Exam 2 questions Flashcards
Microbial protein antigens are mainly captured by __1__ cells and concentrated in __2__, where immune responses are initiated.
Answer 1: dendritic Answer 2: lymph nodes
__1__ are membrane proteins on Antigen Presenting Cells that display peptide antigens for recognition by CD8+ 1/1 T lymphocytes.
MHC class I
What are the following features of acquisition and display of antigens by class I MHC molecules? Subcellular location of antigens in the antigen presenting cell: \_\_1\_\_ How antigen fragments to be displayed are created: \_\_2\_\_ How antigen fragments meet class I MHC molecules: \_\_3\_\_ Where the class I MHC molecules loaded with antigen fragments end up: \_\_4_
Answer 1: cytoplasm
Answer 2: ubiquitinated = tagged for degradation via proteasome
Answer 3: transported via TAP channel to the ER, then combined with MHC via Tapasin
Answer 4: from ER –> golgi –> extracellular surface of the plasma membran
A helper T cell response to a protein antigen requires the participation of antigen-presenting cells that express which of the following types of molecules? A: Class II MHC and costimulators B: Class I MHC and CD4 C: Class II MHC and CD8 D: CD4 and costimulators E: Class II MHC and CD4
A: Class II MHC and costimulators
A young adult is exposed to a virus that infects and replicates in mucosal epithelial cells of the upper respiratory. Cytotoxic T lymphocytes (CTLs) are mobilized to combat this infection because:
A: In response to interferon-gamma secreted during the innate immune response to the virus, the mucosal epithelial cells express class II MHC, with bound viral peptides, on their cell surfaces.
B: Mucosal epithelial cells express class I MHC molecules and are able to process cytoplasmic viral proteins and display complexes of class I MHC and bound viral peptides on their cell surfaces.
C: Antibodies specific for viral antigens bind to these antigens on infected cell surfaces and engage Ig Fc receptors on the CTL, thereby targeting the CTL to the infected cells.
D: Virus-infected mucosal epithelial cells migrate to draining lymphoid tissues, where they present viral peptide antigens to naive CD8+ T cells.
E: Viral infection of the mucosal epithelial cells stimulates them to express E-selectin, which promotes CD8+ T cell adhesion.
B: Mucosal epithelial cells express class I MHC molecules and are able to process cytoplasmic viral proteins and display complexes of class I MHC and bound viral peptides on their cell surfaces.
Name a type of antigen recognized by antibodies that is not recognized by T cell receptors.__1__
bacterial polysacchairde
Name a type of antigen recognized by T cell receptors?__1__
Answer 1: peptide fragments (ex: viral peptide fragment)
What mechanism contributes the most to the diversity of antibody molecules?
A: Multiple V, D, and J gene segment combinations
B: Addition and deletion of nucleotides during joining of V, D, and J gene segments
C: Loss of self-reactive B cells
D: Toll-like receptor signaling in B cells due to PAMP binding
E: Fc region diversity created by somatic hypermutation
> B: Addition and deletion of nucleotides during joining of V, D, and J gene segments
Reading left to right, what is the order of events during T lymphocyte maturation leading to development of a mature CD4+ T cell? A: double-negative T cell, double-positive T cell, complete TCR expression, strong recognition of class II MHC plus bound peptide
B: double-negative T cell, pre-TCR expression, double-positive T cell, complete TCR expression, strong recognition of class II MHC plus bound peptide
C: double-negative T cell, pre-TCR expression, double-positive T cell, complete TCR expression, weak recognition of class II MHC plus bound peptide
D: double-negative T cell, pre-TCR expression, double-positive T cell, complete TCR expression, weak recognition of class I MHC plus bound peptide
E: double-negative T cell, complete TCR expression, double-positive T cell, weak recognition of class II MHC plus bound peptide
> C: double-negative T cell, pre-TCR expression, double-positive T cell, complete TCR expression, weak recognition of class II MHC plus bound peptide
Which of the following best describes a condition that leads to negative selection during T-cell development in the thymus?
A: cell does not recognize any peptide bound to a MHC molecule
B: cell weakly recognizes a peptide bound to a MHC molecule
C: cell stops expressing both CD4 and CD8 on the cell surface
D: cell never expresses a complete TCR
E: cell strongly recognizes a peptide bound to a MHC molecule
E: cell strongly recognizes a peptide bound to a MHC molecule
knock CD4 gene, The student is particularly careful to keep this mouse line in a microbe-free animal facility because these mice are
expected to show:
A: No ability to produce IgM antibodies
B: Impaired ability to produce antibodies and activate macrophages
C: No ability to activate naive class I–restricted T cells
D: Complete absence of cytotoxic T lymphocyte (CTL) responses to viral infections
E: Failure to produce neutrophil
> B: Impaired ability to produce antibodies and activate macrophages
What is the most important costimulator for naïve T cell activation?
B7
What signal would stimulate a dendritic cell to produce B7 molecules?
A: peptide antigen binding
B: peptidoglycan binding TLR
C: bacterial lipid binding RIG-like receptor
D: CD40 binding to CD40 ligand
E: FAS binding to FAS ligand
B: peptidoglycan binding TLR
What cytokine is the principal growth factor for T cells? __1__
IL-2
What additional mechanism is required for a CD4+ effector T cell bound to an MHC class II molecule plus antigen on a macrophage to activate the macrophage killing functions?
A: PAMP binding TLR on T cell
B: B7 ligand on macrophage binding to CD28 on T cell
C: B7 ligand on macrophage binding to CTLA-4 on T cell
D: CD40 ligand on T cell binding to CD40 on macrophage
E: CD8 on macrophage binding to MHC class I molecule on T cell
D: CD40 ligand on T cell binding to CD40 on macrophage
What is NOT a property of memory T lymphocytes elicited in response to a particular microbe?
A: Survive after microbe is no longer present
B: Responsible for future response to microbe being faster than primary response
C: Restricted to residing in lymphoid organs
D: Responsible for future response to microbe being stronger than primary response X E: May be CD4+ or CD8+
> C: Restricted to residing in lymphoid organs
What mechanism draws naive T cells out of lymph nodes if they do not recognize an antigen in the lymph node?
A: Increased expression of CCR-7 chemokine receptor by naïve T cells in the lymph node
B: Increased expression of high levels of L-selectin by naïve T cells in the lymph node
C: Increased expression of CD40 ligand by naïve T cells in the lymph node
D: Increased expression of S1P receptor by naïve T cells in the lymph node
E: Expression of high levels of IL-2 by naïve T cells in the lymph node
> D: Increased expression of S1P receptor by naïve T cells in the lymph node
What is a key property of the Th2 subset of CD4 + effector T cells?
A: a signature cytokine is IFN-gamma
B: main target cells are neutrophils
C: main target cells are macrophages
D: main defense role is fighting helminths
E: a signature cytokine is IL-22
> D: main defense role is fighting helminths
What types of pathogens are the main target of the Th-17 subset of CD4 + effector T cells?
A: intracellular bacteria
B: helminths
C: intracellular viruses
D: extracellular bacteria and fungi
E: intracellular and extracellular microbial pathogens
> D: extracellular bacteria and fungi
Granzyme B and Perforin delivery to target cells across an immune synapse is the effector mechanism of what specific immune system cell type? A: CD8+ CTL B: CD4+ helper T cell X C: Macrophage D: Neutrophil E: B cell
> A: CD8+ CTL
What pathogens evade cell-mediated immunity by inhibiting phagosomal-lysosomal fusion? __1__
mycobacteria|mycobacterium|Mycobacterium tuberculosis|Mycobacteria Tuberculosis|
Which one of the following statements about humoral immune responses is true?
A: Naive B cells are required for initiation of primary responses and memory B cells are required for initiation of secondary responses.
B: Antibody responses to bacterial polysaccharide antigens require CD4+ helper T cells.
C: Heavy chain isotype switching typically occurs in response to bacterial polysaccharide antigens.
D: Affinity maturation does not require helper T cells.
E: Antibody-secreting cells generated during a humoral immune response live for only a few hours.
> A: Naive B cells are required for initiation of primary responses and memory B cells are required for initiation of secondary responses.
Which of the following statements about induction or maintenance of T cell tolerance is NOT true? select all that apply
A: Central tolerance is induced when immature developing T cells in bone marrow or thymus encounter self antigens.
B: Peripheral T cell tolerance results when mature naive T cells recognize antigens without adequate B7-1– or B7-2–mediated costimulation.
C: Peripheral T cell tolerance results when T cells recognize antigen in the setting of an innate immune response to the antigen.
D: Peripheral T cell tolerance to some antigens is induced when mature T cells recognize antigen and bind B7-1 or B7-2 via the inhibitory CTLA-4 receptor.
E: Peripheral T cell tolerance to an antigen may be induced by persistent and repeated stimulation of lymphocytes by that antigen in tissues
> A: Central tolerance is induced when immature developing T cells in bone marrow or thymus encounter self antigens.
C: Peripheral T cell tolerance results when T cells recognize antigen in the setting of an innate immune response to the antigen.
E: Peripheral T cell tolerance to an antigen may be induced by persistent and repeated stimulation of lymphocytes by that antigen in tissues
Which type of hypersensitivity disease is caused by deposition of antigen-antibody complexes in blood vessel walls? A: Type I B: Type II C: Type III D: Type IV E: Type V
> C: Type III
Failure of self-tolerance is the cause of which one of the following types of diseases?
autoimmunity
Immunologic tolerance is defined as:
unresponsiveness of IS to self Ag
Which of the following anatomic regions is normally protected from pathogens only by humoral immune responses and not by cell-mediated immune responses? A: Skin B: Intestinal lumen C: Intestinal epithelium D: Central nervous system E: Spleen
> B: Intestinal lumen
Treatment of antibodies with the enzyme papain under conditions of limited proteolysis results in hinge-region cleavage, yielding monovalent antigen-binding Fab fragments that lack a constant region. Which effector function
of antibodies would Fab fragments be able to perform?
A: Complement pathway activation
B: Antibody-dependent cell-mediated cytotoxicity C: Opsonization
D: Antigen cross-linking and precipitation
E: Microbe neutralization
E: Microbe neutralization
Which of the following events does NOT occur within germinal centers?
A: Somatic mutation of Ig V regions B: Generation of memory B cells C: B cell proliferation D: Affinity maturation E: Ig gene V(D)J recombination
E: Ig gene V(D)J recombination
Which of the following statements about Ig isotype switching is NOT true?
A: IL-4 promotes switching to the IgE isotype
B: Isotype switching involves recombination of a V(D)J complex with downstream C region genes and the deletion of intervening DNA including other C region genes.
C: Activation-induced deaminase (AID) is required.
D: Isotype switching only occurs in activated T cells.
E: The same recombined V(D)J gene complex is used to encode the antigen-binding region of the antibodies produced before and after isotype switching.
D: Isotype switching only occurs in activated T cells.
Which one of the following statements about primary and secondary antibody responses is NOT true?
A: Antibodies in primary responses generally have lower affinity for antigen than those produced in secondary responses.
B: Secondary responses reach peak levels more quickly than primary responses.
C: Primary responses require higher concentrations of antigen for initiation than secondary responses.
D: Primary responses occur to all types of antigens, but secondary responses mostly occur only to protein antigens.
E: Primary responses are characterized by IgG antibodies, whereas secondary responses are dominated by IgM antibodies.
E: Primary responses are characterized by IgG antibodies, whereas secondary responses are dominated by IgM antibodies.
__1__ is the enhancement of phagocytosis by binding of IgG-coated microbes to Fc receptors on phagocytes
opsinization
Which of the following is best associated with the viridans Streptococci?
A: toxic shock syndrome B: impetigo C: dental caries D: necrotizing fasciitis E: beta hemolysis
> C: dental caries
Name a population group we discussed in class that is particularly susceptible to meningitis and pneumonia due to infections by Streptococcus agalactiae.__1__
infants
Name a property of Streptococcus pyogenes M protein.__1_
can bind keratinocytes
Over 90% of Staphylococcus aureus strains are resistant to what antibiotic?__1_
penicillin
What bacterial virulence factor reduces phagocyte killing by converting hydrogen peroxide to water and oxygen?
catalase
What organism causes food poisoning due to superantigen toxins?__1__
staphylococcus
Give 2 examples of adhesins from Gram positive bacteria that promote attachment to other cells. __1____2__
Answer 1: fibronectin binding protein (assists with bacterial attachment to host cells)
Answer 2: Srap protein (assits with bacterial aggregation in endocarditis)
Give an example of a bacterial exotoxin that acts outside a host cell to help microbes spread through tissue. __1__
hyalurodinase
What is NOT true about the ADP ribosylation function of some A-B toxins?
A: ADP ribosylation is associated with the A component of the toxin
B: the ADP-ribose comes from host cell NAD
C: ADP ribosylase activity is expressed inside a host cell
D: ADP ribosylation inactivates a target protein of the bacterial pathogen
E: ADP ribosylation inactivates a target protein of host cells
> D: ADP ribosylation inactivates a target protein of the bacterial pathogen
Which of the following is a function of lipopolysaccharide (LPS) on bacterial cells?
A: creates a strong but mostly ineffective lymphocyte response
B: cleaves complement protein C5a, inhibiting neutrophil chemotaxis
C: blocks access of the membrane attack complex to the bacterial plasma membrane
D: binds of Fc portion of IgGs to inhibit their role in opsonization
E: inhibits activation of the complement cascade
C: blocks access of the membrane attack complex to the bacterial plasma membrane
Which of the following is not a mechanism used by bacteria to survive inside phagocytes?
A: inhibition of phagosomal-lysosomal fusion
B: escape from the phagosome into the cytoplasm
C: production of enzymes that resist lysosomal enzymes
D: inhibition of the phagocytic oxidative pathway (respiratory burst) >
E: increasing cAMP levels in the extracellular environment
> E: increasing cAMP levels in the extracellular environment
A 4-year-old girl stepped on a rusty nail in her backyard. Two days later, she is taken to the pediatrician because her heel is painful, red, and swollen and is warm to the touch. All of the following are mechanisms of innate immunity that may be protecting the patient against pathogenic microbes in the heel wound EXCEPT
A: Intraepithelial lymphocytes present in the skin
B: Circulating neutrophils migrating to the site of the wound
C: Soluble cytokines that induce a local inflammatory response
D: Circulating anti-tetanus toxin antibodies
D: Circulating anti-tetanus toxin antibodies
Which of the following comparisons of the innate and adaptive immune systems is FALSE
A: The innate immune system is more likely to recognize normal self, and therefore cause autoimmunity, than is the adaptive immune system.
B: Receptors used for recognition in innate immunity are encoded in the germline, whereas those of the adaptive immune system are encoded by genes generated via somatic recombination of germline receptor gene loci.
C: The innate and adaptive immune systems share some of the same effector mechanisms.
D: Both the innate and adaptive immune systems can recognize nonmicrobial substances.
E: The innate immune system does not have memory but the adaptive immune system does.
> A: The innate immune system is more likely to recognize normal self, and therefore cause autoimmunity, than is the adaptive immune system.
.
Which of the following is a Toll-like receptor ligand? A: peptidoglycan B: transfer RNA (tRNA) X C: IL-2 D: cytosolic DNA E: cytosolic RNA
> A: peptidoglycan
What is NOT a possible eventual response to activation of signaling through Toll-like receptors (TLRs)?
A: inflammation B: stimulation of adaptive immunity C: antiviral state D: tolerance to TLR ligand E: macrophage activation
D: tolerance to TLR ligand
Antigen-presenting cells (APCs) perform which of the following functions in adaptive immune responses?
A: Display major histocompatibility complex (MHC)-associated peptides on their cell surfaces for surveillance by B lymphocytes
B: Initiate T cell responses by specifically recognizing and responding to foreign protein antigens
C: Display MHC-associated peptides on their cell surfaces for surveillance by T lymphocytes
D: Display polysaccharide antigens on their cell surfaces for surveillance by B lymphocytes
X E: Secrete peptides derived from protein antigens for binding to T cell antigen receptors
> C: Display MHC-associated peptides on their cell surfaces for surveillance by T lymphocytes
hich of the following statements about the antigen-presenting function of macrophages is NOT correct?
A: Macrophages are particularly important at presenting peptides derived from particulate or opsonized antigens that are internalized by phagocytosis.
B: Macrophages become activated by the helper T cells to which they present microbial peptides, and as a result of this activation they become efficient at killing the microbes.
C: Resting macrophages express low levels of class II MHC molecules, but higher class II MHC expression is induced on activation by the T cells to which they present antigen.
D: Macrophages express highly variable, high-affinity receptors for many different antigens, and these receptors facilitate the internalization of the antigens for processing and presentation.
E: Macrophages present antigen to T cells in lymphoid organs and many nonlymphoid organs.
> D: Macrophages express highly variable, high-affinity receptors for many different antigens, and these receptors facilitate the internalization of the antigens for processing and presentation.
Which one of the following statements about dendritic cells is true?
A: Immature dendritic cells are ubiquitously present in skin and mucosal tissues.
B: Dendritic cell maturation occurs after migration to lymph nodes in response to signals derived from activated T cells.
C: Class II MHC and T cell costimulators are highly expressed on immature dendritic cells and are down-regulated during maturation.
D: Dendritic cells that enter lymph nodes through draining lymphatics migrate to the B cellrich follicles in response to chemokines.
E: The principal function of mature dendritic cells is antigen capture.
> A: Immature dendritic cells are ubiquitously present in skin and mucosal tissues.
Which of the following is the main criterion that determines whether a protein is processed and presented via the class I MHC pathway in an antigen-presenting cell (APC)?
A: Encoded by a viral gene
B: Present in an acidic vesicular compartment of the APC
C: Present in the cytosol of the APC
D: Internalized into the cell from the extracellular space
E: Small in size
> C: Present in the cytosol of the APC
Which one of the following statements about T cell tolerance to self-proteins is accurate?
A: Self proteins are not presented by the class I pathway because only microbial proteins, and not self proteins, are ubiquinated in the cytosol. B: Peptides derived from self proteins are not presented by the class I or class II pathways because MHC molecules are expressed only in response to infections. C: Self proteins are not presented by the class II pathway because endosomal acidic proteases digest microbial proteins but not eukaryotic proteins. D: Self peptide/self MHC complexes are formed and displayed by antigen-presenting cells in both class I and class II MHC pathways, but T cells that recognize these complexes usually are not present or are functionally inactive. E: Peptides derived from self proteins are not displayed by MHC molecules because they usually are displaced by the more abundant microbial peptides
> D: Self peptide/self MHC complexes are formed and displayed by antigen-presenting cells in both class I and class II MHC pathways, but T cells that recognize these complexes usually are not present or are functionally inactive
Most T lymphocytes have a dual specificity for which one of the following pairs of molecules (i.e. the T lymphocytes recognize both molecules of the pair)?
A: A particular allelic form of a major histocompatibility complex (MHC) molecule and a peptide bound to the MHC molecule
B: Both MHC class I and class II molecules
C: Both peptide and glycolipid antigens
D: Both soluble peptides and peptide-MHC complexes
E: MHC molecules and CD4 or CD8
> A: A particular allelic form of a major histocompatibility complex (MHC) molecule and a peptide bound to the MHC molecule X B: Both MHC class I and class II molecules
