Cytokines and MTB Protection

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Questions and Answers

What is the role of Treg cells in immune responses to M.tb?

Stimulate effective anti-M.tb responses.

Enhance immunopathology.

Provide protection by inhibiting effective anti-M.tb responses. (correct)

Promote granuloma formation.

Which cytokines are involved in the protection from immunopathology associated with Th1 responses?

IL-5 and IL-23

IL-10 and IL-4

IL-12 and IFNγ (correct)

TNFα and IL-18

How does M.tb evade immune responses through macrophage function?

By down-regulating and degrading MHC class II. (correct)

By increasing acidification of phagosomes.

By promoting the upregulation of co-stimulatory molecules.

By enhancing phagosome-lysosome fusion.

What is the primary effect of IL-23 in the context of M.tb infection?

Facilitates Th17 differentiation. Signup and view all the answers

What is the consequence of granuloma disintegration during M.tb infection?

Greater susceptibility to disease progression. Signup and view all the answers

Which route do infected macrophages migrate to stimulate antigen-specific T cells after M.tb infection?

To draining lymph nodes. Signup and view all the answers

Which cytokines inhibit effective anti-M.tb responses as part of the Th2 immune response?

IL-10, IL-4, and IL-5 Signup and view all the answers

What mechanism does M.tb use to prevent phagolysosome acidification within macrophages?

By preventing phagosome-lysosome fusion. Signup and view all the answers

What is the primary role of granulomas in tuberculosis infection?

To isolate and contain the infection Signup and view all the answers

Which immune cell is primarily responsible for phagocytosing Mycobacterium tuberculosis?

Macrophages Signup and view all the answers

How does hypoxia affect the dormancy of Mycobacterium tuberculosis?

Hypoxia establishes a dormant state for the bacteria Signup and view all the answers

What mechanism is essential for T cells to recognize and respond to Mycobacterium tuberculosis?

T cell receptor (TCR) engagement with antigen-presenting cells Signup and view all the answers

Which strategy does Mycobacterium tuberculosis use to evade the host immune system?

Modulating T cell activation Signup and view all the answers

What percentage of infected individuals typically progresses to tuberculosis disease within 12 months?

3-5% Signup and view all the answers

Which of the following is NOT considered a major factor in the risk of Mycobacterium tuberculosis transmission?

Presence of respiratory droplets on surfaces Signup and view all the answers

What defines multi-drug resistant (MDR) Mycobacterium tuberculosis?

Resistance to at least two primary anti-TB drugs Signup and view all the answers

What is the main role of macrophages in the granuloma formation associated with tuberculosis?

To act as antigen presenting cells and contain the infection Signup and view all the answers

Which T cell subtype is essential for effective control of M.tuberculosis infection?

Th1 cells Signup and view all the answers

How does M.tuberculosis evade the host immune response?

By changing its antigen expression to disrupt memory T cells Signup and view all the answers

What consequence arises from the persistent antigen stimulation in tuberculosis?

Suppression of immune response and loss of memory T cells Signup and view all the answers

What is the relationship between hypoxia and dormancy of M.tuberculosis?

M.tuberculosis can enter a dormant state under hypoxic conditions Signup and view all the answers

What is the primary characteristic of the Ghon complex in tuberculosis?

Combination of the Ghon focus and involved hilar lymph nodes Signup and view all the answers

What happens during secondary or post-primary tuberculosis?

Reactivation occurs during immune suppression Signup and view all the answers

Which cytokine secreted by Th1 cells plays a key role in activating macrophages against M.tuberculosis?

IFNγ Signup and view all the answers

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.