembly: Bone marrow expression of diverse B-cell receptors.
b. Negative selection: Modification, elimination or inactivation of autoreactive B cells.
c. Positive selection: Selection of a small subset of immature B cells to become mature B cells in the
bone marrow.
d. Searching for infection: Patrolling for infectious material by recirculating continuously between lymph, blood and secondary lymphoid organ compartments.
e. Finding infection: B cells become activated by antigen in secondary lymphoid tissues and then undergo clonal expansion. Attacking infection: B cells differentiate into plasma cells and memory cells in secondary lymphoid tissues.
c. Positive selection: Selection of a small subset of immature B cells to become mature B cells in the
bone marrow.
Which of the following is characteristic of a large pre-B cell?
a. V is rearranging to DJ at the heavy-chain locus.
b. V–J is rearranging at the light-chain locus.
c. μ (mu) heavy chain and lambda or kappa light chain is made.
d. VDJ is successfully rearranged and mu heavy chain is made.
e. D–J is rearranging at the heavy-chain locus
d. VDJ is successfully rearranged and mu heavy chain is made.
Which of the following statements is correct?
a. The κ light-chain genes rearrange before the λ light-chain genes.
b. The κ light-chain genes rearrange before the heavy-chain genes.
c. The μ heavy-chain genes rearrange first and then the λ light-chain genes rearrange
d. The λ light-chain genes rearrange before the heavy-chain genes.
e. The λ light-chain genes rearrange before the κ light-chain genes.
a. The κ light-chain genes rearrange before the λ light-chain genes.
Which of the following statements is false regarding B cell development:
a. Immature B cells develop into B cells in the secondary lymphoid organs
b. The latest stages of late pro-B-cell development are recognized by the association of a surrogate
light chain with a μ (mu) chain. The surrogate light chain is composed of VpreB and λ5.
c. Large pre-B-cell stage constitutively express RAG-1 and RAG-2 proteins.
d. A developing B cell unable to generate a productive rearrangement on any of the four light-chain loci will undergo allelic exclusion.
e. After the production of a functional μ chain as a pre-B-cell receptor: i) RAG proteins are degraded; ii) the chromatin structure of the heavy-chain locus is reorganized to prevent gene rearrangement; iii) transcription of the RAG1 and RAG2 genes ceases; and iv) there is allelic exclusion of a second mu chain.
d. A developing B cell unable to generate a productive rearrangement on any of the four light-chain loci will undergo allelic exclusion.
