Immune Responses and Evasion Mechanisms

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Questions and Answers

What is the primary cause of tissue damage in HBV and HCV infections?

Direct damage to hepatocytes by the virus

Immune response to infected liver cells (correct)

Presence of viral particles in the liver

Cytopathic effects of the virus

What role do granulomas play in tuberculosis infections?

They allow the bacilli to spread more easily.

They stimulate an increase in T-cell count.

They enhance the replication of the bacilli.

They prevent the spread of bacilli while causing tissue damage. (correct)

What mechanism do pathogens use to evade the host's adaptive immune response?

Inducing a robust phagocytic response

Enhancing cytokine production

Promoting neutrophil activation

Antigenic variation (correct)

Which condition is associated with the formation of immune complexes in the kidneys?

Poststreptococcal glomerulonephritis Signup and view all the answers

Which microbe is mentioned as being associated with cancer due to its role in chronic inflammation?

H. pylori Signup and view all the answers

In inflammatory bowel disease, which event is considered critical to the development of inflammation?

Damage to intestinal epithelial cells Signup and view all the answers

What is a primary method by which microbes resist phagocytosis?

By producing a fibrous capsule Signup and view all the answers

Which of the following best describes the relationship between chronic inflammation and cancer development?

Chronic inflammation provides conditions favorable for cancer development. Signup and view all the answers

Which of the following mechanisms do viruses use to evade the immune system?

Modulation of gene expression Signup and view all the answers

What type of inflammation is primarily observed in infections caused by pyogenic bacteria?

Neutrophil-rich acute suppurative inflammation Signup and view all the answers

What is the hallmark of infections with Mycobacterium tuberculosis?

Chronic granulomatous inflammation Signup and view all the answers

In primary tuberculosis, what is Gohn's Focus characterized by?

Central caseation and granuloma Signup and view all the answers

Which type of mycobacteria is primarily associated with abdominal tuberculosis?

Mycobacterium bovis Signup and view all the answers

What typically occurs in the hilar lymph nodes during primary tuberculosis?

Extensive caseation with enlargement Signup and view all the answers

Which type of inflammation is characterized by mononuclear cell infiltrates?

Chronic infections and some acute viral infections Signup and view all the answers

Which of the following describes the modulation of surface structures by pathogens?

Antigenic variability to avoid recognition Signup and view all the answers

What is the primary stage of syphilis characterized by?

Chancre formation Signup and view all the answers

Which of the following modes of transmission is NOT associated with syphilis?

Sharing food utensils Signup and view all the answers

How long can the tertiary stage of syphilis last?

2-10 years Signup and view all the answers

Which organs are primarily affected during the tertiary stage of syphilis?

Circulatory and nervous systems Signup and view all the answers

Which lesion is associated with the secondary stage of syphilis?

Condyloma lata Signup and view all the answers

How does M.tuberculosis evade the immune response during phagocytosis?

By blocking the fusion of the phagosome with the lysosome. Signup and view all the answers

What role does the carbohydrate capsule play for bacteria causing pneumonia or meningitis?

It prevents phagocytosis by neutrophils, increasing virulence. Signup and view all the answers

Which bacteria are known for using the inside of cells as a hideout to escape immune response?

M.tuberculosis, M.leprae, Shigella Signup and view all the answers

What is the consequence of inflammasome activation in innate immunity?

Promotion of pyroptosis and inflammation. Signup and view all the answers

How do some viruses inhibit the action of interferons during viral infections?

By producing soluble homologues of interferon receptors. Signup and view all the answers

Which virulence mechanism do Yersinia and Salmonella employ to avoid inflammation?

They inhibit the formation of mature inflammasomes. Signup and view all the answers

What effect do DNA viruses like HSV, CMV, and EBV have on CD8+ cytotoxic T cells?

They alter the localization of MHC class I proteins, impairing recognition. Signup and view all the answers

What is one way that Legionella escapes destruction in macrophages?

By creating pores in the phagosome membrane. Signup and view all the answers

What is the primary cause of tissue damage in secondary tuberculosis?

Failure to contain granulomas Signup and view all the answers

Which organ is least commonly affected by secondary tuberculosis granulomas?

Heart Signup and view all the answers

Which of the following statements about primary tuberculosis is true?

Primarily affects non-immunized individuals Signup and view all the answers

In what way can secondary tuberculosis be triggered?

Endogenous reactivation of dormant disease Signup and view all the answers

Which bodily reaction is associated with primary tuberculosis?

Formation of tubercles in solid organs Signup and view all the answers

What characterizes the lesions found in secondary tuberculosis?

Cavities and necrotic lesions Signup and view all the answers

Where are granulomas from secondary tuberculosis most commonly found?

Lung apices and kidneys Signup and view all the answers

Which method of infection is associated with secondary tuberculosis?

Endogenous reactivation of prior infection Signup and view all the answers

Study Notes

Immune Responses to Microbes

Inflammation is a complex biological response to harmful stimuli, including infection.
Immune evasion is a crucial strategy for infectious organisms to proliferate and transmit to new hosts.
Bacteria, viruses, and fungi employ various mechanisms to evade innate and adaptive immune responses.

Immune Evasion Mechanisms

Antigenic Variation

Microbes can escape recognition by the immune system through antigenic variation.

Resisting Phagocytosis and Bacterial Killing in Phagosomes

Many bacteria produce capsules to prevent phagocytosis by neutrophils.
Mycobacterium tuberculosis inhibits phagosome-lysosome fusion, allowing bacteria to proliferate within macrophages.
Legionella releases proteins that degrade the phagosome membrane, escaping into the cytoplasm.

Escaping the Inflammasome

Yersinia and Salmonella use virulence proteins to block inflammasome activation, preventing IL-1 and IL-18 secretion.

Disruption of Interferon Pathways

Some viruses produce soluble IFN receptor homologues to block IFN signaling or inhibit JAK/STAT signaling.

Decreased T-Cell Recognition

DNA viruses can interfere with MHC class I presentation, hindering T-cell recognition.
HIV infects CD4+ T cells, macrophages, and dendritic cells, directly compromising immune function.

Patterns of Host Responses to Microbes

Neutrophil-rich acute suppurative inflammation: Typical of infections with many bacteria.
Mononuclear cell infiltrates: Common in chronic infections and some acute viral infections.
Granulomatous inflammation: Hallmark of Mycobacterium tuberculosis and certain fungal infections.
Cytopathic and proliferative lesions: Caused by some viruses.
Necrosis: Result of tissue-damaging toxins produced by microbes such as Clostridium perfringens.
Chronic inflammation and scarring: Final common pathway of many infections.

Tuberculosis

Chronic granulomatous disease caused by Mycobacterium tuberculosis, Mycobacterium bovis, and atypical mycobacteria.

Primary Tuberculosis

Occurs in individuals with no prior immunity.
Characterized by the formation of a primary complex, including a primary lesion (Gohn's focus) and enlarged hilar lymph nodes.

Secondary (Post-Primary) TB

Can occur due to reinfection, reactivation of dormant disease, or progression of primary TB.
Granulomas are often found in the lung apices, kidneys, meninges, and other organs.
Cavities are a common feature.

Syphilis

Chronic infective granuloma caused by Treponema pallidum.

Stages of Syphilis

Primary syphilis: Characterized by chancre formation on the skin or mucous membranes.
Secondary syphilis: Marked by condyloma lata and widespread skin lesions.
Tertiary syphilis: May occur 2-10 years after secondary syphilis, involving cardiovascular and central nervous systems.

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Description

Explore the complexities of immune responses to microbes, including inflammation and immune evasion strategies. This quiz will cover key concepts such as antigenic variation and mechanisms bacteria employ to resist immune challenges. Test your understanding of how different pathogens escape detection and elimination by the immune system.