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Microbiology An Evolving Science 3rd Edition Slonczewski Foster Test Bank
ISBN-13: 978-0393123685
ISBN-10: 0393123685
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CHAPTER 23: Human Microbiota and Innate Immunity
MULTIPLE CHOICE
- An organism found on human skin that derives benefit from, but does NOT harm, the host is described as a(n):
| a. | parasite | d. | pathogen |
| b. | commensal | e. | mutualist |
| c. | opportunist | ||
ANS: B DIF: Medium REF: 23.1 TOP: I.A.i
MSC: Remembering
- Microbial colonization of the eye is inhibited by the presence of antimicrobial factors, such as:
| a. | interferons | d. | defensins |
| b. | complement | e. | lysozyme |
| c. | mucous | ||
ANS: E DIF: Medium REF: 23.1 TOP: I.A.ii.b
MSC: Remembering
- 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 |
ANS: A DIF: Medium REF: 23.1 TOP: I.A.ii.c
MSC: Remembering
- Which of the following should be relatively free from resident microbes in a healthy individual?
| a. | nose | d. | respiratory tract |
| b. | mouth | e. | genitourinary tract |
| c. | skin | ||
ANS: D DIF: Easy REF: 23.1 TOP: I.A.ii.d
MSC: Remembering
- 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 |
ANS: E DIF: Medium REF: 23.1 TOP: I.A.ii.d
MSC: Remembering
- The aerobe to anaerobe ratio showing the greatest difference in concentrations occurs in the:
| a. | intestinal tract | d. | respiratory tract |
| b. | mouth | e. | genitourinary tract |
| c. | skin | ||
ANS: A DIF: Medium REF: 23.1 TOP: I.A.ii.f
MSC: Remembering
- 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 |
ANS: D DIF: Medium REF: 23.1 TOP: I.A.ii.f
MSC: Remembering
- Which part of the genitourinary tract maintains a normal flora population?
| a. | kidney | d. | urethra |
| b. | ureters | e. | distal urethra |
| c. | bladder | ||
ANS: E DIF: Easy REF: 23.1 TOP: I.A.ii.g
MSC: Remembering
- Which of the following is rarely normal flora of the distal urethra?
| a. | Staphylococcus aureus | d. | Escherichia coli |
| b. | Bacteroides spp. | e. | Peptostreptococcus spp. |
| c. | Mycobacterium spp. | ||
ANS: D DIF: Easy REF: 23.1 TOP: I.A.ii.g
MSC: Remembering
- 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. |
ANS: C DIF: Medium REF: 23.1 TOP: I.A
MSC: Applying
- 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 |
ANS: B DIF: Medium REF: 23.1 TOP: I.A.i.a
MSC: Applying
- Which of the following innate immunity mechanisms is mismatched with its associated structure or body fluid?
| a. | lysozyme—tears and saliva | d. | acidic pH, sebum, fatty acids—skin |
| b. | mucociliary elevator—intestines | e. | low pH—urogenital tract |
| c. | highly acidic pH—stomach | ||
ANS: B DIF: Medium REF: 23.1 TOP: I.A.ii.d
MSC: Applying
- Helicobacter pylori lives in the ___________ because it ____________.
| a. | mouth; binds to gingival crevices | d. | gall bladder; feeds on bile |
| b. | gall bladder; escapes alveolar macrophages | e. | stomach; is lysozyme-resistant |
| c. | stomach; neutralizes acid | ||
ANS: C DIF: Medium REF: 23.1 TOP: I.A.ii.e
MSC: Applying
- Which of the following is NOT found in the epidermis layer?
| a. | hair follicle | d. | sweat glands |
| b. | sebaceous gland | e. | all of the above |
| c. | blood vessels | ||
ANS: C DIF: Medium REF: 23.1 TOP: I.A.ii.a
MSC: Analyzing
- Which of the following are the major phagocytic cells in the body?
| a. | T and B lymphocytes | d. | neutrophils and macrophages |
| b. | basophils and eosinophils | e. | epithelial cells and cilia |
| c. | erythrocytes and platelets | ||
ANS: D DIF: Medium REF: 23.3 TOP: III.A.iii
MSC: Remembering
- Which of the following types of cells are antigen-presenting cells?
| a. | only eosinophils | d. | only neutrophils |
| b. | platelets and macrophages | e. | macrophages and dendritic cells |
| c. | only macrophages | ||
ANS: E DIF: Medium REF: 23.3 TOP: III.A.iii.c
MSC: Remembering
- Which of the following is NOT a lymphoid organ?
| a. | tonsils and adenoids | d. | stomach |
| b. | spleen | e. | bone marrow |
| c. | appendix | ||
ANS: D DIF: Easy REF: 23.3 TOP: III.A.iii.e
MSC: Remembering
- Which of the following is a primary lymphoid organ?
| a. | adenoids | d. | thymus |
| b. | appendix | e. | tonsils |
| c. | Peyer’s patches | ||
ANS: D DIF: Medium REF: 23.3 TOP: III.A.iii.e
MSC: Remembering
- Which of the following cell types would most likely be elevated in a viral infection?
| a. | eosinophils | d. | platelets |
| b. | lymphocytes | e. | complement |
| c. | basophils | ||
ANS: B DIF: Medium REF: 23.3 TOP: III.A.iii.e
MSC: Remembering
- Which of the following would NOT be considered an antigen in the human body?
| a. | a transplanted cell | d. | a lipopolysaccharide |
| b. | the herpes virus | e. | a complement protein |
| c. | Neisseria gonorrhoeae | ||
ANS: E DIF: Medium REF: 23.3 TOP: III.A.i
MSC: Understanding
- Cystic fibrosis patients are __________ prone to infection by mucoid strains of Pseudomonas aeruginosa as compared with the rest of the population.
| a. | less | d. | not at all |
| b. | more | e. | none of the above |
| c. | equally | ||
ANS: B DIF: Easy REF: 23.4 TOP: IV.A.iii
MSC: Remembering
- 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. |
ANS: D DIF: Difficult REF: 23.4 TOP: IV.B
MSC: Remembering
- 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 |
ANS: A DIF: Difficult REF: 23.4 TOP: IV.B
MSC: Understanding
- Polymixin B is a small antimicrobial, cationic peptide that mimics the action of:
| a. | macrophages | d. | natural killer cells |
| b. | lysosomes | e. | antibodies |
| c. | defensins | ||
ANS: C DIF: Medium REF: 23.4 TOP: IV.B
MSC: Applying
- Lysozyme and the antibiotic penicillin have similar mechanisms of action in that they both cause damage to the bacterial:
| a. | cell membrane | d. | DNA |
| b. | capsule | e. | ribosomes |
| c. | cell wall | ||
ANS: C DIF: Medium REF: 23.4 TOP: IV.B
MSC: Applying
- 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 | d. | flushing action of urine |
| b. | lysozyme | e. | skin pH |
| c. | pH of stomach | ||
ANS: C DIF: Medium REF: 23.4 TOP: IV.B
MSC: Applying
- 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 | d. | mitochondria |
| b. | nucleus | e. | phagosome |
| c. | plasma membrane surface | ||
ANS: C DIF: Difficult REF: 23.4 TOP: IV.A.iii
MSC: Analyzing
- Extravasation is the process by which __________ move(s) from the bloodstream into surrounding tissues.
| a. | neutrophils | d. | interferons |
| b. | natural killer cells | e. | complement |
| c. | antibodies | ||
ANS: A DIF: Medium REF: 23.5 TOP: V.A
MSC: Remembering
- 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 |
ANS: E DIF: Medium REF: 23.5 TOP: V.A
MSC: Understanding
- 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. |
ANS: C DIF: Medium REF: 23.5 TOP: V.A.i
MSC: Understanding
- 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 |
ANS: E DIF: Medium REF: 23.5 TOP: V
MSC: Applying
- Interleukin-1 (IL-1) and tumor necrosis factor (TNF) were detected in a patient’s serum. This indicates:
| a. | mucosal IgA has been degraded | d. | cancer cells are forming |
| b. | B lymphocyte activation | e. | natural killer cells have autolyzed |
| c. | a macrophage has encountered an antigen | ||
ANS: C DIF: Difficult REF: 23.5 TOP: V.A.i
MSC: Applying
- 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 |
ANS: C DIF: Difficult REF: 23.6 TOP: VI
MSC: Remembering
- Opsonization is a process whereby the innate and adaptive immune mechanisms work together:
| a. | to phagocytize an invader | d. | to destroy cancer cells |
| b. | to activate complement proteins | e. | during apoptosis |
| c. | for antibody secretion | ||
ANS: A DIF: Easy REF: 23.6 TOP: VI.A
MSC: Remembering
- 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 |
ANS: A DIF: Difficult REF: 23.6 TOP: VI.A
MSC: Remembering
- Which of the following is NOT associated with the oxidative burst employed by phagocytic cells to kill bacteria?
| a. | hydrogen peroxide | d. | catalase |
| b. | oxygen radicals | e. | nitric oxide |
| c. | NADPH oxidase | ||
ANS: D DIF: Difficult REF: 23.6 TOP: VI.B
MSC: Remembering
- A bacterium can live inside a phagocyte by preventing:
| a. | complement activation | d. | fusion of the phagosome with a lysosome |
| b. | interferon production | e. | inflammation |
| c. | defensin production | ||
ANS: D DIF: Medium REF: 23.6 TOP: VI
MSC: Understanding
- 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 | d. | 5, 2, 3. 6, 4, 1 |
| b. | 3, 4, 6, 5, 2, 1 | e. | none of the above |
| c. | 6, 5, 2, 4, 3, 1 | ||
ANS: A DIF: Difficult REF: 23.6 TOP: VI
MSC: Applying
- Which the following creates a channel in target cell membranes?
| a. | complement | d. | A and B |
| b. | defensins | e. | all of the above |
| c. | natural killer cells | ||
ANS: E DIF: Medium REF: 23.7 TOP: IV.B | VII.B | VIII.A
MSC: Remembering
- 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 |
ANS: B DIF: Medium REF: 23.7 TOP: VII.A
MSC: Remembering
- 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. |
ANS: C DIF: Difficult REF: 23.7 TOP: VII.A
MSC: Remembering
- Which of the following, produced by natural killer cells, punctures the membrane of target cells, causing them to burst?
| a. | perforins | d. | lysins |
| b. | trypsins | e. | defensins |
| c. | maganins | ||
ANS: A DIF: Medium REF: 23.7 TOP: VII.B
MSC: Remembering
- 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 |
ANS: D DIF: Difficult REF: 23.7 TOP: VII.C
MSC: Remembering
- 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 |
ANS: D DIF: Difficult REF: 23.7 TOP: VII.C
MSC: Remembering
- 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 |
ANS: A DIF: Medium REF: 23.7 TOP: VII.B
MSC: Applying
- 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 |
ANS: D DIF: Medium REF: 23.8 TOP: VIII.A
MSC: Remembering
- Increased levels of C-reactive protein in the blood have been linked to increased risk of which of the following?
| a. | kidney disease | d. | diabetes |
| b. | liver disease | e. | Crohn’s disease |
| c. | cardiovascular disease | ||
ANS: C DIF: Medium REF: 23.8 TOP: VIII.B
MSC: Remembering
- 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 |
ANS: A DIF: Difficult REF: 23.8 TOP: VIII.A
MSC: Applying
- 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 |
ANS: A DIF: Medium REF: 23.9 TOP: IX.A
MSC: Remembering
SHORT ANSWER
- What factors might explain the prevalence of Gram-positive bacteria on human skin’s epidermal layer?
ANS:
The skin has an acidic pH, as well as high salt secretions and highly keratinized cells. The presence of organic acids and enzymes make it even more unfavorable for bacteria to colonize. However, Staphylococcus epidermidis and other Gram-positives tend to be resistant to these factors.
DIF: Easy REF: 23.1 TOP: I.A.ii.a MSC: Remembering | Evaluating
- Microbes on humans sharpen our immunity and protect us from infection, but these benefits come with considerable risk. Explain.
ANS:
The microbiota of humans are extremely beneficial to the well-being of their human host. However, the ability of these commensals (such as the oral flora) to cause deadly diseases when introduced to sterile body parts, such as the blood, organs, and brain, is worthy of concern. The proximity of the opportunistic pathogens to vulnerable body parts makes the association risky.
DIF: Medium REF: 23.1 TOP: I.A.ii.c | II.A.ii
MSC: Understanding | Evaluating
- Explain how differences in gut microbiota can account for obesity and leanness in humans.
ANS:
About 15%–20% of the human caloric intake is derived from colon bacteria that digest and degrade the complex carbohydrates we consume. Different microbiota will affect the efficiency of calorie harvesting from the same diet and how it is subsequently stored. Studies investigating the connection between the presence of methanogens (a specific type of bacteria) in the intestines and obesity are underway.
DIF: Difficult REF: 23.1 TOP: I.A.ii.f MSC: Understanding | Evaluating
- Why is acne able to be treated with antibiotics?
ANS:
Acne is treated with antibiotics because it is caused by the Gram-positive, anaerobic rod Propionibacterium acnes. Since this is a bacterial infection, some antibiotics (tetracycline or clindamycin) may be helpful in the treatment of acne conditions. However, only antibiotics that are targeted against Gram-positive organisms will be effective.
DIF: Easy REF: 23.1 TOP: I.A.ii.a MSC: Analyzing
- Discuss how Propionibacterium acnes—an anaerobic Gram-positive normal flora of the skin—causes acne, especially in teenagers.
ANS:
It is a normal microbial resident of the skin, but during the adolescent years, increased hormonal activity leads to increased oil production by the sebaceous glands. The triglycerides in these oils are readily degraded by P. acne to free fatty acids, which cause inflammation of the sebaceous gland. A plug of fluid and keratin forms in the gland duct, resulting in the typical acne skin eruption.
DIF: Medium REF: 23.1 TOP: I.A.ii.a MSC: Analyzing
- Explain why healthy individuals are usually “immune” to cholera, whereas malnourished individuals are not.
ANS:
Vibrio cholerae, the causative agent of cholera, is extremely sensitive to low pH. The pH of the stomach of healthy individuals is well below 4, which effectively kills V. cholerae. Malnourished individuals are achlorhydric, or have a loss of stomach acid. The pH of their stomachs permits V. cholerae to travel through the stomach and reach the less acidic intestine. It is here that the organism thrives and causes disease.
DIF: Easy REF: 23.1 TOP: I.A.ii.e MSC: Analyzing
- What explains the ability of Helicobacter pylori to defy stomach acidity?
ANS:
- pylori produces ureases, which generate ammonia, thereby increasing the pH of the stomach in its microenvironment. This enables the organism to survive, although it does not grow and divide until it takes up residence in the mucous lining of the stomach. The mucous of the stomach epithelium has a pH of between 5 and 6, allowing the organism to thrive.
DIF: Easy REF: 23.1 TOP: I.A.ii.e MSC: Analyzing
- How is it that Clostridium difficile, often a part of the normal intestinal microflora, can be the causative agent of pseudomembranous enterocolitis?
ANS:
When a person takes antibiotics, normal flora microbes are killed. These may be competing with and generally keeping C. difficile at bay. In their absence, C. difficile grows unabated, making a toxin that damages and kills host epithelial cells. Small plaques are formed that eventually coalesce to form a pseudomembrane.
DIF: Medium REF: 23.1 TOP: I.A.ii.f MSC: Analyzing
- How can an anaerobic microbe grow on the skin or on body parts that are constantly exposed to air?
ANS:
The microbial niche is microscopic, allowing anaerobic niches on the skin to coexist with aerobic niches. One example is the hair follicle. In fact, the aerobes and the anaerobes are intertwined to the extent that the anaerobic environ is created by the metabolism of the aerobes.
DIF: Easy REF: 23.1 TOP: I.A.ii.a MSC: Evaluating
- How does eating sugar cause dental caries and cavities?
ANS:
Dental plaques are caused by Streptococcus mutans, which attach to teeth enamel, and Streptococcus salivarius, which binds gingival surfaces. Both organisms secrete glycocalyx, which enables them to attach firmly to oral surfaces and to each other, leading to the formation of a stable biofilm. Their acidic fermentation products erode the teeth and create hardened plaques, which is often followed by dental caries. The more sugar consumed, the more fuel there is to promote acidic fermentation.
DIF: Easy REF: 23.1 TOP: I.A.ii.c MSC: Evaluating
- Why is it important for people with mitral valve prolapse to take antibiotics prior to a dental exam or procedure?
ANS:
During a dental procedure, organisms that are generally innocuous in the oral cavity are released into the bloodstream. This causes transient bacteremia in normal individuals, but in individuals with mitral valve prolapse, some organisms may become trapped in the defective valve. In this case, the bacterial vegetations become encased in glycocalyx and then are relatively inaccessible to antibiotics. As a result, the antibiotic needs to be present when the organisms enter the bloodstream, prior to colonization in the valve.
DIF: Medium REF: 23.1 TOP: I.A.ii.c MSC: Evaluating
- How would you explain the distinguishing characteristics of innate and adaptive immunity?
ANS:
Innate immunity is also known as nonadaptive immunity. Innate immunity is hardwired into us and exists prior to any microbial exposure. It involves physical barriers, chemical barriers, and relatively nonspecific cellular responses to infection. Adaptive immunity is the body’s reaction to specific antigens. Once the body has been activated by an antigen, it creates a memory of it such that when it encounters the same antigen again, the specific memory cells are quickly reactivated.
DIF: Medium REF: 23.3 TOP: III.A MSC: Analyzing
- What is the biology underlying the condition of lupus, and how could the symptoms of lupus be lessened on the cellular level?
ANS:
Neutrophil extracellular traps, or NETs, have been shown to be produced by a special neutrophil subset, called low-density granulocytes (LDGs), found in all lupus patients. Autoantibodies, specifically for ribonucleoproteins and the antimicrobial peptide LL-37, accelerate the propagation of NETs, feeding a cycle of more NETs, autoantibodies, LDGs, LL-37, NK cells, CD8 cells, and so on, via enhanced interferon (INF-a) production and ultimately amplifying the inflammation and tissue damage seen in lupus. Blocking NET release would be one way to break the cycle and lessen the symptoms of lupus.
DIF: Difficult REF: 23.3 TOP: III.B MSC: Evaluating
- 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?
ANS:
No, the Langerhans cells are specialized dendritic cells that make up a significant portion of SALT. They phagocytize microbes, migrate to lymph nodes, and serve as antigen-presenting cells that present parts of the microbe to the immune system to activate antimicrobial activity.
DIF: Medium REF: 23.4 TOP: IV.A.i MSC: Analyzing
- Is it correct to state that bacteria introduced through a skin cut will most likely be engulfed by Langerhans cells?
ANS:
Langerhans cells are resident phagocytic cells that make up a significant portion of skin-associated lymphoid tissue (SALT). It is quite probable that these front-line cells will encounter the bacteria first and then provoke inflammation.
DIF: Medium REF: 23.4 TOP: IV.A.i MSC: Evaluating
- Explain how the small polypeptide bradykinin promotes edema and pain.
ANS:
Bradykinin promotes extravasation as well as the degranulation of mast cells. The release of histamine from the mast cells causes fluid accumulation, or edema. Bradykinin also binds to capillary cells and induces prostaglandin synthesis, which stimulates nerve endings, causing pain in the area of swelling.
DIF: Medium REF: 23.5 TOP: V.A.iii MSC: Understanding | Analyzing
- Discuss two methods by which bacteria resist or evade killing by phagocytosis.
ANS:
Some bacteria produce capsules made of human connective tissues. This prevents them from being detected as foreign. This is called molecular mimicry. Polysaccharide capsules are also protective. In addition, some bacteria, such as Listeria and Mycobacterium spp., prevent the fusion of the phagosome with the lysosome or escape into the cytoplasm before the fusion occurs.
DIF: Medium REF: 23.6 TOP: VI MSC: Analyzing
- Describe antibody-induced opsonization, the process in which innate and adaptive immunity work together to engulf an invader.
ANS:
Cells that have a polysaccharide capsule are too slippery to be captured by the innate response of phagocytosis. The adaptive response produces anticapsular antibodies that aid the innate system through opsonization. This process involves the binding of antibodies to the capsule, leaving the Fc regions facing outward to be recognized and bound by receptors on phagocytic cell surfaces.
DIF: Medium REF: 23.6 TOP: VI.A MSC: Analyzing
- Why is the alternative complement cascade NOT considered a part of adaptive immunity?
ANS:
The serum proteins referred to as complement are not induced during infection; rather, they are present in the blood innately. Their activation, however, is enhanced by the presence of invaders. Moreover, the same complement proteins are used to target many different organisms. In contrast, adaptive immunity is highly specific, involving antibodies secreted to neutralize a given pathogen. Antibodies are only needed in inducing the classical complement cascade.
DIF: Difficult REF: 23.8 TOP: VIII.A MSC: Analyzing
- How is it that Gram-positive cells are more resistant to complement than Gram-negative cells?
ANS:
The lipopolysaccharide of outer cell membranes is very efficient at activating the complement cascade. Since Gram-positive cells do not have an outer membrane, the cascade is not as readily activated. The thicker peptidoglycan layer of the Gram-positives also hinders access of the complement components to the bacterial membrane.
DIF: Medium REF: 23.8 TOP: VIII.A.i MSC: Analyzing
