High Yield Immunology Questions HDM

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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

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

What is the most abundant antibody class in the human body? A. IgA B. IgD C. IgG D. IgM E. IgE

A. IgA

The class I MHC pathway of antigen presentation to CD8+ T cells requires that protein antigens be present in the cytosol of infected cells so that these proteins can be degraded in proteasome and can then enter the endoplasmic reticulum via ? A. 1/2 pump of the TAP transporter B. active transport C. Facilitated transport D. Passive transport E. cross presentation.

A. 1/2 pump of the TAP transporter

Which of the following cells are important effector cells in allergic reactions? A. Basophils B. Dendritic cells C. Lymphocytes D. Monocytes E. Neutrophils

A. Basophils Bloodborne basophils and tissue resident mast cells are responsible for allergic responses caused by the release of vasoactive amines within their cytoplasmic granules. Dendritic cells, lymphocytes, and monocytes all play roles in adaptive immune responses but are not the actual effector cells in allergic reactions. Neutrophils actively destroy invasive bacteria.

Which of the following complement components is an opsonin that binds to complement receptor 1 (CR1) on macrophages? A. C3b B. C3a C. Bb D. Ba E. C3bBb.

A. C3b Only C3b deposited on the surface of microbes is recognized by complement receptor 1 (CR1) expressed on macrophages and other phagocytes. Although macrophages express receptors for C3a, those receptors are involved into chemotaxis of the cells. Macrophages do not have receptors for either Bb, Ba, or C3bBb.

A seventeen-year-old patient presents with acute cutaneous lupus erythematosus (SCLE) diagnosed at the age of 15 years old. Prior laboratory measurements showed no detectable C4 proteins, serum C3 levels were lower (77 mg/dL) and C1q inhibitor levels were normal. Which complement activities would be inhibited in this patients? A. Completion of the classic pathway to the splitting of C3 B. Formation of C3b for opsonization C. Formation of C5 convertase via the alternative pathway D. Formation of C5a for chemotactic attractant for neutrophils E. Formation of the membrane attack complex

A. Completion of the classic pathway to the splitting of C3

A patient defective in either the TAP-1 or TAP-2 genes would be expected to have which of the following characteristics? A. Decreased cell-mediated immune response and increased susceptibility to viral and intracellular bacterial pathogens. B. Decreased phagocytosis of microbes C. Increased TLR signaling D. Increased proliferation CD8+ T cells. E. Decreased complement activation

A. Decreased cell-mediated immune response and increased susceptibility to viral and intracellular bacterial pathogens. Because antigenic peptides for the class I pathway are generated by proteases in the cytosol or the nucleus but class I MHC molecules are synthesized in the ER, a mechanism is needed to deliver cytosolic peptides into the ER. This delivery is mediated by a dimeric protein called transporter associated with antigen processing (TAP), which is encoded by TAP-1 and TAP-2 genes.

A 30-year-old woman is admitted to the emergency room with recurrent viral infections. Lab tests show normal levels of circulating lymphocytes and neutrophils in the patients' blood. This woman's condition is most likely caused by a deficiency of which of the following cytokines? A. IL-2 B. IL-3 C. IL-4 D. IL-22 E. IL-23

A. IL-2 IL-2 is a cytokine secreted by helper T lymphocytes that stimulates the growth of helper and cytotoxic T lymphocytes. Even though this patient has a normal number of T lymphocytes, a deficiency in IL-2 could lead to impaired cytotoxic T lymphocyte differentiation and activation. This would result in an increased susceptibility to viral infections.

If B cells class switch in an environment that is rich in TGFβ, they preferentially switch their class from IgM to _______. A. IgA B. IgD C. IgG D. IgM E. IgE

A. IgA

Which antibody is secreted in breast milk? A. IgA B. IgD C. IgG D. IgM E. IgE

A. IgA

Septic shock associated with Gram‐negative bacteria is primarily due to: A. Lipopolysaccharide. B. Enterotoxin superantigen. C. Platelet aggregation. D. Switch off of cytokine release. E. Peptidoglycans.

A. Lipopolysaccharide.

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

A. Peptidoglycan 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.

Which of the following does not describe defensins? A. highly conserved with few variants B. contain a large proportion of arginine residues C. contain three intra-chain disulfide bonds D. amphipathic, with hydrophobic and hydrophilic regions E. disrupt pathogen membranes by penetrating and disrupting their integrity.

A. highly conserved with few variants The defensin family comprises three diverse subfamilies (α-, β- and θ-defensins) of antimicrobial peptides involved in the innate immune response, being a part of the non-specific way in which many living organisms react against invading pathogens. The three subfamilies of defensins mostly differ in peptide length, the location of the disulphide bonds between particular cysteines. Defensins, together with other antimicrobial factors, are stored in cytoplasmic granules of neutrophils and macrophages, while from epithelial cells they are released into extracellular environment. They play an important role as components of the early host defense against infection acting against Gram-positive and Gram-negative bacteria, mycobacteria, fungi, and enveloped viruses. Defensins are categorized as arginine-rich cationic (alkaline) peptides. The primary antimicrobial action of defensins is permeabilization of microbial target membranes.

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

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

Which of the following is a correct pairing of a soluble molecule with its microbicidal action in the respiratory tract? A. β -defensins increase microbial susceptibility to phagocytosis. B. DNase enzymatically damages microbial membranes. 1 0 C. Fatty acids of commensal microbes degrade microbial peptidoglycan. D. Lacrimal secretions facilitate ingestion of microbes by phagocytes. E. Lysozyme degrades DNA and RNA produced by pathogenic microbes.

A. β -defensins increase microbial susceptibility to phagocytosis. β -defensins can attach to microbes and make them more susceptible to ingestion by phagocytes. Peptidoglycan of bacterial cell walls is degraded by lysozyme, not by fatty acids or DNase. Lysozyme does not act on RNA and DNA. The lacrimal fluid contains lysozyme that acts on microbial peptidoglycan, not on host phagocytes.

The percentage of human peripheral blood T‐cells bearing a gamma delta T‐cell receptor is: A. 30-80%. B. 1‐5%. C. 100%. D. 0%. E. Only present during mycobacterial infections.

B. 1‐5%.

Which of the following is C3 convertase of the classical pathway is whereas C3 convertase of the alternative pathway? A. C1a; C3bBb B. C4bC2a; C3bBb C. C3bCR1; C3bBb D. C4bC2a; C3bCR1 E. C1a; C3bCR1

B. C4bC2a; C3bBb

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

B. Granzyme 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.

The molecules mediating signal transduction following antigen binding to cell surface immunoglobulin on a B‐cell are called: A. IgFc B. Ig‐alpha and Ig‐beta C. MHC D. CD4 E. CD8

B. Ig‐alpha and Ig‐beta B‐cell receptor complex usually consist of an Ag‐binding subunit (BCR) and a signaling subunit, which is a disulfide‐linked heterodimer of Ig‐Alpha (CD79A) and Ig‐Beta (CD79B) proteins.

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 All of E. the above statements are false

B. Macrophages derive from monocytes

Anaphylactic Shock is caused by degranulating of which type of cells? A. Eosinophils B. Mast Cells C. Basophils D. Neutrophils E. B Cells

B. Mast Cells Think Allergy and IgE. Histamines and other Chemicals are in the Granules.

Chronic granulomatous disease (CGD), a condition resulting in chronic bacterial and fungal infections, is caused by one or more defects in______, compromising the ability of macrophages to ______. A. CD18; produce cell adhesion molecules B. NADPH oxidase; produce superoxide radical C. CD40 ligand; produce GM‐CSF D. C5-C9; defend against Neisseria E. C3; opsonize capsulated bacteria.

B. NADPH oxidase; produce superoxide radical

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.

B. Some inhibitory receptors on NK cells recognize HLA-A or HLA-C. 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.

Which of the following TLRs do not use a signal transduction cascade involving MyD88? A. TLR1:TLR2 B. TLR3 C. TLR4 D. TLR2:TLR6 E. TRL7

B. TLR3

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

The plasma proteins that counteract the activity of factor P (Properdin) by inactivating C3 convertase through are: A. factor B and factor H B. factor H and factor I C. factor B and factor I D. decay-accelerating factor and factor H E. decay-accelerating factor and membrane cofactor protein.

B. factor H and factor I A. Incorrect answer because only Factor H participates in degradation of C3bBb convertase of the alternative pathway (AP) whereas Factor B is involved in formation of C3bBb convertase of the alternative pathway (AP). B. Correct answer because both factor B and Factor I participate in proteolytic degradation of C3bBb convertase of AP. C. Incorrect answer because only Factor I is involved in degradation of C3bBb convertase of AP. D. Incorrect answer because neither decay-accelerating factor or factor H is involved in degradation of C3bBb convertase. E. Incorrect answer because only membrane cofactor protein (MPC) is involved in degradation of C3bBb convertase of AP.

Which of the following does not accurately describe complement components? A. soluble proteins B. made by the spleen C. located in extracellular spaces D. some function as proteases once activated E. activated by a cascade of enzymatic reactions.

B. made by the spleen The complement system consists of a number of small proteins found in the blood, generally synthesized by the liver, and normally circulating as inactive precursors (pro-proteins). A number of complement proteins are proteases that are themselves activated by proteolytic cleavage. Such enzymes are called zymogens. The complement system activates through a triggered-enzyme cascade.

Which of the following is an acute-phase protein that enhances complement fixation? A. TNF-α B. mannose-binding lectin C. fibrinogen D. LFA-1 E. CXCL8

B. mannose-binding lectin The innate immune system, which includes mannose-binding lectin (MBL), recognizes a broad range of molecular patterns on a broad range of infectious agents and is able to distinguish them from self. MBL is a liver-derived serum protein and is secreted into the serum, where it can activate an immune response before the induction of antigen-specific immunity. Being the leading protein of the lectin complement pathway, this C1q-like molecule has specificity for mannose, N-acetyl-D-glucosamine (GlcNAc), and fucose, but not for antibodies. When one or more of these sugars are present on a microbial surface, binding and subsequent activation of MBL will take place, which indirectly leads to C3b and C3bi deposition on the microbial surface as well.

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

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

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.

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. 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.

A 6‐year‐old girl has lymph node biopsy that shows markedly decreased numbers of lymphocytes in the paracortical areas. Analysis of her peripheral blood leukocytes will likely show normal to elevated numbers of cells expressing surface: A. CD8 B. CD2 C. CD19 D. CD3 E. CD4

C. CD19 Paracortical area is where T cells are. T cells have CD8, CD2, CD3, and CD4. CD19 = B cells so with T cells which are in the paracortical area.

A 55-year-old man is diagnosed with an aggressive form of pancreatic cancer that has been unresponsive to medication or radiation. The patient's physician suggests that the man enroll in a new clinical trial that is exploring the use of gene therapy to treat cancer. The idea behind the trial is to use gene therapy to express a protein on the tumor cell surface that will stimulate T-cell production. Which of the following, if expressed on the surface of tumor cells would be the most effective co-stimulatory protein for T cell activation? A. CD28 B. CD40L C. CD80/CD86 D. PD-1 E. CTLA-4

C. CD80/CD86 The best characterized costimulatory pathway in T cell activation involves the T cell surface receptor CD28, which binds the costimulatory molecules B7-1 (CD80) and B7-2 (CD86) expressed on activated APCs.

Immune responses in the adaptive immune system have to be turned on, and off again when the adequate reaction is fulfilled. Which statement below is correct? A. CTLA‐4 is expressed on activated B‐cells B. CTLA‐4 gives a negative signals to B‐cells C. CTLA‐4 on T‐cells competes with CD28 for binding to B7 on B‐cells D. CTLA‐4 gives an activation signal to T helper cells

C. CTLA‐4 on T‐cells competes with CD28 for binding to B7 on B‐cells Cytotoxic T lymphocyte‐associated molecule‐4 (CTLA‐4) is a cell surface molecule that is expressed nearly exclusively on CD4+ and CD8+ T cells. Investigation into the role of CTLA‐4 in the regulation of T cell immune responses has revealed that CTLA‐4 is a very important molecule involved in the maintenance of T cell homeostasis. CTLA‐4 is a CD28 homolog with much higher binding affinity for B7. However, unlike CD28, binding of CTLA‐4 to B7 does not produce a stimulatory signal. As such, this competitive binding can prevent the costimulatory signal normally provided by CD28:B7 binding.

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

C. Defense against microbial infections 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.

In an individual with an immediate hypersensitivity response (allergy) to dust mites, cross-linking of which of the following dust-mite-specific molecules will trigger inflammatory mediator release? A. histamine B. IgA C. IgE D. IgG E. mast cells

C. IgE Cross-linking of IgE bound to the surfaces of basophils and mast cells results in cellular degranulation and release of vasoactive amine responsible for inflammation. In humans, neither IgA nor IgG is associated with allergic responses. Histamine is released from mast cells are a result of cross-linking of surface-bound IgE.

What is the most abundant antibody class in the blood? A. IgA B. IgD C. IgG D. IgM E. IgE

C. IgG

Which antibody are the longest-lived (with a half-life of 3 weeks)? A. IgA B. IgD C. IgG D. IgM

C. IgG

Which antibody can cross the placental barrier? A. IgA B. IgD C. IgG D. IgM E. IgE

C. IgG

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.

C. Innate immunity is better suited for eliminating virulent, resistant microbes than is adaptive immunity. 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.

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.

C. Lymphocytes must recognize antigen and respond to another signal generated by microbial infection to become activated. 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.

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

C. Mannose binding lectin 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.

Which immune cells express FcεRI and contain granules with pre-synthesized inflammatory mediators? A. Macrophages B. B cells C. Mast cells D. Neutrophils E. T cells

C. Mast cells Although some cells like neutrophils contains granules with pre-synthesized mediators, only mast cells, basophils, and activated eosinophils express high affinity FcεRI for IgE.

A child has a frequent history of infections caused by both bacterial and viral pathogens; these infections have included repeated infections by the same pathogens. Analysis of the child's cells has indicated that his cells do not produce the RAG-1 or RAG-2 protein. Which one of the following cellular phenotypes would be expected in this patient? A. Functional B cells; no functional Dendritic cells B. Functional CD4+ cells; no functional CD8+ cells or B cells C. No functional T cells or B cells D. Functional Treg cells; no functional B cells E. Functional NK cells and memory B cells

C. No functional T cells or B cells RAG-1 and RAG-2 are essential to the generation of mature T and B lymphocytes.

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

C. Smallpox 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.

Which of the following is an example of a normal physiologic pH barrier to microbial colonization? A. Respiratory tract pH between 9.0 and 11.0 B. Skin pH of approximately 8.0 C. Stomach pH between 1.0 and 3.0 D. Upper gastrointestinal tract pH between 6.5 and 7.5 E. Vaginal pH of approximately 7.0

C. Stomach pH between 1.0 and 3.0 Normal stomach pH is between 1.0 and 3.0. The values given for the respiratory tract, skin, upper gastrointestinal tract, and vagina are abnormal.

Which of the following properties is common to macrophages and neutrophils? A. life span B. anatomical location C. ability to phagocytize D. morphology E. formation of pus

C. ability to phagocytize

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

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

C. neutrophil

A 30-year-old female developed vaginal candidiasis (a fungal infection) after receiving antibiotic therapy for a sinus infection. One possible explanation for the fungal infection is antibiotic-induced reduction in vaginal. A. lysozyme secretion. B. mucus secretion. C. normal commensal bacteria. D. pH. E. RNases and DNases.

C. normal commensal bacteria. Use of antibiotics can reduce normal commensal microbe populations, increasing the opportunity for colonization by more pathogenic microbes. Antibiotics do not alter the secretion of mucus and microbicidal molecules from the mucous membranes of the vagina. The pH is likewise not decreased by antibiotic use.

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. ∞

D. 107-109 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.

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

D. Antigen-presenting cells 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.

Which of the following are important in anchoring the membrane-attack complex to the membrane? A. C3 and C5 B. C5 and C6 C. C6 and C7 D. C7 and C8 E. C8 and C9.

D. C7 and C8

A 68-year-old female with no history of perianal abscess was examined in the Emergency Department of the hospital verbalizing complaints of swelling and tenderness in the left inguinal area. Physical examination revealed abscess of the left labial area. The patient was admitted to the hospital and surgical incision and drainage was performed by the physician. Which one of the listed cytokines is most important in formation of an abscess? A. TNF B. IL‐1 C. IL‐6 D. IL‐8 E. IL‐12

D. IL‐8 An abscess is a puss build up from neutrophils. Puss is nothing but dead neutrophils. Major chemokine attractant for neutrophils is IL-8.

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

D. Invariable ζ chains noncovalently linked to the TCR α/β heterodimer 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.

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

D. Mannose receptor 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.

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

D. Reactive oxygen intermediates 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.

Which of the following TLR3 and TLR4 adaptor proteins participates in the activation pathway that culminates in the synthesis of type I interferons? A. C-reactive protein B. MyD88 C. LPS-binding protein D. TRIF and TRAM E. NFκB.

D. TRIF and TRAM

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

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

γ/δ T cells A. contain very extensive antigen recognition repertoires. B. express surface markers that are also characteristic of NK cells. C. generate memory when recognizing antigen on multiple occasions. D. migrate preferentially to respiratory or organs, skin, and peritoneal cavity. E. respond more slowly to antigen than do α/β T cells.

D. migrate preferentially to respiratory or organs, skin, and peritoneal cavity. γ/δ T cells are found predominantly in the respiratory organs, skin, and peritoneal cavity. Their recognition repertoire is far less extensive that found in a T cells. They do not express significant immunologic memory but do react to antigenic stimuli more rapidly than do α/β T cells.

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

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

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.

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.

Class I MHC-restricted T cells against tumor antigens can be found in patients with various types of cancer. Which mechanism correctly explains the activation of naïve CD8+ T cells specific for mutated self- antigens in tumors? A. Malignant transformation of CD8+ T cells B. Tumor secretion of T cell-activating cytokines C. Cross reaction of microbe-specific CD8+ T cells with tumor antigens D. Cross-presentation of tumor antigens by APCs E. Antigenic modulation

E. Antigenic modulation For the induction of antigen-specific CD8+ T cells, antigen needs to be presented in MHC class I molecules in order to be recognized by the TCR/CD3 complex on CD8+ T cells. Peptides derived from endogenous proteins degraded in the cytosol that are transported into the endoplasmic reticulum, are loaded on MHC class I molecules, which will be transported to the plasma membrane as a stable peptide-MHC class I complex. Antigen cross-presentation, the process in which exogenous antigens are presented on MHC class I molecules, is crucial for the generation of effector CD8+ T cell responses. All dendritic cells (DCs) have functional MHC class I and MHC class II presentation pathways. MHC class I molecules present peptides that are derived from proteins degraded mainly in the cytosol, which in most DC types comprise almost exclusively endogenous proteins (synthesized by the cell itself). MHC class II molecules acquire peptide cargo that is generated by proteolytic degradation in endosomal compartments. The precursor proteins of these peptides include exogenous material that is endocytosed from the extracellular environment, and also endogenous components, such as plasma membrane proteins, components of the endocytic pathway and cytosolic proteins that access the endosomes by autophagy. CD8+ DCs have a unique ability to deliver exogenous antigens to the MHC class I (cross-presentation) pathway, although the mechanisms involved in this pathway are still poorly understood. The bifurcated arrow indicates that the MHC class II and the MHC class I cross-presentation pathways may 'compete' for exogenous antigens in CD8+ DCs, or that the endocytic mechanism involved in internalization of a given antigen may determine whether it is preferentially delivered to the MHC class II pathway or the MHC class I cross-presentation pathway. TAP, transporter associated with antigen processing.

The T‐cell receptor antigen recognition signal is transduced by: A. The TCR alpha chain. B. The TCR beta chain. C. CD1. D. CD2. E. CD3.

E. CD3.

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.

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

E. Failure to form viral peptide-class I MHC complexes 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.

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

If B cells class switch in an environment that is rich in IL-4 and IL-5, they preferentially switch their class from IgM to _______. A. IgA B. IgD C. IgG D. IgM E. IgE

E. IgE

A 16-year-old boy has acute appendicitis (infection of the appendix). Which of the following blood cells is most likely to increase in number as a result of his condition? A. Basophils B. Eosinophils C. Lymphocytes D. Monocytes E. Neutrophils

E. Neutrophils A marked increase in blood neutrophils is a hallmark of infection. Basophils and eosinophils are rarely seen in the circulation in numbers that exceed 5% of the blood-borne leukocytes. Monocytes and lymphocytes increase in notable numbers usually only in chronic disorders.

A 77‐year‐old man is admitted to the intensive care unit (ICU) of a university hospital from the operating room. Earlier the same day, he had presented to the emergency department with abdominal pain. In the emergency department, he was drowsy and confused when roused and was peripherally cold with cyanosis. The systemic arterial blood pressure was 75/50 mm Hg, and the heart rate was 125 beats per minute. Which of the following is thought to be a major contributor to the septic shock? A. Clathrin B. Histamine C. Interferon D. Interleukin 2 E. Tumor necrosis factor

E. Tumor necrosis factor

The membrane-bound proteins on human cells that dissociate and inactivate alternative C3 convertase to avoid complement activation are: A. factor B and factor H B. factor H and factor I C. factor B and factor I D. decay-accelerating factor and factor H E. decay-accelerating factor and membrane cofactor protein.

E. decay-accelerating factor and membrane cofactor protein. Both decay-accelerating factor (DAF) and membrane cofactor protein (MCP) are involved in dissociate and inactivate alternative C3 convertase, respectively.

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.

Which of the following is not a characteristic of mannose-binding lectin? A. acts as an opsonin by binding to mannose-containing carbohydrates of pathogens B. synthesized by hepatocytes C. induced by elevated IL-6 D. a member of the collectin family E. triggers the alternative pathway of complement activation

E. triggers the alternative pathway of complement activation Mannose-binding lectin (MBL) is a pattern recognition molecule of the innate immune system. It belongs to the collectin family of proteins in which lectin (carbohydrate-recognition) domains are found in association with collagenous structures. In man, these proteins include serum MBL, lung surfactant protein A (SP-A) and lung surfactant protein D (SP-D). MBL binds to a range of sugars including N-acetyl- d-glucosamine, mannose, N-acetyl-mannosamine, fucose and glucose. This permits the protein to interact with a wide selection of viruses, bacteria, yeasts, fungi and protozoa decorated with such sugars. Unlike the other collectins, MBL bound to microbial surfaces is able to activate the complement system in an antibody and C1-independent manner. This activation is mediated by complexes of MBL with a serine protease called MBL-associated serine protease 2 (MASP-2), which specifically cleaves C4 and C2 to create a C3 convertase enzyme. MBL may also interact directly with cell surface receptors and thereby promote opsonophagocytosis by a complement-independent pathway.

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

a. Helper T lymphocytes and cytotoxic T lymphocytes 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.

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

a. Highly diverse repertoire of specificities for antigens 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.

Match the local and systemic effects in column appropriate cytokine in column B. Note that more than one answer in used. COLUMN A: a. activation of blood-vessel endothelium b. fever c. induction of IL-6 synthesis d. increase in vascular permeability e. localized tissue destruction f. production of acute-phase proteins by hepatocytes g. induction of resistance to viral replication h. activation of NK cells i. leukocyte chemotaxis j. activation of binding by β2 integrins (LFA-1, CR3) k. septic shock l. mobilization of metabolites COLUMN B: 1. IL-1 2. IL-6 3. CXCL8 4. IL-12 5. TNF-α 6. type I interferons

a. activation of blood-vessel endothelium = IL-1 and TNF-α b. fever = IL-1, IL-6, and TNF-α c. induction of IL-6 synthesis = IL-1 d. increase in vascular permeability = TNF-α e. localized tissue destruction = IL-1 f. production of acute-phase proteins by hepatocytes = IL-6 g. induction of resistance to viral replication = type I interferons h. activation of NK cells = IL-12 and type I interferons i. leukocyte chemotaxis = CXCL8 j. activation of binding by β2 integrins (LFA-1, CR3) = CXCL8 k. septic shock = TNF-α l. mobilization of metabolites = TNF-α

A healthy one year old is given an antigen. The immune response shows increasing IgM and no rise in IgG during the next 2 months. Which of the following types of antigens was mostly likely given? a. bacterial polysaccharide b. live attenuated measles c. polio d. tetanus toxiod e. unconjugated hapten

a. bacterial polysaccharide IgG only recognizes PROTEINS. IgM recognizes all types of antigens.

In the classical pathway of complement activation which portion of IgM or IgG antibodies is bound to 2 or more complement proteins (C1 complex)? a. CD36 (scavenger receptor) b. Fc receptor c. Complement receptor d. Fab receptor e. LFA-1

b. Fc receptor

Natural killer cells have receptors on their surface that can bind to the _________ portion of IgG3 antibodies. This process is called "antibody-dependent cellular cytotoxicity" (ADCC). In ADCC, the NK cell does the killing, but the antibody identifies the target. a. CD36 (scavenger receptor) b. Fc receptor c. Complement receptor d. Fab receptor e. ICAM-1

b. Fc receptor

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

b. Passive humoral immunity 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.

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.

b. The innate immune system responds rapidly to the viral infection and keeps the viral infection under control. 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.

Immune cells within the lymphatic circulation are directly deposited into which of the following anatomical sites so that the cells may reenter the bloodstream? a. right aorta b. left subclavian vein c. left carotid artery d. high endothelial venule e. hepatic vein

b. left subclavian vein

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.

c. Innate immunity is better suited for eliminating virulent, resistant microbes than is adaptive immunity. 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.

B cells can change their constant (Fc) region by ____________, and their antigen binding (Fab) region by ______________ and these two modifications produce B cells that are better adapted to deal with invaders.

class switching; somatic hypermutation

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

d. Increased number of lymphocytes with identical specificities, all derived from a single lymphocyte stimulated by a single antigen 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.

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

d. Mannose receptor 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.

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

d. Memory 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.

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

d. NFκB and AP-1 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.

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

d. Unmethylated CpG DNA 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.

The ligand for CR3 and CR4 formed by the cleavage of C3b by the combined action of factors H and I is called: a. C3bBb b. C3a c. C3b2Bb d. iC3b e. C5b.

d. iC3b

Which of the following is the membrane-bound form of C3 convertase of the alternative pathway of complement activation? a. iC3 b. C3a c. C3b d. iC3Bb e. C3bBb.

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