Exam 2 questions Flashcards
1
Q
Microbial protein antigens are mainly captured by __1__ cells and concentrated in __2__, where immune responses are initiated.
A
Answer 1: dendritic Answer 2: lymph nodes
2
Q
__1__ are membrane proteins on Antigen Presenting Cells that display peptide antigens for recognition by CD8+ 1/1 T lymphocytes.
A
MHC class I
3
Q
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_
A
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
4
Q
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
A: Class II MHC and costimulators
5
Q
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.
A
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.
6
Q
Name a type of antigen recognized by antibodies that is not recognized by T cell receptors.__1__
A
bacterial polysacchairde
7
Q
Name a type of antigen recognized by T cell receptors?__1__
A
Answer 1: peptide fragments (ex: viral peptide fragment)
8
Q
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
A
> B: Addition and deletion of nucleotides during joining of V, D, and J gene segments
9
Q
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
A
> C: double-negative T cell, pre-TCR expression, double-positive T cell, complete TCR expression, weak recognition of class II MHC plus bound peptide
10
Q
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
A
E: cell strongly recognizes a peptide bound to a MHC molecule
11
Q
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
A
> B: Impaired ability to produce antibodies and activate macrophages
12
Q
What is the most important costimulator for naïve T cell activation?
A
B7
13
Q
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
A
B: peptidoglycan binding TLR
14
Q
What cytokine is the principal growth factor for T cells? __1__
A
IL-2
15
Q
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
A
D: CD40 ligand on T cell binding to CD40 on macrophage
16
Q
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+
A
> C: Restricted to residing in lymphoid organs
17
Q
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
A
> D: Increased expression of S1P receptor by naïve T cells in the lymph node
18
Q
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
A
> D: main defense role is fighting helminths
19
Q
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
A
> D: extracellular bacteria and fungi
20
Q
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
> A: CD8+ CTL
21
Q
What pathogens evade cell-mediated immunity by inhibiting phagosomal-lysosomal fusion? __1__
A
mycobacteria|mycobacterium|Mycobacterium tuberculosis|Mycobacteria Tuberculosis|
22
Q
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
> A: Naive B cells are required for initiation of primary responses and memory B cells are required for initiation of secondary responses.
23
Q
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
> 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
24
Q
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
A
> C: Type III
25
Failure of self-tolerance is the cause of which one of the following types of diseases?
autoimmunity
26
Immunologic tolerance is defined as:
unresponsiveness of IS to self Ag
27
```
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
28
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
29
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
30
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.
31
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.
32
__1__ is the enhancement of phagocytosis by binding of IgG-coated microbes to Fc receptors on phagocytes
opsinization
33
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
34
Name a population group we discussed in class that is particularly susceptible to meningitis and pneumonia due to infections by Streptococcus agalactiae.__1__
infants
35
Name a property of Streptococcus pyogenes M protein.__1_
can bind keratinocytes
36
Over 90% of Staphylococcus aureus strains are resistant to what antibiotic?__1_
penicillin
37
What bacterial virulence factor reduces phagocyte killing by converting hydrogen peroxide to water and oxygen?
catalase
38
What organism causes food poisoning due to superantigen toxins?__1__
staphylococcus
39
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)
40
Give an example of a bacterial exotoxin that acts outside a host cell to help microbes spread through tissue. __1__
hyalurodinase
41
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
42
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
43
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
44
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
45
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.
.
46
```
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
47
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
48
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
49
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.
50
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.
51
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
52
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
53
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
54
```
A healthy 45-year-old child-care worker becomes infected with a virus and develops a sore throat, cough, and fever. Infected cells in the bronchial mucosa of this patient process virus-encoded proteins through an
intracellular pathway and display peptides derived from the protein on the cell surface bound to class I MHC molecules. CD8 T cells migrate to the mucosa and recognize these peptide-MHC complexes. Which of the following components of the TCR actually bind to the viral peptide-MHC complex?
```
A: Hypermutated regions: 1 in the alpha chain, 2 in the beta chain
B: Complementarity-determining regions: 3 in the alpha chain, 3 in the beta chain
C: Hypervariable regions: 2 in the alpha chain, 2 in the beta chain
D: Congenic regions: 1 in the alpha chain, 1 in the beta chain
E: One peptide-binding groove formed by the alpha chain and the beta2-microglobulin chain
> B: Complementarity-determining regions: 3 in the alpha chain, 3 in the beta chain
55
The T cell receptor (TCR) complex differs from an immunoglobulin molecule in which one of the following ways?
A: On average, a TCR binds antigen with much lower affinity than does an Ig molecule.
B: The TCR can serve as a lymphocyte antigen receptor, but an Ig molecule cannot.
C: Only the TCR can bind soluble antigen directly.
D: The TCRs expressed by one clone of T cells can undergo changes in constant region structure after cellular activation, whereas Ig molecules expressed by one clone of B cells do not.
E: The TCR polypeptide chains have short cytoplasmic tails and rely on associated proteins for signaling functions, whereas membrane Ig receptors are competent signaling molecules on their own
> A: On average, a TCR binds antigen with much lower affinity than does an Ig molecule.
56
Both CD28 and CTLA-4 are receptors on T cells that are critical for regulating T cell activation. In which one of the following ways does CD28 differ from CTLA-4?
A: Only CD28 binds the costimulatory ligands B7-1 and B7-2 expressed on professional antigen-presenting cells.
B: CD28 counteracts positive, pro-proliferative T cell signals delivered by CTLA-4.
C: CD28 is constitutively expressed on naive T cells, whereas CTLA-4 is expressed on activated T cells.
D: CD28 binds its ligand with much greater affinity than does CTLA-4.
C: CD28 is constitutively expressed on naive T cells, whereas CTLA-4 is expressed on activated T cells.
57
All of the following protein-protein interactions are involved in activation of naive helper T cells by antigen- presenting cells (APCs) EXCEPT:
A: Binding of peptide-MHC complexes on the APC to the TCR on the T cell
B: Binding of CD4 on the T cell to nonpolymorphic regions of class II MHC molecules on the APC
C: Binding of B7 molecules on the APC with CD28 molecules on the T cell
D: Binding of CD40L on the T cell with CD40 on the APC
> D: Binding of CD40L on the T cell with CD40 on the APC
58
Which one of the following descriptions of cytokine interleukin-2 (IL-2) is NOT true?
A: Expression of its gene requires multiple transcription factors, such as Fos, Jun, and NFAT.
B: It acts as an autocrine growth factor for T cells.
C: It binds to a receptor on T cells that are secreting IL-2.
D: It is only involved in the proliferation of helper T cells and not CTLs.
E: It promotes susceptibility of T cells to apoptosis.
> D: It is only involved in the proliferation of helper T cells and not CTLs.
59
```
What type of molecule on antigen-presenting cells (APCs) binds to CD28 on naive T cells in a co-stimulatory role for T cell activation?
A: B7
B: CTLA-4 X C: CD40
D: S1P
E: IL-2
```
B7
60
```
Increased expression of what cell surface molecule on naive T cells contributes to migration of the cells to lymph nodes by binding chemokines only made in lymphoid tissue?
A: CCR-7
B: E-selectin
C: CD40 ligand
D: S1P receptor
E: IL-2 receptor
```
> A: CCR-7
61
Activated macrophages perform all of the following functions EXCEPT:
18
A: Reduce expression of MHC molecules
B: Produce of lysosomal enzymes that kill phagocytosed microbes
C: Present antigen to helper T cells
D: Secrete inflammatory cytokines such as tumor necrosis factor and interleukin-1
E: Increase expression of B7 molecules
> A: Reduce expression of MHC molecules
62
```
Which pair of molecules is a component of cytolytic T lymphocyte (CTL) granules and is important in the mechanism of CTL killing of target cells?
A: Perforin and Fas ligand
B: P-selectin and tumor necrosis factor
C: Major basic protein and granzyme B
D: C9 and interferon-gamma
E: Perforin and granzyme B
```
> E: Perforin and granzyme B
63
Which subset of CD4+ helper T lymphocytes activate eosinophils?
```
A: Th1
B: Th2
C: Th3
D: Th17
E: cytotoxic T cells
```
> B: Th2
64
Which subset of CD4+ helper T lymphocytes activate macrophages to kill phagocytosed microbes?
```
A: Th1
B: Th2
C: Th3
D: Th17
E: cytotoxic T cells
```
> A: Th1
65
Which one of the following statements about primary and secondary antibody responses is NOT true?
A: Antibodies in primary responses generally have higher 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 IgM antibodies, whereas secondary responses are dominated by IgG antibodies.
> A: Antibodies in primary responses generally have higher affinity for antigen than those produced in secondary responses.
66
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.
67
Which of the following events does NOT occur within germinal centers?
```
A: Somatic mutation of Ig V genes
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
68
Which of the following statements about Ig isotype switching is true?
A: IL-4 promotes switching to the IgM isotype
B: Isotype switching involves recombination of a V(D)J complex with downstream V region genes and the deletion of intervening DNA including other V region genes.
C: Activation-induced deaminase (AID) is not required.
D: Isotype switching only occurs in activated B cells.
E: Different recombined V(D)J gene complexes are used to encode the antigen-binding region of the antibodies produced before and after isotype switching.
> D: Isotype switching only occurs in activated B cells.
69
n 1890, Emil von Behring and Shibasaburo Kitasato demonstrated the efficacy of serum transfer at conferring infection resistancea process now known as passive immunity. The researchers isolated serum from animals that had recovered from infection with the diphtheria bacilli and subsequently injected the serum into other healthy animals. This procedure conferred specific resistance against the pathologic effects of diphtheria infection in the recipient animals. Which of the following immune phenomena were primarily responsible for these effects?
A: Pathogen-specific B and T cells from the original infected animals triggered a robust immune response after re-exposure to diphtheria antigens in the recipient animal.
B: Inflammatory cytokines in the transferred serum increased the strength and efficacy of innate immune system activity.
C: Diphtheria-specific antibodies in the transferred serum neutralized bacillus toxins and promoted bacterial elimination by innate effector cells.
D: Serum complement proteins in the transfer directly promoted bacterial cell lysis and phagocytosis.
E: The recipient animals immune response to the foreign serum further activated host immune system function, allowing greater response to the bacillus infection
C: Diphtheria-specific antibodies in the transferred serum neutralized bacillus toxins and promoted bacterial elimination by innate effector cells.
70
Most effective vaccines that are currently in widespread use are specific for pathogenic viruses, and the immunity
induced by the vaccines is mediated largely by antibodies. Which of the following statements accurately
describes the major mechanism by which these vaccine-dependent antibody responses function?
A: The antibodies bind extracellular viral particles and prevent them from infecting cells.
B: The antibodies bind to viral antigens on the surface of infected cells and promote phagocytosis of the cells.
C: The antibodies bind to viral antigens on the surface of infected cells and promote complement-mediated lysis of the cells.
D: The antibodies bind to extracellular viral particles and target Fc receptor-expressing cytolytic T lymphocytes to kill the viruses.
E: The antibodies bind to viral envelope proteins and induce signals that inhibit viral replication.
A: The antibodies bind extracellular viral particles and prevent them from infecting cells.
71
Which of the following binds to and is readily phagocytosed by mononuclear phagocytes and neutrophils?
```
A: Antigen-IgM complexes
B: Complement protein C3b bound to a bacterium
C: Free serum IgG
D: IgE bound to a helminthic parasite
E: Mannose-binding lectin (MBL)
```
> B: Complement protein C3b bound to a bacterium
72
```
The classical pathway of the complement system starts with recognition of antigen-engaged antibodies by
A: complement C5a protein
B: complement C3b protein
C: complement C3d protein
D: complement C1 protein
E: a Fc receptor
```
> D: complement C1 protein
73
```
Unresponsiveness of the immune system to an antigen, which is induced by previous exposure to that antigen is called:
A: Immunologic tolerance
B: Autoimmunity
C: Inflammation
D: Apoptosis
E: Anergy
```
> A: Immunologic tolerance
74
Central T lymphocyte tolerance
A: is induced when immature developing T cells in bone marrow or thymus encounter self antigens.
B: results when mature naive T cells recognize antigens with B7mediated costimulation.
C: results when T cells recognize antigen in the setting of an innate immune response to the antigen.
D: is induced when mature T cells recognize antigen and bind B7 via the CD-28 receptor.
E: may be induced by persistent and repeated stimulation of lymphocytes by that antigen in tissues
> A: is induced when immature developing T cells in bone marrow or thymus encounter self antigens.
75
A mechanism of central B lymphocyte tolerance is
A: receptor editing by expression of a new Ig G heavy chain
B: receptor editing by expression of a new Ig V light chain
C: receptor editing by expression of a new Ig M heavy chain
D: receptor editing by expression of a new Ig K light chain
E: receptor editing by expression of a new Ig G light chain
> B: receptor editing by expression of a new Ig V light chain
76
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
77
```
What virulence factor is expressed on the surface of bacterial cells (EPEC E. coli for example) and mediates bacterial entry into host cells by interacting with a receptor that has been translocated into the host cell?
A: invasin
B: intimin
C: internalin
D: fibronectin binding protein
E: sialic acid binding protein
```
intimin
78
Gram-negative bacteria often bind to host cells by
A: bacterial fimbriae proteins interacting with host cell glycolipids
B: binding to host fibronectin
C: lipid A interacting with host integrins
D: bacterial sialic acid binding to host neuraminidase
E: bacterial protein A binding to host cell IgG
> A: bacterial fimbriae proteins interacting with host cell glycolipids X B: binding to host fibronectin
79
Gram-positive bacteria often bind to host cells by
A: bacterial fimbriae proteins interacting with host cell glycolipids
B: binding to host fibronectin
C: lipid A interacting with host integrins
D: bacterial sialic acid binding to host neuraminidase
E: bacterial protein A binding to host cell IgG
B: binding to host fibronectin
80
LPS
38
A: is a normal cell surface component of gram positive bacteria
B: contains the K antigen used for identifying strains of pathogenic bacteria
C: causes fever in the host organism
D: is an exotoxin produced by pathogenic E. coli
E: is a host defense factor present in the lumen of the gut
> C: causes fever in the host organism
81
Which of the following is NOT an example of a means by which pathogenic bacteria can cause death of human host cells either directly or indirectly?
A: bacterial production of lipases
B: cell-mediated immune response
C: lipid peroxidation caused by bacterial growth within host cells
D: LPS activiation of the complement system
E: ADP ribosylation of translation factor EF-2 by an A-B toxin
D: LPS activiation of the complement system
82
What is true about the ADP ribosylation function of some A-B toxins?
A: ADP ribosylation activates a target protein of the bacterial pathogen
B: the ADP-ribose comes from host cell RNA molecules
C: ADP ribosylation activates a target protein of host cells
D: ADP ribosylation inactivates a target protein of the bacterial pathogen
E: ADP ribosylation inactivates a target protein of host cells
> E: ADP ribosylation inactivates a target protein of host cells
83
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
84
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 peptid
C: double-negative T cell, pre-TCR expression, double-positive T cell, complete TCR expression, weak recognition of class II MHC plus bound peptide
85
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
86
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
87
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
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
88
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
89
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.
90
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
91
Both CD28 and CTLA-4 are receptors on T cells that are critical for regulating T cell activation. In which one of the following ways does CD28 differ from CTLA-4?
A: Only CD28 binds the costimulatory ligands B7-1 and B7-2 expressed on professional antigen-presenting cells.
B: CD28 counteracts positive, pro-proliferative T cell signals delivered by CTLA-4.
C: CD28 is constitutively expressed on naive T cells, whereas CTLA-4 is expressed on activated T cells.
D: CD28 binds its ligand with much greater affinity than does CTLA-4.
> C: CD28 is constitutively expressed on naive T cells, whereas CTLA-4 is expressed on activated T cells.
92
All of the following protein-protein interactions are involved in activation of naive helper T cells by antigen- presenting cells (APCs) EXCEPT:
A: Binding of peptide-MHC complexes on the APC to the TCR on the T cell
B: Binding of CD4 on the T cell to nonpolymorphic regions of class II MHC molecules on the APC
C: Binding of B7 molecules on the APC with CD28 molecules on the T cell
D: Binding of CD40L on the T cell with CD40 on the APC
> D: Binding of CD40L on the T cell with CD40 on the APC
93
Which one of the following statements about primary and secondary antibody responses is NOT true?
A: Antibodies in primary responses generally have higher 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 IgM antibodies, whereas secondary responses are dominated by IgG antibodies.
> A: Antibodies in primary responses generally have higher affinity for antigen than those produced in secondary responses.
94
Which one of the following statements about humoral immune responses is true?
8
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.
95
```
Which of the following events does NOT occur within germinal centers?
A: Somatic mutation of Ig V genes
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
96
Which of the following statements about Ig isotype switching is true?
A: IL-4 promotes switching to the IgM isotype
B: Isotype switching involves recombination of a V(D)J complex with downstream V region genes and the deletion of intervening DNA including other V region genes.
C: Activation-induced deaminase (AID) is not required.
D: Isotype switching only occurs in activated B cells.
E: Different recombined V(D)J gene complexes are used to encode the antigen-binding region of the antibodies produced before and after isotype switching.
> D: Isotype switching only occurs in activated B cells.
97
n 1890, Emil von Behring and Shibasaburo Kitasato demonstrated the efficacy of serum transfer at conferring infection resistancea process now known as passive immunity. The researchers isolated serum from animals that had recovered from infection with the diphtheria bacilli and subsequently injected the serum into other healthy animals. This procedure conferred specific resistance against the pathologic effects of diphtheria infection in the recipient animals. Which of the following immune phenomena were primarily responsible for these effects?
A: Pathogen-specific B and T cells from the original infected animals triggered a robust immune response after re-exposure to diphtheria antigens in the recipient animal.
B: Inflammatory cytokines in the transferred serum increased the strength and efficacy of innate immune system activity.
C: Diphtheria-specific antibodies in the transferred serum neutralized bacillus toxins and promoted bacterial elimination by innate effector cells.
D: Serum complement proteins in the transfer directly promoted bacterial cell lysis and phagocytosis.
E: The recipient animals immune response to the foreign serum further activated host immune system function, allowing greater response to the bacillus infection.
> C: Diphtheria-specific antibodies in the transferred serum neutralized bacillus toxins and promoted bacterial elimination by innate effector cells.
98
Most effective vaccines that are currently in widespread use are specific for pathogenic viruses, and the immunity induced by the vaccines is mediated largely by antibodies. Which of the following statements accuratelydescribes the major mechanism by which these vaccine-dependent antibody responses function?
A: The antibodies bind extracellular viral particles and prevent them from infecting cells.
B: The antibodies bind to viral antigens on the surface of infected cells and promote phagocytosis of the cells.
C: The antibodies bind to viral antigens on the surface of infected cells and promote complement-mediated lysis of the cells.
D: The antibodies bind to extracellular viral particles and target Fc receptor-expressing cytolytic T lymphocytes to kill the viruses.
E: The antibodies bind to viral envelope proteins and induce signals that inhibit viral replication.
A: The antibodies bind extracellular viral particles and prevent them from infecting cells.
99
The classical pathway of the complement system starts with recognition of antigen-engaged antibodies by
```
A: complement C5a protein
B: complement C3b protein
C: complement C3d protein
D: complement C1 protein
E: a Fc receptor
```
> D: complement C1 protein
100
A helper T cell response to a protein antigen requires the participation of antigen-presenting cells that express
14 which of the following types of molecules? 1/1
A: Class II MHC and costimulators
B: Class I MHC and CD4
C: Class II MHC and CD8
D: CD4 and costimulators
A: Class II MHC and costimulators
101
Name a type of antigen recognized by T cell receptors?__1__
| 15
Answer 1: Peptide
102
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
103
What is the most important costimulator for naïve T cell activation?
```
A: ICOS ligand
B: B7 ligand
C: PD-L ligand
D: CD40 ligand
E: FAS ligand
```
B7
104
What cytokine is the principal growth factor for T cells? __1__
Answer 1: IL-2
105
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
106
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
107
```
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
C: Macrophage
D: Neutrophil
E: B cell
```
> A: CD8+ CTL
108
What pathogens evade cell-mediated immunity by inhibiting phagosomal-lysosomal fusion? __1__
Answer 1: Mycobacterium
109
Immunologic tolerance is defined as:
A: The removal of an antigen, or the microbes expressing the antigen, by the immune system, so that the host can tolerate the infection
B: Activation of only B cells, and not T cells, on exposure to an antigen
C: Unresponsiveness of the immune system to self antigens
D: The production of memory B cells and T cells on primary exposure to an antigen, which allows the host to tolerate a secondary exposure to the antigen
E: Vaccination of individuals against particular pathogens to prevent subsequent infections
> C: Unresponsiveness of the immune system to self antigens
110
```
Failure of self-tolerance is the cause of which one of the following types of diseases?
25
A: Allograft rejection
B: Autoimmunity
C: Atopy
D: Anergy
E: Acne
```
B: Autoimmunity
111
Which of the following statements about induction or maintenance of T cell tolerance is NOT true?
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 B7-2mediated 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.
> C: Peripheral T cell tolerance results when T cells recognize antigen in the setting of an innate immune response to the antigen.
112
What role does catalase have for those pathogenic bacteria that express it?
27
A: Inhibits phagocytic cysteine proteases
B: Degrades collagen, allowing bacteria to penetrate tissue
C: Removes hydrogen peroxide produced by phagocytes
D: Creates a fibrin coat around bacteria, preventing phagocytosis
E: converts plasminogen to plasmin, dissolving fibrin clots
> C: Removes hydrogen peroxide produced by phagocytes
113
What role does protein A play for Staphylococcus aureus?
A: inhibits phagocytic cysteine proteases
B: degrades collagen, allowing bacteria to penetrate tissue
C: competes with neutrophils for binding of Fc part of IgGs
D: creates a fibrin coat around bacteria
E: converts plasminogen to plasmin, dissolving fibrin clots
> C: competes with neutrophils for binding of Fc part of IgGs
114
```
What is false about Staphylococcus aureus ?
29
A: some strains produce superantigens
B: is a facultative anaerobe
C: has a capsule
D: is coagulase negative
E: is catalase positive
```
> D: is coagulase negative
115
```
What bacterial virulence factor has an activity that results in creation of a fibrin coat around bacteria?
30
A: catalase
B: coagulase
C: protein A
D: beta-lactamase
E: exfoliative toxin
```
> B: coagulase
116
```
Scarlet fever is a caused by what organism?
31
A: Streptococcus pyogenes
B: Streptococcus pneumonia
C: Staphylococcus aureus
D: Bacteroides fragilis
E: Neisseria meningitidis
```
> A: Streptococcus pyogenes
117
Which of the following lists one or more virulence factors for Streptococcus pneumoniae?
32 1/1
A: Staphylokinase
B: Protein A and LPS
C: Pneumolysin O and a polysaccharide capsule
D: Tracheal cytotoxin
E: Alginate
> C: Pneumolysin O and a polysaccharide capsule
118
What is true about Streptococcus pneumoniae?
33
A: is an alpha-hemolytic, encapsulated bacterium
B: is only found in individuals with symptomatic lung infections (coughing, fever, etc.)
C: causes a mild, "walking pneumonia"
D: is an enterobacterium
E: is not a vaccine target
> A: is an alpha-hemolytic, encapsulated bacterium
119
```
What Streptococcus pyogenes virulence factor binds to keratinocytes, binds to fibrinogen, and also binds to complement factor H?
A: Streptokinase
B: F protein
C: M protein
D: G protein
E: Lipoteichoic acid
```
> C: M protein
120
Which of the following is associated with Neisseria gonorrhoeae?
35
A: gram positive
B: encapsulated
C: agent of meningitis
D: undergoes antigenic variation of Opa protein
E: infections are frequently asymptomatic
E: infections are frequently asymptomatic
121
hat is true about antigenic variation involving the pilin protein of Neisseria gonorrhoeae?
36
A: is an on/off switch for pilin protein expression
B: allows the creation of effective vaccines to prevent gonorrhea
C: involves recombination between silent and expressed copies of the pilin gene
D: allows bacteria to maintain the same surface antigens throughout an infection
E: involves slipped strand mispairing of repeated sequences within the pilin gene
> C: involves recombination between silent and expressed copies of the pilin gene
122
Which of the following is true about infections by Neisseria meningitidis?
A: preventable by vaccination against surface pilin protein for some meningiococcal strains
B: no vaccine is available against meningiococci because of coating of surface by sialic acid
C: preventable by vaccination against surface lipooligosaccharides for some meningiococcal strains
D: no vaccine is available against meningiococci because of phase variation of Opa proteins
E: preventable by vaccination against capsular polysaccharides for some meningiococcal strains
> E: preventable by vaccination against capsular polysaccharides for some meningiococcal strains
123
What factor is the most important in allowing intravascular survival of Neisseria meningitidis?
A: bacterial capsule
B: release of bacterial lipooligosaccharride (LOS) into vasculature
C: secretion of bacterial IgA protease
D: shut off of Opa protein expression on bacterial surface
E: presence of long O antigens covering bacterial surface
> A: bacterial capsule
124
```
Bacteroides fragilis is a strict anaerobe but is oxygen resistant because among its other properties it possesses
A: superoxide dismutase
B: neuraminidase
C: capsule
D: lipases
E: LPS
```
A: superoxide dismutase
125
Which of the following is a feature of infections caused by a breach in the gut wall?
A: only strictly anaerobic bacteria will be involved throughout the course of the infection
B: Streptococcus pyogenes is the main bacteria found in abscesses that are the result of these infections
C: abscess formation proceeds from an anaerobic to an aerobic state due to bacterial metabolism
D: Bacteroides is one of the first organisms to extensively grow in the infected area
E: host production of a thick fibrin capsule at the infection site decreases blood flow into the area
> E: host production of a thick fibrin capsule at the infection site decreases blood flow into the area
126
Which of the following is not a mechanism that pathogenic bacteria use to evade host immune system defenses?
A: site specific inversion of gene promoters
B: gain/loss of repeat sequences at the 5' ends of genes
C: addition of sialic acid to LPS
D: stable attachment to the surface of host cells
E: production of a polysaccharide capsule
> D: stable attachment to the surface of host cells
127
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
128
```
What virulence factor is expressed on the surface of bacterial cells (EPEC E. coli for example) and mediates bacterial entry into host cells by interacting with a receptor that has been translocated into the host cell?
A: invasin
B: intimin
C: internalin
D: fibronectin binding protein
E: sialic acid binding protein
```
> B: intimin
129
Gram-negative bacteria often bind to host cells by
A: bacterial fimbriae proteins interacting with host cell glycolipids
B: binding to host fibronectin
C: lipid A interacting with host integrins
D: bacterial sialic acid binding to host neuraminidase
E: bacterial protein A binding to host cell IgG
A: bacterial fimbriae proteins interacting with host cell glycolipids
130
LPS
A: is a normal cell surface component of gram positive bacteria
B: contains the K antigen used for identifying strains of pathogenic bacteria
C: activates the complement cascade in the host organism
D: is an exotoxin produced by pathogenic E. coli
E: is a host defense factor present in the lumen of the gut
> C: activates the complement cascade in the host organism
131
Which of the following is NOT an example of a means by which pathogenic bacteria can cause death of human host cells either directly or indirectly? 1
A: bacterial production of lipases
B: cell-mediated immune response
C: lipid peroxidation caused by bacterial growth within host cells
D: binding Fc portion of IgG by bacterial surface proteins
E: ADP ribosylation of translation factor EF-2 by an A-B toxin
D: binding Fc portion of IgG by bacterial surface proteins
132
What is true about the ADP ribosylation function of some A-B toxins?
A: ADP ribosylation activates a target protein of the bacterial pathogen
B: the ADP-ribose comes from host cell RNA molecules
C: ADP ribosylation activates a target protein of host cells
D: ADP ribosylation inactivates a target protein of the bacterial pathogen
E: ADP ribosylation inactivates a target protein of host cell
E: ADP ribosylation inactivates a target protein of host cell
133
Give an example of a bacterial exotoxin that acts outside a host cell to help microbes spread through tissue. __1__
Answer 1: hyluronase
