Nokea
With regard to NADPH oxidase, which of the following statements in not correct?
- A. It is the enzyme involved in the respiratory burst that follows the engagement of phagocytic receptors
- B. Individuals with mutations of NADPH oxidase subunits suffer repeated infections because of defective killing of phagocytosed pathogens
- C. It is constitutively expressed as a complex of 5 subunits in unstimulated cells
- D. It controls the formation of reactive oxygen species
Correct Answer: C
Rationale: The correct answer is C because NADPH oxidase is not constitutively expressed as a complex of 5 subunits in unstimulated cells. Instead, it is assembled and activated upon stimulation, such as during the respiratory burst following phagocytosis. Choice A is correct as NADPH oxidase is indeed involved in the respiratory burst. Choice B is correct as mutations in NADPH oxidase subunits lead to impaired pathogen killing and recurrent infections. Choice D is correct as NADPH oxidase controls the production of reactive oxygen species.
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A good vaccine will:
- A. Be highly pathogenic
- B. Be highly immunogenic
- C. Induce herd immunity in a vaccinated individual
- D. All of the above
Correct Answer: B
Rationale: The correct answer is B: Be highly immunogenic. A good vaccine should effectively stimulate the immune system to produce a strong immune response against the targeted pathogen while being safe for the individual. This is crucial for developing immunity without causing harm.
Choice A (Be highly pathogenic) is incorrect because a vaccine should not cause disease or harm to the individual receiving it. Choice C (Induce herd immunity in a vaccinated individual) is also incorrect as herd immunity refers to protection of a population, not an individual.
In summary, a good vaccine should be highly immunogenic to effectively trigger an immune response without causing harm, leading to protection against the targeted pathogen.
Virulence factors can be transferred from pathogenic to non-pathogenic bacterial strains that are part of the normal flora. An example of a commensal bacterial species that has turned into a pathogenic strain is:
- A. E. coli 0157:H7
- B. M. tuberculosis
- C. Group A S. pyogenes
- D. All opportunistic bacterial species
Correct Answer: A
Rationale: The correct answer is A: E. coli 0157:H7. This strain of E. coli has acquired virulence factors that allow it to cause severe illness in humans, such as bloody diarrhea and kidney failure. The transformation of E. coli from a commensal to a pathogenic strain is well-documented. In contrast, choices B and C involve species that are inherently pathogenic and not commensal. Choice D is too broad and includes a wide range of bacterial species that do not necessarily originate from the normal flora. Therefore, E. coli 0157:H7 is the best example of a commensal bacterium that has turned pathogenic due to the acquisition of virulence factors.
A cytokine essential for clonal expansion of T cells is
- A. IL-1
- B. IL-2
- C. IL4
- D. IL-5
Correct Answer: B
Rationale: The correct answer is B: IL-2. IL-2 is essential for the clonal expansion of T cells as it promotes T cell proliferation. It is produced by activated T cells themselves and plays a crucial role in regulating immune responses. IL-1 is involved in inflammation, not T cell expansion. IL-4 is important for Th2 cell differentiation, while IL-5 is critical for eosinophil activation. In summary, IL-2 specifically promotes T cell clonal expansion, making it the correct choice in this context.
What is the main purpose of complement component C5a?
- A. Opsonization
- B. Cell lysis
- C. Recruitment and activation of immune cells
- D. Inhibition of inflammation
Correct Answer: C
Rationale: The correct answer is C: Recruitment and activation of immune cells. C5a is a potent chemoattractant that attracts immune cells to the site of infection or inflammation. It also activates these immune cells, leading to enhanced immune responses. Option A (Opsonization) and B (Cell lysis) are not the main functions of C5a. Option D (Inhibition of inflammation) is incorrect because C5a actually promotes inflammation by recruiting and activating immune cells.
Which of the following correctly explains an epitope?
- A. Region of antibody that binds with antigen
- B. Region of antigen that elicit secretion of specific antibody
- C. Heavy chain of an antibody
- D. V-region of the light chain of antibody
Correct Answer: B
Rationale: Explanation:
An epitope is a specific region on an antigen that elicits the immune response and triggers the production of a specific antibody. Therefore, choice B is correct as it accurately defines an epitope. Choices A, C, and D are incorrect because they do not accurately describe what an epitope is. Choice A refers to the paratope, the region of the antibody that binds to the epitope. Choice C refers to a component of the antibody structure, and choice D refers to a specific region of the antibody structure.