Nokea
Which cytokine group is most commonly associated with antiviral responses?
- A. Interleukins
- B. Interferons
- C. Tumor necrosis factors
- D. Transforming growth factors
Correct Answer: B
Rationale: Interferons are the correct answer as they are a cytokine group primarily associated with antiviral responses. They play a key role in the immune response against viral infections by inhibiting viral replication and spreading to other cells. Interleukins are more diverse and involved in various immune responses, not specifically antiviral. Tumor necrosis factors are more related to inflammation and cell death. Transforming growth factors are involved in cell growth and differentiation, not primarily antiviral responses. Therefore, B: Interferons is the most appropriate choice for cytokine group associated with antiviral responses.
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Multi-photon microscopy has proved to be an invaluable tool for the evaluation of the dynamics of immune responses in vivo. The following is a list of observations derived from intra-vital microscopy. Identify the incorrect statement.
- A. T cells make stable and prolonged contacts with APC presenting the specific antigen in the paracortex
- B. In the absence of antigens B cells move at the same speed and randomly in follicles
- C. In the presence of infection specific B cells quickly direct themselves towards the source of antigen
- D. Dendritic cells move rapidly through the germinal centre during an immune response
Correct Answer: D
Rationale: The correct answer is D because dendritic cells do not typically move rapidly through the germinal center during an immune response. Dendritic cells usually interact with T cells in the paracortex to present antigens, and they are not known to migrate rapidly through the germinal center.
A: This statement is correct as T cells do make stable and prolonged contacts with APCs in the paracortex during immune responses.
B: This statement is incorrect as B cells do not move at the same speed and randomly in follicles in the absence of antigens. They respond to signals and cues in the microenvironment.
C: This statement is correct as specific B cells can quickly direct themselves towards the source of antigen during an infection.
In summary, choice D is incorrect because dendritic cells do not move rapidly through the germinal center during an immune response, while the other choices accurately describe behaviors of immune cells during immune responses.
TLRs contain a cytoplasmic TIR domain also found in the receptor of
- A. Type I Interferons
- B. IL-1β
- C. TNF-α
- D. IL-8
Correct Answer: B
Rationale: Step-by-step rationale for Choice B (IL-1β) being correct:
1. The TIR domain is present in Toll-like receptors (TLRs) and IL-1 receptor.
2. TLRs recognize various microbial products, while IL-1 receptor binds IL-1 cytokines.
3. Both TLRs and IL-1 receptor signal through the TIR domain.
4. IL-1β is a cytokine that binds to IL-1 receptor, which contains a TIR domain.
Summary of why the other choices are incorrect:
A: Type I Interferons - Type I interferons signal through JAK-STAT pathway, not TIR domain.
C: TNF-α - TNF receptor family signals through TNF receptor-associated death domain, not TIR domain.
D: IL-8 - IL-8 binds to CXCR1 and CXCR2 receptors, which do not contain a TIR domain.
In summary, Choice B
The gut immune system at homeostasis is 'tolerogenic'. This is achieved by:
- A. The production of anti-inflammatory cytokines such as TGF-beta by resident dendritic cells
- B. Responding to innocuous microbiota antigens with production of antimicrobial peptides that limit microbiota overgrowth
- C. Induction of Tregs
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D. Resident dendritic cells in the gut produce anti-inflammatory cytokines like TGF-beta, promoting tolerance. The production of antimicrobial peptides in response to microbiota antigens helps maintain a balance with the microbiota. Induction of regulatory T cells (Tregs) also plays a crucial role in preventing excessive immune responses. Therefore, all of the choices (A, B, and C) contribute to maintaining gut immune system homeostasis by promoting tolerance and preventing inflammation.
Superoxide dismutase is an enzyme that catalyzes the conversion of oxygen radicals to peroxides. Which groups of organisms do not have this enzyme?
- A. aerobes
- B. facultative anaerobes
- C. oxyduric anaerobes
- D. oxylabile anaerobes
Correct Answer: D
Rationale: The correct answer is D: oxylabile anaerobes. These organisms cannot survive in the presence of oxygen and are sensitive to oxygen radicals. Superoxide dismutase is essential for organisms that are exposed to oxygen, as it helps convert harmful oxygen radicals into less harmful peroxides. Therefore, organisms that lack this enzyme, like oxylabile anaerobes, would not be able to detoxify oxygen radicals and would not survive in aerobic environments.
A: Aerobes have superoxide dismutase to protect against oxygen radicals.
B: Facultative anaerobes can switch between aerobic and anaerobic metabolism and would benefit from having superoxide dismutase.
C: Oxyduric anaerobes are resistant to oxygen and can still benefit from superoxide dismutase for detoxification.
Which T lymphocytes are involved in direct attack and destruction of foreign pathogens?
- A. Dendritic cells
- B. Natural killer cells
- C. T helper (CD4) cells
- D. T cytotoxic (CD8) cells
Correct Answer: D
Rationale: T cytotoxic (CD8) cells directly attack and destroy infected or abnormal cells, making them crucial for eliminating pathogens.