Deck 23: Human Microbiota and Innate Immunity

Question 1

Which of the following is rarely normal flora of the distal urethra?

A) Staphylococcus aureus
B) Bacteroides spp.
C) Mycobacterium spp.
D) Escherichia coli
E) Peptostreptococcus spp.

Answer 1

D

Question 2

Which of the following are the major phagocytic cells in the body?

A) T and B lymphocytes
B) basophils and eosinophils
C) erythrocytes and platelets
D) neutrophils and macrophages
E) epithelial cells and cilia

Answer 2

D

Question 3

Which of the following is a primary lymphoid organ?

A) adenoids
B) appendix
C) Peyer's patches
D) thymus
E) tonsils

Answer 3

D

Question 4

Which of the following would NOT be considered an antigen in the human body?

A) a transplanted cell
B) the herpes virus
C) Neisseria gonorrhoeae
D) a lipopolysaccharide
E) a complement protein

Question 5

Which of the following is NOT a lymphoid organ?

A) tonsils and adenoids
B) spleen
C) appendix
D) stomach
E) bone marrow

Question 6

Which of the following innate immunity mechanisms is mismatched with its associated structure or body fluid?

A) lysozyme-tears and saliva
B) mucociliary elevator-intestines
C) highly acidic pH-stomach
D) acidic pH, sebum, fatty acids-skin
E) low pH-urogenital tract

Question 7

Neisseria species:

A) are found in the mouth within hours of birth
B) cause serious diarrhea
C) are used as probiotics
D) are obligate intracellular parasites
E) are Gram-positive cocci

Question 8

The aerobe to anaerobe ratio showing the greatest difference in concentrations occurs in the:

A) intestinal tract
B) mouth
C) skin
D) respiratory tract
E) genitourinary tract

Question 9

The mucociliary elevator functions to:

A) trap and sweep pathogens into the urine
B) kill via lysozyme activity
C) harbor normal flora that discourage pathogens from colonizing
D) produce fatty acids with a low pH that kills microbes
E) trap and sweep microbes from the bronchi back up to the throat to be swallowed

Question 10

Which part of the genitourinary tract maintains a normal flora population?

A) kidney
B) ureters
C) bladder
D) urethra
E) distal urethra

Question 11

Helicobacter pylori lives in the ___________ because it ____________.

A) mouth; binds to gingival crevices
B) gall bladder; escapes alveolar macrophages
C) stomach; neutralizes acid
D) gall bladder; feeds on bile
E) stomach; is lysozyme-resistant

Question 12

Which of the following should be relatively free from resident microbes in a healthy individual?

A) nose
B) mouth
C) skin
D) respiratory tract
E) genitourinary tract

Question 13

An organism found on human skin that derives benefit from, but does NOT harm, the host is described as a(n):

A) parasite
B) commensal
C) opportunist
D) pathogen
E) mutualist

Question 14

All of the following statements are correct about microbial colonization of the human body EXCEPT:

A) The skin is a highly selective niche for certain microbes.
B) Oral microbiota can cause endocarditis after dental surgery.
C) Normal cardiovascular flora are commensal species.
D) There are 1,000 times more anaerobes in the colon than aerobes.
E) Intestinal bacteria help modulate human mucosal immunity.

Question 15

Microbial colonization of the eye is inhibited by the presence of antimicrobial factors, such as:

A) interferons
B) complement
C) mucous
D) defensins
E) lysozyme

Question 16

Which of the following types of cells are antigen-presenting cells?

A) only eosinophils
B) platelets and macrophages
C) only macrophages
D) only neutrophils
E) macrophages and dendritic cells

Question 17

Which of the following is NOT found in the epidermis layer?

A) hair follicle
B) sebaceous gland
C) blood vessels
D) sweat glands
E) all of the above

Question 18

Which of the following cell types would most likely be elevated in a viral infection?

A) eosinophils
B) lymphocytes
C) basophils
D) platelets
E) complement

Question 19

A scientist working on a human metagenome project would most likely discover:

A) new cytokines released by macrophages during inflammation
B) previously unknown commensal organisms colonizing the gut
C) DNA up-regulated during phagocytosis
D) control of RNA replication in RNA virus
E) new defensins produced by the body

Question 20

Which of the following two organisms are commonly used as probiotics?

A) Streptococcus mutans and Lactobacillus acidophilus
B) Bacteroides and Lactobacillus acidophilus
C) Enterococcus and Enterobacter species
D) Bifidobacterium and Lactobacillus acidophilus
E) Diphtheroids and Fusobacterium species

Question 21

Interleukin-1 (IL-1) and tumor necrosis factor (TNF) were detected in a patient's serum. This indicates:

A) mucosal IgA has been degraded
B) B lymphocyte activation
C) a macrophage has encountered an antigen
D) cancer cells are forming
E) natural killer cells have autolyzed

Question 22

A man has been taking excessive amounts of antacids for heartburn. These tablets are very alkaline. Which innate defense mechanism might be altered by his actions?

A) mucociliary elevator
B) lysozyme
C) pH of stomach
D) flushing action of urine
E) skin pH

Question 23

Extravasation is the process by which __________ move(s) from the bloodstream into surrounding tissues.

A) neutrophils
B) natural killer cells
C) antibodies
D) interferons
E) complement

Question 24

Which the following creates a channel in target cell membranes?

A) complement
B) defensins
C) natural killer cells
D) A and B
E) all of the above

Question 25

List the correct order of the following events in phagocytosis: (1) discharge of waste material; (2) fusion of the phagosome with a lysosome; (3) adherence of the microbe to phagocytes; (4) digestion of the ingested microbe; (5) formation of a phagosome; (6) ingestion of the microbe by the phagocyte.

A) 3, 6, 5, 2, 4, 1
B) 3, 4, 6, 5, 2, 1
C) 6, 5, 2, 4, 3, 1
D) 5, 2, 3. 6, 4, 1
E) none of the above

Question 26

Cystic fibrosis patients are __________ prone to infection by mucoid strains of Pseudomonas aeruginosa as compared with the rest of the population.

A) less
B) more
C) equally
D) not at all
E) none of the above

Question 27

Which of the following can interfere with adherence of phagocytic cells to the pathogen?

A) polysaccharide capsule of Streptococcus pneumonia
B) lipid cell wall produced by Mycobacterium tuberculosis
C) leukocidin released by Staphylococci sp.
D) lipopolysaccharide of Gram-negative bacteria
E) ability of Rickettsia rickettsii to prevent release of lysosomal enzymes

Question 28

Which of the following is correct regarding inflammation?

A) The cardinal signs include rash.
B) Some of the phagocytes are stimulated to secrete antibodies specific for the invading pathogen.
C) The response is the same for Hepatitis virus, Escherichia coli bacteria, and/or cellular injury to the body.
D) Differentiation of B cells into plasma cells occurs at the site of infection.
E) AIDS patients have little or no inflammatory response when they are infected.

Question 29

Which of the following is NOT associated with the oxidative burst employed by phagocytic cells to kill bacteria?

A) hydrogen peroxide
B) oxygen radicals
C) NADPH oxidase
D) catalase
E) nitric oxide

Question 30

A woman falls and suffers a cut on her leg. The cut went through her skin and she is bleeding. Which of the following defense mechanisms will participate in eliminating microbes contaminating the cut?

A) mucociliary elevator
B) normal skin flora
C) acidic skin secretions
D) lysozyme
E) phagocytosis and the inflammatory response

Question 31

Lysozyme and the antibiotic penicillin have similar mechanisms of action in that they both cause damage to the bacterial:

A) cell membrane
B) capsule
C) cell wall
D) DNA
E) ribosomes

Question 32

Polymixin B is a small antimicrobial, cationic peptide that mimics the action of:

A) macrophages
B) lysosomes
C) defensins
D) natural killer cells
E) antibodies

Question 33

Which of the following is NOT an integral part of the inflammatory process?

A) dilation of blood vessels
B) release of histamines and prostaglandins
C) chemotaxis of polymorphonuclear leukocytes
D) extravasation
E) antibody synthesis

Question 34

Which of the following pairs is mismatched?

A) extravasation-movement of leukocytes through endothelial cells into tissues
B) pus-tissue debris and dead phagocytes in a white or yellow fluid
C) vasoactive-chemical degradation inside a phagolysosome
D) autophagy-destruction of intraphagocytic pathogen
E) scab-dried blood clot over injured tissue

Question 35

A bacterium can live inside a phagocyte by preventing:

A) complement activation
B) interferon production
C) defensin production
D) fusion of the phagosome with a lysosome
E) inflammation

Question 36

Opsonization is a process whereby the innate and adaptive immune mechanisms work together:

A) to phagocytize an invader
B) to activate complement proteins
C) for antibody secretion
D) to destroy cancer cells
E) during apoptosis

Question 37

Defensins are short cationic peptides that:

A) are produced by skin, GI-tract, and lung cells for defense when stimulated
B) bind to specific protein receptors to gain entry into microbial cells
C) are only produced by phagocytes upon activation
D) inhibit microbial DNA synthesis
E) are equally effective at killing eukaryotic and prokaryotic cells

Question 38

In cystic fibrosis, a mutation has rendered the receptor for binding and inactivating Pseudomonas defective. The affected gene is the CFTR. Where is the CFTR gene product located?

A) cytosol
B) nucleus
C) plasma membrane surface
D) mitochondria
E) phagosome

Question 39

All of the following statements are correct regarding defensins EXCEPT:

A) They are produced by skin, GI-tract, and lung cells for defense when stimulated.
B) They form channels in bacterial cytoplasmic membranes, ultimately killing the cell.
C) The transmembrane electrical potential allows defensins to penetrate and kill cells.
D) Like antibodies, they are highly specific in pathogen neutralization.
E) Variation in defensins produced by different animals partially explains the varying susceptibility of hosts to pathogens.

Question 40

Interferons:

A) are antibacterial agents produced by skin, GI-tract, and lung cells
B) are secreted by eukaryotic cells in response to intracellular infection
C) are only produced by activated phagocytes
D) are host-specific and virus-specific
E) can block bacterial replication

Question 41

Increased levels of C-reactive protein in the blood have been linked to increased risk of which of the following?

A) kidney disease
B) liver disease
C) cardiovascular disease
D) diabetes
E) Crohn's disease

Question 42

Natural killer cells target:

A) infected cells that have lost MHC class I
B) bacterial cells that have lost MHC class I
C) bacterial cells that are coated with complement
D) infected cells that have lost C-reactive protein
E) infected cells that secrete cytokines

Question 43

How does eating sugar cause dental caries and cavities?

Question 44

Why is it important for people with mitral valve prolapse to take antibiotics prior to a dental exam or procedure?

Question 45

The hypothalamus is important because it regulates:

A) body temperature
B) release of complement proteins from the liver
C) neutrophil phagocytosis
D) white blood cell differentiation
E) pain perception

Question 46

Toll-like receptors are eukaryotic membrane proteins that bind with bacterial surface molecules and:

A) form channels through which bacterial proteins can enter the eukaryotic cell
B) cause the cell to phagocytize the bacteria
C) cause the release of antibiotics to kill the bacteria
D) cause the release of cytokines that trigger host defenses against the bacteria
E) activate the complement cascade

Question 47

Which of the following is an example of a semispecific, innate immune mechanism associated with mucosal surfaces?

A) secretory IgA prevents adhesion to mucosal surface
B) extravasation of neutrophils is triggered by specific signals
C) interferons produced by host will act on specific viruses in the mucosa
D) Toll-like receptors on host bind a specific microbe-associated molecular pattern, or MAMP
E) the type of inflammation mounted varies with pathogen

Question 48

Discuss how Propionibacterium acnes-an anaerobic Gram-positive normal flora of the skin-causes acne, especially in teenagers.

Question 49

How can an anaerobic microbe grow on the skin or on body parts that are constantly exposed to air?

Question 50

How does IFN-gamma protect the host?

A) It induces dsRNA endonucleases.
B) It interferes directly with viral replication.
C) It has an immunomodulatory role.
D) It induces fever at the hypothalamus.
E) It blocks adhesion of pathogens.

Question 51

How does the membrane attack complex, or MAC, kill Gram-negative bacteria?

A) through opsonization
B) it dissolves the cell wall
C) digests the bacterial DNA
D) it creates a pore on the bacterial membranes
E) through antibody-dependent cell cytotoxicity, or ADCC

Question 52

How is it that Clostridium difficile, often a part of the normal intestinal microflora, can be the causative agent of pseudomembranous enterocolitis?

Question 53

What explains the ability of Helicobacter pylori to defy stomach acidity?

Question 54

Detection of high levels of mannose-binding lectin in the blood could signify:

A) the presence of an invading pathogen
B) virus replication is ongoing
C) NK cells have been activated
D) high levels of interferons
E) differentiation of leukocytes is in progress

Question 55

Explain why healthy individuals are usually "immune" to cholera, whereas malnourished individuals are not.

Question 56

What factors might explain the prevalence of Gram-positive bacteria on human skin's epidermal layer?

Question 57

Explain how differences in gut microbiota can account for obesity and leanness in humans.

Question 58

Microbes on humans sharpen our immunity and protect us from infection, but these benefits come with considerable risk. Explain.

Question 59

Which of the following, produced by natural killer cells, punctures the membrane of target cells, causing them to burst?

A) perforins
B) trypsins
C) maganins
D) lysins
E) defensins

Question 60

Why is acne able to be treated with antibiotics?

Question 61

Describe antibody-induced opsonization, the process in which innate and adaptive immunity work together to engulf an invader.

Question 62

Explain how the small polypeptide bradykinin promotes edema and pain.

Question 63

Is it correct to state that bacteria introduced through a skin cut will most likely be engulfed by Langerhans cells?

Question 64

What is the biology underlying the condition of lupus, and how could the symptoms of lupus be lessened on the cellular level?

Question 65

Why is the alternative complement cascade NOT considered a part of adaptive immunity?

Question 66

Discuss two methods by which bacteria resist or evade killing by phagocytosis.

Question 67

How would you explain the distinguishing characteristics of innate and adaptive immunity?

Question 68

How is it that Gram-positive cells are more resistant to complement than Gram-negative cells?

Question 69

Are the Langerhans cells of skin-associated lymphoid tissue (SALT) related to the islets of Langerhans of the pancreas that secrete insulin? What is their function?