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Basic Immunology: Functions and Disorders of the Immune System 4th Edition Test Bank

Basic Immunology: Functions and Disorders of the Immune System 4th Edition Test Bank simplifies tough topics and provides all the necessary study resources for a stress-free exam.

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    Abbas: Basic Immunology, 4 th Edition Chapter 01: Introduction to the Immune System Test Bank MULTIPLE CHOICE 1. 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. 2. 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. 3. 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.

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    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. ANS: 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. 4. 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 ANS: 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. Antibodies and T lymphocytes are the respective mediators of which two types of immunity? A. Innate and adaptive B. Passive and active C. Specific and nonspecific D. Humoral and cell - mediated E. Adult and neonatal ANS: D Both B and T lymphocytes are principal components of adaptive immunity. B lymphocytes produce antibodies, which are the recognition and effector molecules of humoral immune responses to extracellular pathogens. T cells recognize and promote eradication of intracellular pathogens in cell - mediated immunity. Passive and active immunity both can be mediated by either B or T lymphocytes. Specific immunity is another term for adaptive immunity. Both B and T lymphocytes participate in adult adaptive immunity but are still developing in the neonatal period.

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    6. 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 ANS: 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. 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 ANS: 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. 8. A vaccine administered in the autumn of one year may protect against the prevalent strain of influenza virus that originated in Hong Kong that same year, but it will not protect against another strain of influenza virus that originated in Russia. This phenomenon illustrates which property of the adaptive immune system? A. Specificity B. Amnesia C. Specialization D. Cultural diversity E. Self - tolerance ANS: A

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    Adaptive immune responses are highly specific for distinct molecular structures, which may be present in a vaccine and be produced by one strain of virus but not by a closely related strain. Amnesia, although generally not used in immunology, implies lack of memory, but the efficacy of the vaccine against the Hong Kong strain implies it has induced memory. The same effector mechanisms would be required to combat different strains of influenza, and therefore failure of a vaccine to protect against two different strains of virus is not related to specialization of effector functions. 9. 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 ANS: 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. 10. Which of the following cell types is required for all humoral immune responses? A. Natural killer cells B. Dendritic cells C. Cytolytic T lymphocytes D. B lymphocytes E. Helper T lymphocytes ANS: D Humoral immune responses are antibody - mediated immune responses, and all antibodies are made by B lymphocytes and by no other cell type. 11. During a humoral immune response to a newly encountered bacterial infection, B cells are first stimulated to proliferate and then secrete antibodies specific for the bacterium. The antibodies may then bind to the bacteria and facilitate ingestion of the microbes by phagocytic cells. In what phase of the humoral immune response does the binding of secreted antibodies to bacteria occur? A. Recognition phase B. Activation phase C. Effector phase D. Homeostatic phase E. Memory phase ANS: C The effector phase of an immune response occurs when cells or molecules eliminate the microbe or microbial toxin. In a humoral immune response, the effector phase includes secretion of antibody, binding of the antibody to the microbe or toxin, and subsequent

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    antibody - dependent elimination of the microbe or toxin. The recognition phase is the initial binding of the antigen by the naive lymphocyte. The activation phase includes proliferation and differentiation of lymphocytes in response to antigen recognition. The homeostatic phase follows the effector phase, during which the response wanes. In the memory phase, memory B cells and antibodies secreted by long - lived antibody - secreting cells are “waiting” for a repeat exposure to the microbe. 12. Which of the following statements is consistent with the process of clonal selection? A. The specificity of a lymphocyte antigen receptor changes to accommodate the structure of an antigen that binds to it. B. Many different antigen receptors with different specificities are expressed on each lymphocyte. C. Lymphocytes do not express antigen receptors on their cell surfaces until after exposure to antigen. D. The diversity of the lymphocyte repertoire for antigens is very small before exposure to antigen but increases significantly after antigen exposure. E. The diversity of the lymphocyte repertoire for antigens is very large before exposure to antigen, with millions of different clones of lymphocytes, each having a different specificity. ANS: E The clonal selection hypothesis accurately predicted that individuals possess large numbers of different clones of lymphocytes before antigen exposure, with cells in each clone expressing antigen receptors with a single identical specificity, but with different specificities from other clones. Thus, the diversity of the lymphocyte repertoire is very large even before antigen exposure. These receptors are expressed before antigen exposure, and their specificities generally do not change in response to antigen. 13. 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 ANS: 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

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    exposure. Expansion does not refer to the size of the cells, although activated lymphocytes are larger than their naive precursors. 14. The estimated number of distinct struct ures that can be recognized by the mammalian adaptive immune system is A. 1 - 10 B. 10 2 - 10 3 C. 10 3 - 10 5 D. 10 7 - 10 9 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 10 7 - 10 9 . This number is large enough to accommodate most of the diversity in molecular structures that the microbial world is capable of producing. 15. 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. 16. 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

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    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.

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    Abbas: Basic Immunology, 4 th Edition Chapter 02: Innate Immunity Test Bank MULTIPLE CHOICE 1. 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. 2. 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. Epithelial barrier function of the skin of her foot B. Intraepithelial lymphocytes present in the skin C. Circulating neutrophils migrating to the site of the wound D. Soluble cytokines that induce a local inflammatory response E. Circulating anti - tetanus toxin antibodies ANS: E Secreted antibodies against protein antigens are effectors of humoral immunity, a component of the adaptive immune system. All other mechanisms listed are part of the innate immune system. Intact epithelial surfaces prevent microbial entry, and epithelial cells express anti - microbial factors, such as defensins. Neutrophils are effector cells that

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    function in early phagocytosis and killing of microbes. Cytokines that mediate inflammation (e.g., tumor necrosis factor, interleukin - 1, chemokines) are components of innate immunity. Intraepithe - lial T lymphocytes present in the epidermis and mucosal epithelia express a limited diversity of antigen receptors; as such, they are considered effector cells of innate immunity and function in host defense by secreting cytokines, activating phagocytes, and killing infected cells. 3. 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. ANS: A Innate immune system receptors are encoded by germline genes that have evolved to recognize microbial structures or molecules produced by stressed self, and therefore there is little chance of innate immune responses to normal self. Because the specificities of adaptive immune system receptors (Ig or T cell receptor molecules) are randomly generated by somatic recombination and junctional - diversity mechanisms, there is a greater chance that the adaptive immune system receptors may recognize normal self molecules, leading to autoimmunity. Mechanisms of tolerance minimize this possibility, but these mechanisms can fail. The adaptive immune system receptors can recognize nonmicrobial structures. Although most innate immune system receptors recognize microbial structures, some Toll - like receptors and activating receptors of natural killer cells do recognize nonmicrobial self proteins expressed by stressed, damaged, or infected cells. Memory is a unique property of the adaptive and not the innate immune system. 4. 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 ANS: 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

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    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. 5. 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 phosphatidylinosit ol dimannoside are present in mycobacteria. 6. 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. NF  B and AP - 1 E. Lck and Jun ANS: D The predominant signaling pathway used by Toll - like receptors (TLRs) results in the activation of the NF -  B transcription factor. Ligand binding to the TLR at the cell surface leads to recruitment of several cytoplasmic sign aling molecules through specific domain - domain interactions, resulting in degradation of I  B and subsequent activation of NF  B. 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

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    not a transcription factor, but rather a tyrosine protein kinase involved in antigen - receptor signaling in T cells. 7. Toll - like receptors and other receptors are potent activators of various components of the innate immune system. All of the following proteins are expressed in response to signaling by these receptors EXCEPT: A. Interleukin - 12 B. E - selectin C. Tumor necrosis factor D. Inducible nitric oxide synthase (iNOS) E. CD28 ANS: E CD28, the activating receptor for B7 - 1 and B7 - 2 costimulatory molecules, is constitutively expressed on the surface of many T cells and is not induced by Toll - like receptor (TLR) signaling. TLR signaling does induce expression of B7 - 1 and B7 - 2 on antigen - presenting cells. Other genes expressed in response to TLR signaling encode proteins important in many different components of innate immune responses. These include inflammatory cytokines such as tumor necrosis factor -  (TNF -  ), interleukin - 1 (IL - 1), and IL - 12; endothelial adhesion molecules such as E - selectin; and proteins involved in microbial ki lling mechanisms, including inducible nitric oxide synthase (iNOS). The specific genes expressed depend on the cell type of the responding cell. 8. 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. 9. Which one of the following comparisons between neutrophils and macrophages is true? A. Neutrophils that enter inflammatory sites can survive for days, but macrophages are very short lived and only survive for hours. B. Both neutrophils and macrophages are phagocytic and can kill internalized microbes. C. Neutrophils proliferate at inflammatory sites, but macrophages are terminally differentiated and cannot proliferate. D. Neutrophils, but not macrophages, express the high - affinity Fc  RI receptor, which recognizes specific opsonins bound to microbes and facilitates phagocytosis.

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    E. Both neutrophils and macrophages contain abundant cytoplasmic granules containing lysozyme, collagenase, and elastase. ANS: B Neutrophils and macrophages can both actively phagocytose and kill microbes, and both express opsonin receptors, such as Fc  RI or complement receptors that enhance phagocytosis. Neutrophils are short lived, whereas macrophages can survive for days or weeks. Macrophages are not terminally differentiated and can undergo cell division at inflammatory sites, but neutrophils cannot . Only neutrophils have cytoplasmic granules filled with enzymes, including lysozyme, collagenase, and elastases; these are called specific granules. 10. A 43 - year - old man with a history of kidney transplantation is on immunosuppressive drugs. He presents to the emergency department 84 days after transplantation with a slight fever, accompanied by violent shaking chills, rapid heart rate, and dangerously low blood pressure. Blood cultures are positive for gram - negative bacteria, including Klebsiella and Pseudomonas. Although the patient was initially alert and responsive to fluids and antibiotic therapy, his condition rapidly deteriorates into disseminated intravascular coagulation (DIC), hypoglycemia, and cardiovascular failure. Which of the following is an essential mediator of this patient’s condition? A. Transforming growth factor -  B. Tumor necrosis factor -  C. Interleukin (IL) - 2 D. IL - 10 E. IL - 3 ANS: B This patient is suffering from septic shock, characterized by the clinical triad of disseminated intravascular coagulation (DIC), hypoglycemia, and cardiovascular failure. This co ndition is most often initiated by endotoxin, also known as lipopolysaccharide (LPS), a component of the outer cell walls of gram - negative bacteria. LPS is a potent stimulus for tumor necrosis factor (TNF) -  secretion by mononuclear phagocytes and other ce ll types. Most of the biologic effects of LPS are mediated through TNF -  . Transforming growth factor -  (TGF -  ) and interleukin (IL) - 10 are anti - inflammatory cytokines, IL - 2 is a T cell growth factor, and IL - 3 is a hematopoietic cytokine. These cytokines ar e not mediators of septic shock. 11. 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

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    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. 12. All of the following molecules are opsonins that facilitate efficient phagocytosis of microbes by neutrophils and macrophages EXCEPT: A. C3b B. C5a C. C - reactive protein D. IgG E. Mannose - binding lectin ANS: B C5a is a peptide released after cleavage of C5 protein during the complement cascade. It stimulates the influx of neutrophils to the site of infection, thus acting as a chemoattractant, not as an opsonin. C3b (covalently bound to microbes on which complement activation has taken place) and IgG bound to antigen, are particularly potent opsonins, because phagocytes have receptors for both C3b and the Fc region of IgG. C - reactive protein and mannose - binding lectin also can coat microbes and be recognized by phagocyte receptors; thus they serve as opsonins. 13. 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 bacteria 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.

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    14. 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 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 interferon (IFN) -  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. 15. 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. So me 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 i nhibitory motifs (ITIMs), but not immunoreceptor tyrosine - based a ctivation 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 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.

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    16. 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. 17. 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) -  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 o f 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 -  expression by fibroblasts, inducin g 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 effec tor 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.

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