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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Which condition is caused by a Type IV hypersensitivity reaction?
- A. Anaphylaxis
- B. Sarcoidosis
- C. Grave's disease
- D. Goodpasture's syndrome
Correct Answer: B
Rationale: The correct answer is B: Sarcoidosis. Type IV hypersensitivity reactions are mediated by T cells and are characterized by delayed onset inflammatory responses. Sarcoidosis is a granulomatous disease where T cells form granulomas in affected tissues. Anaphylaxis (A) is a Type I hypersensitivity reaction involving IgE antibodies. Grave's disease (C) is an autoimmune disorder caused by Type II hypersensitivity reaction mediated by antibodies. Goodpasture's syndrome (D) is a Type II hypersensitivity reaction involving antibodies attacking basement membranes. Therefore, the correct answer is B as it fits the characteristics of a Type IV hypersensitivity reaction.
Which of the following statements is incorrect?
- A. Activation of receptors such as TLRs often precedes inflammasome formation
- B. Extracellular ATP triggers inflammasome formation
- C. Some environmental triggers, such as asbestos, can induce inflammasome formation
- D. NLRP3 is found in complex with pro-caspase 1 in resting, non-activated cells
Correct Answer: D
Rationale: The correct answer is D because NLRP3 is not found in complex with pro-caspase 1 in resting, non-activated cells. Inflammasome formation requires assembly of NLRP3 with ASC and pro-caspase 1. Choices A, B, and C are correct statements because activation of receptors like TLRs can trigger inflammasome formation, extracellular ATP can induce inflammasome formation, and environmental triggers such as asbestos can also lead to inflammasome activation.
Which vitamin is essential in treating osteoporosis?
- A. Vitamin A
- B. Vitamin D
- C. Vitamin B12
- D. Vitamin C
Correct Answer: B
Rationale: The correct answer is B: Vitamin D. Vitamin D is essential in treating osteoporosis because it helps the body absorb calcium, a crucial mineral for bone health. Without sufficient Vitamin D, the body cannot effectively utilize calcium, leading to weakened bones. Vitamin A (Choice A) is not directly linked to osteoporosis treatment. Vitamin B12 (Choice C) is important for red blood cell production but not specifically for osteoporosis. Vitamin C (Choice D) aids in collagen formation but does not play a primary role in treating osteoporosis.
The process of somatic hypermutation:
- A. Can lead to the formation of antibodies with higher affinity for the antigen
- B. Occurs mainly in the CDR regions of immunoglobulin heavy and light chain genes
- C. Occurs in germinal centres
- D. All of the above are correct
Correct Answer: D
Rationale: The correct answer is D because somatic hypermutation can lead to the formation of antibodies with higher affinity for the antigen by introducing point mutations in the variable regions of immunoglobulin genes. This process mainly occurs in the complementarity-determining regions (CDRs) of immunoglobulin heavy and light chain genes, which are critical for antigen binding. Somatic hypermutation takes place in the germinal centers of secondary lymphoid organs, where B cells undergo rapid proliferation and selection based on antigen binding affinity. Therefore, all the statements in choices A, B, and C are correct, making option D the right answer.
An example of a recombinant vaccine is
- A. DPT (Diphteria/Pertussis/Tetanus)
- B. Hepatitis B
- C. BCG
- D. Measles
Correct Answer: B
Rationale: The correct answer is B: Hepatitis B. Recombinant vaccines are made by inserting genetic material from a pathogen into another organism to stimulate an immune response. Hepatitis B vaccine is produced using recombinant DNA technology to create a non-infectious protein that triggers an immune response against the hepatitis B virus. DPT, BCG, and Measles vaccines are not examples of recombinant vaccines as they are made using different methods without genetic engineering.