Immunology Exam 1 Practice Questions

16. Which of the following pairs is mismatched? A. T-cell activation: cell division and differentiation B. effector B cell: plasma cell C. plasma cell: antibody secretion D. helper T cell: kills pathogen-infected cells E. helper T cell: facilitates differentiation of B cells

D. helper T cell: kills pathogen-infected cells

5. Which of the following pairs is mismatched? A. lymphocytes: innate immune response B. natural killer cell: kills virus-infected cells C. macrophage: phagocytosis and killing of microorganisms D. erythrocyte: oxygen transport E. eosinophil: defense against parasites.

A. lymphocytes: innate immune response

4. Which of the following is not a characteristic of inflammation? A. inactivation of macrophages B. increased vascular permeability and edema C. vasodilation D. pain E. influx of leukocytes.

A. inactivation of macrophages

11. Which of the following pairs of associations is mismatched? A. large granular lymphocyte- T cell B. megakaryocyte: platelet C. B cell: plasma cell D. monocyte: macrophage E. myeloid progenitor: neutrophil

A. large granular lymphocyte- T cell

13. A 67-year-old homeless man is brought to the emergency department after being found behind a neighborhood bar in freezing weather. On arrival, he has a shaking chill, fever, and cough productive of blood-tinged sputum. A chest radiograph shows lobar consolidations consistent with bacterial pneumonia. Blood cultures are positive for Streptococcus pneumoniae. Which of the following molecular patterns recognized by Toll-like receptors expressed on the surface of this patient's phagocytes is important for activating his innate immune system against this gram- positive bacterial infection? A. Peptidoglycan B. Double-stranded RNA C. Lipopolysaccharide (LPS) D. Lipoarabinomannan E. Phosphatidylinositol dimannoside

ANS: A Gram-positive bacteria contain cell walls rich in peptidoglycan. When shed by bacteria such as Streptococcus pneumoniae, peptidoglycan serves as a ligand that binds Toll-like receptor 2 (TLR2), stimulating an innate immune response. The other choices listed are also ligands that stimulate TLRs, but they are not present in gram-positive bacteria. Double-stranded RNA is found in replicating viruses, lipopolysaccharide (LPS) is a component of the outer cell wall of gram-negative bacteria, and both lipoarabinomannan and phosphatidylinositol dimannoside are present in mycobacteria.

1. Macrophages and neutrophils express several enzymes that are involved in biochemical mechanisms that kill ingested microbes. Which of the following is NOT an enzyme expressed by these cells? A. Inducible nitric oxide synthase (iNOS) B. Granzyme B C. Phagocyte oxidase D. Myeloperoxidase E. Lysozyme

ANS: B Granzyme B, a proteolytic enzyme component of cytolytic T lymphocyte (CTL) and natural killer (NK) cell granules, is involved in initiating caspase-dependent CTL killing of target cells. Granzyme B is not involved in phagocyte killing of ingested microbes. Inducible nitric oxide synthase (iNOS) generates NO in macrophages, and NO is toxic to microbes. Phagocyte oxidase and myeloperoxidase are involved in generating free radical species that kill ingested microbes in phagocytes. Lysozyme is a proteolytic enzyme in neutrophil granules that contributes to microbial killing.

15. Macrophages and neutrophils express several enzymes that are involved in biochemical mechanisms that kill ingested microbes. Which of the following is NOT an enzyme expressed by these cells? A. Inducible nitric oxide synthase (iNOS) B. Granzyme B C. Phagocyte oxidase D. Myeloperoxidase E. Lysozyme

ANS: B Granzyme B, a proteolytic enzyme component of cytolytic T lymphocyte (CTL) and natural killer (NK) cell granules, is involved in initiating caspase-dependent CTL killing of target cells. Granzyme B is not involved in phagocyte killing of ingested microbes. Inducible nitric oxide synthase (iNOS) generates NO in macrophages, and NO is toxic to microbes. Phagocyte oxidase and myeloperoxidase are involved in generating free radical species that kill ingested microbes in phagocytes. Lysozyme is a proteolytic enzyme in neutrophil granules that contributes to microbial killing.

4. Which one of the following statements about inhibitory receptors on natural killer (NK) cells is true? A. Inhibitory receptors on NK cells express ITAM motifs in their cytoplasmic tails. B. Some inhibitory receptors on NK cells recognize HLA-A or HLA-C. C. Some inhibitory receptors on NK cells are members of the integrin family. D. Some inhibitory receptors on NK cells are members of the Toll-like receptor family. E. Inhibitory receptors on NK cells are not expressed on the same NK cells that express activating receptors.

ANS: B Natural killing (NK) inhibitory receptors recognize class I MHC molecules that are normally and constitutively expressed, including various alleles of HLA-A and HLA-C. The cytoplasmic tails of NK inhibitory receptors contain immunoreceptor tyrosine-based inhibitory motifs (ITIMs), but not immunoreceptor tyrosine-based activation motifs (ITAMs). Some inhibitory receptors on NK cells are members of the Ig superfamily, but not the integrin or TLR families. NK cells usually express both activating and inhibitory receptors, and activation is regulated by a balance between signals generated from both types of receptors. The inhibitory receptors on NK cells bind to self Ag - class I MHC molecules, which are expressed on most normal cells. When activating and inhibitory receptors are simultaneously engaged, the inhibitory receptor signals dominate and the NK cell is not activated.

8. Which of the following infectious diseases was prevented by the first successful vaccination? A. Polio B. Tuberculosis C. Smallpox D. Tetanus E. Rubella

ANS: C In 1798, Edward Jenner reported the first intentional successful vaccination, which was against smallpox in a boy, using material from the cowpox pustules of a milkmaid. In 1980, smallpox was reported to be eradicated worldwide by a vaccination program. Effective vaccines against tetanus toxin, rubella virus, and poliovirus were developed in the 20th century and are widely used. There is no effective vaccine against Mycobacterium tuberculosis.

19. Which of the following is an example of how the innate immune response stimulates or modifies adaptive immunity? A. Tumor necrosis factor (TNF) secreted by helper T cells enhances adhesion molecules on endothelial cells and promotes recruitment of inflammatory cells. B. Interferon (IFN)-γ produced by T helper cells is a potent activator of macrophages, allowing killing of phagocytosed microbes. C. B7-1 expression on antigen-presenting cells is up-regulated in response to signaling through Toll-like receptors, thus enabling costimulation of T cells. D. Infected cells coated by IgG3 are recognized by Fc receptors on natural killer cells, allowing efficient killing of the infected cells. E. Double-stranded RNA of replicating viruses potently stimulates IFN-γ expression by fibroblasts, inducing an "antiviral state" in neighboring, uninfected cells.

ANS: C Innate immune responses are important stimulators of adaptive immunity. Increased expression of B7-1 and B7-2 on antigen-presenting cells after microbial activation of Toll-like receptors (innate immunity) is critical in providing costimulatory signals for T cell activation (adaptive immunity) via binding to CD28 receptors on T cells. T helper cell-mediated endothelial or macrophage activation is an example of adaptive immunity using the effector mechanisms of innate immunity. Neither IgG3 opsonization facilitating natural killer cytolytic activity nor double-stranded RNA stimulating interferon- secretion involve innate immunity enhancing adaptive immunity.

6. Which of the following is an example of how the innate immune response stimulates or modifies adaptive immunity? A. Tumor necrosis factor (TNF) secreted by helper T cells enhances adhesion molecules on endothelial cells and promotes recruitment of inflammatory cells. B. Interferon (IFN)-γ produced by T helper cells is a potent activator of macrophages, allowing killing of phagocytosed microbes. C. B7-1 expression on antigen-presenting cells is up-regulated in response to signaling through Toll-like receptors, thus enabling costimulation of T cells. D. Infected cells coated by IgG3 are recognized by Fc receptors on natural killer cells, allowing efficient killing of the infected cells. E. Double-stranded RNA of replicating viruses potently stimulates IFN-γ expression by fibroblasts, inducing an "antiviral state" in neighboring, uninfected cells.

ANS: C Innate immune responses are important stimulators of adaptive immunity. Increased expression of B7-1 and B7-2 on antigen-presenting cells after microbial activation of Toll-like receptors (innate immunity) is critical in providing costimulatory signals for T cell activation (adaptive immunity) via binding to CD28 receptors on T cells. T helper cell-mediated endothelial or macrophage activation is an example of adaptive immunity using the effector mechanisms of innate immunity. Neither IgG3 opsonization facilitating natural killer cytolytic activity nor double-stranded RNA stimulating interferon- secretion involve innate immunity enhancing adaptive immunity.

12. Which of the following statements about the innate immune system is NOT true? A. Innate immunity is present in all multicellular organisms, including plants and insects. B. Deficiencies in innate immunity markedly increase host susceptibility to infection, even in the setting of an intact adaptive immune response. C. Innate immunity is better suited for eliminating virulent, resistant microbes than is adaptive immunity. D. The innate immune response can be divided into recognition, activation, and effector phases. E. The innate immune response against microbes influences the type of adaptive immune response that develops.

ANS: C Innate immunity is the first line of defense against infections, yet many pathogenic microbes have evolved strategies to resist innate immunity. Adaptive immunity, being more potent and specialized, plays a critical role in defending against these virulent microbes. Innate immunity is the phylogenetically oldest mechanism of microbial defense, and it is present in all multicellular organisms, including plants and insects. Studies have shown that hampering effector mechanisms of innate immunity renders hosts much more susceptible to infection, even with a functional adaptive immune system. It is also true that, like the adaptive response, the innate immune response consists of recognition, activation, and effector phases. Although it provides the initial, rapid response against microbes, innate immunity can influence adaptive immune responses to tailor them against particular microbes.

18. Complement activation in the innate immune system can be initiated in the absence of antibody. Which of the following molecular components of the complement system is involved in initiation of antibody-independent complement activation? A. C1 B. C9 C. Mannose binding lectin D. CR2 E. Mannose receptor

ANS: C Mannose-binding lectin (MBL) is a soluble serum component that is structurally similar to C1 of the classical complement pathway. MBL binds to mannan residues on microbial surfaces and triggers proteolytic cleavage and activation of downstream components of the complement system. C9 is not involved in initiation of complement activation but is part of the common final membrane attack complex (MAC) pathway. CR2 is a cell surface receptor for complement fragments. A mannose receptor is a cell surface receptor on phagocytes that binds mannan residues and promotes phagocytosis of microbes.

5. Complement activation in the innate immune system can be initiated in the absence of antibody. Which of the following molecular components of the complement system is involved in initiation of antibody-independent complement activation? A. C1 B. C9 C. Mannose binding lectin D. CR2 E. Mannose receptor

ANS: C Mannose-binding lectin (MBL) is a soluble serum component that is structurally similar to C1 of the classical complement pathway. MBL binds to mannan residues on microbial surfaces and triggers proteolytic cleavage and activation of downstream components of the complement system. C9 is not involved in initiation of complement activation but is part of the common final membrane attack complex (MAC) pathway. CR2 is a cell surface receptor for complement fragments. A mannose receptor is a cell surface receptor on phagocytes that binds mannan residues and promotes phagocytosis of microbes.

10. Which of the following statements best describes the "two-signal requirement" for naive lymphocyte activation? A. Lymphocytes must recognize two different antigens to become activated. B. Lymphocytes must recognize the same antigen at two sequential times to become activated. C. Lymphocytes must recognize antigen and respond to another signal generated by microbial infection to become activated. D. Both naive B and naive T lymphocytes must simultaneously recognize antigen for either to be activated. E. When lymphocytes recognize antigen, the antigen receptors must activate two-signal transduction pathways to become activated.

ANS: C Naive lymphocytes will not become activated by antigen alone (signal 1). In addition, they require "costimulatory" signals (signal 2), which are either microbial products or molecules on host cells induced by microbial infection. The molecules that provide signal 2 bind to receptors on the lymphocytes that are distinct from the clonally distributed antigen receptors. Each lymphocyte cannot generally recognize more than one antigen. Although lymphocyte activation may require recognition of antigen molecules by more than one antigen receptor, the two-signal requirement does not refer to this. There is no general requirement for both T and B cells to recognize the same antigen for activation of either to occur. The two-signal requirement does not refer to antigen receptor-associated signal transduction pathways.

7. The principal function of the immune system is: A. Defense against cancer B. Repair of injured tissues C. Defense against microbial infections D. Prevention of inflammatory diseases E. Protection against environmental toxins

ANS: C The immune system has evolved in the setting of selective pressures imposed by microbial infections. Although immune responses to cancer may occur, the concept that "immunosurveillance" against cancer is a principal function of the immune system is controversial. Repair of injured tissues may be a secondary consequence of the immune responses and inflammation. Although the immune system has regulatory features that are needed to prevent excessive inflammation, prevention of inflammatory diseases is not a primary function. The immune system can protect against microbial toxins, but it generally does not offer protection against toxins of nonbiologic origin.

9. The estimated number of distinct structures that can be recognized by the mammalian adaptive immune system is A. 1-10 B. 102-103 C. 103-105 D. 107-109 E. ∞

ANS: D Although the theoretical number of antigen specificities of the adaptive immune system is higher, estimates of the actual number of different antibody and T cell antigen receptor specificities are in the range of 107-109. This number is large enough to accommodate most of the diversity in molecular structures that the microbial world is capable of producing.

16. A 3-year-old boy, who is small for his age, has a history of pyogenic (pus-producing) infections and cutaneous skin abscesses. Physical examination is remarkable for high fever, enlarged liver and spleen, and swollen cervical lymph nodes. A culture from an abscess on his arm reveals Staphylococcus aureus, a gram-positive bacterium that is also catalase-positive. Immunoglobulin and complement levels are normal. Results of the nitroblue tetrazolium test are consistent with a diagnosis of chronic granulomatous disease (CGD). The boy's immunodeficiency involves impaired generation of which of the following? A. C5a B. C-reactive protein C. Mannose-binding lectin D. Reactive oxygen intermediates E. Membrane attack complex

ANS: D Chronic granulomatous disease (CGD) is a rare, inherited immunodeficiency disease associated with a defective intracellular respiratory burst in phagocytes. It consists of a group of heterogeneous disorders of oxidative metabolism in which the pathways required for generation of toxic reactive oxygen species (ROIs) are impaired. In patients with CGD, phagocytosis occurs normally, but the engulfed microbes are not killed and they multiply within the cell. In this way, patients are susceptible to recurrent infections with organisms such as Staphylococcus, which are of low virulence in normal hosts.

2. A 3-year-old boy, who is small for his age, has a history of pyogenic (pus-producing) infections and cutaneous skin abscesses. Physical examination is remarkable for high fever, enlarged liver and spleen, and swollen cervical lymph nodes. A culture from an abscess on his arm reveals Staphylococcus aureus, a gram-positive bacterium that is also catalase-positive. Immunoglobulin and complement levels are normal. Results of the nitroblue tetrazolium test are consistent with a diagnosis of chronic granulomatous disease (CGD). The boy's immunodeficiency involves impaired generation of which of the following? A. C5a B. C-reactive protein C. Mannose-binding lectin D. Reactive oxygen intermediates E. Membrane attack complex

ANS: D Chronic granulomatous disease (CGD) is a rare, inherited immunodeficiency disease associated with a defective intracellular respiratory burst in phagocytes. It consists of a group of heterogeneous disorders of oxidative metabolism in which the pathways required for generation of toxic reactive oxygen species (ROIs) are impaired. In patients with CGD, phagocytosis occurs normally, but the engulfed microbes are not killed and they multiply within the cell. In this way, patients are susceptible to recurrent infections with organisms such as Staphylococcus, which are of low virulence in normal hosts.

11. In addition to T cells, which cell type is required for initiation of all T cell-mediated immune responses? A. Effector cells B. Memory cells C. Natural killer cells D. Antigen-presenting cells E. B lymphocytes

ANS: D T cell-mediated immune responses are initiated when naive T cells are activated. Antigen-presenting cells, such as dendritic cells, are required to display antigens (peptide-MHC molecule complexes) for naive T cell recognition and to express costimulatory molecules also needed for T cell activation. Memory cells, cytotoxic T cells, and B lymphocytes are not involved in the initial activation of naive T lymphocytes

20. The T cell receptor (TCR) complex contains: A. A highly variable antigen coreceptor B. CD28 C. Three homologous CD3 chains, each covalently linked to the TCR α/β heterodimer D. Invariable ζ chains noncovalently linked to the TCR α/β heterodimer E. Igβ

ANS: D The T cell receptor (TCR) complex contains a highly variable antigen receptor, usually composed of a heterodimer of α and β chains, called the TCR, which is responsible for antigen recognition, as well as invariant signaling proteins, CD3δ, CD3ε, and CD3λ, and the ζ protein. These signaling molecules are all noncovalently associated with the TCR. Coreceptors for T cells include CD4 and CD8 these are invariant proteins and are not part of the TCR complex itself. CD28 is involved in T cell costimulation, but it is not a member of the TCR complex. Igβ is a component of the B lymphocyte antigen receptor complex.

14. Which of the following is a receptor on macrophages that is specific for a structure produced by bacteria but not by mammalian cells? A. CD36 (scavenger receptor) B. Fc receptor C. Complement receptor D. Mannose receptor E. ICAM-1

ANS: D The macrophage mannose receptor binds to terminal mannose and fucose residues on bacterial glycoproteins and glycolipids. Mammalian cells do not typically contain these residues. CD36 binds many different ligands, including microbial and self molecules. Fc receptors, complement receptors, and ICAM-1 are receptors for mammalian complement fragments, Ig, and LFA-1, respectively.

17. A 4-year-old-girl sees her physician because of a severe necrotizing, oropharyngeal herpes simplex viral (HSV) infection. She has a past medical history of cytomegalovirus (CMV) pneumonitis and cutaneous HSV infection. Phenotypic analysis of her blood cells shows an absence of CD56+ and CD16+ cells. There are normal numbers of CD4+ and CD8+ cells in the blood, and serum antibody titers are normal. The patient's CD8+ T cells were able to kill virally infected target cells in vitro. Which of the following is NOT characteristic of this girl's immunodeficiency disease? A. Lack of cells whose activation is normally inhibited by class I MHC B. Impaired granzyme B-dependent killing of virally infected target cells C. Lack of cells that are activated by IL-15 D. Impaired interferon (IFN)-γ- production during early phases of viral infection E. Failure to form viral peptide-class I MHC complexes

ANS: E The presence of normal numbers of CD8+ T cells and the ability of these cells to kill virally infected target cells indicates that the class I major histocompatibility complex (MHC) pathway of viral peptide antigen presentation is intact. The patient's immunodeficiency is due to a lack of natural killer (NK) cells. NK cells express CD56 and/or CD16. NK cells are activated by interleukin-15 (IL-15) and IL-12, are normally inhibited by recognizing class I MHC on other cells, kill target cells with altered class I MHC expression through a granzyme B-dependent mechanisms (similar to cytolytic T lymphocyte killing), and produce interferon- as part of the early innate response to viral infection.

3. A 4-year-old-girl sees her physician because of a severe necrotizing, oropharyngeal herpes simplex viral (HSV) infection. She has a past medical history of cytomegalovirus (CMV) pneumonitis and cutaneous HSV infection. Phenotypic analysis of her blood cells shows an absence of CD56+ and CD16+ cells. There are normal numbers of CD4+ and CD8+ cells in the blood, and serum antibody titers are normal. The patient's CD8+ T cells were able to kill virally infected target cells in vitro. Which of the following is NOT characteristic of this girl's immunodeficiency disease? A. Lack of cells whose activation is normally inhibited by self Ag - class I major histocompatibility complex (MHC) B. Impaired granzyme B-dependent killing of virally infected target cells C. Lack of cells that are activated by IL-15 D. Impaired IFN-γ-production during early phases of viral infection E. Failure to form viral peptide-class I MHC complexes

ANS: E The presence of normal numbers of CD8+ T cells and the ability of these cells to kill virally infected target cells indicates that the class I major histocompatibility complex (MHC) pathway of viral peptide antigen presentation is intact. The patient's immunodeficiency is due to a lack of natural killer (NK) cells. NK cells express CD56 and/or CD16. NK cells are activated by interleukin-15 (IL-15) and IL-12, are normally inhibited by recognizing class I MHC on other cells, kill target cells with altered class I MHC expression through a granzyme B-dependent mechanisms (similar to cytolytic T lymphocyte killing), and produce interferon- as part of the early innate response to viral infection.

9. Which of the following statements are correct? A. Macrophages are granulocytes B. Macrophages derive from monocytes C. Macrophages are non-phagocytic D. Macrophages reside in the circulation E. All of the above statements are false

B. Macrophages derive from monocytes

12. Which of the following statements is false? A. During human development, hematopoiesis takes place at different anatomical locations. B. The hematopoietic stem cell gives rise to white blood cells but a different stem cell is the progenitor of red blood cells. C. Hematopoietic stem cells are self-renewing. D. Platelets participate in clotting reactions to prevent blood loss. E. Megakaryocytes do not circulate and reside only in the bone marrow

B. The hematopoietic stem cell gives rise to white blood cells but a different stem cell is the progenitor of red blood cells

7. Examples of granulocytes include all of the following except: A. neutrophil B. monocyte C. basophil D. eosinophil E. All of the above are examples of granulocytes.

B. monocyte

17. Vaccination is best described as prevention of severe disease by: A. deliberate introduction of a virulent strain of an infectious agent B. prior exposure to an infectious agent in an attenuated or weakened form C. prophylactic treatment with antibiotics D. stimulating effective innate immune responses E. using effective public health isolation regimens such as quarantine

B. prior exposure to an infectious agent in an attenuated or weakened form

13. Which of the following describes the flow of lymph through a lymph node draining an infected tissue? A. efferent lymphatic vessel → lymph node → afferent lymphatic vessel B. venule → lymph node → efferent lymphatic vessel C. afferent lymphatic vessel → lymph node → efferent lymphatic vessel D. artery → lymph node → efferent lymphatic vessel E. afferent lymphatic vessel → lymph node → artery

C. afferent lymphatic vessel → lymph node → efferent lymphatic vessel

8. The most abundant type of leukocyte in human peripheral blood is: A. eosinophil B. basophil C. neutrophil D. monocyte E. lymphocyte

C. neutrophil

1. A previously healthy 8-year-old boy is infected with an upper respiratory tract virus for the first time. During the first few hours of infection, which one of the following events occurs? a. The adaptive immune system responds rapidly to the virus and keeps the viral infection under control. b. The innate immune system responds rapidly to the viral infection and keeps the viral infection under control. c. Passive immunity mediated by maternal antibodies limits the spread of infection. d. B and T lymphocytes recognize the virus and stimulate the innate immune response. e. The virus causes malignant transformation of respiratory mucosal epithelial cells, and the malignant cells are recognized by the adaptive immune system.

Correct answer: B The innate immune response to microbes develops within hours of infection, well before the adaptive immune response. B and T lymphocytes are components of the adaptive immune response, and they would not be able to respond to a newly encountered virus before the innate immune response. An 8-year-old boy would no longer have maternal antibodies from transplacental passive transfer and is unlikely to be breast-feeding, which is another potential source of maternal antibodies. Malignant transformation takes months or years to develop.

2. Which of the following is a unique property of the adaptive immune system? a. Highly diverse repertoire of specificities for antigens b. Self-nonself discrimination c. Recognition of microbial structures by both cell-associated and soluble receptors d. Protection against viral infections e. Responses that have the same kinetics and magnitude on repeated exposure to the same microbe

Correct: A Highly diverse repertoires of specificities for antigens are found only in T and B lymphocytes, which are the central cellular components of the adaptive immune system. Both the innate and the adaptive immune systems use cell-associated and soluble receptors to recognize microbes, display some degree of self-nonself discrimination, and protect against viruses. On repeated exposure to the same microbe, the adaptive immune response becomes more rapid and of greater magnitude, this is the manifestation of memory.

5. The two major functional classes of effector T lymphocytes are a. Helper T lymphocytes and cytotoxic T lymphocytes b. Natural killer cells and cytotoxic T lymphocytes c. Memory T cells and effector T cells d. Helper cells and antigen-presenting cells e. Cytotoxic T lymphocytes and target cells

Correct: A T cells can be classified into effector subsets that perform different effector functions. Most effector T cells are either helper T lymphocytes, which promote macrophage and B cell responses to infections, or cytotoxic T lymphocytes, which directly kill infected cells. Natural killer cells are not T lymphocytes. Antigen-presenting cells usually are not T cells. Memory T cells are not effector T cells.

3. A standard treatment of animal bite victims, when there is a possibility that the animal was infected with the rabies virus, is administration of human immunoglobulin preparations containing anti-rabies virus antibodies. Which type of immunity would be established by this treatment? a. Active humoral immunity b. Passive humoral immunity c. Active cell-mediated immunity d. Passive cell-mediated immunity e. Innate immunity

Correct: B Humoral immunity is mediated by antibodies. The transfer of protective antibodies made by one or more individuals into another individual is a form of passive humoral immunity. Active immunity to an infection develops when an individual's own immune system responds to the microbe. Cell-mediated immunity is mediated by T lymphocytes, not antibodies, and innate immunity is not mediated by either antibodies or T lymphocytes.

7. Which of the following statements about the innate immune system is NOT true? a. Innate immunity is present in all multicellular organisms, including plants and insects. b. Deficiencies in innate immunity markedly increase host susceptibility to infection, even in the setting of an intact adaptive immune response. c. Innate immunity is better suited for eliminating virulent, resistant microbes than is adaptive immunity. d. The innate immune response can be divided into recognition, activation, and effector phases. e. The innate immune response against microbes influences the type of adaptive immune response that develops.

Correct: C Innate immunity is the first line of defense against infections, yet many pathogenic microbes have evolved strategies to resist innate immunity. Adaptive immunity, being more potent and specialized, plays a critical role in defending against these virulent microbes. Innate immunity is the phylogenetically oldest mechanism of microbial defense, and it is present in all multicellular organisms, including plants and insects. Studies have shown that hampering effector mechanisms of innate immunity renders hosts much more susceptible to infection, even with a functional adaptive immune system. It is also true that, like the adaptive response, the innate immune response consists of recognition, activation, and effector phases. Although it provides the initial, rapid response against microbes, innate immunity can influence adaptive immune responses to tailor them against particular microbes.

6. Which of the following best describes clonal expansion in adaptive immune responses? a. Increased number of different lymphocyte clones, each clone specific for a different antigen during the course of an infection b. Increased number of different lymphocyte clones, each clone specific for a different antigen during development of the immune system, before exposure to antigen c. Increased number of lymphocytes with identical specificities, all derived from a single lymphocyte due to nonspecific stimuli from the innate immune system d. Increased number of lymphocytes with identical specificities, all derived from a single lymphocyte stimulated by a single antigen e. Increased size of the lymphocytes of a single clone due to antigen-induced activation of the cells

Correct: D Clonal expansion occurs during the activation phase of an adaptive immune response. A single lymphocyte is stimulated to divide by antigen, and the progeny go through several rounds of division until there are many lymphocytes, all with identical specificities, all derived from one cell. The number of different clones is not influenced by antigen exposure. Expansion does not refer to the size of the cells, although activated lymphocytes are larger than their naive precursors.

8. Toll-like receptors (TLRs) are a family of homologous receptors expressed on many cell types and are involved in innate immune responses. Ten different mammalian TLRs have been identified, and several ligands for many of these receptors are known. Which of the following is a TLR ligand? a. Single-stranded RNA b. Transfer RNA c. Double-stranded DNA d. Unmethylated CpG DNA e. Heterochromatin

Correct: D More than 10 mammalian Toll-like receptors (TLRs) have been identified, and each appears to recognize a different set of structures that are found in pathogenic microbes but not in mammalian cells. Such structures are called pathogen-associated molecular patterns (PAMPs). Unmethylated cytosine guanosine (CpG) motifs are typical of bacterial and protozoan DNA, but not mammalian DNA, and are therefore PAMPs. TLR9 binds CpG DNA. Transfer RNA, single-stranded RNA, double-stranded DNA, and heterochromatin are all normal components of mammalian cells and are not recognized by TLRs. Double-stranded RNA is produced by some viruses but not by mammalian cells and is recognized by TLR3.

4. At 15 months of age, a child received a measles-mumps-rubella vaccine (MMR). At age 22, she is living with a family in Mexico that has not been vaccinated and she is exposed to measles. Despite the exposure, she does not become infected. Which of the following properties of the adaptive immune system is best illustrated by this scenario? a. Specificity b. Diversity c. Specialization d. Memory e. Nonreactivity to self

Correct: D Protection against infections after vaccination is due to immunologic memory of the adaptive immune system. Memory is manifested as a more rapidly developing and vigorous response on repeat exposure to an antigen compared with the first exposure. Specificity and diversity are properties related to the range of antigenic structures recognized by the immune system, and specialization is the ability of the adaptive immune system to use distinct effector mechanisms for distinct infections.

10. Which of the following is a receptor on macrophages that is specific for a structure produced by bacteria but not by mammalian cells? a. CD36 (scavenger receptor) b. Fc receptor c. Complement receptor d. Mannose receptor e. ICAM-1

Correct: D The macrophage mannose receptor binds to terminal mannose and fucose residues on bacterial glycoproteins and glycolipids. Mammalian cells do not typically contain these residues. CD36 binds many different ligands, including microbial and self-molecules. Fc receptors, complement receptors, and ICAM-1 are receptors for mammalian complement fragments, Ig, and LFA-1, respectively.

9. The signaling pathways triggered by Toll-like receptors typically result in activation of which of the following pairs of transcription factors? a. NFAT and T-bet b. AP-1 and GATA-3 c. Fos and STAT-6 d. NFκB and AP-1 e. Lck and Jun

Correct: D The predominant signaling pathway used by Toll-like receptors (TLRs) results in the activation of the NF-κB transcription factor. Ligand binding to the TLR at the cell surface leads to recruitment of several cytoplasmic signaling molecules through specific domain-domain interactions, resulting in degradation of IB and subsequent activation of NFB. In some cell types, certain TLRs also engage other signaling pathways, such as the MAP kinase cascade, leading to activation of the AP-1 transcription factor. T-bet and GATA-3 are transcriptional regulators involved in helper T cell differentiation. Fos is a component of AP-1, and STAT-6 is a transcription factor activated by IL-4 binding to cells. Lck is not a transcription factor, but rather a tyrosine protein kinase involved in antigen-receptor signaling in T cells.

15. Which of the following is the predominant route by which pathogens are brought from a site of infection into a lymph node? A. efferent lymphatics B. artery C. vein D. afferent lymphatics E. high endothelial venule

D. afferent lymphatics

10. Which of the following pairs is mismatched? A. monocyte progenitor: macrophage B. erythroid progenitor: megakaryocyte C. myeloid progenitor: neutrophil D. lymphoid progenitor: natural killer cell E. None of the above is mismatched

E. None of the above is mismatched

1. One reason that pathogenic microorganisms have an advantage in the host they infect is because they A. have previously been encountered through natural exposure B. have previously been encountered through vaccination C. strengthen the host's immune response D. reproduce and evolve more rapidly than the host can eliminate them E. reproduce and evolve more slowly than the host can eliminate them.

D. reproduce and evolve more rapidly than the host can eliminate them

3. Which of the following is not associated with mucosal surfaces? A. mucus-secreting goblet cells B. lysozyme C. M cells D. white pulp E. beating cilia.

D. white pulp

2. Examples of pathogens that cause human disease include: A. bacteria B. viruses C. fungi D. parasites (protozoans and worms) E. All of the above are examples of pathogens that cause human disease.

E. All of the above are examples of pathogens that cause human disease

14. Which of the following best describes the movement of a T cell through a lymph node? A. Enters via efferent lymphatics and exits via bloodstream B. Enters via afferent lymphatics and exits via bloodstream C. Enters via bloodstream and exits via afferent lymphatics D. Enters via bloodstream and exits via bloodstream E. Enters via bloodstream and exits via efferent lymphatics.

E. Enters via bloodstream and exits via efferent lymphatics

18. Which of the following explains why immunity to influenza may appear to be relatively short-lived? A. Effective immunological memory fails to develop. B. Immune responses to influenza involve innate immune mechanisms only. C. The primary and secondary immune responses are equivalent. D. Influenza virus targets memory cells. E. New influenza variants able to escape prior immunity regularly.

E. New influenza variants able to escape prior immunity regularly

6. A term generally used to describe all white blood cells is: A. hematopoietic cells B. myeloid progenitor C. dendritic cells D. monocytes E. leukocytes.

E. leukocytes