Questions and Answers
What is the role of Treg cells in immune responses to M.tb?
Which cytokines are involved in the protection from immunopathology associated with Th1 responses?
How does M.tb evade immune responses through macrophage function?
What is the primary effect of IL-23 in the context of M.tb infection?
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What is the consequence of granuloma disintegration during M.tb infection?
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Which route do infected macrophages migrate to stimulate antigen-specific T cells after M.tb infection?
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Which cytokines inhibit effective anti-M.tb responses as part of the Th2 immune response?
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What mechanism does M.tb use to prevent phagolysosome acidification within macrophages?
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What is the primary role of granulomas in tuberculosis infection?
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Which immune cell is primarily responsible for phagocytosing Mycobacterium tuberculosis?
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How does hypoxia affect the dormancy of Mycobacterium tuberculosis?
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What mechanism is essential for T cells to recognize and respond to Mycobacterium tuberculosis?
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Which strategy does Mycobacterium tuberculosis use to evade the host immune system?
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What percentage of infected individuals typically progresses to tuberculosis disease within 12 months?
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Which of the following is NOT considered a major factor in the risk of Mycobacterium tuberculosis transmission?
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What defines multi-drug resistant (MDR) Mycobacterium tuberculosis?
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What is the main role of macrophages in the granuloma formation associated with tuberculosis?
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Which T cell subtype is essential for effective control of M.tuberculosis infection?
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How does M.tuberculosis evade the host immune response?
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What consequence arises from the persistent antigen stimulation in tuberculosis?
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What is the relationship between hypoxia and dormancy of M.tuberculosis?
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What is the primary characteristic of the Ghon complex in tuberculosis?
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What happens during secondary or post-primary tuberculosis?
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Which cytokine secreted by Th1 cells plays a key role in activating macrophages against M.tuberculosis?
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Study Notes
Cytokines and Immune Response in Tuberculosis (TB)
- Different T cell phenotypes (Th1, Th2, Th17, Treg) provide protection against Mycobacterium tuberculosis (MTB) and are assessed for previous exposure.
- Cytokines play dual roles in protecting from immunopathology and inhibiting effective anti-MTB responses.
- Treg cells secrete TGFβ and IL-10, which can limit Th1 and Th2 responses.
Importance of T Cell Subsets
- Th1 cells (producing INFγ, TNFα, IL-12) are crucial for effective MTB control.
- Th2 cells contribute to immunological balance but can impede Th1 function if overactive.
- Th17 cells are involved in granuloma formation and maintaining granuloma integrity through cytokines like IL-23.
Mechanisms of Macrophage Subversion by MTB
- MTB interferes with phagosome-lysosome fusion, preventing acidification of phagosomes.
- Reduced induction of immune responses via IFN-gamma and downregulation of MHC class II molecules occur during infection.
- MTB's evasion tactics include a lack of upregulation of co-stimulatory molecules.
MTB Infection Dynamics
- Approximately one-third of the global population is infected, with latent MTB infection serving as a reservoir for potential active disease.
- Around 9 million new TB cases are reported annually, with deaths attributed to bacterial infection numbering around 3 million.
- The presence of HIV increases the risk of MTB transmission and disease progression.
Transmission of MTB
- MTB is primarily transmitted through inhalation of aerosolized droplets produced when an infected person coughs or sneezes.
- A single cough can release approximately 3,000 infectious droplets; transmission typically occurs indoors during prolonged exposure.
- Large respiratory droplets and non-aerosolized surfaces (fomites) are less significant in transmission.
Infection and Disease Progression
- Not all exposed individuals become infected; roughly 3-5% of infections progress to disease within a year.
- Host factors, particularly impaired immunity and genetic predispositions, significantly influence disease outcomes.
- MTB can alter its antigenic profile, complicating the adaptive immune response and exhausting memory T cells over time.
Pathological Features of TB
- Granuloma formation is crucial for containing MTB, with structures formed by infected macrophages and activated lymphocytes.
- The Ghon complex is formed during primary tuberculosis, encompassing the Ghon focus (initial infection site) and involved hilar lymph nodes.
- Secondary or post-primary TB may arise from reactivation of latent infection, particularly during immune suppression.
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Description
This quiz explores the role of cytokines in providing protection and susceptibility to Mycobacterium tuberculosis (MTB). It covers various T cell phenotypes, including Th1, Th2, Th17, and Treg, and their significance in immune responses. Test your understanding of cytokine dynamics and their protective mechanisms against infections.
