Question 1

Viruses, like many good pathogens, have adapted to survive in their hosts.Which of the following scenarios would be MOST favorable to viral transmission and long-term survival of the viral species?

Accepted Answer

This scenario allows the virus to persist in the host without killing the host cells immediately, enabling continuous low-level production of virions and reducing the likelihood of triggering a strong immune response, thus favoring long-term survival and transmission.

Question 2

Which of the following is NOT important for controlling infections at either barrier or mucosal sites?

Accepted Answer

IgG is not important for controlling infections at either barrier or mucosal sites.

Question 3

Which of the following is recognized by the innate immune system and triggers an immune response that will produce antiviral cytokines and trigger effector molecules?

Accepted Answer

PAMPs (Pathogen-Associated Molecular Patterns) are recognized by the innate immune system's pattern recognition receptors (PRRs), triggering an immune response that includes the production of antiviral cytokines and the activation of effector molecules. This is a fundamental mechanism for the early defense against pathogens.

Question 4

One mechanism that viruses use to avoid the immune response is to bind up immune effector molecules.All of the following methods are used by antibodies to block viral infection EXCEPT

Accepted Answer

Antibodies primarily function by directly neutralizing pathogens, activating the complement system, and facilitating phagocytosis. They do not directly stimulate the activation of cytotoxic T cells; this is a function of antigen-presenting cells and helper T cells.

Question 5

Viruses such as Epstein-Barr virus, cytomegalovirus, and HIV are capable of suppressing the immune system by

Accepted Answer

Viruses like Epstein-Barr virus, cytomegalovirus, and HIV can suppress the immune system by infecting lymphocytes or phagocytic cells, which are crucial components of the immune response, and by producing cytokine antagonists, which interfere with the signaling pathways that activate the immune response.

Question 6

By which mechanisms can bacterial pathogens evade a host immune response?

Accepted Answer

All of the options listed are mechanisms by which bacterial pathogens can evade the host immune response. A) Bacteria can avoid phagocytosis by producing a capsule that makes it difficult for immune cells to recognize and engulf them. B) Some bacteria can escape from the phagolysosome after being engulfed by phagocytic cells, allowing them to survive and replicate within the host. C) Others can neutralize the digestive enzymes within phagocytic cells, preventing their destruction.

Question 7

Which pathogen would be LEAST affected by a host complement attack?

Accepted Answer

Rotavirus, being a nonenveloped virus, lacks a lipid membrane, making it inherently more resistant to the complement system, which primarily targets cellular membranes.

Question 8

Each of the following is a step in bacterial infection EXCEPT

Accepted Answer

Feeling tired or uncomfortable is a symptom of infection rather than a step in the bacterial infection process. Steps in bacterial infection include attachment to host cells, invasion of host tissue, proliferation of bacterial cells, and toxin-induced damage to host cells.

Question 9

_____ is/are known as an endotoxin.

Accepted Answer

Lipid A, a component of the lipopolysaccharides (LPS) in the outer membrane of Gram-negative bacteria, is recognized as an endotoxin. It can trigger strong immune responses in the host.

Question 10

Anaphylatoxins stimulate a localized inflammatory response, which includes mast-cell degranulation, vasodilation, and recruitment of lymphocytes and phagocytic cells.What is the purpose of this localized immune response?

Accepted Answer

The localized immune response, including mast-cell degranulation, vasodilation, and recruitment of lymphocytes and phagocytic cells, serves multiple purposes: increasing blood flow to bring more white blood cells to the area, neutralizing pathogens and toxins, potentially affecting the temperature to denature bacterial proteins, and causing symptoms like tenderness and swelling to protect the area.

Question 11

Which of the following are anaphylatoxins?

Accepted Answer

Anaphylatoxins are small peptides that are produced as part of the complement system's activation, which plays a role in the body's immune response. C3a and C5a are well-known anaphylatoxins that have the ability to trigger degranulation of mast cells and basophils, leading to an inflammatory response.

Question 12

Parasitic infections include

Accepted Answer

Parasitic infections can be caused by protozoans (single-celled organisms) and helminths (worm-like parasites), but not by prions, viruses, or bacteria, which are agents of different types of infections.

Question 13

Sleeping sickness and Chagas's disease are caused by members of the genus Trypanosoma, protozoans that reside in the bloodstream.What is the principle way trypanosomes evade the immune response?

Accepted Answer

Trypanosomes evade the immune response primarily through periodic changes in their surface antigen (VSG), which allows them to stay ahead of the host's antibody-mediated immune response. This antigenic variation ensures that some of the trypanosomes can always evade detection and destruction by the host's immune system.

Question 14

How do Plasmodium cells avoid immune clearance?

Accepted Answer

The answer of How do Plasmodium cells avoid immune clearance?
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Question 15

Schistosomiasis is a debilitating and potentially fatal disease caused by the helminthic parasite Schistosoma.Which antibody is specific for helminth response?

Accepted Answer

IgE is specifically involved in the immune response against helminths, including Schistosoma, by promoting inflammation and activating eosinophils to attack the parasites.

Question 16

Leishmaniosis is a disease that can either be fatal to its host or will be cleared by the immune response of the host.Which pathway is responsible for clearing leishmaniosis?

Accepted Answer

T_H cells, specifically T_H1 cells, are responsible for activating macrophages to kill the intracellular Leishmania parasites, thus playing a crucial role in clearing the infection.

Question 17

Some species of fungi are part of the normal microbiota or normal microbial flora of a host organism.How does the immune system differentiate between "good" fungi and "bad" fungi?

Accepted Answer

The answer of Some species of fungi are part of...

Question 18

Cryptococcus may spread throughout an infected host.By what mechanism is Cryptococcus controlled by the acquired immune system?

Accepted Answer

Granuloma formation is a key mechanism by which the acquired immune system controls Cryptococcus infection. This involves the aggregation of immune cells to isolate and contain the infection, preventing its spread.

Question 19

Primary virulence in fungi indicates

Accepted Answer

Primary virulence in fungi refers to the ability of a fungal species to cause disease in a healthy individual due to its inherent pathogenic characteristics, rather than due to an opportunistic infection or the compromised state of the host's immune system.

Question 20

People encounter fungi on a daily basis, yet few healthy individuals develop fungal infections.Each of the following are mechanisms of the innate immune system that help prevent or limit fungal infections in healthy individuals EXCEPT

Accepted Answer

E is the correct choice because it describes a mechanism by which fungi evade the immune system, rather than a mechanism of the innate immune system that helps prevent or limit fungal infections.

Quiz 17: Infectious Diseases and Vaccines