Immunology Mechanisms and Responses

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Which of the following mechanisms primarily contributes to tissue injury during a bacterial infection?

Inhibition of complement pathway activation by bacterial surface proteins.
Direct cytopathic effects caused by viral replication within host cells.
Secretion of exotoxins by bacteria and the effects of endotoxins released upon bacterial death. (correct)
Release of endotoxins from gram-positive bacteria during active growth.

Leprosy outcomes are influenced by the balance between Th1 and Th2 responses. What is the primary role of Th1 responses in controlling leprosy infection?

Inducing immune tolerance to prevent autoimmune reactions against nerve tissues.
Enhancing intracellular killing of mycobacteria by macrophages and cell-mediated immunity. (correct)
Suppressing inflammation to minimize tissue damage at the site of infection.
Promoting humoral immunity through B cell activation and antibody production.

How do mucosal secretory IgA antibodies protect against pathogens at mucosal surfaces?

By activating NK cells to kill infected cells expressing microbial antigens.
By neutralizing pathogens and preventing their adherence to epithelial cells. (correct)
By opsonizing pathogens for enhanced phagocytosis by dendritic cells.
By directly lysing infected host cells via complement activation.

NOD1 recognizes intracellular infections, playing a role in innate immunity. What type of microbial molecule does NOD1 typically detect?

Peptidoglycan fragments from bacterial cell walls. (C) Signup and view all the answers

Activation of the complement pathway can lead to inflammation. Which of the following complement pathway outcomes directly contributes to the inflammatory response?

Release of anaphylatoxins that recruit and activate immune cells. (C) Signup and view all the answers

Which mechanism does not describe how microbes evade immune responses?

Increasing the immunogenicity of their surface antigens to enhance antibody recognition. (C) Signup and view all the answers

A researcher is studying a new bacterial pathogen that infects epithelial cells lining the respiratory tract. Which of the following would be the MOST effective strategy for the pathogen to establish a chronic infection?

Modulating its surface antigens to evade antibody recognition and altering host cell signaling to inhibit apoptosis. (A) Signup and view all the answers

A patient is infected with a virus that undergoes frequent antigenic drift. What is the MOST likely consequence of this viral characteristic on the patient's long-term immunity?

The patient will be susceptible to reinfection with slightly different viral strains, requiring annual vaccination updates. (C) Signup and view all the answers

What is the primary difference between exotoxins and endotoxins in bacterial infections?

Exotoxins are actively secreted during bacterial growth and are highly toxic; endotoxins are released upon bacterial death and are moderately toxic. (D) Signup and view all the answers

Following an acute viral infection, what is the typical sequence of immune events?

Viral entry, innate immunity, adaptive immunity, resolution of infection. (B) Signup and view all the answers

How do TH1 and TH2 responses differ in their roles in controlling intracellular bacterial infections?

TH1 responses activate macrophages to kill intracellular bacteria, while TH2 responses promote antibody production to neutralize extracellular bacteria. (D) Signup and view all the answers

How do antibodies protect against pathogens through neutralization?

By binding to pathogens and preventing them from infecting host cells. (B) Signup and view all the answers

What is the function of mucosal γδ T cells in the immune response?

Directly killing infected epithelial cells and secreting cytokines to enhance local inflammation. (B) Signup and view all the answers

How does a virus's ability to undergo antigenic shift MOST significantly impact the host's immune response?

It enables the virus to evade immunological memory, leading to repeated infections. (B) Signup and view all the answers

How do some microbes use sequential DNA rearrangements of their surface antigens to evade the immune system?

By constantly changing their surface proteins, making it difficult for the immune system to target them effectively. (D) Signup and view all the answers

How does NOD1 contribute to the innate immune response against intracellular pathogens?

By recognizing intracellular bacterial components and activating inflammatory signaling pathways. (B) Signup and view all the answers

Which of the following is the MOST significant difference between endotoxins and exotoxins regarding their source and mechanism?

Endotoxins are structural components of bacterial cell walls, while exotoxins are actively secreted proteins. (A) Signup and view all the answers

Considering the time course of an immune response to an acute infection, what immunological event typically occurs FIRST?

Recruitment of complement and phagocytes to the site of infection. (D) Signup and view all the answers

In the context of immune responses to infection, what is the primary role of TH1 cells?

Stimulating phagocytosis and intracellular killing of pathogens. (B) Signup and view all the answers

How do secreted antibodies mediate pathogen clearance?

Blocking pathogen entry into host cells. (A) Signup and view all the answers

What is the MAIN function of mucosal γδ T cells?

Rapidly responding to tissue stress and infection. (C) Signup and view all the answers

How does the intracellular receptor NOD1 contribute to innate immunity?

By detecting bacterial peptidoglycans and activating inflammatory signaling pathways. (B) Signup and view all the answers

A bacterium has evolved a mechanism to alter its surface antigens frequently. What is the MOST likely immunological consequence of this adaptation?

Reduced effectiveness of immunological memory. (B) Signup and view all the answers

A virus undergoes antigenic shift. What is an expected consequence of this?

A new vaccine will likely be required to provide protection. (D) Signup and view all the answers

Primary Infection Route

Microbes enter the body through epithelial tissues like the lungs and gut, adhering to and invading these surfaces.

Endotoxins vs. Exotoxins

Endotoxins are released from dead gram-negative bacteria (moderately toxic). Exotoxins are secreted by both gram-positive and gram-negative bacteria during growth (highly toxic).