Deck 3: Innate Immunity

Question 1

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

Answer 1

Circulating anti-tetanus toxin antibodies

Question 2

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

Answer 2

Unmethylated CpG DNA

Question 3

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

Answer 3

CD28

Question 4

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

Question 5

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- $\beta$
B)Tumor necrosis factor- $\alpha$
C)Interleukin (IL)-2
D)IL-10
E)IL-3

Question 6

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 $\gamma$ RI receptor,which recognizes specific opsonins bound to microbes and facilitates phagocytosis.
E)Both neutrophils and macrophages contain abundant cytoplasmic granules containing lysozyme,collagenase,and elastasE.

Question 7

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 $\kappa$ B and AP-1
E)Lck and Jun

Question 8

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

Question 9

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)- $\gamma$ production during early phases of viral infection
E)Failure to form viral peptide-class I MHC complexes

Question 10

Which of the following is a receptor on macrophages that is specific for a structure produced by bacteria but not by mammalian cells?

A)CD36 (scavenger receptor)
B)Fc receptor
C)Complement receptor
D)Mannose receptor
E)ICAM-1

Question 11

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.

Question 12

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

Question 13

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.

Question 14

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

Question 15

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)- $\gamma$ 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- $\beta$ expression by fibroblasts,inducing an "antiviral state" in neighboring,uninfected cells.

Question 16

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.

Question 17

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