Unit III: Mechanisms of Self-Defense

Unit III: Mechanisms of Self-Defense

1.            Which of the following is an example of a physical barrier?

A.            Antibacterial fatty acids

B.            Lysozymes in tears

C.            Epithelial cells

D.            Earwax



Epithelial cells form tight junctions that are a physical barrier to entry for organisms.

2.            Which statement is true regarding the inflammatory response?

A.            Inflammatory response is the third line of defense.

B.            Inflammatory response relies on cellular components only.

C.            Inflammatory response generates a nonspecific response.

D.            Inflammatory response occurs at healthy tissue.



The inflammatory response is the second line of defense. It occurs at the site of tissue injury and generates a nonspecific response that involves cellular and chemical components.

3.            Which complement factor is considered an anaphylatoxin?

A.            C3a

B.            C1

C.            C7

D.            C9



C3a, C5a, and C4a are anaphylatoxins. They can induce the rapid degranulation of mast cells and the release of histamine.

4.            Which receptor is expressed on macrophages and facilitates recognition and phagocytosis of bacterial pathogens?

A.            Complement receptors

B.            Scavenger receptors

C.            Toll-like receptors

D.            Pattern recognition receptors



The scavenger receptors are primarily expressed on macrophages and facilitate recognition and phagocytosis of bacterial pathogens. Complement receptors recognize a variety of fragments produced through activation of the complement system. Toll-like receptors are expressed on the surface of cells, including epithelial, mast, neutrophils, macrophages, dendritic cells, and lymphocytes. They recognize pathogen-associated molecular patterns or stressed host cells. Pattern recognition receptors recognize patterns of infectious molecules. These receptors are found on cells involved in innate resistance.

5.            Which statement regarding mast cells is true?

A.            Histamine causes vasoconstriction.

B.            Mast cells are found only in blood vessels.

C.            Snake bites, bee venoms, and toxins may cause activation.

D.            Mast cells are not involved in allergic reactions.



A number of things cause the activation of mast cells, including physical injury, chemical agents (including toxins, bee venom, and snake bites), immunologic means, and activation of an inflammatory response. Histamine is released from mast cells and causes vasodilation. Mast cells are found in loose connective tissue close to blood vessels. Mast cells are involved in initiating many allergic reactions.

6.            Which term describes an acidic sulfur-containing lipid that produces effects similar to histamine?

A.            Leukotriene

B.            Prostaglandin

C.            Adhesion molecule

D.            Phagocyte



Leukotrienes act similar to histamine and cause smooth muscle contraction, increased vascular permeability, and chemotaxis. Prostaglandins cause increased vascular permeability, chemotaxis, and pain. Adhesion molecules increase the stickiness between cells. Phagocyte cells ingest and dispose of foreign material.

7.            Which statement is true regarding neutrophils?

A.            Neutrophils are agranular.

B.            Neutrophils are the predominant phagocytes of early inflammation.

C.            Neutrophils are the largest blood cells.

D.            Neutrophils enter the site of injury after lymphocytes and macrophages.



Neutrophils are the predominant phagocytes of early inflammation. They arrive before lymphocytes and macrophages. Monocytes are the largest blood cells and are granular.

8.            What biochemical messenger is produced by macrophages and lymphocytes in response to a bacterial pathogen?

A.            Interleukins

B.            Interferons

C.            Chemokines

D.            Tumor necrosis factor



Interleukins are biochemical messengers produced by macrophages and lymphocytes in response to a bacterial pathogen. Interferons primarily protect against viral infections. Chemokines induce leukocyte chemotaxis. Tumor necrosis factor, produced by macrophages and lymphocytes, induces a multitude of proinflammatory effects including the enhancement of endothelial cell adhesion.

9.            Chronic inflammation is characterized by a(an):

A.            Lack of giant cells

B.            Absence of exudate

C.            Dense infiltrate of lymphocytes and macrophages

D.            Inflammation that lasts less than 2 weeks



Chronic inflammation is characterized by a dense infiltrate of lymphocytes and macrophages. Giant cells are multinucleated cells that are formed by fused macrophages during granuloma formation. Chronic inflammation often results in pus formation, purulent discharge, and incomplete wound healing. Chronic inflammation of any cause lasts longer than 2 weeks.

10.          Which of the following are not natural barriers? (Select all that apply.)

A.            Physical

B.            Resistance

C.            Biochemical

D.            Mechanical

Answer: , C, and D


Resistance is a means by which the body may avoid being infected, but it is not a natural barrier. The natural barriers include physical, biochemical, and mechanical, as well as inflammation at the body’s surfaces.

11.          Which characteristics are observable of vascular injury and inflammation? (Select all that apply.)

A.            Redness

B.            Coolness to the touch

C.            Warmth to the touch

D.            Increased swellin


E.            Pain

Answer: , C, D, and E


The four characteristics that are observable for inflammation in vascular tissue are redness, heat, swelling, and pain.

12.          Which pathways activate the complement system? (Select all that apply.)

A.            Antigen-antibody

B.            Classical

C.            Lectin

D.            Alternative

Answer:B, C, and D


The complement system may be activated by the classical, lectin, and alternative pathways.

13.          Which functions of the clotting system are exhibited at the site of injury or inflammation? (Select all that apply.)

A.            Prevents the spread of infection to adjacent tissues.

B.            Traps microorganisms at the site of greatest inflammatory cell activity.

C.            Prevents clot formation at the site of injury.

D.            Provides a framework for future repair and healing.

Answer: , B, and D


The clotting system exhibits the following functions: (1) prevents the spread of infection to adjacent tissues; (2) traps microorganisms and foreign bodies at the site of inflammation for removal by infiltrating cells such as neutrophils and macrophages; (3) forms a clot that stops bleeding; and (4) provides a framework for future repair and healing.

14.          Which of the following are systemic effects of inflammation? (Select all that apply.)

A.            Abscess formation

B.            Fever

C.            Leukocytosis

D.            Increased levels of plasma proteins

E.            Decreased levels of plasma proteins

Answer: , C, and D


The three primary systemic changes associated with an acute inflammatory response are fever, leukocytosis, and increased levels in circulating plasma proteins. Abscesses are a local manifestation of inflammation and are walled-off lesions filled with purulent exudates.

15.          Which is a foreign or nonself substance?

A.            Immunoglobulins

B.            Lymphocytes

C.            Antibodies

D.            Antigens



Antigens are recognized as foreign and initiate the immune response. Immunoglobulins and antibodies are part of the adaptive immune response; they attack the antigen. Lymphocytes are a type of blood cell that is part of the adaptive response.

16.          Which statement is true regarding the immune response in humans?

A.            Before birth, lymphocytes are not produced.

B.            B lymphocytes come from the thymus.

C.            The thymus releases mature lymphocytes.

D.            Generation of clonal diversity occurs in primary lymphoid organs.



Generation of clonal diversity occurs in the primary lymphoid organs, which includes the thymus (T lymphocytes) and bone marrow (B lymphocytes). Before birth, T and B lymphocytes that recognize almost any foreign antigen predominate. The thymus releases immature T cells that have the ability to recognize foreign antigens.

17.          Which statement best describes the cells and their functions in the humoral arm of the immune system?

A.            Cells undergo differentiation and develop into subpopulations.

B.            Cells attack cancerous cells.

C.            Antibodies are primarily responsible for protection.

D.            Cells in the humoral arm are also called cellular immunity.



Antibodies are primarily responsible for protection against viruses and bacteria and are part of the humoral arm of the immune system. The antibody can directly invade a microorganism or activate the immune response. T cells undergo differentiation, attack cancerous cells, and are part of cellular immunity.

18.          Which term describes the type of immunity that occurs when preformed antibodies are transferred from a donor to a recipient?

A.            Passive

B.            Active

C.            Memory

D.            Cellular



The two types of adaptive immunity are active and passive. Passive immunity occurs when preformed antibodies are transferred from a donor to a recipient. An example of passive immunity is the passage of maternal antibodies across the placenta to the fetus. Active immunity is produced by an individual after either a natural exposure or an immunization. Memory cells are formed through cellular and humoral immunity; they remember the antigen.

19.          What is the precise portion of the antigen that is configured for recognition and binding of an antibody?

A.            Paratope

B.            Epitope

C.            Self-antigen

D.            Immunogen



The antigenic determinant or epitope is the precise portion of the antigen that is configured for recognition and binding of an antibody. A paratope is the matching portion on the antibody or lymphocyte receptor. A self-antigen is one that is not foreign to the host. An immunogen is an antigen that induces an immune response.

20.          Which antigen is too small to initiate an immune response?

A.            Carrier

B.            Allergen

C.            Hapten

D.            Self-antigen



A hapten is a molecule that is foreign but too small to induce an immune response alone. However, when it binds to a larger carrier molecule, it is able to induce an immune response. An allergen is an antigen that can induce an allergic response. A self-antigen is not foreign but has the three other criteria to be an immunogen.

21.          Which statement is true regarding immunoglobulin A (IgA) antibodies?

A.            IgA-2 is predominantly found in blood.

B.            IgA-1 is predominantly found in the body’s secretions.

C.            The J chain anchors together the IgA molecules.

D.            The gamma heavy chain is predominant.



The J chain anchors together the IgA molecules to form dimers and helps them resist degradation from enzymes. IgA-1 is found in the blood, and IgA-2 is found in the secretions of the body.

22.          It is true that immunoglobulin E (IgE) is:

A.            Designed to protect the host from large viruses.

B.            The primary cause of common allergies.

C.            The only inflammatory cell that can damage a virus.

D.            Specifically designed to prevent the invasion and attachment of pathogens through mucous membranes.



IgE is an antibody that is designed to protect the host from parasites and is the only inflammatory cell that can damage a parasite.

23.          Which statement is true regarding aging and the immune system function?

A.            Older adults have decreased circulating antibodies.

B.            T-cell function is increased.

C.            Antibody production to specific antigens is inferior.

D.            Response to infection is rapid.



T-cell function is decreased, and immune responses are delayed. B-cell production is inferior; however, the cells have increased circulating antibody levels.

24.          Which criteria influence the degree of immunogenicity? (Select all that apply.)

A.            Foreignness to the host

B.            Appropriate size

C.            Appropriate quantity

D.            Chemical simplicity

E.            Chemical complexity

Answer:A, B, C, and E


The four criteria that influence the degree of immunogenicity are foreignness to the host, appropriate size, appropriate quantity, and adequate complexity.

25.          Which of the following are molecular classes of immunoglobulins? (Select all that apply.)

A.            IgC

B.            IgD

C.            IgE

D.            IgM

E.            IgN

Answer: , C, and D


The five classes of immunoglobulin are IgG, IgA, IgM, IgD, and IgE.

26.          Which definition is true?

A.            Allergy means the deleterious effects of hypersensitivity.

B.            Immunity means an altered immunologic response.

C.            Hypersensitivity means the protective response to an antigen.

D.            Autoimmunity means the normal response to foreign antigens.



Allergy means the deleterious effects of a hypersensitivity reaction.

27.          Which statement is true regarding hypersensitivity reactions?

A.            They require sensitization against a particular antigen.

B.            They occur after the primary immune response.

C.            Reactions are always delayed.

D.            The most delayed reaction is anaphylaxis.



A hypersensitivity reaction requires sensitivity to an antigen and occurs after an adequate secondary immune response. These reactions may then be immediate or delayed. The most immediate reaction is anaphylaxis.

28.          Which statement best describes a type I reaction?

A.            Most type I reactions are mediated by IgA.

B.            Most type I reactions are allergic.

C.            Most occur against medications.

D.            Seldom does this type contribute to autoimmune diseases.



Most type I reactions are allergic. They are mediated by IgE. Most occur against environmental antigens and can contribute to some autoimmune diseases.

29.          What antibody binds to a mast cell?

A.            Cytotropic

B.            Allergen

C.            Antigen

D.            Fc



A cytotropic antibody (also called a skin-sensitizing antibody or reagin) is the antibody that binds to the mast cell. An allergen is an environmental antigen that induces an allergic response. An antigen stimulates the immune response and antibody to bind to the mast cell. The Fc is the portion of the mast cell where IgE binds.

30.          Which statement is true regarding atopic individuals?

A.            If one parent has allergies, then a 4% chance exists that the offspring will have similar allergies.

B.            If two parents have allergies, then a 50% chance exists that their offspring will have similar allergies.

C.            Atopic individuals tend to produce higher quantities of IgE.

D.            No genes are associated with an atopic state.



Higher quantities of IgE are present in atopic individuals. If one parent has an allergy, then the individual has a 40% of having allergies; with two parents, the individual has an 80% of having allergies. Multiple genes have been associated with the atopic state.

31.          Which statement is true of serum sickness?

A.            The formation of immune complexes in the blood cause serum sickness.

B.            It is the deposition of complexes in the blood vessels.

C.            It occurs through cytotoxic T cells.

D.            It binds antigen to the cell surface.



Serum sickness reactions are caused by the formation of immune complexes in the blood and their deposition in target tissues. An Arthus reaction deposits complexes into the walls of blood vessels. Type IV mechanisms occur through either cytotoxic T lymphocytes or lymphokine-producing T-helper (Th) 1 cells. Antigen is bound to the cell surface in type II reactions.

32.          The Arthus reaction is an example of which type of sensitivity reaction?

A.            I

B.            II

C.            III

D.            IV



The Arthus reaction is a type III hypersensitivity reaction.

33.          Which statement is true regarding a type IV allergic reaction?

A.            Is immediate in its action.

B.            Is infiltrated with B cells.

C.            Has a red, soft center.

D.            Can be transferred by cells.



Type IV hypersensitivity reactions can be transferred by cells but not by serum. Their actions are delayed because their onset takes from 24 to 72 hours. The site is infiltrated with T lymphocytes and macrophages. A clear hard center surrounds the erythema (redness).

34.          Which is an example of an alloimmune disease?

A.            Tuberculin reaction

B.            Graves disease

C.            Contact dermatitis

D.            Penicillin allergy



Graves disease, myasthenia gravis, immune thrombocytopenic purpura, alloimmune neutropenia, and systemic lupus erythematosus are all examples of alloimmune diseases during which the child can be affected because the mother has the disease. Tuberculin reaction is a type IV reaction. Contact dermatitis is a type I reaction. Penicillin is an allergen that induces type I hypersensitivity.

35.          Which statement is true regarding unmatched packed red blood cell (RBC) transfusions?

A.            Only three different RBC antigens have been identified.

B.            Approximately 80 major carbohydrate antigens exist.

C.            People with O type blood have neither A or B antigens.

D.            A person with type A blood contains anti-O antibodies.



Type O blood does not contain type A or B antigens. However, 80 major different RBC antigens are present. A person with type A blood carries anti-B antibodies and a person with type B blood carries anti-A antibodies. Those with type O blood have anti-A and anti-B antibodies.

36.          Histamine release leads to which of the following? (Select all that apply.)

A.            Bronchial smooth muscle contraction

B.            Bronchoconstriction

C.            Decreased vascular permeability

D.            Vasoconstriction

E.            Edema

Answer: , B, and E


Histamine contracts bronchial smooth muscle, which causes bronchoconstriction. Vascular permeability, edema, and vasodilation also increase.

37.          Which term describes an agent’s ability to produce disease?

A.            Virulence

B.            Pathogenicity

C.            Infectivity

D.            Immunogenicity



Pathogenicity is the ability of an agent to produce disease and depends on the speed of reproduction, the extent of tissue damage, and the production of toxins. Virulence is the capacity of a pathogen to cause severe disease. Infectivity is the ability of the pathogen to invade and multiply in the host. Immunogenicity is the ability of pathogens to induce an immune response.

38.          Which statement is true regarding bacteremia?

A.            It occurs with a normal defense system of the body.

B.            Gram-positive bacteria typically cause bacteremia.

C.            Endotoxins often cause symptoms such as vasodilation.

D.            Symptoms include increased blood pressure.



Endotoxins are often produced by bacteria that grow in the blood. Common symptoms include vasodilation, hypotension (reduced blood pressure), and decreased oxygen delivery and can produce cardiovascular shock. Bacteremia is often caused by gram-negative bacteria and usually occurs with a failure of the body’s defense mechanisms.

39.          Which statement regarding viruses is true?

A.            Viruses are less common than bacterial infections.

B.            Viruses actively produce exotoxins.

C.            Viruses bypass many defense mechanisms by developing intracellularly.

D.            Viruses contain all their genetic information in ribonucleic acid (RNA).



Viruses enter the cell and may bypass many defense mechanisms. Viruses are the most common form of infection. They contain deoxyribonucleic acid (DNA) and RNA for their genetic information. They do not produce exotoxins or endotoxins.

40.          Which statement regarding fever is true?

A.            Fever is a failure of the body to regulate temperature.

B.            An endogenous pyrogen may produce fever.

C.            The body’s central thermostat is the pituitary gland.

D.            Fever is a failure of the body’s defense system.



A pyrogen is a substance that causes fever. Exogenous and endogenous pyrogens exist and affect the regulatory set point in the hypothalamus, which is the body’s thermostat. Fever is not a failure of the body’s defense system but may actually be beneficial. The body does not fail to regulate temperature; rather, the temperature is regulated at a higher level than normal with a fever.

41.          What contributes to antibiotic-resistant pathogens?

A.            Inadequate sanitation

B.            Genetic mutation

C.            Loss of multidrug transporters

D.            Limited use of antibiotics



Antibiotic resistance usually results from genetic mutations in the microorganism that can be directly transmitted to neighboring microorganisms. Sanitation and clean drinking water can help control infection. Multidrug transporters on the microorganism’s membrane affect the rate of intracellular accumulation of antibiotics by preventing entrance or increasing the efflux of the antibiotic into the cell. Overuse of antibiotics can lead to the destruction of the normal flora and selective overgrowth of antibiotic-resistant strains.

42.          The stages of pathologic infection include which of the following? (Select all that apply.)

A.            Invasion

B.            Death

C.            Colonization

D.            Metastasis

E.            Multiplication

Answer: , C, and E


The stages of pathologic infection include colonization, invasion, spread, and multiplication. Death and metastasis are not stages of pathologic infection.

43.          Which of the following are mechanisms of antigenic variation? (Select all that apply.)

A.            Siderophoric switching

B.            Mutation

C.            Recombination

D.            Gene switching

Answer: , C, and D


Mutation, recombination, and gene switching all are forms of antigenic variation. Siderophores are iron receptors on bacteria that assist in replication, and they have nothing to do with antigenic variation.

44.          Which mechanisms are used by viruses to evade the immune response? (Select all that apply.)

A.            Rapid division

B.            Antigenic specificity

C.            Self-protein coat

D.            Immune suppression

E.            Lipopolysaccharide

Answer: , C, and D


Viruses have developed a number of ways to evade the immune system, including rapid division, the ability to survive inside a host cell, coating the viral capsid with self-antigens from the host cell, antigenic variation, neutralization of immune complexes, complement evasion, immune suppression, and tissue damage.

45.          What is the definition of the reactive response?

A.            Mounting a response in anticipation of a stressor

B.            Mounting a response in reaction to a stressor

C.            Mounting a response to a learned stressor

D.            Mounting a response to a physical stressor



A reactive response is a psychologic response to a stressor. An anticipatory response is a psychologic response to an anticipated response. A conditioned response is an anticipated psychologic (learned) response to stimuli that have been associated with danger.

46.          A stress response is initiated in what part of the nervous system?

A.            Peripheral nervous system

B.            Exocrine system

C.            Parasympathetic nervous system

D.            Central nervous system



The stress response is initiated in the central nervous and endocrine systems.

47.          A stress response results in the stimulation of which sympathetic nervous system receptors?

A.            α-Adrenergic receptors

B.            β-Receptors

C.            Adrenocorticotropic hormone (ACTH)

D.            Growth hormone (GH)



The alpha receptors of the sympathetic nervous system are stimulated during the stress response.

48.          Which statement is true regarding the effects of circulating epinephrine in the body?

A.            The heart rate will slow down.

B.            The heart’s contractility will decrease.

C.            Blood vessels to skeletal muscle will constrict.

D.            Transient hyperglycemia will result.



Epinephrine dilates blood vessels of the muscles and causes transient hyperglycemia. The epinephrine will increase heart rate and contractility. The venous return to the heart will increase, thus increasing cardiac output and blood pressure.

49.          Which statement is true regarding how cortisol reacts when activated by ACTH?

A.            Cortisol is plasma bound to corticotropin.

B.            Gluconeogenesis is halted.

C.            Cortisol increases blood glucose.

D.            Cortisol decreases protein synthesis.



Cortisol has many actions. It is bound to a protein called transcortin. It stimulates gluconeogenesis, increases glucose production, and increases protein synthesis.

50.          Which statement is true regarding the immune system in response to stress?

A.            T-helper 1 (Th1) cells increase.

B.            A shift in Th1 cells occurs.

C.            The immune system is not affected.

D.            Cortisol is released.



Stress can activate an excessive immune response through cortisol. It can cause the suppression of Th1 cells and a shift in Th2 cells.

51.          Which of the following is a function of norepinephrine?

A.            Increases contraction of the heart

B.            Constricts smooth muscle in all blood vessels

C.            Secretes steroid hormones

D.            Stimulates adrenal medulla



Norepinephrine is released from the adrenal medulla and regulates blood pressure by constricting smooth muscle in all blood vessels. Epinephrine increases myocardial contractility and heart rate. The steroid hormones are stimulated by the hypothalamus, which sets off a chain of events during which steroid hormones are secreted from the adrenal cortex. Cortisol is one of the primary steroid hormones.

52.          Which statement regarding corticotropin-releasing hormone (CRH) and its influence on the immune system is true?

A.            CRH is also released from peripheral inflammatory sites.

B.            CRH causes vasoconstriction.

C.            CRH causes decreased vascular permeability.

D.            Red blood cells are the peripheral targets.



CRH is released from the hypothalamus and from peripheral inflammatory sites. Because this hormone is proinflammatory, it causes vasodilation and increased vascular permeability. The primary target of peripheral CRH is the mast cell.

53.          Which statement is true regarding stress and the immune system?

A.            Seasonal allergies are related to stress.

B.            Cardiovascular disease is one condition that is related to stress.

C.            The level of proinflammatory cytokines is decreased.

D.            Negative emotions cause few alterations in cytokine production.



Cardiovascular disease, aging, cancer, osteoporosis, arthritis, type II diabetes mellitus, and chronic obstructive pulmonary disease (COPD) are associated with the prolonged presence of proinflammatory cytokines. These proinflammatory cytokines increase during stress. Negative emotions are directly associated with the increased level of these proinflammatory cytokines.

54.          Which of the following are stages in the development of the general adaptation syndrome? (Select all that apply.)

A.            Alarm

B.            Exposure

C.            Resistance

D.            Exhaustion

Answer: , C, and D


The three successive stages in the development of the general adaptation syndrome are alarm, resistance, and exhaustion.