6.2.E: Innate Nonspecific Host Defenses (Exercises)
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17.1: Physical Defenses
Nonspecific innate immunity provides a first line of defense against infection by nonspecifically blocking entry of microbes and targeting them for destruction or removal from the body. The physical defenses of innate immunity include physical barriers, mechanical actions that remove microbes and debris, and the microbiome, which competes with and inhibits the growth of pathogens. The skin, mucous membranes, and endothelia throughout the body serve as physical barriers.
Multiple Choice
Which of the following best describes the innate nonspecific immune system?
- a targeted and highly specific response to a single pathogen or molecule
- a generalized and nonspecific set of defenses against a class or group of pathogens
- a set of barrier mechanisms that adapts to specific pathogens after repeated exposure
- the production of antibody molecules against pathogens
- Answer
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B
Which of the following constantly sheds dead cells along with any microbes that may be attached to those cells?
- epidermis
- dermis
- hypodermis
- mucous membrane
- Answer
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A
Which of the following uses a particularly dense suite of tight junctions to prevent microbes from entering the underlying tissue?
- the mucociliary escalator
- the epidermis
- the blood-brain barrier
- the urethra
- Answer
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C
Fill in the Blank
The muscular contraction of the intestines that results in movement of material through the digestive tract is called ________.
- Answer
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peristalsis
______ are the hair-like appendages of cells lining parts of the respiratory tract that sweep debris away from the lungs.
- Answer
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cilia
Secretions that bathe and moisten the interior of the intestines are produced by _______ cells.
- Answer
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goblet
Short Answer
Differentiate a physical barrier from a mechanical removal mechanism and give an example of each.
Identify some ways that pathogens can breach the physical barriers of the innate immune system.
17.2: Chemical Defenses
Numerous chemical mediators produced endogenously and exogenously exhibit nonspecific antimicrobial functions. Many chemical mediators are found in body fluids such as sebum, saliva, mucus, gastric and intestinal fluids, urine, tears, cerumen, and vaginal secretions. Antimicrobial peptides (AMPs) found on the skin and in other areas of the body are largely produced in response to the presence of pathogens. These include dermcidin, cathelicidin, defensins, histatins, and bacteriocins.
Multiple Choice
Which of the following serve as chemical signals between cells and stimulate a wide range of nonspecific defenses?
- cytokines
- antimicrobial peptides
- complement proteins
- antibodies
- Answer
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A
Bacteriocins and defensins are types of which of the following?
- leukotrienes
- cytokines
- inflammation-eliciting mediators
- antimicrobial peptides
- Answer
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D
Which of the following chemical mediators is secreted onto the surface of the skin?
- cerumen
- sebum
- gastric acid
- prostaglandin
- Answer
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B
Identify the complement activation pathway that is triggered by the binding of an acute-phase protein to a pathogen.
- classical
- alternate
- lectin
- cathelicidin
- Answer
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C
Histamine, leukotrienes, prostaglandins, and bradykinin are examples of which of the following?
- chemical mediators primarily found in the digestive system
- chemical mediators that promote inflammation
- antimicrobial peptides found on the skin
- complement proteins that form MACs
- Answer
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B
Fill in the Blank
________ are antimicrobial peptides produced by members of the normal microbiota.
- Answer
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bacteriocins
________ is the fluid portion of a blood sample that has been drawn in the presence of an anticoagulant compound.
- Answer
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plasma
The process by which cells are drawn or attracted to an area by a microbe invader is known as ________.
- Answer
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chemotaxis
Short Answer
Differentiate the main activation methods of the classic, alternative, and lectin complement cascades.
What are the four protective outcomes of complement activation?
17.3: Cellular Defenses
The formed elements of the blood include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Of these, leukocytes are primarily involved in the immune response. All formed elements originate in the bone marrow as stem cells (HSCs) that differentiate through hematopoiesis. Granulocytes are leukocytes characterized by a lobed nucleus and granules in the cytoplasm. These include neutrophils (PMNs), eosinophils, and basophils.
Multiple Choice
White blood cells are also referred to as which of the following?
- platelets
- erythrocytes
- leukocytes
- megakaryocytes
- Answer
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C
Hematopoiesis occurs inwhich of the following?
- liver
- bone marrow
- kidneys
- central nervous system
- Answer
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B
Granulocytes are which type of cell?
- lymphocyte
- erythrocyte
- megakaryocyte
- leukocyte
- Answer
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D
Matching
Match each cell type with its description.
| ___natural killer cell | A. stains with basic dye methylene blue, has large amounts of histamine in granules, and facilitates allergic responses and inflammation |
| ___basophil | B. stains with acidic dye eosin, has histamine and major basic protein in granules, and facilitates responses to protozoa and helminths |
| ___macrophage | C. recognizes abnormal cells, binds to them, and releases perforin and granzyme molecules, which induce apoptosis |
| ___eosinophil | D. large agranular phagocyte that resides in tissues such as the brain and lungs |
- Answer
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C, A, D, B
Match each cellular defense with the infection it would most likely target.
| ___natural killer cell | A. virus-infected cell |
| ___neutrophil | B. tapeworm in the intestines |
| ___eosinophil | C. bacteria in a skin lesion |
- Answer
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A, C, B
Fill in the Blank
Platelets are also called ________.
- Answer
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thrombocytes
The cell in the bone marrow that gives rise to all other blood cell types is the ________.
- Answer
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pluripotent hematopoietic stem cell (HSC)
PMNs are another name for ________.
- Answer
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neutrophils
Kupffer cells residing in the liver are a type of ________.
- Answer
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macrophage
_____________ are similar to basophils, but reside in tissues rather than circulating in the blood.
- Answer
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mast cells
Short Answer
Explain the difference between plasma and the formed elements of the blood.
List three ways that a neutrophil can destroy an infectious bacterium.
Critical Thinking
Neutrophils can sometimes kill human cells along with pathogens when they release the toxic contents of their granules into the surrounding tissue. Likewise, natural killer cells target human cells for destruction. Explain why it is advantageous for the immune system to have cells that can kill human cells as well as pathogens.
Refer to Figure 17.3.2 . In a blood smear taken from a healthy patient, which type of leukocyte would you expect to observe in the highest numbers?
17.4: Pathogen Recognition and Phagocytosis
Phagocytes are cells that recognize pathogens and destroy them through phagocytosis. Recognition often takes place by the use of phagocyte receptors that bind molecules commonly found on pathogens, known as pathogen-associated molecular patterns (PAMPs). The receptors that bind PAMPs are called pattern recognition receptors, or PRRs. Toll-like receptors (TLRs) are one type of PRR found on phagocytes.
Multiple Choice
PAMPs would be found on the surface of which of the following?
- pathogen
- phagocyte
- skin cell
- blood vessel wall
- Answer
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A
________ on phagocytes bind to PAMPs on bacteria, which triggers the uptake and destruction of the bacterial pathogens?
- PRRs
- AMPs
- PAMPs
- PMNs
- Answer
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A
Which of the following best characterizes the mode of pathogen recognition for opsonin-dependent phagocytosis?
- Opsonins produced by a pathogen attract phagocytes through chemotaxis.
- A PAMP on the pathogen’s surface is recognized by a phagocyte’s toll-like receptors.
- A pathogen is first coated with a molecule such as a complement protein, which allows it to be recognized by phagocytes.
- A pathogen is coated with a molecule such as a complement protein that immediately lyses the cell.
- Answer
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C
Fill in the Blank
________, also known as diapedesis, refers to the exit from the bloodstream of neutrophils and other circulating leukocytes.
- Answer
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extravasation
Toll-like receptors are examples of ________.
- Answer
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pattern-recognition receptors (PRRs)
Short Answer
Briefly summarize the events leading up to and including the process of transendothelial migration.
17.5: Inflammation and Fever
Inflammation results from the collective response of chemical mediators and cellular defenses to an injury or infection. Acute inflammation is short lived and localized to the site of injury or infection. Chronic inflammation occurs when the inflammatory response is unsuccessful, and may result in the formation of granulomas (e.g., with tuberculosis) and scarring (e.g., with hepatitis C viral infections and liver cirrhosis).
Multiple Choice
Which refers to swelling as a result of inflammation?
- erythema
- edema
- granuloma
- vasodilation
- Answer
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B
Which type of inflammation occurs at the site of an injury or infection?
- acute
- chronic
- endogenous
- exogenous
- Answer
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A
Fill in the Blank
A(n) ________ is a walled-off area of infected tissue that exhibits chronic inflammation.
- Answer
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granuloma
The ________ is the part of the body responsible for regulating body temperature.
- Answer
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hypothalamus
Heat and redness, or ________, occur when the small blood vessels in an inflamed area dilate (open up), bringing more blood much closer to the surface of the skin.
- Answer
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erythema
Short Answer
Differentiate exogenous and endogenous pyrogens, and provide an example of each.
Critical Thinking
If a gram-negative bacterial infection reaches the bloodstream, large quantities of LPS can be released into the blood, resulting in a syndrome called septic shock. Death due to septic shock is a real danger. The overwhelming immune and inflammatory responses that occur with septic shock can cause a perilous drop in blood pressure; intravascular blood clotting; development of thrombi and emboli that block blood vessels, leading to tissue death; failure of multiple organs; and death of the patient. Identify and characterize two to three therapies that might be useful in stopping the dangerous events and outcomes of septic shock once it has begun, given what you have learned about inflammation and innate immunity in this chapter.
In Lubeck, Germany, in 1930, a group of 251 infants was accidentally administered a tainted vaccine for tuberculosis that contained live Mycobacterium tuberculosis . This vaccine was administered orally, directly exposing the infants to the deadly bacterium. Many of these infants contracted tuberculosis, and some died. However, 44 of the infants never contracted tuberculosis. Based on your knowledge of the innate immune system, what innate defenses might have inhibited M. tuberculosis enough to prevent these infants from contracting the disease?