Question 1

The effects of endotoxins consist of dramatic changes in all the following except:
A)blood pressure.
B)fluid imbalance.
C)clotting.
D)body temperature.

Accepted Answer

Unlike shock caused by fluid loss, such as that seen in severe bleeding, septic shock is unaffected by fluid administration.An increase in body temperature occurs within an hour after exposure.Severe hypotension occurs within 30 minutes after exposure.The endotoxin also initiates coagulation, which can result in intravascular coagulation.

Question 2

A patient is brought to the emergency room with the following symptoms: body temperature of 102° F, low blood pressure, elevated WBC, and disseminated intravascular coagulation.This person has gram-negative rods growing in the blood.What is responsible for these symptoms?
A)Exotoxin
B)Extracellular enzymes
C)Endotoxin
D)Exfoliating toxin

Accepted Answer

Effects of the lipid A portion of the lipopolysaccharide present in the cell walls of gram-negative bacteria include increased body temperature, hypotension, intravascular clotting, neutropenia, metabolic changes, changes in humoral and cellular immunity, and changes resistance to infection.

Question 3

The process that results in enhanced phagocytosis by neutrophils is:
A)opsonization.
B)chemotaxis.
C)digestion.
D)glycolysis.

Accepted Answer

Chemotaxis is the process of phagocytes migrating toward the site of the infection.Digestion is when the contents of the lysozyme is mixed with the phagocytized bacteria.Glycolysis is a metabolic process where glucose is broken down and energy is generated.

Question 4

What virus causes immune suppression in the host by targeting and destroying the host's CD4+ T cells?
A)HIV
B)Hepatitis B
C)Epstein-Barr
D)Cytomegalovirus

Accepted Answer

HIV is known to destroy CD4+ T cells.Hepatitis B causes disease in liver cells, not white blood cells.The Epstein-Barr virus and cytomegalovirus show depressed T-cell or antibody responses to other unassociated antigens.

Question 5

After attachment to host cells, a pathogen may use the following mechanisms to establish itself and cause disease except:
A)uses lactoferrin for iron.
B)produces an IgA protease that degrades the IgA at mucosal surfaces.
C)produces lysozyme to kill the host cell.
D)circumvents host antibodies by shifting key cell-surface antigens.

Accepted Answer

After engulfing bacteria, the host cell releases lysosomal contents that kill the organism.The bacteria do not produce lysozyme.

Question 6

The major constituents of the adaptive or specific immune response are:
A)neutrophils.
B)macrophages.
C)monocytes.
D)lymphocytes.

Accepted Answer

Lymphocytes produce antibodies in response to specific antigens present in the blood.Neutrophils, macrophages, and monocytes are all phagocytic cells that function in innate immunity, not the specific immune response.

Question 7

What are low-molecular-weight proteins secreted by T cells called?
A)Antibodies
B)Opsonins
C)Lymphokines
D)Lysozyme

Accepted Answer

Antibodies are produced by B cells.Opsonins are antibodies or pieces of complement that help make a pathogen ready to be phagocytized.Lysozyme is the enzyme present in host cell vacuoles that assist in killing a phagocytized microorganism.Lymphokines are produced by T cells as a result of antigen binding, activation, cell division, and differentiation.

Question 8

Innate immunity consists of which of the following components?
A)Physical and chemical barriers, such as the skin and mucous membranes
B)Blood proteins that act as mediators of infection
C)Cells capable of phagocytosis
D)All of the above are part of the innate immune system.

Accepted Answer

Innate immunity includes (1) physical and chemical barriers, such as the skin and mucous membranes; (2) blood proteins that act as mediators of infection; and (3) a cellular mechanism capable of phagocytosis, such as neutrophils and macrophages, and other leukocytes such as natural killer cells.

Question 9

Healthy skin secretes what substances to help prevent colonization by transient and possibly pathogenic organisms?
A)Long-chain fatty acids
B)Sebaceous glands
C)Carbohydrates
D)Antibodies

Accepted Answer

Long-chain fatty acids produced by the sebaceous glands allow the skin environment to be acidic, leading to a low pH environment.Many pathogens prefer the near-neutral environment in the body to produce disease.Bacteriocidal substances are produced by the microbial flora that colonize the skin, and antibodies are produced by lymphocytes.

Question 10

Interferon is a substance produced by the body that inhibits viral replication.Interferon accomplishes this task by:
A)digesting the virus that is attempting to attach to the host cell.
B)destroying the host cell before the virus can attach and replicate.
C)binding to surface receptors that stimulate the cell to synthesize enzymes that inhibit viral replication over several days.
D)stimulating platelets to produce b-lysins.

Accepted Answer

Interferon is produced by eukaryotic cells in response to a viral infection, and it stimulates the cell to synthesize enzymes that inhibit viral replication over several days.Interferons are not enzymes and cannot digest viruses.Destroying the host cell before the virus can attach would be counterproductive, because the purpose is to keep the host cells viable and free of infection.The b-lysin's cationic proteins are produced by platelets during coagulation and are active against gram-positive bacteria, not viruses.

Question 11

All the following activities must occur for phagocytosis to take place and be effective in host defense except:
A)attachment of the particle to the phagocyte.
B)ingestion.
C)killing.
D)migration of lymphocytes to the area of infection (chemotaxis).

Accepted Answer

Phagocytes are neutrophils or macrophages.Lymphocytes are not phagocytic and cannot engulf bacteria.

Question 12

A physician notices that several patients are infected with Clostridium difficile, but only a few of the patients are symptomatic for disease.The reason for this discrepancy is:
A)only those strains of the organism carrying the extrachromosomal DNA coding for the toxin gene will produce toxin and cause the individuals to be symptomatic.
B)only those strains of the organism carrying DNA coding for the toxin within its main DNA molecule will produce toxin and cause the individuals to be symptomatic.
C)the exotoxin produced contains only the nontoxic portion.
D)the exotoxin must be produced in conjunction with extracellular enzymes to cause problems.

Accepted Answer

The exotoxin gene is commonly encoded for by phages, plasmids, or transposons and does not normally reside within an organism's main DNA molecule.Exotoxins are highly characterized molecules that are composed of a nontoxic subunit that binds the toxin to the host cells, allowing attachment of the toxin.Exotoxins exhibit their effects without the aid of extracellular enzymes.Extracellular enzymes are another factor that contributes to the virulence and invasiveness of organisms.

Question 13

Pathogens can be transmitted through all the following routes except:
A)ingestion.
B)handwashing.
C)sexual contact.
D)air.

Accepted Answer

Handwashing is a major method to prevent spread of infections.Pathogens can be transmitted by ingestion, sexual contact, and air.

Question 14

Immunity to intracellular bacterial pathogens, such as Mycobacterium tuberculosis, is primarily cell mediated, through the activities of:
A)interferons and macrophages.
B)antibodies and lymphokines.
C)lysozyme, T lymphocytes, and antibodies.
D)T lymphocytes, lymphokines, and macrophages.

Accepted Answer

T lymphocytes, lymphokines, and macrophages are used by the immune system to battle intracellular pathogens most effectively.Interferons are useful against viruses, not bacteria.Macrophages are effective against intracellular pathogens because they are phagocytes.Antibodies are not useful against intracellular pathogens because they cannot reach the pathogen that lives inside the cell.Lysozyme is an enzyme that is used to kill bacteria once they are phagocytized.

Question 15

Lysozyme is a(n):
A)antibody produced by the skin.
B)low-molecular-weight enzyme that hydrolyzes the peptidoglycan layer of bacterial cell walls.
C)exotoxin that digests the lipopolysaccharide layer of the bacterial cell wall.
D)radical similar to hydrogen peroxide.

Accepted Answer

Antibodies are produced only by the lymphocytes.Exotoxins are produced by bacteria and are toxic to the host.Lysozyme is a low-molecular-weight enzyme that hydrolyzes the peptidoglycan layer of bacterial cell walls.

Question 16

Changes in what host structures can result in lower virulence of a microorganism?
A)Pili
B)Adhesin receptors
C)Surface polysaccharides
D)Phagocytes

Accepted Answer

Adhesin receptors are structures found on the host cell that are necessary for attachment of bacterial adhesins and the beginnings of an infection.Pili and surface polysaccharides are the main bacterial structures of attachments called adhesins.Phagocytes are white blood cells that engulf invading microorganisms.

Question 17

A subsequent exposure to the same antigen elicits a(n) _____ immune response characterized by a rapid increase in IgG antibody associated with higher levels, a prolonged elevation, and a more gradual decline in antibody levels.
A)primary
B)anamnestic
C)opsonin
D)innate

Accepted Answer

The primary immune response consists of production of IgM antibodies.The innate immune response does not consist of antibody production but rather physical and chemical barriers to infection and phagocytosis.

Question 18

Dissemination of a pathogen is when:
A)a pathogen penetrates and grows in tissues.
B)a pathogen multiplies intracellularly.
C)a pathogen circumvents host antibodies by shifting key cell-surface antigens.
D)infection with a pathogen spreads from the initial infection site to distant sites such as organs and tissues.

Accepted Answer

Invasion of a pathogen allows the microbe to take advantage of the host's transport system (the blood) and seek out other areas that can be infected.This occurs only if the pathogen can elude the host's immune system during this journey.Invasion is when a pathogen penetrates and grows in tissues.Intracellular multiplication of a pathogen occurs when an organism can survive phagocytosis.When a pathogen shifts key cell-surface antigens, it is evading a host's immune system.

Question 19

Which class of antibodies is usually found as a pentamer?
A)IgM
B)IgG
C)IgA
D)IgE

Accepted Answer

IgM is made up of five basic immunoglobulin subunits and is considered a pentamer.IgG is a monomer, IgA is a dimer, and IgE is a monomer.

Question 20

One of the most effective defenses bacteria have against phagocytosis is:
A)enzymes.
B)the capsule.
C)plasmids.
D)lipopolysaccharide layer.

Accepted Answer

Enzymes facilitate host cell destruction but do not have any effect on phagocytosis.Plasmids carry small pieces of DNA that can code for toxins, enzymes, and antibiotic resistance.The lipopolysaccharide layer acts as an endotoxin that causes septic shock.

Quiz 2: Host-Parasite Interaction

The effects of endotoxins consist of dramatic changes in all the following except:

A patient is brought to the emergency room with the following symptoms: body temperature of 102° F, low blood pressure, elevated WBC, and disseminated intravascular coagulation.This person has gram-negative rods growing in the blood.What is responsible for these symptoms?

The process that results in enhanced phagocytosis by neutrophils is:

What virus causes immune suppression in the host by targeting and destroying the host's CD4+ T cells?

After attachment to host cells, a pathogen may use the following mechanisms to establish itself and cause disease except:

The major constituents of the adaptive or specific immune response are:

What are low-molecular-weight proteins secreted by T cells called?

Innate immunity consists of which of the following components?

Healthy skin secretes what substances to help prevent colonization by transient and possibly pathogenic organisms?

Interferon is a substance produced by the body that inhibits viral replication.Interferon accomplishes this task by:

All the following activities must occur for phagocytosis to take place and be effective in host defense except:

A physician notices that several patients are infected with Clostridium difficile, but only a few of the patients are symptomatic for disease.The reason for this discrepancy is:

Pathogens can be transmitted through all the following routes except:

Immunity to intracellular bacterial pathogens, such as Mycobacterium tuberculosis, is primarily cell mediated, through the activities of:

Lysozyme is a(n) :

Changes in what host structures can result in lower virulence of a microorganism?

A subsequent exposure to the same antigen elicits a(n) _____ immune response characterized by a rapid increase in IgG antibody associated with higher levels, a prolonged elevation, and a more gradual decline in antibody levels.

Dissemination of a pathogen is when:

Which class of antibodies is usually found as a pentamer?

One of the most effective defenses bacteria have against phagocytosis is: